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- Aerospace, Vol. 11, Pages 693: A Physical and Spectroscopic Survey of the
Lunar South Pole with the Galileo Telescope of the Asiago Astrophysical
Observatory
Authors: Nicolò Trabacchin, Paolo Ochner, Giacomo Colombatti
First page: 693
Abstract: In recent years, interest in the Moon has grown exponentially, thanks mainly to space programs with strong international cooperation, such as the NASA Artemis program. Several scientific committees have identified the lunar south pole as the region of greatest interest for building a lasting and sustainable human settlement. However, the knowledge we have of this area is still limited. This work aims to provide a general overview of the main physical and morphological features of the lunar south pole and to propose a first iteration of spectroscopic observations within the visible range from the Asiago Astrophysical Observatory, giving a new and different perspective. The objective is to verify the feasibility of an Earth-based spectroscopic survey to detect water and the abundances of other volatiles and elements.
Citation: Aerospace
PubDate: 2024-08-23
DOI: 10.3390/aerospace11090693
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 694: Thermo-Mechanical Jitter in Slender Space
Structures: A Simplified Modeling Approach
Authors: Maurizio Parisse, Federica Angeletti
First page: 694
Abstract: Thermally induced vibrations usually affect spacecraft equipped with light and slender appendages such as booms, antennas or solar panels. This phenomenon occurs when a thermal shock, resulting from the sudden cooling and warming phases at the entrance and exit from eclipses, triggers mechanical vibrations. The study proposed hereafter concerns the modeling and prediction of jitter of thermal origin in a long and thin plate with a sun-pointing attitude in geostationary orbit. The system’s temperature and dynamics are described by a set of equations expressing the two-way coupling between the thermal bending moment and the shape of the panel. The structure is discretized and reduced to a one-degree-of-freedom simplified model able to identify a mechanism of thermal pumping that could lead to instability. Finally, the results of the analysis are compared with those obtained with a more accurate FEM modelization.
Citation: Aerospace
PubDate: 2024-08-25
DOI: 10.3390/aerospace11090694
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 695: Validation of Experimental Data for the
Application of the Magnesium Alloy “Elektron 43”
Authors: Michele Guida
First page: 695
Abstract: The behaviour of a structural component, such as the spreader installed on an aeroplane passenger seat made of the magnesium alloy Elektron® 43, is evaluated under a variety of load conditions. The purpose of this research project is to considerably reduce weight by employing the new alloy while keeping the strength and ductility necessary to meet the dynamic standards for both the 16 g forward and 14 g downward tests. A comprehensive campaign of static and dynamic testing on coupons was conducted to characterise the mechanical behaviour of the E43 magnesium alloy, from quasi-static to dynamic loading, and across a wide range of deformation rates. The elastic–plastic and strain rate sensitive material model of E43 is then calibrated using an FEA approach and LS-DYNA software, utilising stress–strain curves and properties determined from standardised experimental tensile and compression trials at varied strain rates. Finally, this material model was used to perform a finite element structural study of a major component of an aeroplane seat built using Elektron® 43 under typical in-flight stresses.
Citation: Aerospace
PubDate: 2024-08-25
DOI: 10.3390/aerospace11090695
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 696: Special Issue “Gust Influences on
Aerospace”
Authors: Zhenlong Wu, Michael Hölling
First page: 696
Abstract: An important prerequisite for the design, assessment, and certification of aircraft, their propulsion systems, and associated control systems is a quantitative specification of the environment in which the aircraft are intended to operate [...]
Citation: Aerospace
PubDate: 2024-08-26
DOI: 10.3390/aerospace11090696
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 697: Multiscale Modeling of Plasma-Assisted
Non-Premixed Microcombustion
Authors: Giacomo Cinieri, Ghazanfar Mehdi, Maria Grazia De Giorgi
First page: 697
Abstract: This work explores microcombustion technologies enhanced by plasma-assisted combustion, focusing on a novel simulation model for a Y-shaped device with a non-premixed hydrogen-air mixture. The simulation integrates the ZDPlasKin toolbox to determine plasma-produced species concentrations to Particle-In-Cell with Monte Carlo Collision analysis for momentum and power density effects. The study details an FE-DBD plasma actuator operating under a sinusoidal voltage from 150 to 325 V peak-to-peak and a 162.5 V DC bias. At potentials below 250 V, no hydrogen dissociation occurs. The equivalence ratio fitting curve for radical species is incorporated into the plasma domain, ensuring local composition accuracy. Among the main radical species produced, H reaches a maximum mass fraction of 8% and OH reaches 1%. For an equivalence ratio of 0.5, the maximum temperature reached 2238 K due to kinetic and joule heating contributions. With plasma actuation with radicals in play, the temperature increased to 2832 K, and with complete plasma actuation, it further rose to 2918.45 K. Without plasma actuation, the temperature remained at 300 K, reflecting ambient conditions and no combustion phenomena. At lower equivalence ratios, temperatures in the plasma area consistently remained around 2900 K. With reduced thermal power, the flame region decreased, and at Φ = 0.1, the hot region was confined primarily to the plasma area, indicating a potential blow-off limit. The model aligns with experimental data and introduces relevant functionalities for modeling plasma interactions within microcombustors, providing a foundation for future validation and numerical models in plasma-assisted microcombustion applications.
Citation: Aerospace
PubDate: 2024-08-26
DOI: 10.3390/aerospace11090697
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 698: An Endurance Equation for Hybrid-Electric
Aircraft
Authors: Aman Batra, Reiko Raute, Robert Camilleri
First page: 698
Abstract: This paper introduces a new endurance equation for a hybrid-electric aircraft. This research follows the derivation of a range equation for a hybrid-electric aircraft case using constant power split that was carried out by authors in their earlier work. Thus, the derivation of the endurance equation maintains the use of efficiency-based degree of hybridization (φ) used in the earlier research. For coherence, the paper also uses the same case study to assess endurance values over a range of battery energy density values and degree of hybridization (φ) values. Results show that any aircraft design has an Energy Density Threshold (EDT) value, before which the endurance of the aircraft reduces with an increase in the degree of hybridization values. Conversely, once EDT is exceeded, the endurance of the aircraft enhances with the increase in the degree of hybridization values. The EDT values are specific to the aircraft type, its specifications and key design parameters.
Citation: Aerospace
PubDate: 2024-08-26
DOI: 10.3390/aerospace11090698
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 699: Lessons Learnt from the Simulations of
Aero-Engine Ground Vortex
Authors: Wenqiang Zhang, Tao Yang, Jun Shen, Qiangqiang Sun
First page: 699
Abstract: With the startup of the aero-engine, the ground vortex is formed between the ground and the engine intake. The ground vortex leads to total pressure and swirl distortion, which reduces the performance of the engine. The inhalation of the dust and debris through a ground vortex can erode the fan blade, block the seals and degrade turbine cooling performance. As the diameter of the modern fan blade becomes larger, the clearance between the intake lip and the ground surface is smaller, which enhances the strength of the ground vortex. Though considerable numerical studies have been conducted with the predictions of the ground vortex, it is noted that the accurate simulation of the ground vortex is still a tough task. This paper presents authors’ simulation work of the ground vortex into an intake model with different crosswind speeds. This paper tackles the challenge with a parametric study to provide useful guidelines on how to obtain a good match with the experimental data. The influence of the mesh density, performance of different turbulence models and how the boundary layer thickness affects the prediction results are conducted and analysed. The detailed structure of the flow field with ground vortex is presented, which can shed light on the experimental observations. A number of suggestions are presented that can pave the road to the accurate flow field simulations with strong vorticities.
Citation: Aerospace
PubDate: 2024-08-26
DOI: 10.3390/aerospace11090699
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 700: Optimization of Pyroshock Test Conditions
for Aerospace Components to Enhance Repeatability by Genetic Algorithms
Authors: Wonki Bae, Junhong Park
First page: 700
Abstract: Electronic components assembled in satellites should be able to withstand the vibration, noise, and impact loads generated by space vehicles during launch. To simulate the impact loading in a laboratory environment, a pyroshock test simulates an impact load resulting from explosions during the stage and pairing separation of launch vehicles, which imposes significant stress on the components, potentially leading to failures and damage. To ensure component reliability before the flight model (FM) stage, where components are mounted on the actual launch vehicle and sent into orbit, a pyroshock test is conducted during the qualification model (QM) stage using identical parts and specifications. This process involves measurements of the acceleration induced by pyroshock to calculate the shock response spectrum (SRS) and evaluate the components’ reliability against the required SRS to confirm their ability to endure the shock and operate normally in post-tests. The aerospace developer determines the SRS requirements based on the space launch vehicle and the installation location of the electronic components. Configuring a suitable pyroshock test to meet these requirements typically involves extensive trial and error. This study aims to minimize such trial and error by examination of SRS changes through a numerical approach by table structural vibration analysis. The structure is subjected to in-plane impacts using a steel ball via a pendulum method. Various SRS profiles are calculated by test factors such as the weight of the steel ball, the pendulum angle, and the installation position of the test specimen. Furthermore, a genetic algorithm is utilized to derive the optimal test conditions that satisfy the required SRS. An automated pyroshock test system is developed to enhance repeatability and reduce human errors.
Citation: Aerospace
PubDate: 2024-08-26
DOI: 10.3390/aerospace11090700
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 701: Numerical Study on the Influence of Inlet
Turbulence Intensity on Turbine Cascades
Authors: Xuan Wu, Yanfeng Zhang, Junqiang Zhu, Xingen Lu
First page: 701
Abstract: The turbulence intensity of the high-pressure turbine inlet plays an important role in the development of secondary flow and boundary layer evolution in the turbine passage. Unfortunately, current research often overlooks the coupling effect between boundary layer separation and endwall secondary flow, and lacks comprehensive exploration of loss variation. To complement existing research, this study utilizes numerical simulation techniques to investigate the evolution of the boundary layer and secondary flow in high-pressure turbine cascades under varying turbulence intensities, with experimental research results as the basis. Furthermore, the relationship between profile loss and endwall secondary flow loss is analyzed. The research results indicate that higher turbulence intensity can enhance the anti-separation ability of the boundary layer, thereby reducing the blade profile loss caused by separation in the boundary layer. However, higher turbulence intensities (Tu) enhance the development of secondary flow within the cascade, leading to a significant increase in secondary flow losses. Q-criterion methods are employed to display the vortex structures within the passage, while loss decomposition is leveraged to uncover the variations of different losses under different turbulence intensities (Tu of 1% and 6%).With the exception of a minor decrease in total pressure loss (Yp) when Tu increases from 1% to 2%, Yp demonstrates a substantial increase in all other cases with increasing Tu. Additionally, this study explains why the loss of high-pressure turbine cascades shows a trend of first increasing and then decreasing with the increase in inlet turbulence intensity.
Citation: Aerospace
PubDate: 2024-08-27
DOI: 10.3390/aerospace11090701
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 702: Open-Source Data Formalization through
Model-Based Systems Engineering for Concurrent Preliminary Design of
CubeSats
Authors: Giacomo Luccisano, Sophia Salas Cordero, Thibault Gateau, Nicole Viola
First page: 702
Abstract: Market trends in the space sector suggest a notable increase in satellite operations and market value for the coming decade. In parallel, there has been a shift in the industrial and academic sectors from traditional Document-Based System Engineering to Model-based systems engineering (MBSE) combined with Concurrent engineering (CE) practices. Due to growing demands, the drivers behind this change have been the need for quicker and more cost-effective design processes. A key challenge in this transition remains to determine how to effectively formalize and exchange data during all design stages and across all discipline-specific tools; as representing systems through models can be a complex endeavor. For instance, during the Preliminary design (PD) phase, the integration of system models with external mathematical models for simulations, analyses, and system budgeting is crucial. The introduction of CubeSats and their standard has partly addressed the question of standardization and has aided in reducing overall development time and costs in the space sector. Nevertheless, questions about how to successfully exchange data endure. This paper focuses on formalizing a CubeSat model for use across various stages of the PD phase. The entire process is conducted with the exclusive use of open-source tools, to facilitate the transparency of data integration across the PD phases, and the overall life cycle of a CubeSat. The paper has two primary outcomes: (i) developing a generic CubeSat model using Systems modeling language (SysML) that includes data storage and visualization through the application of Unified modeling language (UML) stereotypes, streamlining in parallel information exchange for integration with various simulation and analysis tools; (ii) creating an end-to-end use case scenario within the Nanostar software suite (NSS), an open-source framework designed to streamline data exchange across different software during CE sessions. A case study from a theoretical academic space mission concept is presented as the illustration of how to utilize the proposed formalization, and it serves as well as a preliminary validation of the proposed formalization. The proposed formalization positions the CubeSat SysML model as the central data source throughout the design process. It also supports automated trade-off analyses by combining the benefits of SysML with effective data instantiating across all PD study phases.
Citation: Aerospace
PubDate: 2024-08-27
DOI: 10.3390/aerospace11090702
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 703: A Peak-Finding Siamese Convolutional Neural
Network (PF-SCNN) for Aero-Engine Hot Jet FT-IR Spectrum Classification
Authors: Shuhan Du, Wei Han, Zhenping Kang, Fengkun Luo, Yurong Liao, Zhaoming Li
First page: 703
Abstract: Aiming at solving difficulties related to aero-engine classification and identification, two telemetry Fourier transform infrared spectrometers are utilized to measure the infrared spectra of six types of aero-engine hot jets, and create a spectral data set, which is divided into a training set (80%), a validation set (10%), and a prediction set (10%). A peak-finding Siamese convolutional neural network (PF-SCNN) is used to match and classify the spectral data. During the training stage, the Siamese convolutional neural network (SCNN) is designed to extract spectral features and calculate the distance similarity. In order to improve the efficiency of the SCNN, a peak-finding method is introduced to extract the spectral peaks, which are used to train the model instead of the original spectral data. During the prediction stage, the trained model is used to calculate the similarity between the prediction set and the combined set of the training set and validation set, and the label of the most similar training data in each prediction set is used as the prediction label. The performance measures of the classification results include accuracy, precision, recall, confusion matrix, and F1-score. The experimental results show that the PF-SCNN can achieve a high classification accuracy rate of 99% and can complete the task of classifying the infrared spectra of aero-engine hot jets.
Citation: Aerospace
PubDate: 2024-08-28
DOI: 10.3390/aerospace11090703
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 704: Research, Analysis, and Improvement of
Unmanned Aerial Vehicle Path Planning Algorithms in Urban Ultra-Low
Altitude Airspace
Authors: Jianwei Gao, Weijun Pan
First page: 704
Abstract: Urban ultra-low altitude airspace (ULAA) presents unique challenges for unmanned aerial vehicle (UAV) path planning due to high building density and regulatory constraints. This study analyzes and improves classical path planning algorithms for UAVs in ULAA. Experiments were conducted using A*, RRT, RRT*, and artificial potential field (APF) methods in a simulated environment based on building data from Chengdu City, China. Results show that traditional algorithms struggle in dense obstacle environments, particularly APF due to local minima issues. Enhancements were proposed: a density-aware heuristic for A*, random perturbation for APF, and a hybrid optimization strategy for RRT*. These modifications improved computation time, path length, and obstacle avoidance. The study provides insights into the limitations of classical algorithms and suggests enhancements for more effective UAV path planning in urban environments.
Citation: Aerospace
PubDate: 2024-08-28
DOI: 10.3390/aerospace11090704
Issue No: Vol. 11, No. 9 (2024)
- Aerospace, Vol. 11, Pages 605: SE-CBAM-YOLOv7: An Improved Lightweight
Attention Mechanism-Based YOLOv7 for Real-Time Detection of Small Aircraft
Targets in Microsatellite Remote Sensing Imaging
Authors: Zhenping Kang, Yurong Liao, Shuhan Du, Haonan Li, Zhaoming Li
First page: 605
Abstract: Addressing real-time aircraft target detection in microsatellite-based visible light remote sensing video imaging requires considering the limitations of imaging payload resolution, complex ground backgrounds, and the relative positional changes between the platform and aircraft. These factors lead to multi-scale variations in aircraft targets, making high-precision real-time detection of small targets in complex backgrounds a significant challenge for detection algorithms. Hence, this paper introduces a real-time aircraft target detection algorithm for remote sensing imaging using an improved lightweight attention mechanism that relies on the You Only Look Once version 7 (YOLOv7) framework (SE-CBAM-YOLOv7). The proposed algorithm replaces the standard convolution (Conv) with a lightweight convolutional squeeze-and-excitation convolution (SEConv) to reduce the computational parameters and accelerate the detection process of small aircraft targets, thus enhancing real-time onboard processing capabilities. In addition, the SEConv-based spatial pyramid pooling and connected spatial pyramid convolution (SPPCSPC) module extracts image features. It improves detection accuracy while the feature fusion section integrates the convolutional block attention module (CBAM) hybrid attention network, forming the convolutional block attention module Concat (CBAMCAT) module. Furthermore, it optimizes small aircraft target features in channel and spatial dimensions, improving the model’s feature fusion capabilities. Experiments on public remote sensing datasets reveal that the proposed SE-CBAM-YOLOv7 improves detection accuracy by 0.5% and the mAP value by 1.7% compared to YOLOv7, significantly enhancing the detection capability for small-sized aircraft targets in satellite remote sensing imaging.
