Authors:Liu Jizhou, Li Ming, Yang Kaimin, Gao Lei Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. This paper investigates the influence of the fuselage arm cross-section shape on the aerodynamic and aeroacoustic performance of quadcopter Unmanned Aerial Vehicles in hover state by numerical simulation. The unsteady simulations of the flow field around one generic two-blade rotor and one fuselage arm are conducted by the Reynolds Averaged Navier-Stokes solver with the [math] SST turbulence model. The total thrust forces and the sound pressure level spectra of five fuselage arm cross-section shapes with the same cross-section area are simulated and compared. Results show that the fuselage arm with a square cross-section has the highest aerodynamic performances for all the tested speeds of rotation. The fuselage arm with a circular cross-section ranks second in aerodynamic performance. However, it has the best aeroacoustic performance. The other three tested cross-section shapes show less thrust forces and higher sound pressure levels at the blade passing frequencies than the circular cross-section, which are not optimal neither aerodynamically nor aeroacoustically. Citation: International Journal of Micro Air Vehicles PubDate: 2023-09-07T07:17:54Z DOI: 10.1177/17568293231200281 Issue No:Vol. 15 (2023)
Authors:Kejing Chen, Wei Meng, Jinhan Wang, Kun Liu, Zhenbo Lu Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. In order to solve the structural damage problem of the first generation of large multi-rotor manned drones, the present work has designed to study the structural vibration problems of multi-rotor drones. On a small multi-rotor drone, the laser vibration meter verified the reliability of acceleration sensor measurement of vibration and found that circular shape carbon fiber arms have strong damping abilities, with the strongest vibration in the Z-axis direction. To improve the design of the second generation of large multi-rotor manned drones, elliptical shape carbon fiber arms were employed instead of circular arms. Experiments showed that the main vibrations of the large multi-rotor manned drone’s arm are low-frequency vibrations below 200Hz, producing mainly torsional and bending modes, and the elliptical carbon fiber arms significantly reduce vibrations in the Z-axis direction. This study provides experimental data support for multi-rotor manned drones and further presents an improvement strategy for suppressing the vibrations of the multi-rotor manned drones. Citation: International Journal of Micro Air Vehicles PubDate: 2023-09-06T08:23:15Z DOI: 10.1177/17568293231199097 Issue No:Vol. 15 (2023)
Authors:Carl Runco, Moble Benedict Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. This paper discusses the development of a micro air vehicle scale quad-cyclocopter for the purpose of investigating cyclorotor application to low Reynolds number ([math]) flight. The 70-gram vehicle is the lightest quad-cyclocopter developed to date by an order of magnitude and only the second to achieve forward flight. It utilized two counter-rotating pairs of cyclorotors operating at [math] [math] to generate thrust and balance the reaction torque. Each cyclorotor had two control parameters, thrust direction and magnitude, giving the quad-cyclocopter eight independent control parameters. Flight tests were conducted to demonstrate several unique maneuvers made possible by the over-actuated system: changing pitch attitude in a point hover and forward translation via thrust vectoring. Data was collected for longitudinal maneuvers to compare forward flight performance when using strictly thrust vectoring for propulsion versus pitching without thrust vectoring. Similar performance was observed between the two modes for the achieved speeds. Citation: International Journal of Micro Air Vehicles PubDate: 2023-09-04T02:39:50Z DOI: 10.1177/17568293231189999 Issue No:Vol. 15 (2023)
Authors:Yuanfeng Shang, Chang Liu, Dawei Qiu, Zixu Zhao, Ruikang Wu, Shuyuan Tang Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. UAV (Unmanned Aerial Vehicle) black flight at low altitude could cause serious safety risks. Consequently, it is crucial to detect and manage low altitude small UAVs. The existing methods of low altitude small UAV detection suffer from problems such as high false alarm rate, and poor real-time performance. In order to solve the above problems, we present a novel approach, named AD-YOLOv5s, to achieve low altitude small UAV detection with high precision and high real-time performance. Firstly, the feature enhancement method is used to expand the dataset. We optimize the model feature fusion, the prediction head structure, and the loss function. Based on the CBAM (Convolutional Block Attention Module) attention mechanism, feature enhancement is performed to improve the detection accuracy. Secondly, the ghost module and depthwise separable convolution are used to reduce the number of parameters of the model, and we propose the method of lightweight design of model to improve the detection speed. Compared with the YOLOv5s model, the experiment result shows that our proposed AD-YOLOv5s model improves the value of mAP by 2.2% and the value of Recall by 1.8%, reduces the value of GFLOPs by 29.9% and parameters by 38.8%, and achieves 27.6 FPS when the proposed model deploy on a low-cost edge computing device (jetson nano). Citation: International Journal of Micro Air Vehicles PubDate: 2023-07-27T08:03:34Z DOI: 10.1177/17568293231190017 Issue No:Vol. 15 (2023)
