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Aerospace and Electronic Systems, IEEE Transactions on
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0018-9251
Published by IEEE Homepage  [191 journals]
  • IEEE Aerospace and Electronic Systems Society
    • Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • From the Editor-in-Chief
    • Pages: 2628 - 2628
      Abstract: Presents the introductory editoral for this issue of the publication.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Generalized Ambiguity Function for MIMO Radar Systems
    • Authors: Christos V. Ilioudis;Carmine Clemente;Ian K. Proudler;John Soraghan;
      Pages: 2629 - 2646
      Abstract: In this paper, a generalized signal model is presented to accommodate both narrowband and wideband signals in a multi-input multi-output (MIMO) sensor system scenarios. The derived model is then used to define a MIMO ambiguity function based on the Kullback-Leibler divergence. Moreover, the proposed formulation is parametrized using the signal and channel correlation matrices to account for different waveform and sensor placement designs, thereby allowing a flexible modeling approach. A comparison between the proposed definition and the more conventional approach of summing the squared matched filter outputs is presented for different sensors and waveforms configurations.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Design and Implementation of Distributed Path Planning Algorithm for a
           Fleet of UAVs
    • Authors: Adel Belkadi;Hernan Abaunza;Laurent Ciarletta;Pedro Castillo;Didier Theilliol;
      Pages: 2647 - 2657
      Abstract: This paper presents the development of a controller for a fleet of unmanned aerial vehicles based on a distributed path planning strategy under a multiagent systems framework. The issue, treated as an online optimization problem, is solved using a particle swarm optimization (PSO) algorithm. The proposal was validated in experiments, considering different scenarios like fixed and mobile targets, external disturbances, and the loss of an agent. The proposed PSO is implemented independently in each vehicle in order to determine, by minimizing a cost function, the best paths that ensure the fleet formation control, target tracking, and collision avoidance.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Detection–Localization Algorithms in the Around-the-Corner Radar
    • Authors: Khac-Phuc-Hung Thai;Olivier Rabaste;Jonathan Bosse;Dominique Poullin;Israel D. Hinostroza Sáenz;Thierry Letertre;Thierry Chonavel;
      Pages: 2658 - 2673
      Abstract: Detection and localization in urban environments is a very recent radar problem. In this paper, we investigate the possibility of detecting and locating targets not in direct line of sight (NLOS) areas with a single portable radar by exploiting multipath returns. We propose two algorithms, which handle the information provided by multipath returns in different ways to detect and estimate the NLOS target position. We also present an original method to select the number of paths to take into account in the algorithms in order to maximize detection probabilities. Numerical results show good efficiency of the proposed algorithms for problems of both detection and localization. We show that applying these algorithms improves detection performance compared to a classic matched filter in a typical urban scenario. Experimental results on a real dataset allow us to validate our multipath model in urban environments, and in particular to show that it is possible to retrieve the target location even with rough knowledge of the scene geometry.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Interplanetary Magnetic Attitude Control Based on an IMF Kalman filter in
           Small Spacecraft
    • Authors: Takaya Inamori;Satoshi Ikari;Takahiro Ito;Rei Kawashima;
      Pages: 2674 - 2686
      Abstract: Recently, a variety of small spacecraft have been launched and used for interplanetary missions. Conventionally, reaction wheels (RWs) and thrusters are used for these attitude control systems in almost all interplanetary spacecraft. While these actuators are promising for attitude control, the lifetime of the spacecraft mission is limited by the extra fuel needed for the thrusters. Moreover, it is difficult to install thrusters in all small spacecraft due to low reliability and strict limitations on mass and power consumption. To obtain both fuel-free and available attitude control for small spacecraft, this study proposes an interplanetary magnetic attitude control system including attitude stabilization and angular momentum unloading based on an interplanetary magnetic field (IMF) Kalman filter. In the proposed method, an electromagnetic coil interacting with the IMF is used for an attitude control system. To achieve the proposed method, the faint magnetic field must be detected. However, the IMF is too weak to sense using only on-board magnetic sensors. To deal with the technical issue, this study proposes a magnetic attitude control system with an unscented Kalman filter using gyro measurements and generated magnetic moment by the electromagnetic coil to estimate the weak magnetic field. With the estimated magnetic field vector, the spacecraft can achieve fuel-free attitude stabilization and RW unloading under the constraints. This proposed system does not require fuel for attitude control. Furthermore, the simple structure and electronic circuits of the electromagnetic coil allow the spacecraft to achieve a simple and reliable attitude control system. Numerical simulations demonstrate the effectiveness of the proposed attitude stabilization and RW unloading methods.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • DeepTarget: An Automatic Target Recognition Using Deep Convolutional