Citation: Aerospace
PubDate: 2024-07-24
DOI: 10.3390/aerospace11080605
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 606: Influence of Double-Ducted Serpentine
Nozzle Configurations on the Interaction Characteristics between the
External and Nozzle Flow of Aircraft
Authors: Jilong Zhu, Yi Zhang, Yaohua Li, Liquan Zeng, Lei Miao, Neng Xiong, Yang Tao
First page: 606
Abstract: To clarify the influence of the serpentine nozzle configurations on the flow characteristics and aerodynamic performance of aircraft, the flow features and aerodynamic performances of the double-ducted serpentine nozzles with different aspect ratios (AR), length–diameter ratios (LDR) and shielding ratios (SR) are numerically investigated. The results show that the asymmetric nozzle flow occurs due to the curved profile of serpentine nozzles, and a local accelerating effect exists at the S-bend, causing the increase in wall shear stress. The unilateral unsymmetrical expansion of the tail jet in the upward direction interacts with the separated external flow of the afterbody, forming an obvious cross-shock wave and shear layer structure. The surface pressure of the afterbody increases along the external flow direction, and decreases sharply in the separation point of the boundary layer. With the increase in AR and LDR, the local accelerating effect of the nozzle flow weakens, while with the increase in SR, the accelerating effect increases. The total pressure recovery coefficient, flow coefficient and axial thrust coefficient all decrease with the increase in AR, LDR, and SR. The thrust vector angle decreases with the increase in AR but is less affected by LDR and SR.
Citation: Aerospace
PubDate: 2024-07-24
DOI: 10.3390/aerospace11080606
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 607: Nonlinear Surrogate Model Design for
Aerodynamic Dataset Generation Based on Artificial Neural Networks
Authors: Guillermo Suarez, Emre Özkaya, Nicolas R. Gauger, Hans-Jörg Steiner, Michael Schäfer, David Naumann
First page: 607
Abstract: In this work we construct a surrogate model using artificial neural networks (ANN) to predict the steady-state behavior of an unmanned combat aircraft. We employ various strategies to improve the model’s accuracy, including the consideration of design tolerances, creating independent surrogate models for the different flow regimes and encoding non-numeric input features. We also explore alternative machine learning models, albeit they demonstrated a lower reliability than ANNs. Two scenarios are considered for the target variable: one focusing solely on predicting the pitching moment coefficient, and the other incorporating the roll moment coefficient as well. We investigate different methods for handling multiple targets, finding that constructing a single model with multiple outputs consistently outperforms developing separate models for each target variable. Overall, the ANN provides predictions that show excellent agreement with the experimental data, demonstrating its effectiveness and reliability in aerodynamic modeling.
Citation: Aerospace
PubDate: 2024-07-24
DOI: 10.3390/aerospace11080607
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 608: Analysis and Evaluation of Fault
Propagation Behavior in Integrated Avionics Systems Considering Cascading
Failures
Authors: Lei Dong, Bo Peng, Xi Chen, Jiachen Liu
First page: 608
Abstract: As the synthesis, modularization, and integration of avionics systems increase, the interconnections between systems and equipment within subsystems become increasingly complex, posing risks to the safety and reliability of the integrated avionics system. To address the risk of fault propagation due to functional cascade failures in integrated avionics systems, this paper proposes a discrete dynamic fault propagation analysis method, which was applied to an all-electric braking system to assess its feasibility. First, the architectural features of the Distributed Integrated Modular Avionics system are summarized. Subsequently, the constructed system layer model is described, establishing the function–resource hierarchical architecture. Subsequently, the behavior of cascading failure propagation in discrete dynamic systems is analyzed by integrating the cascading failure analysis method from SAE ARP 4761A and considering the coupling characteristics between system properties and functions comprehensively. This approach facilitates the development of a cascading failure propagation model for DIMA based on discrete dynamic systems. Finally, by using the all-electric braking system under DIMA architecture as a case study, key Core Processing Modules and failure-prone functions are identified. The findings reveal that within this system, CPM2 and CPM6 are particularly susceptible to failure propagation, and the automatic brake function is notably vulnerable. Data show that the system’s failure rate escalates markedly after 2×104 h of operation. Performing maintenance before reaching this threshold can further mitigate risks. This practice aligns with current international aircraft maintenance time regulations. The method proposed in this paper can be applied early in the allocation of DIMA resources to enhance security and support DIMA design.
Citation: Aerospace
PubDate: 2024-07-25
DOI: 10.3390/aerospace11080608
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 609: Restrain Performance of Child Restraint
Systems for 1.5-Year-Old Children on Commercial Airplanes: An Experimental
Study
Authors: Xiaopeng Shi, Yifan Zhou, Chen Xiong, Yafeng Wang, Yonglong He, Zhenyu Feng, Jiang Xie
First page: 609
Abstract: This study aims to compare the restraint performance of two child restraint systems (CRSs) used on airplanes—a rear-facing child seat (RFCS) and the child aviation restraint system (CARES)—for 1.5-year-old children, along with their compatibility with different types of aircraft seats. 16 g longitudinal dynamic tests were conducted on two types of aircraft seats with CRSs. Results indicate poor compatibility of CARES with Type A seats, significantly increasing the risk of head, neck, and abdominal injuries, with Nij exceeding the acceptable limit. In contrast, CARES exhibited good compatibility with Type B seats and effectively protected children. RFCS tests demonstrated effective injury risk reduction on both types of seats. It can be found that the performance of CARES depends on restraint status and seat dimensions; RFCSs provide adequate protection for 1.5-year-olds. Optimal protection can be achieved with smaller restrain angles of CRS and using thinner seat cushions. Compared to CARES, RFCSs better adapt to various aircraft seat structures, offering superior child protection.
Citation: Aerospace
PubDate: 2024-07-25
DOI: 10.3390/aerospace11080609
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 610: Fuzzy Control for Aircraft Engine: Dynamics
Clustering Modeling, Compensation and Hardware-in-Loop Experimental
Verification
Authors: Muxuan Pan, Hao Wang, Chenchen Zhang, Yun Xu
First page: 610
Abstract: This paper presents an integrated framework for aircraft engines, which consists of three phases: modeling, control, and experimental testing. The engine is formulated as an uncertain T–S fuzzy model. By a hierarchical dynamical parameter clustering, the number and premise variables of fuzzy rules are optimized, which keeps the engine’s prime and representative dynamics. For each fuzzy rule, a global stability-guaranteed method is developed for the identification of the consequent uncertain dynamic model. The resulting stable T–S fuzzy model accurately approximates the actual engine dynamics in the operation space. Based on this fuzzy model, a new robust control is constructed with hierarchical compensators. The control parameters take advantage of the fuzzy blend of engine prime dynamics and uncertainty thresholds. Extensive hardware-in-loop (HIL) experimental tests in the flight envelope and a flight task cycle demonstrate the effectiveness and real-time performance of the proposed control. The settling times and overshoots of engine response are suppressed to be under 2.5 s and 10%, respectively.
Citation: Aerospace
PubDate: 2024-07-25
DOI: 10.3390/aerospace11080610
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 611: Numerical Analysis of the Water Entry
Process of the Cabin Structure of the Trans-Domain Morphing Aircraft
Considering Structural Deformation
Authors: Yu Zhang, Ziyi He, Chen Wang, Qi Hu, Songwen Dong, Xing Shen, Jun Zhang, Taoxi Wang
First page: 611
Abstract: During the water entry process of a trans-domain morphing aircraft, significant impact forces are generated when the aircraft hits the water surface, which will potentially cause the deformation of the cabin structure and might damage the structure or onboard devices. Thus, it is necessary to investigate the water entry process of the cabin structure. This paper analyses changes in fluid loads and the corresponding structural responses during the water entry process. Firstly, the numerical model is established for the water entry process and the modeling method is validated by comparing the results to the experimental data. An empirical formula is developed to correlate the impact loads with the water entry velocities. Then, fluid–structure interaction analysis of the water entry process is performed using a two-way coupling approach. The relationship between structural deformation and the water entry process is then investigated. The results are compared with those without considering the structural deformation. The empirical formula is then modified to reflect the effects of the deformation. The results show that structural deformation will disperse the impact load, which represents different responses compared to the rigid cabin structure.
Citation: Aerospace
PubDate: 2024-07-25
DOI: 10.3390/aerospace11080611
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 612: Leader-Following Connectivity Preservation
and Collision Avoidance Control for Multiple Spacecraft with Bounded
Actuation
Authors: Xianghong Xue, Xin Wang, Nannan Han
First page: 612
Abstract: This paper investigates the distributed formation control of a group of leader-following spacecraft with bounded actuation and limited communication ranges. In particular, connectivity-preserving and collision-avoidance controllers are proposed for the leader with constant or time-varying velocity, respectively. The communication graph between the spacecraft is modeled via a distance-induced proximity graph. By designing a virtual proxy for each spacecraft, the spacecraft–proxy couplings address the actuator saturation constraints. The inter-proxy dynamics incorporated with a bounded artificial potential function fulfill the coordination of all proxies. In addition, the bounded potential function can simultaneously tackle connectivity preservation and collision avoidance problems. The distributed formation controllers are proposed for multiple spacecraft with constant or time-varying velocities relative to the leader. A sliding mode control approach and the proxies’ dynamics are used in the design of a distributed cooperative controller for spacecraft to address the cooperative problem between the followers and the leader. Numerical simulations confirm the effectiveness of the anti-saturation distributed connectivity preservation controller.
Citation: Aerospace
PubDate: 2024-07-26
DOI: 10.3390/aerospace11080612
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 613: Advancing the Diagnosis of Aero-Engine
Bearing Faults with Rotational Spectrum and Scale-Aware Robust Network
Authors: Jin Li, Zhengbing Yang, Xiang Zhou, Chenchen Song, Yafeng Wu
First page: 613
Abstract: The precise monitoring of bearings is crucial for the timely detection of issues in rotating mechanical systems. However, the high complexity of the structures makes the paths of vibration signal transmission exceedingly intricate, posing significant challenges in diagnosing aero-engine bearing faults. Therefore, a Rotational-Spectrum-informed Scale-aware Robustness (RSSR) neural network is proposed in this study to address intricate fault characteristics and significant noise interference. The RSSR algorithm amalgamates a scale-aware feature extraction block, a non-activation convolutional network, and an innovative channel attention block, striking a balance between simplicity and efficacy. We provide a comprehensive analysis by comparing traditional CNNs, transformers, and their respective variants. Our strategy not only elevates diagnostic precision but also judiciously moderates the network’s parameter count and computational intensity, mitigating the propensity for overfitting. To assess the efficacy of our proposed network, we performed rigorous testing using two complex, publicly available datasets, with additional artificial noise introductions to simulate challenging operational environments. On the noise-free dataset, our technique increased the accuracy by 5.11% on the aero-engine dataset compared with the current mainstream methods. Even under maximal noise conditions, it enhances the average accuracy by 4.49% compared with other contemporary approaches. The results demonstrate that our approach outperforms other techniques in terms of diagnostic performance and generalization ability.
Citation: Aerospace
PubDate: 2024-07-26
DOI: 10.3390/aerospace11080613
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 614: Twist Angle Error Statistical Analysis and
Uncertain Influence on Aerodynamic Performance of Three-Dimensional
Compressor Rotor
Authors: Yue Dan, Ruiyu Li, Limin Gao, Huawei Yu, Yuyang Hao
First page: 614
Abstract: Twist angle errors along the blade radial direction are uncertain and affected by cutting force, tool wear, and other factors. In this paper, the measured twist angle errors of 13 sections of 72 rotor blades were innovatively analyzed to obtain the rational statistical distribution. It is surprisingly found that the under-deflection systematic deviation of twist angle errors shows a gradually increasing W-shaped distribution along the radial direction, while the scatter is nearly linear. Logically, the statistical model is established based on the linear correlation of the scatter by regression analysis to reduce variable dimension from 13 to 1. The influence of the radial non-uniform twist angle errors’ uncertainty on the aerodynamic performance of the three-dimensional compressor rotor is efficiently quantified combining the non-intrusive polynomial chaos method. The results show that the mean values of mass flow rate, total pressure ratio, and isentropic efficiency at the typical operating conditions are lower than the nominal values due to the systematic deviation, indicating that the under-deflection twist angle errors lead to the decrease in compressor thrust. The compressor’s stable operating range is more sensitive to the scatter of twist angle errors, which is up to an order of magnitude greater than that of the total pressure ratio and isentropic efficiency, indicating the compressor’s safe and stable operation risk increases. Additionally, the flow field at the tip region is significantly affected by twist angle errors, especially at the shock wave position of the near-stall condition.
Citation: Aerospace
PubDate: 2024-07-26
DOI: 10.3390/aerospace11080614
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 615: Spectral Properties of Bistatic Radar
Signals Using the Ray Tracing Technique and a Facet Approach
Authors: Mingcheng Zuo, Rukiah S. Mitri, Igor Gai, Giancorrado Brighi, Paolo Tortora
First page: 615
Abstract: Bistatic radar experiments have been used to study surface characteristics of extra-terrestrial bodies in the Solar System, including the Moon, Venus, Mars, and Titan. This paper proposes a 3D model to characterize the scattered field of a gaussian rough surface on an extra-terrestrial body for an orbital bistatic radar configuration. Specifically, this model will investigate how the variability of surface roughness impacts the spectral broadening of the received signal using physical optics approximations and ray tracing on a surface model using a facet approach with Gaussian properties. A linear relationship between spectral broadening of the signal and surface roughness was found. This relationship is in line with results obtained by commonly used analytical models for bistatic radar on planetary surfaces.
Citation: Aerospace
PubDate: 2024-07-26
DOI: 10.3390/aerospace11080615
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 616: A Comparative Study on the Efficiencies of
Authors: Özge Özkaya Yılmaz, Altan Kayran
First page: 616
Abstract: This paper presents the effect of wing elasticity on the efficiency of a nonintrusive reduced order model using a three-dimensional sweptback wing. For this purpose, a computationally low-cost but highly accurate nonintrusive reduced order method is constructed utilizing proper orthogonal decomposition (POD) coupled with radial basis function (RBF) interpolation. The results are evaluated in terms of order reduction and prediction capability of rigid and aeroelastic ROMs. Our results show that compared to the rigid wing, reduced order modeling is more effectively applied to the aeroelastic sweptback wing due to the postponement of flow separation caused by bending–torsion coupling, when the pressure coefficient (Cp) is considered as the output. We further show that for flexible wings, utilizing rigid nodes is not sufficient for presenting the Cp distribution accurately; hence, separate ROMs must be generated for the deformed positions of the nodes. Moreover, the RBF method is also exploited for prediction of the results with direct interpolation of the data ensemble by generating a surrogate model. Finally, the proposed methods are compared in terms of accuracy, computational cost and practicality.
Citation: Aerospace
PubDate: 2024-07-27
DOI: 10.3390/aerospace11080616
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 617: Position Calculation for Front Fin of
Rocket Forebody Using Variable Step Scheme
Authors: Zeyang Zhou, Jun Huang
First page: 617
Abstract: In order to determine the installation position of the front fin on the example rocket forebody, an optimized method based on a comprehensive evaluation indicator and variable step search is presented. The comprehensive indicator consists of four weight coefficients, two lateral aerodynamic forces and two aerodynamic moments. The computational fluid dynamics method based on a shear stress transport turbulence model is established to analyze the flow field characteristics of the forebody. The results indicate that under equal weight coefficients, the presented search algorithm can provide an optimized solution for the front fin to achieve the minimum value of the comprehensive evaluation indicator. When the range of the current wing movement changes or the weight coefficient distribution changes, this search algorithm can still provide the optimal solution and some feasible solutions. Under the given conditions, there is a difference between the optimal solution of the aerodynamic force priority and that of the aerodynamic moment priority. For the case of the aerodynamic moment priority, the mean level of the pressure coefficient corresponding to the optimal solution on the given observation plane is low. The presented method is effective in learning the appropriate installation position of the rocket’s front fins.
Citation: Aerospace
PubDate: 2024-07-27
DOI: 10.3390/aerospace11080617
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 618: Wind Tunnel Experiment and Numerical
Simulation of Secondary Flow Systems on a Supersonic Wing
Authors: Sheng Zhang, Zheng Lin, Zeming Gao, Shuai Miao, Jun Li, Lifang Zeng, Dingyi Pan
First page: 618
Abstract: Aircraft secondary flow systems are small-flow circulation devices that are used for thermal and cold management, flow control, and energy generation on aircraft. The aerodynamic characteristics of main-flow-based inlets have been widely studied, but the secondary-flow-based small inlets, jets, and blowing and suction devices have seldom been studied. Two types of secondary flow systems embedded in a supersonic aircraft wing, a ram-air intake and a submerged intake, are researched here. Firstly, wind tunnel tests under subsonic, transonic, and supersonic conditions are carried out to test the total pressure recovery and total pressure distortion. Secondly, numerical simulations are used to analyze the flow characteristics in the secondary flow systems. The numerical results are validated with experimental data. The calculating errors of the total pressure recovery on the ram-air and submerged secondary flow systems are 8% and 10%, respectively. The simulation results demonstrate that the total pressure distortion tends to grow while the total pressure recovery drops with the increasing Mach number. As the Mach number increases from 0.4 to 2, the total pressure recovery of the ram-air secondary flow system decreases by 68% and 71% for the submerged system. Moreover, the total pressure distortion of the ram-air and submerged secondary flow systems is increased by 19.7 times and 8.3 times, respectively. Thirdly, a detailed flow mechanism is studied based on the simulation method. It is found that the flow separation at the front part of the tube is induced by adverse pressure gradients, which primarily determine the total pressure recovery at the outlet. The three-dimensional vortex in the tube is mainly caused by the change in cross-sectional shape, which influences the total pressure distortion.