Authors:Xin Fang, Jianghao Wu, Feng Du Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. A theoretical model is built to reveal the effect of the joint clearance on the kinematic performance of the transmission mechanism of a flapping wing micro aerial vehicle (FWMAV). Massless link approach is used to model the joint clearance and the reciprocal screw is introduced to solve the kinematic model. Finite element method simulations are also performed to validate the model. The kinematic model reveals that the inertia force of the transmission mechanism contributes little to the flapping motion whereas the sign of the resultant moment of aerodynamic drag and wing inertia force plays decisive role. Besides, the joint clearance can either increase or decrease the flapping angle of the wing during a flapping period and it will significantly affect the flapping amplitude while involves little in the mean flapping angle. The effects of the positions of the joint with clearance and its magnitude on the flapping motion are also revealed. Citation: International Journal of Micro Air Vehicles PubDate: 2023-06-08T06:13:20Z DOI: 10.1177/17568293231179945 Issue No:Vol. 15 (2023)
Authors:Thomas Roelandt, Dirk Vandepitte Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. Maneuverability of flapping wing fliers inevitably goes with inherent system instability. Inherent instability means that flapping wing systems require a flight controller and that these vehicles are prone to crashing. This work proposes a design feature to stabilize the descent of a flapping wing aerial vehicle. The vehicle is based on the KUlibrie, a flapping wing nano robot that is under development at KU Leuven. A computational study indicates that upwardly elevated wings provide inherently stable descending flight. The vehicle performs a free flight starting from different initial conditions. The system dynamics display convergence towards a limit cycle. Wing elevation and center of gravity position determine pitch and roll stiffness with respect to vertical descent and climb. The same effects that stabilize descent also destabilize climbing flight. Citation: International Journal of Micro Air Vehicles PubDate: 2023-06-01T06:00:47Z DOI: 10.1177/17568293231178263 Issue No:Vol. 15 (2023)
Authors:Qian Li Weng, Guan Jun Liu, Pei Zhou, Hao Ran Shi, Kai Wen Zhang Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. UAV application research has attracted more and more attention of researchers. However, in the field of UAV transportation, especially in the case of multi-UAV cooperation, there is little research or design on the overall system of multi-UAV cooperative transportation due to the complexity of the task and many factors need to be considered. In this paper, we first introduce a 2-UAV cooperative transportation task scenario and we call it Co-TS. Then according to the scenario, we design a task planning system, which describes the entire process of 2-UAV performing transportation tasks; in order to solve the design complexity of this UAV upper-layer software, we propose a model architecture of 2-UAV transportation application, design the functions of each module and analyze the relationship between modules in the model architecture; in addition, to realize the correct execution of the 2-UAV cooperative transportation task, the task execution is divided into four states which include preparation, rising, forwarding, and landing states, and the corresponding cooperative transportation control flow algorithm is designed for four states. Finally, we develop this system and conduct experiments. The quantitative and qualitative results demonstrate the effectiveness of our method. Citation: International Journal of Micro Air Vehicles PubDate: 2023-02-21T06:05:21Z DOI: 10.1177/17568293231158443 Issue No:Vol. 15 (2023)
Authors:Ze Wang, Jingang Qu, Pascal Morin Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. This article concerns airflow-based odometry for estimating MAV flight speed from airflow measurements provided by a set of thermal anemometers. Our approach relies on a Gated Recurrent Unit (GRU) based deep learning approach to extract deep features from noisy and turbulent measurement signals of triaxial thermal anemometers, in order to establish the underlying mapping between the airflow measurement and the flight speed. The proposed solution is validated on a multi-rotor MAV. The results show that the GRU-based model can effectively extract noise features and perform denoising, and compensate for induced velocity effects along the propellers’ rotation axis. As a consequence, robust prediction of the flight speed is performed, including during takeoff and landing that induce ground effects and strong variations of vertical airflow. Citation: International Journal of Micro Air Vehicles PubDate: 2023-01-13T06:53:39Z DOI: 10.1177/17568293221148385 Issue No:Vol. 15 (2023)
Authors:Erkan Caner Ozkat, Oguz Bektas, Michael Juul Nielsen, Anders la Cour-Harbo Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. Unmanned Aircraft Systems (UAS) has become widespread over the last decade in various commercial or personal applications such as entertainment, transportation, search and rescue. However, this emerging growth has led to new challenges mainly associated with unintentional incidents or accidents that can cause serious damage to civilians or disrupt manned aerial activities. Machine failure makes up almost 50% of the cause of accidents, with almost 40% of the failures caused in the propulsion systems. To prevent accidents related to mechanical failure, it is important to accurately estimate the Remaining Useful Life (RUL) of a UAS. This paper proposes a new method to estimate RUL using vibration data collected from a multi-rotor UAS. A novel feature called mean peak frequency, which is the average of peak frequencies obtained at each time instance, is proposed to assess degradation. The Long Short-Term Memory (LSTM) is employed to forecast the subsequent 5 mean peak frequency values using the last 7 computed values as input. If one of the estimated values exceeds the predefined 50 Hz threshold, the time from the estimation until the threshold is exceeded is calculated as the RUL. The estimated mean peak frequency values are compared with the actual values to analyze the success of the estimation. For the 1st, 2nd, and 3rd replications, RUL results are 4 s, 10 s, and 10 s, and root mean square error (RMSE) values are 3.7142 Hz, 1.4831 Hz, and 1.3455 Hz, respectively. Citation: International Journal of Micro Air Vehicles PubDate: 2023-01-12T06:40:54Z DOI: 10.1177/17568293221150171 Issue No:Vol. 15 (2023)