           Neural Networks
    • Authors: Nasser M. Nasrabadi;
      Pages: 2687 - 2697
      Abstract: Automatic target recognition (ATR) is an important part for many computer vision applications. Despite the extensive research which has been carried out in this area for many years, there is no ATR system which performs well on all applications. Recently, different object recognition frameworks have been proposed which yield a high performance in baseline databases. However, our experiments showed that they can fail in real-world scenarios, when dealing with a limited number of data samples. In this paper, we propose a new ATR system, based on deep convolutional neural network (DCNN), to detect the targets in forward looking infrared (FLIR) scenes and recognize their classes. In our proposed ATR framework, a fully convolutional network is trained to map the input FLIR imagery data to a fixed stride correspondingly-sized target score map. The potential targets are identified by applying a threshold on the target score map. Finally, the corresponding regions centered at these target points are fed to a DCNN to classify them into different target types while at the same time rejecting the false alarms. The proposed architecture achieves a significantly better performance in comparison with that of the state-of-the-art methods on two large FLIR image databases.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Simple-Structured Quaternion Estimator Separating Inertial and Magnetic
           Sensor Effects
    • Authors: Young Soo Suh;
      Pages: 2698 - 2706
      Abstract: This paper presents a new filter estimating quaternion using inertial and magnetic sensors. Using a reference coordinate system multiplicative quaternion error representation and a constrained structure filter gain, the proposed filter has a separation property, where the magnetic sensor output does not affect pitch and roll angle estimation. Furthermore, the proposed filter gain can be computed just from five scalar equations. Through simulation, the separation property of the proposed filter is verified.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Burst-Mode Synchronization for SOQPSK
    • Authors: Ehsan Hosseini;Erik Perrins;
      Pages: 2707 - 2718
      Abstract: We consider a comprehensive synchronization strategy for burst-mode transmission of shaped-offset quadrature phase-shift keying (SOQPSK) signals over the additive white Gaussian noise channel. Due to the similarities between SOQPSK and continuous phase modulation (CPM), we make use of recent results for synchronization of burst-mode CPMs. We first derive a training sequence that is optimal in the sense that it jointly minimizes the Cramér-Rao bounds (CRBs) for frequency offset, phase offset, and timing offset estimation. Additionally, we develop a maximum likelihood data-aided algorithm for joint estimation of the synchronization parameters for SOQPSK signals. We show that the proposed algorithm for the optimal training sequence can be adapted to work with the suboptimal training sequence that is being considered for use in burst-mode integrated network enhanced telemetry. This demonstrates an immediate practical application for our approach. We present numerical results on the mean-squared error performance of the proposed algorithm for both training sequences and for different versions of SOQPSK. The numerical results show that our joint estimation algorithm yields performance that is very close to the CRBs for all three synchronization variables. Finally, we compare the overall performance of our proposed training sequence and synchronization algorithm for different sequence lengths by simulating a burst-mode SOQPSK receiver. This allows us to employ the right training sequence length based on the desired complexity and bit error rate performance.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Efficient Estimation of Probability of Conflict Between Air Traffic Using
           Subset Simulation
    • Authors: Chinmaya Mishra;Simon Maskell;Siu-Kui Au;Jason F. Ralph;
      Pages: 2719 - 2742