Citation: Aerospace
PubDate: 2024-07-28
DOI: 10.3390/aerospace11080618
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 619: Identification of Key Nodes in Multi-Layer
Heterogeneous Aviation Network through Aggregating Multi-Source
Information
Authors: Qi Gao, Minghua Hu, Lei Yang, Zheng Zhao
First page: 619
Abstract: Aviation networks exhibit multi-layer characteristics and heterogeneity of nodes and edges. Identifying key nodes in a multi-layer heterogeneous aviation network (MHAN) and elucidating its cascading failure process are of great practical significance for enhancing the ability to resist failure and strengthening network resilience. Therefore, this paper first establishes the basic model of MHAN and then designs an intra-layer node importance evaluation method based on the improved TOPSIS-grey correlation analysis (ITG) method and an inter-layer influence weight quantification method based on the gravity model. By integrating the information transmission characteristics between network nodes, a key node identification method in MHAN through aggregating multi-source information is proposed. Finally, based on the actual overload operation of aviation networks, the initial load adjustment coefficient, capacity limit, and overload coefficient are introduced based on the traditional capacity–load model, a cascading failure model of MHAN considering overload condition and failure probability is constructed, and a node influence index based on this model is defined to verify the accuracy of the key node identification results. The instance analysis conducted on the aviation network in western China demonstrates that the intra-layer node importance evaluation method based on ITG yields results with better distinguishability and higher accuracy. The key nodes are predominantly hub en-route nodes and sector nodes. In the cascading failure model, increasing the overload coefficient and capacity limit within a specific range while reducing the initial load adjustment coefficient helps reduce the network failure scale. The key nodes identified by the node influence index are consistent with those identified by the method proposed in this paper, validating the accuracy and effectiveness of the key node identification method in MHAN through aggregating multi-source information herein.
Citation: Aerospace
PubDate: 2024-07-29
DOI: 10.3390/aerospace11080619
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 620: Experimental Parameter Identification and
an Evaluation of the Impact of Tire Models on the Dynamics of Fixed-Wing
Unmanned Aerial Vehicles
Authors: Hikaru Eguchi, Daisuke Nakata
First page: 620
Abstract: Because fixed-wing unmanned aerial vehicles (UAVs) require high-speed taxiing for takeoff and landing, the aircraft’s stability during taxiing is critical. However, despite research on the taxiing stability of fixed-wing UAVs conducted in taxiing motion simulations employing various tire models, the applicability of the models to fixed-wing UAV taxiing simulations remains unclear, as does the rationale behind the parameter settings in the models. Therefore, in our study, we measured the forces acting on the tires of a fixed-wing UAV under various conditions, including tire loads of 1.6–3.6 kg and tire slip angles of 0–40 deg. Based on the results, we modified conventional tire models and assessed their applicability in taxiing simulations. Among our findings, the parameter values of the models significantly differed from those used in crewed aircraft taxiing simulations, and the presence or absence of load parameters in the lateral force tire models significantly affected the dynamics. Furthermore, the aerodynamics acting on the aircraft enhanced the straight-line stability during taxiing, resulting in reduced forces on the tires.
Citation: Aerospace
PubDate: 2024-07-29
DOI: 10.3390/aerospace11080620
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 621: Experimental and Numerical Simulation of
Ejecta Size and Velocity of Hypervelocity Impact Rubble-Pile Asteroid
Authors: Wenjin Liu, Qingming Zhang, Renrong Long, Jiankang Ren, Juncheng Li, Zizheng Gong, Qiang Wu, Siyuan Ren
First page: 621
Abstract: Rubble-pile asteroids may be the type of near-Earth object most likely to threaten Earth in a future collision event. Small-scale impact experiments and numerical simulations for large-scale impacts were conducted to clarify the size ratio of the boulder/projectile diameter effects on ejecta size–velocity distribution. A series of small-scale impact cratering experiments were performed on porous gypsum–basalt targets at velocities of 2.3 to 5.5 km·s−1. Three successive ejection processes were observed by high-speed and ultra-high-speed cameras. The momentum transfer coefficient and cratering size were measured. A three-dimensional numerical model reflecting the random distribution of the interior boulders of the rubble-pile structure asteroid is established. The size ratio (length to diameter) of the boulder size inside the asteroid to the projectile diameter changed from 0.25 to 1.7. We conducted a smoothed particle hydrodynamics numerical simulation in the AUTODYN software to study the boulder size effect on the ejecta size–velocity distribution. Simulation results suggest that the microscopic porosity on regolith affects the propagation of shock waves and reduces the velocity of ejecta. Experiments and numerical simulation results suggest that both excavation flow and spalling ejection mechanism can eject boulders (0.12–0.72 m) out of the rubble-pile asteroid. These experiments and simulation results help us select the potential impact site in a planetary defense scenario and reduce deflection risk. are comprised primarily of boulders of a range of sizes.
Citation: Aerospace
PubDate: 2024-07-29
DOI: 10.3390/aerospace11080621
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 622: Theoretical Investigation of Laser Ablation
Propulsion Using Micro-Scale Fluid in Atmosphere
Authors: Chentao Mao, Luyun Jiang, Baosheng Du, Yongzan Zheng, Haichao Cui, Diankai Wang, Jifei Ye, Jianhui Han, Yanji Hong
First page: 622
Abstract: Laser ablation propulsion based on liquid propellants is a type of propulsion technology with a high specific impulse and good controllability that can be applied to space thrusters, gas metal arc welding, and extreme ultraviolet light. However, its basic mechanisms, such as flow evolution and thrust formation, have not yet been described in detail. In this study, the laser ablation of micro-scale fluid in the atmosphere was investigated. Flow evolution with different laser energy and fluid mass was observed using a schlieren system. According to the characteristic of flow evolution, a theoretical model of laser ablation propulsion in the atmosphere was established. For the first time, a theoretical hypothesis was proposed that the laser energy is divided into two parts, which act on fluid and air respectively. The model indicates that the impulses generated by fluids and air follow power laws with the laser energy, while the exponentials are 0.5 and 1, respectively. In the atmosphere, due to the shielding effect of a laser-maintained detonation wave on laser, the energy absorbed by the fluid is basically unchanged, while only the energy absorbed by the air changes. Significantly, the theoretical model is consistent with the impulse experiment and current studies.
Citation: Aerospace
PubDate: 2024-07-30
DOI: 10.3390/aerospace11080622
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 623: A Frequency Domain PID Control Strategy for
an In-House Friction and Wear Test Rig
Authors: Di Li, Jing Wang, Hongguang Li, Guang Meng, Anlue Li
First page: 623
Abstract: The contact behavior greatly influences the damping performance of frictional interfaces. Numerous experimental studies on friction and fretting wear have investigated the evolution of contact parameters. An in-house friction and wear test rig has been developed to obtain hysteresis loops at certain normal forces. However, the test rig lacks load control and is thus unable to ensure precise stabilization at a preset normal force, which affected the hysteresis behavior. In this paper, we developed a frequency-domain PID controller to ensure the stable application of a target normal force with constant (0–300 N) and harmonic (0–50 N) components. Compared to the commonly used time-domain strategy, the control signal error is reduced from 6.30% to 0.54% at 50 Hz. With a 3% error as the standard, the controller enables stabilized control of signals with frequencies up to 300 Hz. Friction experiments on various typical materials are conducted using this improved test rig. The results indicate a general tendency for contact stiffness to increase with a rising normal force, while the relationship between the friction coefficient and the normal force does not exhibit a clear pattern. The contact stiffness is not sensitive to the relative displacement or vibration frequency.
Citation: Aerospace
PubDate: 2024-07-30
DOI: 10.3390/aerospace11080623
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 624: Ballistic Limit Equation Derivation for
Thin Tape Tethers
Authors: Lorenzo Olivieri, Cinzia Giacomuzzo, Alessandro Francesconi
First page: 624
Abstract: Electromagnetic tethers of hundreds or thousands of meters have been proposed for maneuvring spacecraft in Low Earth Orbit, and in particular, for post-mission disposals. The debate on tether survivability to debris impact is still influencing further advances in the implementation of such technology because of the large area they expose to the debris environment; thin tape geometries have been proposed instead of round ones to increase the survivability to hypervelocity impacts. In this context, this paper introduces a new Ballistic Limit Equation (BLE) for thin tape tethers, derived from experimental results, numerical simulations, and literature data. The resulting equation is non-monotonic with respect to impact angle, presenting a minimum depending on the debris velocity and size; for high obliquities, the debris fragmentation triggered by shock waves propagating into the material reduces the damage. This feature allows to set a minimum particle diameter for risk assessment, excluding a significant part of the debris flux. The proposed BLE confirms the performance of thin tape tethers, with respect to round wires, due to their better ballistic response as well as their reduced cross-section at high-obliquity impacts.
Citation: Aerospace
PubDate: 2024-07-30
DOI: 10.3390/aerospace11080624
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 625: Bidirectional Long Short-Term Memory
Development for Aircraft Trajectory Prediction Applications to the UAS-S4
Ehécatl
Authors: Seyed Mohammad Hashemi, Ruxandra Mihaela Botez, Georges Ghazi
First page: 625
Abstract: The rapid advancement of unmanned aerial systems in various civilian roles necessitates improved safety measures during their operation. A key aspect of enhancing safety is effective collision avoidance, which is based on conflict detection and is greatly aided by accurate trajectory prediction. This paper represents a novel data-driven trajectory prediction methodology based on applying the Long Short-Term Memory (LSTM) prediction algorithm to the UAS-S4 Ehécatl. An LSTM model was designed as the baseline and then developed into a Staked LSTM to better capture complex and hierarchical temporal trajectory patterns. Next, the Bidirectional LSTM was developed for a better understanding of the contextual trajectories from both its past and future data points, and to provide a more comprehensive temporal perspective that could enhance its accuracy. LSTM-based models were evaluated in terms of mean absolute percentage errors. The results reveal the superiority of the Bidirectional LSTM, as it could predict UAS-S4 trajectories more accurately than the Stacked LSTM. Moreover, the developed Bidirectional LSTM was compared with other state-of-the-art deep neural networks aimed at aircraft trajectory prediction. Promising results confirmed that Bidirectional LSTM exhibits the most stable MAPE across all prediction horizons.
Citation: Aerospace
PubDate: 2024-07-31
DOI: 10.3390/aerospace11080625
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 626: Influence of Herringbone Grooves Inspired
by Bird Feathers on Aerodynamics of Compressor Cascade under Different
Reynolds Number Conditions
Authors: Shaobing Han, Zhijie Yang, Jingjun Zhong, Yuying Yan
First page: 626
Abstract: Nowadays, high aerodynamic load has made blade separation an issue for compact axial compressors under high-altitude low-Reynolds-number conditions. In this study, herringbone grooves inspired by bird feathers were applied to suppress the suction side separation and reduce loss. To study the effect of bio-inspired herringbone grooves on the aerodynamic performance of compressor cascades, a high subsonic compressor cascade was taken as the research object. Under the conditions of different Reynolds numbers, the effects of herringbone grooves of different depths on the flow separation were numerically studied. The research results show that at a high-Reynolds-number condition (Re = 5.6 × 105), the sawtooth-shaped wake induced by herringbone grooves increases the turbulent mixing loss near the suction surface, and the blade performance deteriorates. At a low-Reynolds-number condition (Re = 1.3 × 105), the span-wise secondary flow and micro-vortex structure induced by the herringbone grooves effectively suppress the laminar separation on the suction surface of the blade, and there is an optimal depth for the herringbone grooves that reduces the profile loss by 8.33% and increases the static pressure ratio by 0.55%. The selection principle of the optimal groove depth with the Re is discussed based on the research results under six low-Reynolds-number conditions.
Citation: Aerospace
PubDate: 2024-07-31
DOI: 10.3390/aerospace11080626
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 627: High-Precision Composite Control of Driving
Current for Non-Contact Annular Electromagnetic Stabilized Spacecraft
Subject to Multiple Disturbances
Authors: He Liao, Haoxiang Yuan, Jinjin Xie
First page: 627
Abstract: Based on the design concept of dynamic and static isolation, disturbance-free payload (DFP) satellites can isolate the effects of interference on sensitive payloads, and can realize the high-precision control of the payload better than a traditional spacecraft. Among these, non-contact annular electromagnetic stabilized spacecraft (NCAESS) can effectively alleviate control output problems such as the six-degree-of-freedom coupling and nonlinear effects found in traditional non-contact spacecraft. As a key actuator, the driving current control of the non-contact annular electromagnetic actuator (NCAEA) will have a direct impact on the attitude performance of NCAESS. However, there are multiple interference effects present in the actual driving current control. Therefore, this paper proposes a composite control scheme to improve the driving accuracy by suppressing these multiple disturbances. Firstly, the variable-switching-frequency pulse-width modulation is used to adjust the switching frequency adaptively to reduce switch ripple. Secondly, feedforward compensation is employed to mitigate the back electromotive force. Thirdly, the robust Smith predictor is utilized to compensate for the digital control delay. Finally, an internal model proportional–integral controller with fuzzy rule is applied to adjust the parameters adaptively. The numerical simulation results demonstrate that the proposed approach can be adopted to enhance the robustness and dynamic response of the driving current effectively, which leads to precise control of the non-contact annular electromagnetic stabilized spacecraft.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080627
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 628: Rotorcraft Airfoil Performance in Martian
Environment
Authors: Enrico Giacomini, Lars-Göran Westerberg
First page: 628
Abstract: In 2021, the Ingenuity helicopter performed the inaugural flight on Mars, heralding a new epoch of exploration. However, the aerodynamics on Mars present unique challenges not found on Earth, such as low chord-based Reynolds number flows, which pose significant hurdles for future missions. The Ingenuity’s design incorporated a Reynolds number of approximately 20,000, dictated by the rotor’s dimensions. This paper investigates the implications of flows at a Reynolds number of 50,000, conducting a comparative analysis with those at 20,000 Re. The objective is to evaluate the feasibility of using larger rotor dimensions or extended airfoil chord lengths. An increase in the Reynolds number alters the size and position of Laminar Separation Bubbles (LSBs) on the airfoil, significantly impacting performance. This study leverages previous research on the structure and dynamics of LSBs to examine the flow around a cambered plate with 6% camber and 1% thickness in Martian conditions. This paper details the methods and mesh used for analysis, assesses airfoil performance, and provides a thorough explanation of the results obtained.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080628
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 629: Simulation and Experimental Study of Gas
Turbine Blade Tenon-Root Detachment on Spin Test
Authors: Maoyu Yu, Jianfang Wang, Haijun Xuan, Wangjiao Xiong, Zekan He, Mingmin Qu
First page: 629
Abstract: This paper addresses the critical issue of turbine blade containment in aircraft engines, crucial for ensuring flight safety. Through a comprehensive approach integrating numerical simulations and experimental validations, the containment capabilities of gas turbine engine casings are thoroughly analyzed. The study investigates the impact dynamics, deformation characteristics, and energy absorption mechanisms during blade detachment events, shedding light on the containment process. Based on the multi-stage nature of gas turbines, two different blade structures were designed for turbine blades. Utilizing finite element simulation and the Johnson–Cook constitutive equation, this study accurately simulated single-blade and dual-blade containment scenarios. The simulation results of the single blade indicate that the process of a gas turbine blade impacting the casing primarily consists of three stages. The second stage, where the tenon root strikes the casing, is identified as the main cause of casing damage. Meanwhile, in the dual-blade simulation, the second blade, influenced by the first blade, directly impacts the casing after fracturing, resulting in greater damage. Then, eight corresponding containment tests were conducted based on the simulation results, validating the accuracy of the simulation parameters. Experimental verification of simulation results further confirms the validity of the proposed containment curves, providing essential insights for optimizing casing design and enhancing the safety and reliability of aircraft engines.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080629
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 630: Control-Oriented System Identification of
Turbojet Dynamics
Authors: Francisco Villarreal-Valderrama, Eduardo Liceaga-Castro, Diana Hernandez-Alcantara, Carlos Santana-Delgado, Selcuk Ekici, Luis Amezquita-Brooks
First page: 630
Abstract: The autonomous operation of turbojets requires reliable, accurate, and manageable dynamical models for several key processes. This article describes a practical robust method for obtaining turbojet thrust and shaft speed models from experimental data. The proposed methodology combines several data mining tools with the intention of handling typical difficulties present during experimental turbojet modeling, such as high noise levels and uncertainty in the plant dynamics. The resulting shaft speed and thrust models achieved a percentage error of 0.8561% and 3.3081%, respectively, for the whole operating range. The predictive power of the resulting models is also assessed in the frequency domain. The turbojet cut frequencies are experimentally determined and were found to match those predicted by the identified models. Finally, the proposed strategy is systematically tested with respect to popular aeroengine models, outperforming them both in the time and frequency domains. These results allow us to conclude that the proposed modeling method improves current modeling approaches in both manageability and predictive power.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080630
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 631: Dynamic Fault Tree Model of Civil Aircraft
Avionics Network Transmission Failure Based on Optimized Extended Fuzzy
Algorithm
Authors: Zhaojun Gu, Yinuo Zhang, He Sui
First page: 631
Abstract: The avionics network supports high-safety-level flight operations, with the analysis of transmission failures serving as a crucial means for its safety evaluation. Due to the time-dependent nature of the failure probability in avionics networks, traditional constant and unchangeable probability values can deviate from the actual situation under specific conditions. This deviation may lead to inadequate responses to occasional events and potentially cause flight accidents. A Dynamic Fault Tree (DFT) model for civil aircraft avionics network transmission failures, based on an optimized extended fuzzy algorithm, is introduced in this paper. Initially focusing on event correlations, a DFT is established for the transmission failure of the Avionics Full Duplex Switched Ethernet (AFDX). Subsequently, considering the variations between events, triangular fuzzy processing is applied to the event failure rates based on relative confidence levels. Finally, by optimizing the weakest t-norm operator, the failure probability intervals are aggregated and the fuzzy scale is regulated. Experimental results demonstrate that, compared to the static-minimum t-norm and traditional weakest t-norm methods, the proposed approach enhances the accuracy of the fuzzy failure probability intervals by 66.15% and 40.59%, respectively. Concurrently, it maintains consistency in the ranking of event importance, highlighting the superior effectiveness of the proposed method in analyzing transmission failures in avionics networks.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080631
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 632: Investigations on Trimming Strategy and
Authors: Guoqing Zhao, Zhuangzhuang Cui, Qijun Zhao, Xi Chen, Peng Li
First page: 632
Abstract: Numerical simulations were conducted to analyze the unsteady aerodynamic characteristics of a tiltrotor aircraft with different conversion strategies. Firstly, the CFD method was established by taking the interaction between the rotor and wing into account, as well as the body-fitted grid of the tiltrotor. Then, the trimming approach of the rotor and wing was developed to ensure longitudinal balance of the aircraft, and the method for determining the conversion corridor of the tiltrotor aircraft was proposed by considering the limitations imposed by wing stall and the required power of the rotor. Finally, the aerodynamic characteristics of the rotor and wing during the continuous conversion process were investigated, considering various tilting angular velocities and horizontal accelerations of the tiltrotor. The numerical results indicated that a smaller acceleration can enhance the efficiency of the tiltrotor. However, this would increase the complexity of trimming the fuselage attitude angle. It was also found that excessive acceleration could exceed the required power limit of the tiltrotor, rendering the conversion strategy infeasible.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080632
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 633: Integrated Design and Simulation of
Helicopter Nuclear, Biological, and Chemical Protection System
Authors: Yilong Wen, Xiaodong Mao, Hexiang Wang, Liping Pang, Quanyu Zhao
First page: 633
Abstract: The helicopter’s aircrew faces significant challenges in nuclear, biological, and chemical (NBC) environments due to limited protection devices and crowded space. To safeguard the security and ensure the comfort of the aircrew, the development of a helicopter NBC protection system is crucial. In this study, a helicopter NBC protection system was designed using a top-level architecture with an advanced system-integrated approach. Detailed configuration designs were developed for each subsystem, including air source pressurization, renewable NBC filtration ventilation, cabin temperature, and pressure control system. To verify the reliability of the adsorbent model, a Langmuir isotherm equation was adapted and validated using the experiment data. To verify the performance of the designed system, a dynamic simulation model was created using AMESIM. The findings demonstrate that the cabin temperature and pressure control system can greatly satisfy the demand for aircrews under various working conditions. Furthermore, the renewable NBC filtration ventilation system effectively adsorbs NBC substances and achieves onboard regeneration, thereby extending the working lifespan in contaminated environments. This study contributes to providing an innovative idea for helicopter NBC protection systems.