Authors:Simon Wilshin, Stephen Amos, Richard J Bomphrey Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. Here, we demonstrate obstacle and secondary drone avoidance capability by quadcopter drones that can perceive and react to modulation of their self-generated acoustic environment when in proximity to surfaces. A ground truth for the interpretation of self-noise was established by measuring the intrinsic, three-dimensional, acoustic signature of a drone in an anechoic chamber. This was used to design sensor arrangements and machine learning algorithms to estimate the position of external features, obstacles or another drone, within the environment. Our machine learning approach took short segments of recorded sound and their Fourier transforms, fed these into a convolutional neural network, and output the location of an obstacle or secondary drone in the environment. The convolutional layers were constructed with a suitable topology that matched the physical arrangement of the sensors. Our surface detection and avoidance algorithms were refined during tethered flight within an anechoic chamber, followed by an exercise in free flight without obstacle avoidance, and finally free flight obstacle detection and avoidance. Our acoustic sense-and-avoid capability extends to vertical and horizontal planar surfaces and tethered secondary drones. Citation: International Journal of Micro Air Vehicles PubDate: 2023-01-05T06:41:37Z DOI: 10.1177/17568293221148377 Issue No:Vol. 15 (2023)
Authors:Van Duc Nguyen, Viet Dung Duong, Minh Hoang Trinh, Hoang Quan Nguyen, Dang Thai Son Nguyen Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. Low order modelings are performed in this paper, including iterative Brinkman penalized vortex method (IBVM) and data-driven dynamic mode decomposition (DMD) for dynamic stall study of symmetric airfoil. The data are extracted from IBVM as input for flow field reconstruction using combinations of DMD dominant modes, representing extracted flow features. The primary mode together with its harmonics, and the mean mode are termed to be dominant for the airfoil wake duplication at fixed angles of attack ([math]) ranging from [math] to [math]. For the dynamic stall duplication, at small and large pitching amplitudes, the nearfield and farfield vorticty contours from the DMD generally agree well with those from the IBVM. In addition, the lift coefficient from the DMD collapses well with that from the IBVM and the experiment. Citation: International Journal of Micro Air Vehicles PubDate: 2023-01-04T07:15:04Z DOI: 10.1177/17568293221147923 Issue No:Vol. 15 (2023)
Authors:Gautier Hattenberger, Murat Bronz, Jean-Philippe Condomines Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. This paper focuses on the quadrotor drag coefficient model and its estimation from flight tests. Precise assessment of such a model permits the use of a quadrotor as a sensor for wind estimation purposes without the need for additional onboard sensors. Firstly, the drag coefficient has been estimated in a controlled environment via wind generator and motion capture system. Later, the evolution of the coefficient is observed for various mass and fuselage shapes. Finally, an estimation method is proposed, based on the least-squares optimization, that evaluates the drag of the quadrotor directly from outdoor flight data. The latter leads the methodology towards easier adoption in other researchers’ systems without the need for complex and expensive flight testing facilities. The accuracy of the proposed method is presented both in simulation, based on a realistic flight dynamics model, and also for real outdoor flights. Citation: International Journal of Micro Air Vehicles PubDate: 2023-01-03T11:24:04Z DOI: 10.1177/17568293221148378 Issue No:Vol. 15 (2023)
Authors:L Bergantin, C Coquet, J Dumon, A Negre, T Raharijaona, N Marchand, F Ruffier Abstract: International Journal of Micro Air Vehicles, Volume 15, Issue , January-December 2023. Estimating distance traveled is a frequently arising problem in robotic applications designed for use in environments where GPS is only intermittently or not at all available. In UAVs, the presence of weight and computational power constraints makes it necessary to develop odometric strategies based on minimilastic equipment. In this study, a hexarotor was made to perform up-and-down oscillatory movements while flying forward in order to test a self-scaled optic flow based odometer. The resulting self-oscillatory trajectory generated series of contractions and expansions in the optic flow vector field, from which the flight height of the hexarotor could be estimated using an Extended Kalman Filter. For the odometry, the downward translational optic flow was scaled by this current visually estimated flight height before being mathematically integrated to obtain the distance traveled. Here we present three strategies based on sensor fusion requiring no, precise or rough prior knowledge of the optic flow variations generated by the sinusoidal trajectory. The “rough prior knowledge” strategy is based on the shape and timing of the variations in the optic flow. Tests were performed first in a flight arena, where the hexarotor followed a circular trajectory while oscillating up and down over a distance of about [math] m under illuminances of [math] lux and [math] lux. Preliminary field tests were then performed, in which the hexarotor followed a longitudinal bouncing [math]-long trajectory over an irregular pattern of grass. Citation: International Journal of Micro Air Vehicles PubDate: 2023-01-03T11:10:54Z DOI: 10.1177/17568293221148380 Issue No:Vol. 15 (2023)
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