      Abstract: This paper presents an efficient method for estimating the probability of conflict between air traffic within a block of airspace. Autonomous sense-and-avoid is an essential safety feature to enable unmanned air systems to operate alongside other (manned or unmanned) air traffic. The ability to estimate the probability of conflict between traffic is an essential part of sense-and-avoid. Such probabilities are typically very low. Evaluating low probabilities using naive direct Monte Carlo generates a significant computational load. This paper applies a technique called subset simulation. The small failure probabilities are computed as a product of larger conditional failure probabilities, reducing the computational load while improving the accuracy of the probability estimates. The reduction in the number of samples required can be one or more orders of magnitude. The utility of the approach is demonstrated by modeling a series of conflicting and potentially conflicting scenarios based on the standard Rules of the Air.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Adaptive Fault-Tolerant Control for HSV With Unknown Control Direction
    • Authors: Binyan Xu;Ruiyun Qi;Bin Jiang;
      Pages: 2743 - 2758
      Abstract: This paper proposes an adaptive antiwindup fault-tolerant control system for a hypersonic vehicle with parametric uncertainties. Not only the loss-of-effectiveness and stuck-type elevator fault, but also the reverse-type fault causing the uncertainty of control direction is considered. The fault-tolerant controller designed through feedback linearization is combined with an online parameter estimator and a Nussbaum gain function, so that the uncertainties can be estimated adaptively. An antiwindup compensator is introduced to the control system to handle the input constraints.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Fusion of Finite-Set Distributions: Pointwise Consistency and Global
    • Authors: Murat Üney;Jérémie Houssineau;Emmanuel Delande;Simon J. Julier;Daniel E. Clark;
      Pages: 2759 - 2773
      Abstract: A recent trend in distributed multisensor fusion is to use random finite-set filters at the sensor nodes and fuse the filtered distributions algorithmically using their exponential mixture densities (EMDs). Fusion algorithms that extend covariance intersection and consensus-based approaches are such examples. In this paper, we analyze the variational principle underlying EMDs and show that the EMDs of finite-set distributions do not necessarily lead to consistent fusion of cardinality distributions. Indeed, we demonstrate that these inconsistencies may occur with overwhelming probability in practice, through examples with Bernoulli, Poisson, and independent identically distributed cluster processes. We prove that pointwise consistency of EMDs does not imply consistency in global cardinality and vice versa. Then, we redefine the variational problems underlying fusion and provide iterative solutions thereby establishing a framework that guarantees cardinality consistent fusion.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Efficient Channel Estimation for Aerial Wireless Communications
    • Authors: Dennis Ogbe;David J. Love;Matthew Rebholz;T. Patrick Bidigare;
      Pages: 2774 - 2785
      Abstract: We present a technique to jointly estimate the channel taps and the frequency offset due to the Doppler effect of a special class of doubly dispersive aeronautical channels. The algorithm includes the use of pulse repetition techniques at the transmitter and the “power method” subspace iteration at the receiver. We show that transmitting constant-amplitude zero-autocorrelation sequences for channel sounding yields estimators with low computational complexity. Numerical simulations indicate performance comparable to the estimation-theoretic lower bound.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Estimation for a Thrusting/Ballistic Object With Mass Ejection From a
           Single Fixed Passive Sensor With Delayed Acquisition
    • Authors: Kaipei Yang;Qin Lu;Yaakov Bar-Shalom;Peter Willett;Ziv Freund;Ronen Ben-Dov;Benny Milgrom;
      Pages: 2786 - 2795
      Abstract: The trajectory estimation problem of a thrusting/ballistic object in three-dimensional (3-D) space has been previously solved with 2-D measurements (azimuth and elevation angles from a fixed passive sensor, either starting from the launch time or with a delayed acquisition) under the assumption of constant mass. However, since the mass decreases as the fuel burns, this should be accounted for. This paper investigates several approaches with different parameter vectors to solve the trajectory estimation and impact point prediction (IPP) with measurements starting after the launch time, i.e., delayed acquisition for both constant mass motion model and mass ejection motion model. For the mass ejection motion model, the mass ejection rate is an extra component of the parameter vector to be estimated. The invertibility of the Fisher information matrix (FIM) of the parameter vectors is also used to confirm the observability (estimability) of the system. The Cramer-Rao lower bound (CRLB) is the inverse of the FIM if it is invertible. The CRLB of the IPP is also derived. We develop the maximum likelihood estimator of the considered motion parameter vectors. Performance comparison between the models considered is given and the statistical efficiency of the best model is confirmed via simulation results.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Mission Analysis for Vesta and Ceres Exploration Using Electric Sail With
           Classical and Advanced Thrust Models
    • Authors: Mingying Huo;Shilei Cao;Yanfang Liu;He Liao;Naiming Qi;
      Pages: 2796 - 2804