Citation: Aerospace
PubDate: 2024-08-01
DOI: 10.3390/aerospace11080633
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 634: The Bond Graph Modeling and Experimental
Verification of a Hydraulic Inertial Vibration Isolator Including
Nonlinear Effects
Authors: Niuniu Liu, Cheng Li, Liwei Zhang, Zhiyang Lei, Jing Yang, Fuqiang Lai
First page: 634
Abstract: Passive vibration isolation techniques with low-frequency characteristics have been a hot topic in the aerospace field. A hydraulic inertial vibration isolator is a highly effective type of isolator for controlling low-frequency vibrations. It typically consists of a main spring, a minor spring, an inertial mass, and a fluid domain. Due to its multi-domain nature, analyzing the isolation mechanism of this type of isolator is challenging. The bond graph method is employed to establish the dynamic model of the isolator. Subsequently, the state equations of the isolator are derived, and the energy equations of both the mechanical and the fluid parts of the isolator are obtained. Based on this, the energy transfer characteristics between the mechanical and fluid domains inside the isolator under external excitation are discussed. The time-domain response of the forces transmitted to the foundation is analyzed. It is shown that the anti-resonance frequency occurs when the forces transmitted to the foundation generated by the main spring and the fluid pressure are equal to that of the minor spring. To verify the proposed method’s correctness, a prototype of the isolator is designed and a carefully designed experiment is conducted. The acceleration transmissibility of the isolator is used to conduct a comparative study. The results show that the theoretical results are in good agreement with the experimental results. To depict the dynamic characteristics of the isolator under large amplitude vibration, the nonlinear dynamic model of the isolator is developed, and the corresponding force transmissibility of the isolator is formulated. The energy flow between the mechanical and the fluid domains under this condition is also analyzed. The results indicate that the energy flow responses exhibit a similar change tendency to the force transmissibility. However, the peak of the energy ratio between the mechanical subsystem and the fluid is the same as the linear condition, suggesting that this value is determined by the amplification ratio of the isolator. This research provides enhanced physical insight to understand the dynamic characteristics of this type of isolator and will help to shorten the design cycle of the isolator.
Citation: Aerospace
PubDate: 2024-08-02
DOI: 10.3390/aerospace11080634
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 635: Fuelless On-Orbit Assembly of a Large Space
Truss Structure Using Repulsion of the Service Spacecraft by Robotic
Manipulators
Authors: Vladislav Orlov, Uliana Monakhova, Mikhail Ovchinnikov, Danil Ivanov
First page: 635
Abstract: A servicing spacecraft motion control approach for the problem of on-orbit truss structure assembly is developed in this paper. It is considered that a cargo container with a rod set and servicing spacecraft are in orbit initially. The assembly procedure is based on spacecraft free-flight motion between the structure’s specified points. The spacecraft is equipped with two robotic manipulators capable of attaching to the structure and holding rods. In addition, the spacecraft can repulse from the structure with a given relative velocity using a manipulator, so the spacecraft and the structure receive impulses. The repulsion velocity vector is calculated in order to reach the structure target point to deliver and install the rod into the truss structure, or to reach the cargo container and take a rod. The problem of searching the repulsion velocity is formulated as an optimization problem with constraints, taking into account the limited value of the repulsion velocity, collision avoidance with structure, restrictions on the angular velocity and translational motion of the structure in the orbital reference frame. This problem is solved numerically with an initial guess vector obtained analytically for simplified motion cases. The application of the proposed control scheme to the assembly of a truss-based antenna is demonstrated. It is shown that the servicing spacecraft is successfully transferred between the structure points by means of manipulator repulsion. Main features and limitations of the assembly problem using a spacecraft with two manipulators are discussed.
Citation: Aerospace
PubDate: 2024-08-02
DOI: 10.3390/aerospace11080635
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 636: Flutter Optimization of Carbon/Epoxy Plates
Based on a Fast Tree Algorithm
Authors: Mirko Dinulović, Aleksandar Bengin, Branimir Krstić, Marjan Dodić, Miloš Vorkapić
First page: 636
Abstract: This study focuses on optimizing carbon/epoxy laminate configurations to maximize the flutter speed of composite structures using a Fast Tree Regression algorithm. Initially, a seed dataset was created, using finite element method (FEM) modal analysis for common stack-ups used in composite fins and UAV components. The FEM analysis, based on the Lanczos algorithm for extracting modal frequencies in bending and torsion, was verified through experimental modal analysis using an AS-4/3501-6 composite system. Custom software was developed to interface with the FEA modal software, enabling the generation and augmentation of laminate dataset scenarios. The seed dataset was expanded until the coefficient of determination (R2) reached at least 0.95. Various regression algorithms, including Fast Forest Regression, Fast Tree Regression, Sdca Regression, and Lbfgs Poisson Regression, were evaluated. The Fast Tree Regression algorithm was selected for further analysis due to its superior performance. This algorithm was applied to a design space of nearly 2000 potential laminate candidates, focusing on symmetric lay-ups to avoid undesirable coupling between bending and torsion in UAV and missile control surfaces. The final optimized lay-ups, exhibit the highest Delta function values (the squared difference of modal frequencies in torsion and bending), indicating the expected highest flutter speeds. The results demonstrate the efficacy of tailored composite materials in achieving specific aerodynamic performance goals.
Citation: Aerospace
PubDate: 2024-08-03
DOI: 10.3390/aerospace11080636
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 637: Dispersion Analysis of Plane Wave
Propagation in Lattice-Based Mechanical Metamaterial for Vibration
Suppression
Authors: Natsuki Tsushima, Yuta Hayashi, Tomohiro Yokozeki
First page: 637
Abstract: Phononic crystals based on lattice structures provide important wave dispersion characteristics as band structures, showing excellent compatibility with additive manufacturing. Although the lattice structures have shown the potential for vibration suppression, a design guideline to control the frequency range of the bandgap has not been well established. This paper studies the dispersion characteristics of plane wave propagation in lattice-based mechanical metamaterials to realize effective vibration suppression for potential aerospace applications. Triangular and hexagonal periodic lattice structures are mainly studied in this paper. The influence of different geometric parameters on the bandgap characteristics is investigated. A finite element approach with Floquet–Bloch’s principles is implemented to effectively evaluate the dispersion characteristics of waves in lattice structures, which is validated numerically and experimentally with a 3D-printed lattice plate. Based on numerical studies with the developed analysis framework, the influences of the geometric parameters of lattice plate structures on dispersion characteristics can mainly be categorized into three patterns: change in specific branches related to in-plane or out-of-plane vibrations, upward/downward shift in frequency range, and drastic change in dispersion characteristics. The results obtained from the study provide insight into the design of band structures to realize vibration suppression at specific frequencies for engineering applications.
Citation: Aerospace
PubDate: 2024-08-04
DOI: 10.3390/aerospace11080637
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 638: A Survey of Aero-Engine Blade Modeling and
Dynamic Characteristics Analyses
Authors: Yaqiong Zhang, Fubin Wang, Jinchao Liu, Heng Zhao, Chao Fu, Weihao Zhai, Kuan Lu
First page: 638
Abstract: The rotating blade is a key component of an aero-engine, and its vibration characteristics have an important impact on the performance of the engine and are vital for condition monitoring. This paper reviews the research progress of blade dynamics, including three main aspects: modeling of blades, solution methods, and vibration characteristics. Firstly, three popular structural dynamics models for blades are reviewed, namely lumped-mass model, finite element model, and semi-analytical model. Then, the solution methods for the blade dynamics are comprehensively described. The advantages and limitations of these methods are summarized. In the third part, this review summarizes the properties of the modal and vibration responses of aero-engine blades and discusses the typical forms and mechanisms of blade vibration. Finally, the deficiencies and limitations in the current research on blade modeling and vibration analysis are summarized, and the directions for future efforts are pointed out. The purpose of this review is to provide meaningful insights to researchers and engineers in the field of aero-engine blade modeling and dynamic characteristics analysis.
Citation: Aerospace
PubDate: 2024-08-05
DOI: 10.3390/aerospace11080638
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 639: Effects of Wire-Wrapping Patterns and Low
Temperature on Combustion of Propellant Embedded with Metal Wire
Authors: Qiu Wu, Jiangong Zhao, Quanbin Ren
First page: 639
Abstract: Incorporating silver wires into propellant has emerged as a highly effective strategy for enhancing propellant burning rates, a technique extensively deployed in the construction of numerous fielded sounding rockets and tactical missiles. Our research, employing a multi-faceted approach encompassing thermogravimetric-differential scanning calorimetry measurements (TG-DSC), combustion diagnoses, burning rate tests, and meticulous collection of condensed combustion products, sought to elucidate how variations in silver wire quantity and winding configuration impact the combustion properties of propellants. Our findings underscore the remarkable efficacy of double tightly twisted silver wire in significantly boosting propellant burning rates under ambient conditions. Moreover, at lower temperatures, the reduced gap between the propellant and silver wire further magnifies the influence of silver wire on burning rates. However, it is noteworthy that the relationship between burning speed and combustion efficiency is not deterministic. While a smaller cone angle of the burning surface contributes to heightened burning rates, it concurrently exacerbates the polymerization effect of vapor phase aluminum particles, consequently diminishing propellant combustion efficiency. Conversely, propellants configured with sparsely twinned silver wires exhibit notable enhancements in combustion efficiency, despite a less pronounced impact on the burning rate attributed to the larger cone angle of the burning surface. Remarkably, these trends persist at lower temperatures. Based on the principle of heat transfer balance, a theoretical model for the combustion of propellants with wire inserts is developed. The reliability of this theoretical model is validated through a comparison of calculated values with experimental data. Our research outcomes carry significant implications for guiding the application and advancement of the silver wire method in solid propellants for solid rocket motors, offering valuable insights to inform future research and development endeavors in this domain.
Citation: Aerospace
PubDate: 2024-08-06
DOI: 10.3390/aerospace11080639
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 640: Approximation of Closed-Loop Sensitivities
in Robust Trajectory Optimization under Parametric Uncertainty
Authors: Tuğba Akman, Joseph Z. Ben-Asher, Florian Holzapfel
First page: 640
Abstract: Trajectory optimization is an essential tool for the high-fidelity planning of missions in aerospace engineering in order to increase their safety. Robust optimal control methods are utilized in the present study to address environmental or system uncertainties. To improve robustness, holistic approaches for robust trajectory optimization using sensitivity minimization with system feedback and predicted feedback are presented. Thereby, controller gains to handle uncertainty influences are optimized. The proposed method is demonstrated in an application for UAV trajectories. The resulting trajectories are less prone to unknown factors, which increases mission safety.
Citation: Aerospace
PubDate: 2024-08-06
DOI: 10.3390/aerospace11080640
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 641: Test Scheme Design and Numerical Simulation
of Composite Thrust Reverser Cascade
Authors: Dingzhou Wu, Xiuhua Chen, Hongyan Qiu
First page: 641
Abstract: The thrust reverser system stands as the critical component in contemporary large civil aviation, significantly impacting operational efficiency. Owing to their significant weight-reduction benefits, composite materials have emerged as a prominent trend in structural design in recent years. The aim of this research is to optimize the design of the thrust reverser cascade by replacing metal materials with composite materials and to propose a method for conducting mechanical tests on the cascade without a wind tunnel using a new loading scheme and a device that is simpler, more convenient, and less expensive. Focusing on a composite thrust reverser cascade with an inclined blade and beam, the structural and operational load characteristics of the cascade were analyzed and a finite element model incorporating progressive damage analysis was established. The progressive damage analyses of both the global and sub-model elucidated that initial structural degradation manifests near the mounting holes, with the matrix compression failure mode. In addition, a static test method was devised employing levers and hooks. Comparative analyses between test and numerical results demonstrate congruence. The research in this paper provides guidance for the design and testing of the composite thrust reverser cascade.
Citation: Aerospace
PubDate: 2024-08-07
DOI: 10.3390/aerospace11080641
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 642: Investigation of the Film Cooling
Performance of Laminated SiCfSiC Composite Plates
Authors: Zhaoguo Mi, Zhenhua Chen, Kanghe Jiang, Weihua Yang
First page: 642
Abstract: Silicon carbide fiber-reinforced silicon carbide matrix ceramic composites (SiCf/SiC) are extensively utilized in high-temperature resistant materials in the aerospace industry. This study investigated the influence of stacking structure on the performance of SiCf/SiC laminated composite plates with film cooling. Initially, the thermal conductivity of cross-piled SiCf/SiC composites was determined using the laser flash analysis (LFA) method and differential scanning calorimetry (DSC) method. Subsequently, a representative volume element (RVE) model that reflected the stacking structure was established. The anisotropic thermal conductivity of the unidirectional SiCf/SiC layer was calculated using numerical methods and experimental results. Finally, numerical simulations were carried out to assess the film cooling effectiveness of various stacking sequences and layers. The results showed that the thermal conductivity values predicted by the RVE model for the laminated composite aligned well with the experimental results, and the unidirectional SiCf/SiC composite thermal conductivities at different temperatures were obtained. The stacking sequence impacted the temperature distribution near the film hole, with the [0-90-0] structure exhibiting a more pronounced effect on film cooling performance compared with the [0-90] and [0-90-90-0] structures. The performance of the film cooling in the laminated SiCf/SiC composites was consistent across all stacking layers [0-90]1, [0-90]2, and [0-90]3. The maximum difference in overall cooling efficiency was 1.7% between [0-90-0]1 and [0-90]1 and [0-90-90-0]1
Citation: Aerospace
PubDate: 2024-08-07
DOI: 10.3390/aerospace11080642
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 643: A Multi-Objective Dynamic
Mission-Scheduling Algorithm Considering Perturbations for Earth
Observation Satellites
Authors: Hai Li, Yongjun Li, Yuanhao Liu, Kai Zhang, Xin Li, Yu Li, Shanghong Zhao
First page: 643
Abstract: The number of real-time dynamic satellite observation missions has been rapidly increasing recently, while little attention has been paid to the dynamic mission-scheduling problem. It is crucial to reduce perturbations to the initial scheduling plan for the dynamic mission-scheduling as the perturbations have a significant impact on the stability of the Earth observation satellites (EOSs). In this paper, we focus on the EOS dynamic mission-scheduling problem, where the observation profit and perturbation are considered simultaneously. A multi-objective dynamic mission-scheduling mathematical model is first formulated. Then, we propose a multi-objective dynamic mission-scheduling algorithm (MODMSA) based on the improved Strength Pareto Evolutionary Algorithm (SPEA2). In the MODMSA, a novel two-stage individual representation, a minimum perturbation random initialization, multi-point crossover, and greedy mutation are designed to expand the search scope and improve the search efficiency. In addition, a profit-oriented local search algorithm is introduced into the SPEA2 to improve the convergence speed. Furthermore, an adaptive perturbation control strategy is adopted to improve the diversity of non−dominated solutions. Extensive experiments are conducted to evaluate the performance of the MODMSA. The simulation results show that the MODMSA outperforms other comparison algorithms in terms of solution quality and diversity, which demonstrates that the MODMSA is promising for practical EOS systems.