      Abstract: The electric sail is an innovative concept for spacecraft propulsion, which can generate continuous thrust without propellant by reflecting solar wind ions. In previous studies, the thrust of an electric sail is described by a classical model that neglects the effects of the electric sail attitude on the propulsive thrust modulus and direction. This paper reappraised the performance of the electric sail in the Vesta and Ceres exploration mission with an advanced thrust model that considers the effect of the spacecraft attitude on both the thrust modulus and direction. By using a hybrid optimization method, the trajectory optimization of the electric-sail-based spacecraft from earth to Vesta and Ceres is implemented in an optimization framework. Numerical results show that the minimal flight time with the advanced thrust model is longer than that with the classical model. The difference in performance between the classical and advanced models is attributable to overestimation of the maximum thrust cone angle and the thrust modulus by the classical model.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • On the Tradeoffs Between Coverage Radius, Altitude, and Beamwidth for
           Practical UAV Deployments
    • Authors: Haneya Naeem Qureshi;Ali Imran;
      Pages: 2805 - 2821
      Abstract: Current studies on unmanned aerial vehicle (UAV) based cellular deployment consider UAVs as aerial base stations for air-to-ground communication. However, they analyze UAV coverage radius and altitude interplay while omitting or over-simplifying an important aspect of UAV deployment, i.e., effect of a realistic antenna pattern. This paper addresses the UAV deployment problem while using a realistic three-dimensional directional antenna model. New tradeoffs between UAV design space dimensions are revealed and analyzed in different scenarios. The sensitivity of coverage area to both antenna beamwidth and height is compared. The analysis is extended to multiple UAVs and a new packing scheme is proposed for multiple UAVs coverage that offers several advantages compared to prior approaches.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Zigzag-Division Multiple Access for Wireless Networks With Long and
           Heterogeneous Delays
    • Authors: Mingjun Dai;Bailu Mao;Xueqing Gong;Chi Wan Sung;Weihua Zhuang;Xiaohui Lin;
      Pages: 2822 - 2835
      Abstract: A new random channel access framework, named as zigzag-division multiple access (ZDMA), is proposed for wireless networks with long and heterogeneous propagation delays to achieve system throughput significantly larger than 1. The key idea is to allow simultaneous transmissions at the transmitters and employ zigzag decoding at the receiver. After studying the zigzag decoding, we present three new random access protocols. Extensive numerical studies show that incorporating ZDMA in existing slotted Aloha and tree splitting protocols can significantly increase system throughput. The third protocol of greedy scheduling with ZDMA achieves the highest throughput performance.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Autonomous Surface Vehicle Multistep Look-Ahead Measurement Location
           Planning for Optimal Localization of Underwater Acoustic Transponders
    • Authors: Jesse R. Garcia;Jay A. Farrell;Zaher M. Kassas;Michael T. Ouimet;
      Pages: 2836 - 2849
      Abstract: An underwater vehicle may utilize underwater transponders (UTs) for navigation in the absence of global navigation satellite system signals. However, the position of each UT must be known by the underwater vehicle. The problem of an autonomous surface vehicle (ASV) optimally planning measurement locations to localize a set of arbitrarily predeployed acoustic UTs is considered. The ASV is assumed to make noisy range measurements to the UTs. A maximum a posteriori estimator is derived to localize the UTs. In addition, a multistep look-ahead (MSLA) ASV optimal measurement location planning (OMLP) strategy is developed. This planning strategy prescribes future multistep measurement locations. A physical interpretation of the proposed planner in the single-step, single transponder case is provided. Simulation results are presented demonstrating the tradeoff between expected localization performance and computational time associated with various look-ahead horizons and travel distances. Experimental results are given illustrating the proposed MSLA OMLP strategy's performance in environments containing one and two UTs. The proposed OMLP strategy is able to localize UTs to within 4 m of their true locations. Additionally, increasing the planning horizon is demonstrated to yield better UT localization at the cost of increased computational burden.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Higher-Order Implementations of Polyphase-Coded FM Radar Waveforms
    • Authors: Peng Seng Tan;John Jakabosky;James M. Stiles;Shannon David Blunt;
      Pages: 2850 - 2870
      Abstract: The recently developed polyphase-coded FM implementation for physical radar waveforms is generalized to higher-order representations to facilitate greater design freedom (with MATLAB scripts provided in the appendix). Being FM, waveforms realized with these implementations have the benefit of being readily amenable to a high-power radar transmitter while possessing parameterized structures that are advantageous for optimization. Here various attributes of these implementations are examined. Specifically, it is shown that higher-order representations can, in special cases, be made equivalent, and through these relationships appropriate signal structure attributes can be inferred. Higher-order coding guidelines are also derived based on the need to ensure spectral containment. Example waveforms are optimized for each particular implementation to highlight their individual properties, towards the ultimate goal of establishing new ways to realize waveform-diverse emission structures that are physically realizable.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • A Damped Oscillation Model for Tracking Near Space Hypersonic Gliding
    • Authors: Fan Li;Jiajun Xiong;Zhiguo Qu;Xuhui Lan;
      Pages: 2871 - 2890
      Abstract: Maneuver models are dedicated to accurate representation of unknown motion pattern. However, for near space hypersonic jump gliding targets of high speed, diverse movement pattern, and mobility, the conventional maneuver models are difficult to describe the complex movement characteristics, and then leading to high and unstable tracking error. In order to solve this problem, a new model is proposed based on the attenuation of oscillation function. The core of the model is to consider the target acceleration as a zero mean random process with attenuation oscillation. With the model, the equations of the maneuvering target are constructed and the system dynamic error of this model was deduced taking Kalman filter as the filtering algorithm. Moreover, the corresponding relations among parameters are discussed, and an adaptive method is proposed for setting parameters appropriately in the situations when a priori information is unknown. In this way, the parameters can be adjusted online through jumping point identification. Theoretical analysis and simulation experiments are conducted to demonstrate the effectiveness of the proposed model. Comparing to commonly used models, it shows lower filtering errors tracking near space hypersonic jump gliding targets. Finally, the rationality and validity of the parameters adaptive method are explained.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Design of Low-Sidelobe Phase-Coded Waveforms
    • Authors: Peter J. Kajenski;
      Pages: 2891 - 2898
      Abstract: A method for using interior point methods for generating phase-coded waveforms that have low autocorrelation sidelobes is described. The procedure is capable of generating polyphase Barker codes as well as non-Barke sequences that have comparatively low sidelobes. An analysis of the estimated number of possible polyphase Barker codes is presented.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Design Algorithm of an Aircraft Power Generation System
    • Authors: Flur Rashitovich Ismagilov;Mikhail Anatolyevich Kiselev;Viacheslav Evgenievich Vavilov;Denis Valerievich Gusakov;
      Pages: 2899 - 2910
      Abstract: The paper deals with the design and testing of a power generation system for the future and existing aircrafts. A new design algorithm of the power generation components is presented. The proposed design algorithm was tested on a prototype: a full-size starter-generator and transformer-rectifier unit prototype was created with a transformer magnetic core made up of an amorphous magnetic material. Its stand tests were carried out both for each element and for the entire system. The proposed algorithm can be used to create power supply systems for aircraft with different voltage levels, including 270 Vdc and 200 Vac. The developed power generation system turned out to be 25-40% better than serial solutions by mass and efficiency.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • A Fractional Nonlinear PI-Structure Control for Robust Attitude Tracking
           of Quadrotors
    • Authors: Fátima Oliva-Palomo;Aldo Jonathan Muñoz-Vázquez;Anand Sánchez-Orta;Vicente Parra-Vega;Carlos Izaguirre-Espinosa;Pedro Castillo;
      Pages: 2911 - 2920
      Abstract: A robust attitude quadrotor control based on a novel fractional order PI nonlinear structure is proposed and experimentally validated. The proportional action depends on a nonlinear transformation of the sliding variable, while the integral action of fractional order rejects nondifferentiable disturbances, such as turbulent effects and gust winds, enforcing a sliding motion in finite time. The exponential convergence of a quaternion-based error is guaranteed for well-posed attitude tracking, and the regularity of the control signal can be adjusted with respect to the fractional order. Notably, the proposal includes, as particular cases, first-order and second-order sliding mode control schemes. Experiments illustrate the viability of the proposal, and a comparative study versus PD, PI-like, first-order sliding mode and second-order sliding mode supertwisting controllers is presented and discussed.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Distributed Mode Selection for FDD Communication in Multihop Wireless