Citation: Aerospace
PubDate: 2024-08-08
DOI: 10.3390/aerospace11080643
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 644: Number of Blades’ Influence on the
Performance of Rotor with Equal Solidity in Open and Shrouded
Configurations: Experimental Analysis
Authors: Abdallah Dayhoum, Alejandro Ramirez-Serrano, Robert J. Martinuzzi
First page: 644
Abstract: This study explores the implications of the number of blades on the performance of both open and shrouded rotors. By conducting a thorough experimental analysis at a fixed solidity ratio, this research seeks to enhance our understanding of rotor dynamics and efficiency. Two-, three-, four-, and five-bladed rotors were designed and manufactured to have the same solidity ratio. This leads to smaller chord distribution values for higher blade numbers. The experimental analysis aims to quantify the effects of the number of blades and provides a comparative analysis of performance differences between the two rotor configurations (shrouded and open). For the open rotor, results indicate that increasing the number of blades has a minimal impact on overall performance. This is due to the decrease in the tip loss factor being counterbalanced by a decline in efficiency caused by the two-dimensional airfoil performance, which results from a smaller chord and a lower Reynolds number. In contrast, the shrouded rotor exhibits a noticeable performance decay with an increased blade count. Since tip loss is inherently absent in shrouded designs, the decline is primarily attributed to the two-dimensional airfoil performance. This decay occurs while maintaining a constant solidity ratio, highlighting the significant effect of blade count on shrouded rotor efficiency, thereby contributing to the optimization of rotor design in various engineering applications.
Citation: Aerospace
PubDate: 2024-08-08
DOI: 10.3390/aerospace11080644
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 645: Numerical Study on Far-Field Noise
Characteristic Generated by Wall-Mounted Swept Finite-Span Airfoil within
Transonic Flow
Authors: Runpei Jiang, Peiqing Liu, Jin Zhang, Hao Guo
First page: 645
Abstract: This study seeks to develop a fundamental comprehension of the noise challenges encountered by commercial aircraft fuselage surface attachments, such as blade antennas and pitot tubes. The study examines the flow characteristics and far-field noise directivity of a wall-mounted NACA0012 airfoil with various sweep angles (−35°, −15°, 0°, +15°, and +35°) and an aspect ratio of 1.5. The Mach numbers of the incoming flow range from 0.8 to 0.9 with a Reynolds number of about 7 × 105. Delayed Detached Eddy Simulation (DDES) and the Ffowcs Williams–Hawkings (FW-H) equation are utilized. The results show that the shock wave intensity at the junction between the airfoil and the bottom wall is enhanced by the forward-swept angle. The shock wave moves and changes into a λ-type structure, while the boundary layer separates and produces shedding vortices in the junction at a smaller Mach number on the forward-swept airfoil compared to the straight airfoil and the backward-swept airfoil. These phenomena cause significant surface pressure fluctuations in the junction and result in a significant dipole noise in the far field, which is the primary source of noise in the far field. In addition, the normal Mach number and the absolute sweep angle also contribute to the far-field noise.
Citation: Aerospace
PubDate: 2024-08-08
DOI: 10.3390/aerospace11080645
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 646: On the Exploration of Temporal Fusion
Transformers for Anomaly Detection with Multivariate Aviation Time-Series
Data
Authors: Bulent Ayhan, Erik P. Vargo, Huang Tang
First page: 646
Abstract: In this work, we explored the feasibility of using a transformer-based time-series forecasting architecture, known as the Temporal Fusion Transformer (TFT), for anomaly detection using threaded track data from the MITRE Corporation’s Transportation Data Platform (TDP) and digital flight data. The TFT architecture has the flexibility to include both time-varying multivariate data and categorical data from multimodal data sources and conduct single-output or multi-output predictions. For anomaly detection, rather than training a TFT model to predict the outcomes of specific aviation safety events, we train a TFT model to learn nominal behavior. Any significant deviation of the TFT model’s future horizon forecast for the output flight parameters of interest from the observed time-series data is considered an anomaly when conducting evaluations. For proof-of-concept demonstrations, we used an unstable approach (UA) as the anomaly event. This type of anomaly detection approach with nominal behavior learning can be used to develop flight analytics to identify emerging safety hazards in historical flight data and has the potential to be used as an on-board early warning system to assist pilots during flight.
Citation: Aerospace
PubDate: 2024-08-09
DOI: 10.3390/aerospace11080646
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 647: Assessment of Flyby Methods as Applied to
Close Encounters among Asteroids
Authors: Nicolò Stronati, Marco Fenucci, Marco Micheli, Marta Ceccaroni
First page: 647
Abstract: Orbital flybys have been extensively studied for spacecraft missions, resulting in effective mathematical and physical models. However, these models’ applicability to natural encounters involving asteroids has not been explored. This paper examines the applicability of two such theories, patched conics (PC) and the Keplerian map (KM), to asteroid encounters. A review of the two methods will be provided, highlighting their assumptions and range of applicability. Simulations of asteroid–asteroid encounters will then be performed to evaluate their effectiveness in these scenarios. The simulation parameters are set by collecting data on actual asteroid–asteroid encounters, hereby presented, generally characterised by high close approach distances and small masses of the perturbing bodies, if compared to those used to build the flyby theories. Results show that the PC theory’s effectiveness diminishes with increasing approach distances, aligning with its assumptions. Moreover, the prediction of the model is better in the geometric configurations where the flyby has major effects on the orbital energy change. The KM theory has shown good effectiveness for encounters occurring outside the sphere of influence of the perturbing body, even for very high distances. This research investigates flyby models’ strengths and weaknesses in asteroid encounters, offering practical insights and future directions.
Citation: Aerospace
PubDate: 2024-08-09
DOI: 10.3390/aerospace11080647
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 648: A Novel Aircraft Trajectory Generation
Method Embedded with Data Mining
Authors: Xuhao Gui, Junfeng Zhang, Xinmin Tang, Daniel Delahaye, Jie Bao
First page: 648
Abstract: Data mining has achieved great success in air traffic management as a technology for learning knowledge from historical data that benefits people. However, data mining can rarely be embedded into the trajectory optimization process since regular optimization algorithms cannot utilize the functional and implicit knowledge extracted from historical data in a general paradigm. To tackle this issue, this research proposes a novel data mining-based trajectory generation method that is compatible with existing optimization algorithms. Firstly, the proposed method generates trajectories by combining various maneuvers learned from operation data instead of reconstructing trajectories with generative models. In such a manner, data mining-based trajectory optimization can be achieved by solving a combinatorial optimization problem. Secondly, the proposed method introduces a majorization–minimization-based adversarial training paradigm to train the generation model with more general loss functions, including non-differentiable flight performance constraints. A case study on Guangzhou Baiyun International Airport was conducted to validate the proposed method. The results illustrate that the trajectory generation model can generate trajectories with high fidelity, diversity, and flyability.
Citation: Aerospace
PubDate: 2024-08-09
DOI: 10.3390/aerospace11080648
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 649: Brushless DC Motor Sizing Algorithm for
Small UAS Conceptual Designers
Authors: Farid Saemi, Moble Benedict
First page: 649
Abstract: Accurately sizing vehicle components is an impactful step in the aircraft design process. However, existing methods of sizing brushless DC (BLDC) motors for small unmanned aerial systems (SUAS) ignore how cooling affects motor size. Moreover, the literature methods do not predict a notional motor’s electrical constants, namely winding resistance, torque constant, and figure of merit. We developed a sizing algorithm that predicts the optimal mass and electrical constants using a combination of sizing, efficiency, and thermal models. The algorithm works for radial-flux BLDC motors with masses up to 800 g. An experimental teardown of seven motors informed the algorithm’s sizing models. The teardown motors varied in mass (24–600 g) and geometry (stator aspect ratio of 1.4–9.0). Validated against an independent catalog of 30 motors, the sizing models predicted mass and resistance within 10% and 20% of catalog specifications, respectively. Validated against experimental data, the full algorithm predicted mass, efficiency, and temperature within 20%, 5%, and 10% accuracy, respectively. The algorithm also captured how lowering mass would increase losses and temperature, which the literature models ignore. The algorithm can help users develop more viable concepts that save costs in the long run.
Citation: Aerospace
PubDate: 2024-08-10
DOI: 10.3390/aerospace11080649
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 650: Modified Zweifel Coefficient and Lift
Coefficient Definition Considering Compressible Effect
Authors: Ming Ni, Zuojun Wei, Weimin Deng, Guangming Ren, Xiaohua Gan
First page: 650
Abstract: The accurate prediction of blade loading is crucial to designing efficient turbomachinery, but traditional methods often neglect the impact of compressibility, leading to inaccuracies at high speeds. This study investigates the effect of compressibility on the blade loading parameters, particularly the Zweifel coefficient (Zw) and lift coefficient (CL), in turbine cascades. A novel intermediate method (IM), with averaged flow properties derived from both inlet and outlet conditions, is proposed to enhance the accuracy of Zw and CL calculations in compressible flow regimes. This method is based on the extended Kutta–Joukowski theorem for compressible flow and incorporates the Mach number directly into the modified definitions of Zw and CL. The analysis reveals that the averaged flow angle (αm), calculated by using a velocity-weighted approach, serves as a crucial parameter for blade similarity studies. The proposed correction method is applied and validated based on CFD simulations of the VKI-RG turbine cascade. The IM and modified definitions provide a robust framework for accurately predicting blade loading at high speeds, enabling improved design and analysis of turbomachinery.
Citation: Aerospace
PubDate: 2024-08-10
DOI: 10.3390/aerospace11080650
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 651: Investigation of the Overall Damage
Assessment Method Used for Unmanned Aerial Vehicles Subjected to Blast
Waves
Authors: Xiaowei Feng, Zezhou Yang, Yuan Nie
First page: 651
Abstract: With the aim of investigating the assessment methodology for the overall damage effects on an unmanned aerial vehicle (UAV) subjected to a blast wave, the failure criteria for the typical UAV was formulated through an analysis of the structural strength design standards. Specifically, the shear force associated with wing failure can serve as a critical parameter for assessing the overall damage inflicted on the UAV by blast waves. According to the design load criterion of the aircraft, the shear force value corresponding to the overall failure of the typical UAV was calculated. Numerical simulations were conducted to investigate the mechanical response of UAV structures under blast wave loading generated by a 500 g explosive. Combining the critical shear force values obtained from theoretical calculations with the numerical simulation results, two distances between the explosives and the UAV that could produce different damage effects were estimated, namely 1 m and 2.5 m. Subsequently, static explosion experiments with equivalent explosive charges were performed, revealing different damage effects on a typical UAV at two specific distances. The numerical simulation results were highly consistent with the experimental observations, further validating the scientific and rational basis for using shear force as a primary parameter in assessing overall structural damage to fixed-wing UAVs.
Citation: Aerospace
PubDate: 2024-08-10
DOI: 10.3390/aerospace11080651
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 652: Experimental and Numerical Study on the
Plasma-Laser-Induced Ignition of Strut Stabilizer at Different Locations
Authors: Xin Jia, Bin Hu, Wei Zhao, Wen Zeng, Jiangbo Peng, Qingjun Zhao
First page: 652
Abstract: The minimum ignition equivalence ratio of the strut stabilizer is an important parameter in the design of integrated afterburners. The ignition location significantly affects the ignition equivalence ratio and flame propagation, and therefore, it should be deeply studied. The ignition equivalence ratio and flame propagation at different axial ignition locations downstream of the strut stabilizer are studied in this paper. When the ignition distance is approximately the bluff body trailing edge width, a lower ignition equivalence ratio is required for ignition, and the flame propagates faster through the entire combustion chamber. For different ignition locations, the generated flame kernel at different locations all first propagates to the shear layer. Subsequently, the unilateral flame rapidly extends, ultimately igniting the entire combustion chamber. The flame propagation trajectory depends on the ignition location controlled by the non-reacting flow field and the distribution of kerosene concentration. The flame propagation trajectory mainly includes three paths: (1) the flame kernel is directly downstream the shear layer when the ignition location is close to the tail edge of the stabilizer, (2) the flame propagates upstream into the shear layer in a U-shape when the ignition location is far from the stabilizer but still in the recirculation zone, and (3) the flame propagates upstream into the recirculation zone and shear layer in a U-shape when the ignition location is outside the recirculation zone. In addition, the time for flame propagation to the shear layer is directly related to the ignition performance when the ignition location is within the recirculation zone. If the flame reaches the shear layer in a longer time, there will be more energy loss during the flame propagation process, and the ignition performance will deteriorate. The speed of the flame-trailing edge extension is directly related to the ignition fuel-air ratio, and the downstream extension of the flame is mainly affected by the turbulence velocity in the shear layer.
Citation: Aerospace
PubDate: 2024-08-11
DOI: 10.3390/aerospace11080652
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 653: An Intelligent Bait Delivery Control Method
for Flight Vehicle Evasion Based on Reinforcement Learning
Authors: Shuai Xue, Zhaolei Wang, Hongyang Bai, Chunmei Yu, Tianyu Deng, Ruisheng Sun
First page: 653
Abstract: During aerial combat, when an aircraft is facing an infrared air-to-air missile strike, infrared baiting technology is an important means of penetration, and the strategy of effective delivery of infrared bait is critical. To address this issue, this study proposes an improved deep deterministic policy gradient (DDPG) algorithm-based intelligent bait-dropping control method. Firstly, by modeling the relative motion between aircraft, bait, and incoming missiles, the Markov decision process of aircraft-bait-missile infrared effect was constructed with visual distance and line of sight angle as states. Then, the DDPG algorithm was improved by means of pre-training and classification sampling. Significantly, the infrared bait-dropping decision network was trained through interaction with the environment and iterative learning, which led to the development of the bait-dropping strategy. Finally, the corresponding environment was transferred to the Nvidia Jetson TX2 embedded platform for comparative testing. The simulation results showed that the convergence speed of this method was 46.3% faster than the traditional DDPG algorithm. More importantly, it was able to generate an effective bait-throwing strategy, enabling the aircraft to successfully evade the attack of the incoming missile. The strategy instruction generation time is only about 2.5 ms, giving it the ability to make online decisions.
Citation: Aerospace
PubDate: 2024-08-11
DOI: 10.3390/aerospace11080653
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 654: Time Optimal Altitude-Hold Flight Mode
Transition Strategy for a Class of Ducted Fan Tail Sitter UAV
Authors: Zihuan Cheng, Hailong Pei
First page: 654
Abstract: For special tail sitter configurations such as the ducted fan tail sitter unmanned aerial vehicle (UAV), the widely used trajectory planning methodology based on differential flatness might not be applicable due to complex aerodynamic coupling effects. As a result, the flight mode transition remains a challenging task. In this paper, we address the time optimal altitude-hold flight mode transition issue for a class of ducted fan tail sitter UAV. The foundation of the framework is the dynamic transition corridor in which the limitation of jerk is particularly considered, aiming to thoroughly reflect the dynamic feature of aggressive maneuvers. Based on this, we propose a time optimal strategy to generate feasible altitude-hold transition trajectories. Simultaneous, by fully utilizing the manifestation of time optimal altitude-hold flight behavior revealed by the transition corridor, we try to tackle the time optimal altitude-hold transition by means of a novel model-free control scheme. Comparative simulations show that both of the transition strategies achieve satisfactory performance on time optimal altitude-hold transition in the absence of disturbance, while the model-free control scheme exhibits better robustness under external disturbance.
Citation: Aerospace
PubDate: 2024-08-11
DOI: 10.3390/aerospace11080654
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 655: Analysis of Bubble Flow in an Inclined Tube
and Modeling of Flow Prediction
Authors: Xiaodi Liang, Suofang Wang, Wenjie Shen
First page: 655
Abstract: The lubricating oil system is a significant component of aviation engine lubrication and cooling, and the scavenge pipe is an essential component of the lubricating oil system. Accurately identifying and understanding the flow state of the scavenge pipe is very important. This article establishes a visualization test bench for a 45-degree inclined scavenge pipe, with upward and downward flow directions, respectively. The test temperature is 370 K, and a high-speed camera captures the changes in the two-phase flow inside the pipeline. Based on high-speed photography photos, we develop software for analyzing the flow characteristics of bubbles inside the tube and explore the influence of gas phase conversion velocity and liquid phase conversion velocity on the apparent velocity of bubbles inside the tube. Multiple algorithms were used to develop the model by combining machine learning with speed and accuracy to establish a data regression prediction model for the apparent velocity of bubbles inside the tube. Through calculation and analysis, it was found that the root mean square error of the prediction model using the BP neural network algorithm was the lowest, and the decision coefficient of the prediction model using the support vector machine algorithm was the highest.
Citation: Aerospace
PubDate: 2024-08-11
DOI: 10.3390/aerospace11080655
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 656: An Advanced Control Method for Aircraft
Carrier Landing of UAV Based on CAPF–NMPC
Authors: Danhe Chen, Lingfeng Xu, Chuangge Wang
First page: 656
Abstract: This paper investigates a carrier landing controller for unmanned aerial vehicles (UAVs), and a nonlinear model predictive control (NMPC) approach is proposed considering a precise motion control required under dynamic landing platform and environment disturbances. The NMPC controller adopts constraint aware particle filtering (CAPF) to predict deck positions for disturbance compensation and to solve the nonlinear optimization problem, based on a model establishment of carrier motion and wind field. CAPF leverages Monte Carlo sampling to optimally estimate control variables for improved optimization, while utilizing constraint barrier functions to keep particles within a feasible domain. The controller considers constraints such as fuel optimization, control saturation, and flight safety to achieve trajectory control. The advanced control method enhances the solution, estimating optimal control sequences of UAV and forecasting deck positions within a moving visual field, with effective trajectory tracing and higher control accuracy than traditional methods, while significantly reducing single-step computation time. The simulation is carried out using UAV “Silver Fox”, considering several scenarios of different wind scales compared with traditional CAPF–NMPC and the nlmpc method. The results show that the proposed NMPC approach can effectively reduce control chattering, with a landing error in rough marine environments of around 0.08 m, and demonstrate improvements in trajectory tracking capability, constraint performance and computational efficiency.
Citation: Aerospace
PubDate: 2024-08-11
DOI: 10.3390/aerospace11080656
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 657: Framework for Numerical 6DOF Simulation
with Focus on a Wing Deforming UAV in Perch Landing
Authors: Wee-Beng Tay, Woei-Leong Chan, Ren-Ooi Chong, Jonathan Tay Chien-Ming
First page: 657
Abstract: The perch landing maneuver of a wing-deforming unmanned aerial vehicle (UAV) was investigated through a framework that uses the free, open-source OpenFOAM with 6 degrees of freedom (6DOF) simulations. The framework uses a moving grid to follow the trajectory of the UAV, reducing computational resources. Together with the ability to allow internal grid deformation, sliding mesh, and algorithm addition, it can accurately mimic the entire landing process. Different wing deformation speeds, additional elevator rotation and emulated propeller lift were added to the 6DOF simulations to investigate their effects on the landing maneuver. The results showed that the wing deformation retraction speed has a considerable effect on the trajectory and velocity of the UAV. The wing deformation reduced the forward velocity of the UAV by 32%, from 13.89 to 9 m/s. With the elevator control, the velocity was reduced to 5 m/s. Lastly, and an activation time of 1 s for the emulated propeller lift can further decrease the velocity to around 4.2 m/s. A better algorithm for the emulated propeller lift may be able to give a superior performance. This framework allows us to understand the underlying perch landing maneuver aerodynamics. It can also be used on problems like fast-turning agile and flapping wing flight.
Citation: Aerospace
PubDate: 2024-08-12
DOI: 10.3390/aerospace11080657
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 658: An Improved Comprehensive Atomization Model
for Pressure Swirl Atomizers
Authors: Weijia Qian, Jinduo Wang, Xin Hui, Siheng Yang, Ruyue Cheng, Ping Wang
First page: 658
Abstract: This study presents an improved comprehensive atomization model for a pressure swirl atomizer. The model integrates internal flow predictions, linear instability analysis of a swirling annular liquid sheet, primary atomization sub-model, and droplet velocity sub-model. Measurement data combined with the inviscid theory model predict the internal flow, providing liquid sheet velocity and thickness at the atomizer outlet. The dispersion relation of surface disturbances is obtained through linear instability analysis. A primary breakup predictive model for particle size distribution is constructed based on the wavelength and growth rate within the full unstable wavenumber range of the dispersion relation. Assuming uniform circumferential distribution and a normal distribution of spray angles, the droplet velocity is assigned according to the liquid sheet velocity. The model is implemented into Eulerian–Lagrangian simulations as initial conditions for discrete phase droplets to simulate the spray field. Results show the model can accurately predict the Sauter mean diameter with an error of less than 6% and effectively predicts the spray structure and spray cone angle. The dependency of the model on its parameters is also studied, determining that the values of the ligament constant and dispersion angle have an obvious impact on the prediction of Sauter mean diameter and spray structure.
Citation: Aerospace
PubDate: 2024-08-12
DOI: 10.3390/aerospace11080658
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 659: Direct Closed-Loop Control Structure for
the Three-Axis Satcom-on-the-Move Antenna
Authors: Jiao Ren, Xiaoxiang Ji, Lei Han, Jianghong Li, Shubiao Song, Yafeng Wu
First page: 659
Abstract: The traditional Satcom-on-the-Move (SOTM) mechanical structure consists of a dual-axis configuration with an azimuth axis and a pitch axis. In this structure, when the pitch angle is 90 degrees, the rotation of the azimuth axis cannot change the antenna’s direction. To solve this issue, a three-axis SOTM mechanical structure has been developed. The traditional three-axis SOTM servo control system adopts a closed-loop control scheme. In this scheme, due to the difficulty in directly obtaining the antenna’s rotation angle, the angles of rotation for each axis are typically selected to represent the antenna’s rotation angle. The closed-loop feedback includes the angles and angular velocities of the axes, which cannot completely capture the antenna’s motion state, essentially constituting an indirect closed-loop control. Addressing the shortcomings of this indirect closed-loop control, this paper first establishes the kinematic relations between the axes of the three-axis SOTM antenna using the Denavit–Hartenberg (DH) method. Subsequently, the relationship between antenna pointing and the rotational states of the three axes was derived using the Jacobian operator. Building upon this foundation, a direct closed-loop control structure for a three-axis SOTM antenna was designed. To enable the control system to achieve rapid convergence with minimal overshoot, an Active Disturbance Rejection Control (ADRC) algorithm based on smooth continuous functions is introduced as the inner and outer loop controller algorithms within the direct closed-loop control structure. To address the nonlinearity in the design scheme, a piecewise linearization method is proposed to reduce the demands on the microprocessor’s performance and enhance the engineering feasibility of the solution. Finally, the effectiveness of the proposed approach is validated through experiments. The experimental results demonstrate that compared to traditional indirect closed-loop control methods, utilizing the direct closed-loop control method for the three-axis SOTM antenna presented in this paper can lead to higher precision in pointing the antenna towards satellites and enhance communication effectiveness.
Citation: Aerospace
PubDate: 2024-08-12
DOI: 10.3390/aerospace11080659
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 660: Stability of Single-Channel Homing Rolling
Aerospace Vehicle
Authors: Teodor-Viorel Chelaru, Cristian Emil Constantinescu, Valentin Pană, Costin Ene, Adrian Chelaru
First page: 660
Abstract: This paper aims to analyze the stability of a special class of single-channel slow-rotating homing missiles using the Frank–Wall stability criterion. To achieve this, starting from the model of a slow-rolling missile with six degrees of freedom (6 DOFs) in the body frame, a 6-DOFs model in the Resal frame is obtained, which is used to linearize the coupled commanded motion. Based on the linearized model, we obtain the structural scheme of the commanded object and define the flight quality parameters. The obtained linear model has a complex representation (with real and imaginary parts) due to the coupling between longitudinal channels for the rolling missile. Then, the kinematic guidance equations, the seeker equations and the actuator relations using a switching function, specific to the slow-rolling single-channel missile, are defined. The guidance kinematic equations, the seeker equations and the actuator model are linearized in the Resal frame, and the structural diagram of the homing missile is constructed. Starting from this, the characteristic polynomial having complex coefficients is determined and then analyzed with the Frank–Wall stability criterion. Based on the analysis, a stability range is determined for the navigation constant (k), and a minimum and possibly a maximum limit for the time to hit the target tgo is obtained. The stability range defined for the navigation constant in the linear model is finally validated in the nonlinear model in the body frame.
Citation: Aerospace
PubDate: 2024-08-12
DOI: 10.3390/aerospace11080660
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 661: Size-Dependent Finite Element Analysis of
Functionally Graded Flexoelectric Shell Structures Based on Consistent
Couple Stress Theory
Authors: Zhuo Deng, Yan Shang
First page: 661
Abstract: The functionally graded (FG) flexoelectric material is a potential material to determine the structural morphing of aircrafts. This work proposes the penalty 20-node element based on the consistent couple stress theory for analyzing the FG flexoelectric plate and shell structures with complex geometric shapes and loading conditions. Several numerical examples are examined and prove that the new element can predict the size-dependent behaviors of FG flexoelectric plate and shell structures effectively, showing good convergence and robustness. Moreover, the numerical results reveal that FG flexoelectric material exhibits better bending performance and higher flexoelectric effect compared to homogeneous materials. Moreover, the increase in the material length scale parameter leads to a gradual increase in the natural frequencies of the out-of-plane modes of FG flexoelectric plate/shell, while the natural frequencies of the in-plane modes change minimally, resulting in the occurrence of mode-switching phenomena.
Citation: Aerospace
PubDate: 2024-08-12
DOI: 10.3390/aerospace11080661
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 662: An Evaluation of Passive Wall Treatment
with Circumferential Grooves at the Casing of the First and Second Blade
Rotor Rows of a High-Performance Multi-Stage Axial Compressor
Authors: Ruben Bruno Diaz, Jesuino Takachi Tomita, Cleverson Bringhenti, Franco Jefferds dos Santos Silva, Diogo Ferraz Cavalca
First page: 662
Abstract: The internal losses in the tip clearance region strongly influence the compressor performance and its operational range. Previous research proved that passive wall treatments with circumferential grooves in axial compressors effectively increase the compressor stall margin. The vortex generated inside the circumferential grooves creates a resistance to the flow that leaks into the tip clearance region of the compressor. However, most works found in the literature on circumferential grooves in axial compressors deal only with high-performance single-stage axial compressors. Therefore, there is a need to investigate and analyze the behavior of circumferential grooves in a multi-stage environment. In the present work, a passive wall treatment with circumferential grooves was implemented in a multi-stage axial compressor. Different configurations of circumferential grooves were created at the casing of the first and second rotor rows used in a four-stage axial flow compressor. Numerical simulations were performed to evaluate the influence of the circumferential grooves on the performance of a multi-stage axial compressor. The results obtained after the simulations for the different circumferential groove configurations were compared with the results obtained for the compressor without casing treatment (smooth wall) for different rotational speeds. Furthermore, the complete compressor map characteristics were simulated for the different casing treatment configurations, and the results were compared with the compressor characteristics of the smooth wall case. The passive wall treatment with circumferential grooves produced changes in the multi-stage axial compressor flow field, especially in the tip clearance region, improving the compressor stability mainly for part load speeds.
Citation: Aerospace
PubDate: 2024-08-12
DOI: 10.3390/aerospace11080662
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 663: High-Resolution CAD-Based Shape
Parametrisation of a U-Bend Channel
Authors: Rejish Jesudasan, Jens-Dominik Müeller
First page: 663
Abstract: The parametrisation of the geometry in shape optimisation has an important influence on the quality of the optimum and the rate of convergence of the optimiser. Refinement studies for the parametrisation are not shown in the literature, as most methods use non-orthogonal parametrisations, which cause issues with convergence when the parametrisation is refined. The NURBS-based parametrisation with complex constraints (NSPCC) is the only CAD-based parametrisation method that guarantees orthogonal shape modes by constructing an optimal basis. We conduct a parametrisation refinement study for the benchmark turbomachinery cooling bend (U-bend) geometry, an intially symmetric geometry. Using an adjoint RANS solver, we optimise for mininmal total pressure drop. The results show significant effects of the control net density on the final shape, with the finest control net producing an asymmetric optimal shape resembling strakes that induces swirl ahead of the bend. These asymmetric modes have not been reported in the literature so far. We also demonstrate that the convergence rate of the optimiser is not significantly affected by the refinement of the parametrisation. The effectiveness of these shape features obtained with single-point optimisation is evaluated for a range of Reynolds numbers. It is shown that total pressure drop reduction is not sensitive to Reynolds number.
Citation: Aerospace
PubDate: 2024-08-13
DOI: 10.3390/aerospace11080663
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 664: Propeller Effects and Elasticity in
Aerodynamic Analysis of Small Propeller-Driven Aircraft and UAVs
Authors: Mohsen Rostami
First page: 664
Abstract: The importance of propeller effects and power contribution to the aerodynamics of small aircraft and unmanned aerial vehicles (UAVs) is indispensable. The aerodynamic analysis of wings in flight varies from rigid wing analysis due to wing deflection caused by transferred aerodynamic loads. This paper investigates the intertwined influence of propeller effects and elasticity on the aerodynamics of small propeller-driven aircraft and UAVs. Through a detailed methodology, a twin-engine propeller-driven aircraft is analyzed as a case study, providing insights into the proposed approach. Two critical analyses are presented: an examination of propeller effects in rigid aircraft and the incorporation of elastic wing properties. The former establishes a foundational understanding of aerodynamic behavior, while the latter explores the impact of wing elasticity on performance. Validation is achieved through comparative analysis with wind tunnel test results from a similar rigid structure aircraft. Utilizing NASTRAN software V2010.1, aerodynamic analysis of the elastic aircraft is conducted, complemented by semi-empirical insights. The results highlight the importance of these factors across different angles of attack. Furthermore, deviations from the rigid aircraft configuration emphasize the considerable influence of static aeroelasticity analysis, notably increasing longitudinal characteristics by approximately 20%, while showing a lower impact of 5% in lateral-directional characteristics. This study contributes to enhanced design and operational considerations for small propeller-driven aircraft, with implications for future research and innovation, particularly for the purpose of efficient concepts in advanced air mobility.
Citation: Aerospace
PubDate: 2024-08-13
DOI: 10.3390/aerospace11080664
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 665: Fuel Efficiency Evaluation of A380 Aircraft
through Comparative Analysis of Actual Flight Data of the A380–800
and A350–900
Authors: Sungwoo Jang, Seongjoo Yoon, Jae Leame Yoo
First page: 665
Abstract: The Airbus A380 was initially expected to replace existing aircraft due to its remarkable fuel efficiency on long-haul routes when operating with a full passenger load. However, recent changes in the commercial aviation environment have resulted in a decrease in demand for four-engine aircraft. Rising fuel prices have pushed airlines to focus on more efficient operations, while manufacturers prioritize producing advanced twin-engine aircraft. The debate over the long-term economic viability of A380 operations remains ongoing. This study compares and evaluates the fuel efficiency of the Airbus A380 and the Airbus A350 using actual flight data. The analysis employs a fuel efficiency prediction model to compare scenarios based on identical payload and load factor. Results indicate that the A350 is approximately twice as fuel efficient as the A380 under the same payload and about 1.34 times more efficient under the same load factor. The A380’s economic viability is analyzed by considering the balance between revenue per available ton-kilometer (RASK) and cost per available ton-kilometer (CASK). If the A380’s RASK is significantly higher than 1.34 times the A350’s or exceeds its own CASK, it can sustain operations. Achieving a balance between RASK and CASK is essential for the economic sustainability of A380 operations.
Citation: Aerospace
PubDate: 2024-08-13
DOI: 10.3390/aerospace11080665
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 666: A Brief Review of the Actuation Systems of
the Morphing Systems in Wind Tunnel Models and a Case Study
Authors: Guogang Pan, Xiaoyu Cui, Pengfei Sun, Biling Wang
First page: 666
Abstract: Typical wind tunnel testing involves a series of configuration changes (to the angles of control surfaces) to simulate the lift and resistance characteristics of control surfaces in different flight conditions. It is very time-consuming and labor-intensive to manually change the angles of control surfaces, especially in the large continuous reflux wind tunnel. Thus, there is a demand for a morphing system design within the wind tunnel model that can deflect the control surfaces remotely and automatically. The basic design flow and characteristics of different actuator techniques for the morphing systems were summarized in this paper, including electromechanical actuator, pneumatic actuator, shape memory material actuator and piezoelectric actuator. In the case study, the accuracy of the control surface angle and aerodynamic performance of the ultrasonic-driven automatic control surface system reached the level of traditional fixed control surface systems, while its efficiency was much higher than that of the traditional fixed control surface systems.