    • Authors: Moein Parsinia;Qidi Peng;Sunil Kumar;
      Pages: 2921 - 2937
      Abstract: We consider a decentralized, multihop wireless network consisting of frequency division duplex (FDD) nodes, which use separate frequency bands for transmission and reception. The use of FDD communication in a multihop wireless network partitions the nodes in two operating modes (or genders), depending on the frequency bands used for the transmission and reception. Since the FDD nodes of the same gender, located in a one-hop neighborhood, cannot communicate with each other, it can limit the availability of communication links between the neighboring nodes and also lead to network partitioning. Therefore, the operating mode of these nodes should be selected such that every node can establish links with its one-hop neighbors. We model the multihop network as a graph and design a novel, distributed bipartite graph coloring scheme, for mode selection of FDD nodes. Unlike the existing graph coloring schemes, which use the entire network topology and yet do not ensure network connectivity, our algorithm requires only the local information of one-hop neighborhood of each node in a distributed manner. The simulation results show that our mode selection algorithm ensures that every FDD node can establish the communication links with approximately half of its one-hop neighbors for omni as well as directional communication, without introducing any disconnected node. This mode selection algorithm also has a lower computational complexity and provides a robust network connectivity, which would help in fault tolerance and establishing stable routes in the network.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Fuzzy-Logic-Based Fixed-Time Geometric Backstepping Control on SO(3) For
           Spacecraft Attitude Tracking
    • Authors: Yulin Wang;Shengjing Tang;Jie Guo;Xiao Wang;Chao Liu;
      Pages: 2938 - 2950
      Abstract: This paper addresses the fuzzy-logic-based fixed-time geometric backstepping attitude tracking for the rigid-body spacecraft modeled on the nonlinear differential manifold three-dimensional special orthogonal group [SO(3)]. The fixed-time geometric controller is deduced by the backstepping method. Moreover, an adaptive fuzzy logic system is employed to compensate the unknown disturbances. The almost globally fixed-time stabilization of the closed-loop system is verified via Lyapunov analysis. Simulation results demonstrate the effectiveness of the proposed controller.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Multi-Needle Langmuir Probe System for Electron Density Measurements and
           Active Spacecraft Potential Control on CubeSats
    • Authors: Tore André Bekkeng;Espen Sørlie Helgeby;Arne Pedersen;Espen Trondsen;Torfinn Lindem;Jøran Idar Moen;
      Pages: 2951 - 2964
      Abstract: In this paper, we present the CubeSat version of a scientific instrument called the multi-Needle Langmuir Probe (m-NLP). The m-NLP instrument measures the electron density in the ionosphere with kHz sampling rate, yielding meter scale resolution on low Earth orbit satellites. The sounding rocket version of m-NLP has flight heritage from nine sounding rockets. However, to get an in-orbit demonstration of the system a CubeSat implementation has been developed. The m-NLP measurement principle is based on several fixed bias probes, where each probe has to be biased above the spacecraft potential. To ensure that this requirement is fulfilled, the CubeSat version of the m-NLP will feature a new miniaturized thermionic electron emitter, which can actively control the potential of the satellite. The emitter is designed to accommodate the low size, weight, and power challenges of the CubeSat platform. Together with the in-flight determination of the spacecraft floating potential, it can autonomously control the potential of the spacecraft by emitting electrons. Preliminary, test results from the plasma chamber at the European Space and Technology Center in Holland are shown, verifying that a miniaturized electron emitter is able to actively control the floating potential of the spacecraft and, hence, improve the accuracy of the electron density measurements.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Measurement Extraction for Two Closely-Spaced Objects Using an Imaging
    • Authors: Qin Lu;Yaakov Bar-Shalom;Peter Willett;Francesco A. N. Palmieri;Ronen Ben-Dov;Benny Milgrom;
      Pages: 2965 - 2977
      Abstract: This paper considers measurement extraction for two closely-spaced objects with unknown equal intensities in an imaging sensor's focal plane array (FPA). Given a screen of FPA data, the first part of the measurement extractor, target location estimator, can extract the location estimates for two targets or one, with the corresponding accuracy given by the Cramér Rao lower bound (CRLB). The second part of the measurement extractor, target detector, selects among the hypotheses of two resolved targets and a single one using information-theoretic criteria and hypothesis tests. Simulation results have been conducted to evaluate the measurement extraction performance including the probability of resolving the two hypotheses, and the efficiency and unbiasedness of the target location estimates for the selected hypothesis using different hypothesis detection schemes. The generalized likelihood ratio test (GLRT) based on linearized observation model using second order Taylor series expansion is most appealing as it provides an explicit expression of the probability of detecting two targets as a function of the target separations, the signal-to-noise ratio at a given false resolution probability. It is shown that the simulation-based resolution performance for the GLRT using the estimated center location of the two targets matches well with the analytic performance assuming known center.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Multistatic Doppler Estimation Using Global Positioning System Passive