Citation: Aerospace
PubDate: 2024-08-13
DOI: 10.3390/aerospace11080666
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 667: Optimization of Plasma-Propelled Drone
Performance Parameters
Authors: Zewei Xia, Yulong Ying, Heli Li, Tong Lin, Yuxuan Yao, Naiming Qi, Mingying Huo
First page: 667
Abstract: Recently, the world’s first plasma-propelled drone was successfully flown, demonstrating that plasma propulsion technology is suitable for drone flight. The research on plasma propulsion drones has sparked a surge of interest. This study utilized a proxy model and the NSGA-II multi-objective genetic algorithm to optimize the geometric parameters based on staggered thrusters that affect the performance of electroaerodynamics (EAD) thrusters used for solid-state plasma aircraft. This can help address key issues, such as the thrust density and the thrust-to-power ratio of solid-state plasma aircraft, promoting the widespread application of plasma propulsion drones. An appropriate sample set was established using Latin hypercube sampling, and the thrust and current data were collected using a customized experimental setup. The proxy model employed a genetically optimized Bayesian regularization backpropagation neural network, which was trained to predict the effects of variations in the geometric parameters of the electrode assembly on the performance parameters of the plasma aircraft. Based on this information, the maximum achievable value for a given performance parameter and its corresponding geometric parameters were determined, showing a significant increase compared to the sample data. Finally, the optimal parameter combination was determined by using the NSGA-II multi-objective genetic algorithm and the Analytic Hierarchy Process. These findings can serve as a basis for future researchers in the design of EAD thrusters, helping them produce plasma propulsion drones that better meet specific requirements.
Citation: Aerospace
PubDate: 2024-08-14
DOI: 10.3390/aerospace11080667
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 668: Optimisation Design of Thermal Test System
for Metal Fibre Surface Combustion Structure
Authors: Bin Qi, Rong A, Dongsheng Yang, Ri Wang, Sujun Dong, Yinjia Zhou
First page: 668
Abstract: The metal fibre surface combustion structure has the characteristics of strong thermal matching ability, short response time, and strong shape adaptability. It has more advantages in the thermal test of complex hypersonic vehicle surface inlet, leading edge, etc. In this paper, a method of aerodynamic thermal simulation test based on metal fibre surface combustion is proposed. The aim of the study was to create a uniform target heat flow on the inner wall surface of a cylindrical specimen by matching the gas jet flow rate and the geometry of the combustion surface. The research adopted the optimisation design method based on the surrogate model to establish the numerical calculation model of a metal fibre combustion jet heating cylinder specimen. One hundred sample points were obtained through Latin hypercube sampling, and a database of design parameters and heat flux was established through numerical simulation. The kriging surrogate model and the non-dominated sequencing genetic optimisation algorithm with elite strategy were adopted. A bi-objective optimisation design was carried out with the optimisation objective of the coincidence between the predicted and the target heat flux on the inner wall of the specimen. The results showed that the average relative errors of heat flow density on the specimen surface were 8.8% and 6% through the leave-one-out cross-validation strategy and the validation of six test sample points, respectively. The relative error values in most regions were within 5%, which indicates that the established kriging surrogate model has high prediction accuracy. Under the optimal solution conditions, the numerical calculation results of the heat flow on the inner wall of the specimen were in good agreement with the target heat flow values, with an average relative error of less than 5% and a maximum value of less than 8%. These results show that the optimisation design method based on the kriging surrogate model can effectively match the thermal test parameters of metal fibre combustion structures.
Citation: Aerospace
PubDate: 2024-08-14
DOI: 10.3390/aerospace11080668
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 669: Advanced UAV Design Optimization Through
Deep Learning-Based Surrogate Models
Authors: Hasan Karali, Gokhan Inalhan, Antonios Tsourdos
First page: 669
Abstract: The conceptual design of unmanned aerial vehicles (UAVs) presents significant multidisciplinary challenges requiring the optimization of aerodynamic and structural performance, stealth, and propulsion efficiency. This work addresses these challenges by integrating deep neural networks with a multiobjective genetic algorithm to optimize UAV configurations. The proposed framework enables a comprehensive evaluation of design alternatives by estimating key performance metrics required for different operational requirements. The design process resulted in a significant improvement in computational time over traditional methods by more than three orders of magnitude. The findings illustrate the framework’s capability to optimize UAV designs for a variety of mission scenarios, including specialized tasks such as intelligence, surveillance, and reconnaissance (ISR), combat air patrol (CAP), and Suppression of Enemy Air Defenses (SEAD). This flexibility and adaptability was demonstrated through a case study, showcasing the method’s effectiveness in tailoring UAV configurations to meet specific operational requirements while balancing trade-offs between aerodynamic efficiency, stealth, and structural weight. Additionally, these results underscore the transformative impact of integrating AI into the early stages of the design process, facilitating rapid prototyping and innovation in aerospace engineering. Consequently, the current work demonstrates the potential of AI-driven optimization to revolutionize UAV design by providing a robust and effective tool for solving complex engineering problems.
Citation: Aerospace
PubDate: 2024-08-14
DOI: 10.3390/aerospace11080669
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 670: Enhanced Computational Biased Proportional
Navigation with Neural Networks for Impact Time Control
Authors: Xue Zhang, Haichao Hong
First page: 670
Abstract: Advanced computational methods are being applied to address traditional guidance problems, yet research is still ongoing regarding how to utilize them effectively and scientifically. A numerical root-finding method was proposed to determine the bias in biased proportional navigation to achieve the impact time control without time-to-go estimation. However, the root-finding algorithm in the original method might experience efficiency and convergence issues. This paper introduces an enhanced method based on neural networks, where the bias is directly output by the neural networks, significantly improving computational efficiency and addressing convergence issues. The novelty of this method lies in the development of a reasonable structure that appropriately integrates off-the-shelf machine learning techniques to effectively enhance the original iteration-based methods. In addition to demonstrating its effectiveness and performance of its own, two comparative scenarios are presented: (a) Evaluate the time consumption when both the proposed and the original methods operate at the same update frequency. (b) Compare the achievable update frequencies of both methods under the condition of equal real-world time usage.
Citation: Aerospace
PubDate: 2024-08-15
DOI: 10.3390/aerospace11080670
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 671: Adaptive Incremental Nonlinear Dynamic
Inversion Control for Aerial Manipulators
Authors: Chanhong Park, Alex Ramirez-Serrano, Mahdis Bisheban
First page: 671
Abstract: This paper proposes an adaptive incremental nonlinear dynamic inversion (INDI) controller for unmanned aerial manipulators (UAMs). A novel adaptive law is employed to enable aerial manipulators to manage the inertia parameter changes that occur when the manipulator moves or picks up unknown objects during any phase of the UAM’s flight maneuver. The adaptive law utilizes a Kalman filter to estimate a set of weighting factors employed to adjust the control gain matrix of a previously developed INDI control law formulated for the corresponding UAV (no manipulator included). The proposed adaptive control scheme uses acceleration and actuator input measurements of the UAV without necessitating any knowledge about the manipulator, its movements, or the objects being grasped, thus enabling the use of previously developed INDI UAV controllers for UAMs. The algorithm is validated through simulations demonstrating that the adaptive control gain matrix used in the UAV’s INDI controller is promptly updated based on the UAM maneuvers, resulting in effective UAV and robot arm control.
Citation: Aerospace
PubDate: 2024-08-15
DOI: 10.3390/aerospace11080671
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 672: The Effect of 0–8 MPa Environmental
Pressure on the Ignition and Combustion Process of CL20/NEPE Solid
Propellant
Authors: Wenxiang Cai, Wei Li, Zhixiang Wang
First page: 672
Abstract: In order to study the effect of pressure on the ignition and combustion process of CL-20/NEPE solid propellant, the ignition delay, burning rate, and maximum combustion temperature of different solid propellant formulations with an ambient pressure of 0.1~8.0 MPa were measured experimentally by a solid propellant laser ignition experiment system, and the agglomeration process and the characteristics of condensed phase combustion products were analyzed. The experimental results show that, with the increase of pressure, the ignition-delay time decreases, and the burning rate and the maximum combustion temperature increase. With the increase of pressure, the influence on propellant ignition and combustion characteristics becomes smaller. In the experiment, the dynamic agglomeration phenomenon of aluminum particles in the propellant was recorded by a high-speed camera combined with a microscopic camera lens, and the dynamic agglomeration phenomenon of the combustion surface of the propellant and the dynamic agglomeration phenomenon, after the initial agglomeration was separated from the surface, were analyzed and expounded. Based on the experiment and combined with the agglomeration phenomenon, a mathematical model capable of predicting the particle size of aluminum aggregates was proposed.
Citation: Aerospace
PubDate: 2024-08-15
DOI: 10.3390/aerospace11080672
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 673: Four-Dimensional Trajectory Optimization
for CO2 Emission Benchmarking of Arrival Traffic Flow with Point Merge
Topology
Authors: Chao Wang, Chenyang Xu, Wenqing Li, Shanmei Li, Shilei Sun
First page: 673
Abstract: The benchmarking of CO2 emissions serves as the foundation for the accurate assessment of the environmental impact of air traffic. To calculate the environmental benchmarks of arrival traffic flows with Point Merge System (PMS) patterns, this study proposes a 4D trajectory optimization method that combines data-driven and optimal control models. First, the predominant arrival routes of traffic flows are identified using the trajectory spectral clustering method, which provides the horizontal reference for 4D trajectory optimization. Second, an optimal control model for vertical profiles with point merging topology is established, with the objective of minimizing the fuel–time cost. Finally, considering the complex structure of the PMS, a flexible and adaptable genetic algorithm-based vertical profile nonlinear optimization model is created. The experimental results demonstrate that the proposed method is adaptable to variations in aircraft type and cost index parameters, enabling the generation of different 4D trajectories. The results also indicate an environmental efficiency gap of approximately 10% between the actual CO2 emissions of the arrival traffic flow example and the obtained benchmark. With this benchmark trajectory generation methodology, the environmental performance of PMSs and associated arrival aircraft scheduling designs can be assessed on the basis of reliable data.
Citation: Aerospace
PubDate: 2024-08-16
DOI: 10.3390/aerospace11080673
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 674: Analysis of Cable Shielding and Influencing
Factors for Indirect Effects of Lightning on Aircraft
Authors: Zhangang Yang, Yuhao Wei, Xudong Shi
First page: 674
Abstract: The widespread use of composite materials with low electrical conductivity in modern advanced aircraft has placed higher requirements on lightning protection for airborne equipment. To ensure the safe operation of aircraft under a lightning environment, the internal cables and cable tracks of composite aircraft are modeled. The lightning protection performance of cables is calculated for different types and shielding parameters, and the effect of the cable layout inside a composite aircraft on the protection performance is analyzed. The role of the cable track in lightning protection is also verified. The calculation results show that the cable shield and track structure can provide good lightning protection for the cable in the electromagnetic exposure area, and the layout of the cable inside the aircraft has a greater impact on the protection performance. The analysis of cable shielding measures and their influencing factors can provide a reference for the performance improvement of cable screening measures for the lightning protection of composite aircraft.
Citation: Aerospace
PubDate: 2024-08-16
DOI: 10.3390/aerospace11080674
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 675: Mechanistic Insights into Effects of
Perforation Direction on Thermal Hydraulic Performance of Ribs in a
Rectangular Cooling Channel
Authors: Weijia Qian, Ruiyang Shuai, Qingkun Meng, Subhajit Roy, Songbai Yao, Ping Wang
First page: 675
Abstract: This study investigates the turbulent flow characteristics and heat transfer performance within a rectangular cooling channel with an aspect ratio of 5:3 and featuring perforated ribs, then explores the effects of the rib perforation directions on its thermal hydraulic performance. Through experimental tests (transient thermographic liquid crystal technique) and numerical simulations, it is demonstrated that horizontal perforated ribs can effectively reduce pressure loss at a high Reynolds number while maintaining notable heat transfer enhancement. Additionally, changing the rib perforation directions results in diverse effects on flow field and heat transfer. Our results show that horizontal perforated ribs can compress the recirculation vortex behind ribs, enhancing heat transfer by flow scouring, whereas upward-tilted perforated ribs increase flow friction and weaken heat transfer due to coupling of the airflow with the separation vortices behind the ribs. Downward-tilted ribs enhance local heat transfer by directing airflow behind the rib, and can also cause detachment of vortices and reduced friction. Our results indicate that introducing horizontal perforated ribs into a rectangular internal cooling channel can decrease pressure loss without significantly compromising heat transfer performance.
Citation: Aerospace
PubDate: 2024-08-16
DOI: 10.3390/aerospace11080675
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 676: MobGSim-YOLO: Mobile Device Terminal-Based
Crack Hole Detection Model for Aero-Engine Blades
Authors: Xinyao Hou, Hao Zeng, Lu Jia, Jingbo Peng, Weixuan Wang
First page: 676
Abstract: Hole detection is an important means of crack detection for aero-engine blades, and the current technology still mainly relies on manual operation, which may cause safety hazards for visual reasons. To address this problem, this paper proposes a deep learning-based, aero-engine blade crack detection model. First, the K-means++ algorithm is used to recalculate the anchor points, which reduces the influence of the anchor frame on the accuracy; second, the backbone network of YOLOv5s is replaced with Mobilenetv3 for a lightweight design; then, the slim-neck module is embedded into the neck part, and the activation function is replaced with Hard Sigmoid for redesign, which improves the accuracy and the convergence speed. Finally, in order to improve the learning ability for small targets, the SimAM attention mechanism is embedded in the head. A large number of ablation tests are conducted in real engine blade data, and the results show that the average precision of the improved model is 93.1%, which is 29.3% higher; the number of parameters of the model is 12.58 MB, which is 52.96% less, and the Frames Per Second (FPS) can be up to 95. The proposed algorithm meets the practical needs and is suitable for hole detection.
Citation: Aerospace
PubDate: 2024-08-16
DOI: 10.3390/aerospace11080676
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 677: Application of Deep Learning Models to
Predict Panel Flutter in Aerospace Structures
Authors: Yi-Ren Wang, Yu-Han Ma
First page: 677
Abstract: This study investigates the application of deep learning models—specifically Deep Neural Networks (DNN), Long Short-Term Memory (LSTM), and Long Short-Term Memory Neural Networks (LSTM-NN)—to predict panel flutter in aerospace structures. The goal is to improve the accuracy and efficiency of predicting aeroelastic behaviors under various flight conditions. Utilizing a supersonic flat plate as the main structure, the research integrates various flight conditions into the aeroelastic equation. The resulting structural vibration data create a large-scale database for training the models. The dataset, divided into training, validation, and test sets, includes input features such as panel aspect ratio, Mach number, air density, and decay rate. The study highlights the importance of selecting appropriate hidden layers, epochs, and neurons to avoid overfitting. While DNN, LSTM, and LSTM-NN all showed improved training with more neurons and layers, excessive numbers beyond a certain point led to diminished accuracy and overfitting. Performance-wise, the LSTM-NN model achieved the highest accuracy in classification tasks, effectively capturing sequential features and enhancing classification precision. Conversely, LSTM excelled in regression tasks, adeptly handling long-term dependencies and complex non-linear relationships, making it ideal for predicting flutter Mach numbers. Despite LSTM’s higher accuracy, it required longer training times due to increased computational complexity, necessitating a balance between accuracy and training duration. The findings demonstrate that deep learning, particularly LSTM-NN, is highly effective in predicting panel flutter, showcasing its potential for broader aerospace engineering applications. By optimizing model architecture and training processes, deep learning models can achieve high accuracy in predicting critical aeroelastic phenomena, contributing to safer and more efficient aerospace designs.
Citation: Aerospace
PubDate: 2024-08-16
DOI: 10.3390/aerospace11080677
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 678: Study on the Mechanism of Cumulative
Deformation and Method for Suppression in Aircraft Panel Riveting
Authors: Yonggang Kang, Siren Song, Tianyu Wang, Guomao Li, Zihao Wang, Yonggang Chen
First page: 678
Abstract: In aircraft panel assembly, the interference fit unevenly distributed along the axial direction of the rivet holes leads to an uneven stress–strain field around the rivet holes. The uneven stress–strain fields of single rivets, when accumulated through multiple rivets, result in overall bending and twisting deformation, severely impacting the assembly coordination quality of the panel. This study introduces a numerical model using a single row of multiple rivets to explore cumulative deformation during both sequential and changing order riveting. The results show that the deformation in sequential riveting is mainly bending-oriented towards the driven head side, with the maximum displacement exhibiting a fluctuating accumulation trend as the number of rivets increase. In contrast, a changing riveting order can lead to a reduction in deformation accumulation. To reveal the technological mechanism behind deformation accumulation during the riveting process, a model correlating to the residual stress field was established. It was indicated that the continuous increase in the maximum equivalent bending moment in the axial section is the primary factor leading to deformation accumulation. Based on this finding, a pre-bending suppression method aimed at reducing the local maximum equivalent bending moment was proposed. Numerical calculations and experimental results showed that the maximum displacement of the specimen was reduced by 73.27%, proving that this method can effectively suppress the cumulative increase in deformation.
Citation: Aerospace
PubDate: 2024-08-16
DOI: 10.3390/aerospace11080678
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 679: Missile Fault Detection and Localization
Based on HBOS and Hierarchical Signed Directed Graph
Authors: Hengsong Hu, Yuehua Cheng, Bin Jiang, Wenzhuo Li, Kun Guo
First page: 679
Abstract: The rudder surfaces and lifting surfaces of a missile are utilized to acquire aerodynamic forces and moments, adjust the missile’s attitude, and achieve precise strike missions. However, the harsh flying conditions of missiles make the rudder surfaces and lifting surfaces susceptible to faults. In practical scenarios, there is often a scarcity of fault data, and sometimes, it is even difficult to obtain such data. Currently, data-driven fault detection and localization methods heavily rely on fault data, posing challenges for their applicability. To address this issue, this paper proposes an HBOS (Histogram-Based Outlier Score) online fault-detection method based on statistical distribution. This method generates a fault-detection model by fitting the probability distribution of normal data and incorporates an adaptive threshold to achieve real-time fault detection. Furthermore, this paper abstracts the interrelationships between the missile’s flight states and the propagation mechanism of faults into a hierarchical directed graph model. By utilizing bilateral adaptive thresholds, it captures the first fault features of each sub-node and determines the fault propagation effectiveness of each layer node based on the compatibility path principle, thus establishing a fault inference and localization model. The results of semi-physical simulation experiments demonstrate that the proposed algorithm is independent of fault data and exhibits high real-time performance. In multiple sets of simulated tests with randomly parameterized deviations, the fault-detection accuracy exceeds 98% with a false-alarm rate of no more than 0.31%. The fault-localization algorithm achieves an accuracy rate of no less than 97.91%.
Citation: Aerospace
PubDate: 2024-08-17
DOI: 10.3390/aerospace11080679
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 680: Finite-Time Convergence Guidance Law for
Hypersonic Morphing Vehicle
Authors: Dongdong Yao, Qunli Xia
First page: 680
Abstract: Aiming at the interception constraint posed by defensive aircrafts against hypersonic morphing vehicles (HMVs) during the terminal guidance phase, this paper designed a guidance law with the finite-time convergence theory and control allocation methods based on the event-triggered theory, achieving evasion of the defensive aircraft and targeting objectives for a morphing vehicle in the terminal guidance phase. Firstly, this paper established the aircraft motion model; the relative motion relationships between HMV, defensive aircraft, and target; and the control equations for the guidance system. Secondly, a guidance law with finite-time convergence was designed, establishing a controller with the angle between the aircraft–target–defense aircraft triplet as the state variable and lift as the control variable. By ensuring the angle was non-zero, the aircraft maintained a certain relative distance from the defense aircraft, achieving evasion of interception. The delay characteristic of the aircraft’s flight controller was considered, analyzing its delay stability and applying control compensation. Thirdly, a multi-model switching control allocation method based on an event-triggered mechanism was designed. Optimal attack and bank angles were determined based on acceleration control variables, considering different sweep angles. Finally, simulations were conducted to validate the effectiveness and robustness of the designed guidance laws.
Citation: Aerospace
PubDate: 2024-08-18
DOI: 10.3390/aerospace11080680
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 681: Conversion of a Coaxial Rotorcraft to a
UAV—Lessons Learned
Authors: Barzin Hosseini, Julian Rhein, Florian Holzapfel, Benedikt Grebing, Juergen Rauleder
First page: 681
Abstract: A coaxial helicopter with a maximum take-off weight of 600 kg was converted to an unmanned aerial vehicle. A minimally invasive robotic actuator system was developed, which can be retrofitted onto the copilot seat of the rotorcraft in a short period of time to enable automatic flight. The automatic flight control robot includes electromechanical actuators, which are connected to the cockpit inceptors and control the helicopter. Most of the sensors and avionic components were integrated into the modular robotic system for faster integration into the rotorcraft. The mechanical design of the control system, the development of the robot control software, and the control system architecture are described in this paper. Furthermore, the multi-body simulation of the robotic system and the estimation of the linear low-order actuator models from hover-frame flight test data are discussed. The developed technologies in this study are not specific to a coaxial helicopter and can be applied to the conversion of any crewed flight vehicle with mechanical controls to unmanned or fly-by-wire. This agile development of a full-size flying test-bed can accelerate the testing of advanced flight control laws, as well as advanced air mobility-related functions.
Citation: Aerospace
PubDate: 2024-08-19
DOI: 10.3390/aerospace11080681
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 682: Conceptual Design of Compliant Structures
for Morphing Wingtips Using Single-Row Corrugated Panels
Authors: Ziyi He, Siyun Fan, Chen Wang, Songqi Li, Yan Zhao, Xing Shen, Jiaying Zhang
First page: 682
Abstract: Morphing wingtips have the potential to improve aircraft performance. By connecting the wingtips and the wings with a compliant structure, a continuous aerodynamic surface can be achieved for a better aerodynamic performance. However, how to maintain the shape-changing capability while keeping a high stiffness to carry aerodynamic loads is a key problem. In this paper, based on asymmetric stiffness, a type of single-row corrugated panel is designed to satisfy the limited space around the wingtip. A finite element model of the single-row corrugated panels is established, and parameter analysis is performed to investigate the impact of the thickness characteristics of the corrugated panel on the folding angle. The corrugated panel is then optimised to find the maximum folding angle. Based on the optimisation results, corrugated panels with asymmetric and symmetric stiffness are fabricated and tested. The results demonstrate that the asymmetric stiffness corrugated panels have the capability to increase the wingtip folding angle.
Citation: Aerospace
PubDate: 2024-08-19
DOI: 10.3390/aerospace11080682
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 683: Adaptive Attitude Roll Control of Guided
Projectile Based on a Novel Unidirectional Global Sliding Mode Algorithm
Authors: Shouyi Guo, Liangming Wang, Jian Fu
First page: 683
Abstract: Aimed at addressing the strong nonlinearity and strong external disturbances that cause flight control issues in conventional guided projectiles, as well as the slow response and structural vibrations that often occur in sliding mode control systems, which have a detrimental impact on the control effect and ultimate hit precision, a new type of fast and robust control algorithm with a unidirectional mode has been designed. The objective is to design an optimized aerodynamic shape for the projectile and to establish a dynamic model of the roll channel and a motion model of the entire trajectory. The dynamics of a new global terminal sliding mode are proposed, and an adaptive parameter term is realized by calculating the state of the critical sliding mode surface, which ensures that the tracking error converges within a finite time. Its combination with an adaptive approaching law is used to further speed up convergence while damping the structural vibration of the system. The bias error of the roll angle is constructed as the controller and simulation calculations are conducted on the basis of the aforementioned framework. The stability and time convergence of the control system are demonstrated through Lyapunov theory. The results indicate that, in comparison to the conventional terminal sliding mode controller, the designed controller exhibits a markedly rapid convergence rate and stronger robustness in tracking the command signal. Moreover, it also maintains a stable motion attitude of the projectile throughout the entire process. The superior control effect under different guidance schemes and the strong external disturbances also further reflect the anti-jamming capability and tracking performance of the system.
Citation: Aerospace
PubDate: 2024-08-20
DOI: 10.3390/aerospace11080683
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 684: Decoys Deployment for Missile Interception:
A Multi-Agent Reinforcement Learning Approach
Authors: Enver Bildik, Antonios Tsourdos, Adolfo Perrusquía, Gokhan Inalhan
First page: 684
Abstract: Recent advances in radar seeker technologies have considerably improved missile precision and efficacy during target interception. This is especially concerning in the arenas of protection and safety, where appropriate countermeasures against enemy missiles are required to ensure the protection of naval facilities. In this study, we present a reinforcement-learning-based strategy for deploying decoys to enhance the survival probability of a target ship against a missile threat. Our approach involves the coordinated operation of three decoys, trained using the Multi-Agent Deep Deterministic Policy Gradient (MADDPG) and Multi-Agent Twin Delayed Deep Deterministic Policy Gradient (MATD3) algorithms. The decoys operate in a leader–follower dynamic with a circular formation to ensure effective coordination. We evaluate the strategy across various parameters, including decoy deployment regions, missile launch directions, maximum decoy speeds, and missile speeds. The results indicate that, decoys trained with the MATD3 algorithm demonstrate superior performance compared to those trained with the MADDPG algorithm. Insights suggest that our decoy deployment strategy, particularly when utilizing MATD3-trained decoys, significantly enhances defensive measures against missile threats.
Citation: Aerospace
PubDate: 2024-08-20
DOI: 10.3390/aerospace11080684
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 685: Optimal Design of High-Power Density
Medium-Voltage Direct Current Bipolar Power Cables for Lunar Power
Transmission
Authors: Anoy Saha, Mona Ghassemi
First page: 685
Abstract: Power systems on the lunar surface require power lines of varying lengths and capacities to connect generation, storage, and load facilities. These lines must be designed to perform efficiently in the harsh lunar environment, considering factors such as weight, volume, safety, cost-effectiveness, and reliability. Traditional power transmission methods face challenges in this environment due to temperature fluctuations, micrometeoroid impacts, and ionizing radiation. Underground deployment, although generally safer, faces challenges due to low soil thermal conductivity. At a depth of 30 cm, the lunar temperature of −23.15 °C can be advantageous for managing waste heat. This study presents a novel approach, developed using COMSOL Multiphysics, for designing bipolar MVDC cables for lunar subsurface power transmission. Kapton® MT+ is chosen as the insulating material for its exceptional properties, including high thermal conductivity and superior dielectric strength. The cables are designed for voltages of ±10 kV and ±5 kV and capacities of 200 kW (low power), 1 MW (medium power), and 2 MW (high power). Our findings indicate that aluminum conductors offer superior performance compared to copper at medium and high power levels. Additionally, elevated voltage levels (±10 kV) enhance cable design and power transfer efficiency. These specially designed cables are well-suited for efficient operation in the challenging lunar environment.
Citation: Aerospace
PubDate: 2024-08-20
DOI: 10.3390/aerospace11080685
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 686: Shock-Dominated Flow
Authors: He-Xia Huang
First page: 686
Abstract: This 2024 Special Issue of Aerospace, an open-access journal from MDPI, is entitled “Shock-Dominated Flow” and was guest-edited by Dr [...]
Citation: Aerospace
PubDate: 2024-08-21
DOI: 10.3390/aerospace11080686
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 687: Modeling and Control of Reconfigurable
Quadrotors Based on Model Reference Adaptive Control
Authors: Zhiping Liu, Guoshao Chen, Shuping Xu
First page: 687
Abstract: To expand the application prospects of quadrotors in challenging scenes such as those with dense obstacles and narrow corridors, task-driven reconfigurable quadrotors are highly desirable. Aiming to address hazard missions, in this paper, translational reconfigurable quadrotors and rotational reconfigurable quadrotors are proposed with their assumptions and mathematical models. Related motion control laws were designed using model reference adaptive control (MRAC) theory based on Lyapunov stability theory, whose validity was demonstrated by sufficient numerical simulations. The simulation results verify the feasibility of the proposed control laws and reveal the important effect of time delay on the stability of the motion control system. Additionally, the dependence of motion control’s stability on the time constant of reference system was discussed.
Citation: Aerospace
PubDate: 2024-08-21
DOI: 10.3390/aerospace11080687
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 688: Implementation of a 6U CubeSat Electrical
Power System Digital Twin
Authors: Pablo Casado, Cristian Torres, José M. Blanes, Ausiàs Garrigós, David Marroquí
First page: 688
Abstract: This paper presents the design of a digital twin for a 6U CubeSat electrical power system, including the solar arrays, solar array regulators, battery, power distribution unit, and load subsystems. The digital twin is validated by comparing its real-time outputs with those of the physical system. Experimental tests confirm its feasibility, showing that the digital twin’s real-time outputs closely match those of the physical system. Additionally, the digital twin can be used for control-hardware-in-the-loop and power-hardware-in-the-loop tests, allowing the real-time integration of simulated subsystems with hardware. This capability facilitates testing of new subsystems and optimization during the project’s development phases. Additionally, to demonstrate the advanced capabilities of this model, the digital twin is used to simulate the CubeSat electrical power system behavior in real time throughout a complete orbital cycle in low Earth orbit conditions. This simulation provides valuable insights into the CubeSat operation by capturing the transient and steady-state responses of the EPS components under real orbital conditions. The results obtained indicate that the digital twin significantly enhances the testing and optimization process of new subsystems during the development phases of the project. Moreover, the capabilities of the digital twin can be further augmented by incorporating real-time telemetry data from the CubeSat, resulting in a highly accurate replication of the satellite’s in-orbit behavior. This approach is crucial for identifying and diagnosing failures or malfunctions in the electrical power system, ensuring the robust and reliable operation of the CubeSat.
Citation: Aerospace
PubDate: 2024-08-21
DOI: 10.3390/aerospace11080688
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 689: Assembly Simulation and Optimization Method
for Underconstrained Frame Structures of Aerospace Vehicles
Authors: Jinyue Li, Gang Zhao, Jinhua Wei, Zhiyuan Hu, Wenqi Zhang, Pengfei Zhang
First page: 689
Abstract: Aerodynamic contour dimensional accuracy is very important for the stable and safe flight of aerospace vehicles. Nevertheless, due to the influence of various factors such as material properties, machining and manufacturing deviations, and assembly and installation deviations, key structural geometric dimensions are frequently exceeded. Therefore, this paper investigates a data-driven combined vector loop method (VLM)–Skin Model Shapes (SMS) method to realize aerospace vehicle structural geometric accuracy analysis; assembly optimization targeting contour deviation is also achieved. Tests are carried out on a typical aerospace vehicle’s underconstrained structural workpieces to validate the effectiveness of the proposed method.
Citation: Aerospace
PubDate: 2024-08-21
DOI: 10.3390/aerospace11080689
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 690: Enabling High-Power Conditioning and
High-Voltage Bus Integration Using Series-Connected DC Transformers in
Spacecrafts
Authors: Carlos Orts, Ausiàs Garrigós, David Marroquí, Antxon Arrizabalaga, Andreas Franke
First page: 690
Abstract: This article proposes a photovoltaic power processor for high-voltage and high-power distribution bus, between 300 V and 900 V, to be used in future space platforms like large space stations or lunar bases. Solar arrays with voltages higher than 100 V are not available for space application, being necessary to apply power conversion techniques. The idea behind this is to use series-connected zero-voltage and zero-current unregulated and isolated DC converters to achieve high bus voltage from the existing solar arrays. Bus regulation is then achieved through low-frequency hysteretic control. Topology description, semiconductor selection, design procedure, simulation and experimental validation, including tests in vacuum and partial pressures, are presented.
Citation: Aerospace
PubDate: 2024-08-21
DOI: 10.3390/aerospace11080690
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 691: Mental Workload as a Predictor of
ATCO’s Performance: Lessons Learnt from ATM Task-Related Experiments
Authors: Enrique Muñoz-de-Escalona, Maria Chiara Leva, José Juan Cañas
First page: 691
Abstract: Air Traffic Controllers’ (ATCos) mental workload is likely to remain the specific greatest functional limitation on the capacity of the Air Traffic Management (ATM) system. Developing computational models to monitor mental workload and task complexity is essential for enabling ATCOs and ATM systems to adapt to varying task demands. Most methodologies have computed task complexity based on basic parameters such as air-traffic density; however, literature research has shown that it also depends on many other factors. In this paper, we present a study in which we explored the possibility of predicting task complexity and performance through mental workload measurements of participants performing an ATM task in an air-traffic control simulator. Our findings suggest that mental workload measurements better predict poor performance and high task complexity peaks than other established factors. This underscores their potential for research into how different ATM factors affect task complexity. Understanding the role and the weight of these factors in the overall task complexity confronted by ATCos constitutes one of the biggest challenges currently faced by the ATM sphere and would significantly contribute to the safety of our sky.
Citation: Aerospace
PubDate: 2024-08-22
DOI: 10.3390/aerospace11080691
Issue No: Vol. 11, No. 8 (2024)
- Aerospace, Vol. 11, Pages 692: Mars Exploration: Research on Goal-Driven
Hierarchical DQN Autonomous Scene Exploration Algorithm
Authors: Zhiguo Zhou, Ying Chen, Jiabao Yu, Bowen Zu, Qian Wang, Xuehua Zhou, Junwei Duan
First page: 692
Abstract: In the non-deterministic, large-scale navigation environment under the Mars exploration mission, there is a large space for action and many environmental states. Traditional reinforcement learning algorithms that can only obtain rewards at target points and obstacles will encounter the problems of reward sparsity and dimension explosion, making the training speed too slow or even impossible. This work proposes a deep layered learning algorithm based on the goal-driven layered deep Q-network (GDH-DQN), which is more suitable for mobile robots to explore, navigate, and avoid obstacles without a map. The algorithm model is designed in two layers. The lower layer provides behavioral strategies to achieve short-term goals, and the upper layer provides selection strategies for multiple short-term goals. Use known position nodes as short-term goals to guide the mobile robot forward and achieve long-term obstacle avoidance goals. Hierarchical execution not only simplifies tasks but also effectively solves the problems of reward sparsity and dimensionality explosion. In addition, each layer of the algorithm integrates a Hindsight Experience Replay mechanism to improve performance, make full use of the goal-driven function of the node, and effectively avoid the possibility of misleading the agent by complex processes and reward function design blind spots. The agent adjusts the number of model layers according to the number of short-term goals, further improving the efficiency and adaptability of the algorithm. Experimental results show that, compared with the hierarchical DQN method, the navigation success rate of the GDH-DQN algorithm is significantly improved, and it is more suitable for unknown scenarios such as Mars exploration.
Citation: Aerospace
PubDate: 2024-08-22
DOI: 10.3390/aerospace11080692
Issue No: Vol. 11, No. 8 (2024)
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