           Coherent Location
    • Authors: Sean A. Kaiser;Andrew J. Christianson;Ram M. Narayanan;
      Pages: 2978 - 2991
      Abstract: In previous works, methods were explored for position estimation utilizing satellite-borne signals of opportunity, mainly the global positioning system (GPS). The GPS signal was exploited for use in a multistatic passive coherent location (PCL) system. The GPS signal is especially attractive for PCL applications because of the native capability to produce position and velocity estimation. This paper examines the signal specifications for PCL implementation and explores the potential limitations of the proposed solutions. GPS specific methods are developed for multistatic PCL velocity estimation in a three-dimensional plane. The method developed is combined with previously completed work of GPS PCL position estimation for a complete system design in range and Doppler. The PCL system is evaluated against conventional GPS position estimation and velocity estimation and proves to have comparable metrics of performance. Analysis and simulation are performed for verification and validation of the developed methods.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Homodyned-K Distribution With Additive Gaussian Noise
    • Authors: Mark S. Haynes;
      Pages: 2992 - 3002
      Abstract: The homodyned-K (HK) distribution is a three-parameter density function used to study mixed-species radar and ultrasound scattering phenomena. We analyze the distribution that results from corrupting the HK with additive Gaussian noise (HKN). This modification enables analytic study of the HK in the presence of system thermal noise in radar and ultrasound systems. The moments of intensity of the HKN are derived and a new moment method parameter estimation algorithm is tested in simulation.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Fault-Tolerant Control of Singularly Perturbed Systems With Applications
           to Hypersonic Vehicles
    • Authors: Wenjing Ren;Bin Jiang;Hao Yang;
      Pages: 3003 - 3015
      Abstract: This paper studies a fault-tolerant control problem of singularly perturbed systems with faults and disturbances. The original faulty system is decomposed into a reduced subsystem and a boundary-layer subsystem. Then, a composite fault-tolerant controller is designed with one part dealing with the reduced subsystem and the other dealing with the boundary-layer subsystem. Through regulating the two parts of the controller, the original faulty system is input-to-state stable with respect to disturbances when the perturbation parameter is small enough. An application to the longitudinal control system of a hypersonic vehicle is given at last. Its singularly perturbed model is derived and a composite fault-tolerant controller is designed to illustrate the effectiveness of the proposed method.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Cooperative Aerial–Ground Vehicle Route Planning With Fuel Constraints
           for Coverage Applications
    • Authors: Parikshit Maini;Kaarthik Sundar;Mandeep Singh;Sivakumar Rathinam;P. B. Sujit;
      Pages: 3016 - 3028
      Abstract: Low-cost unmanned aerial vehicles (UAVs) need multiple refuels to accomplish large area coverage. We propose the use of a mobile ground vehicle (GV), constrained to travel on a given road network, as a refueling station for the UAV. Determining optimal routes for a UAV and GV, and selecting rendezvous locations for refueling to minimize coverage time is NP-hard. We develop a two-stage strategy for coupled route planning for UAV and GV to perform a coverage mission. The first-stage computes refueling sites that ensure reachability of all points of interest by the UAV and feasible routes for both the UAV and GV. In the second stage, mixed-integer linear programming (MILP) based exact methods are developed to plan optimal routes for the UAV and GV. As the problem is NP-Hard, we also develop computationally efficient heuristics that can find good feasible solutions within a given time limit. Extensive simulations are conducted to corroborate the effectiveness of the developed approaches. Field experiments are also performed to verify the performance of the UAV-GV solution.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • A 16-Element 2.4-GHz Multibeam Array Receiver Using 2-D Spatially Bandpass
           Digital Filters
    • Authors: Sravan Kumar Pulipati;Viduneth Ariyarathna;Arjuna Madanayake;Ravi Tharaka Wijesekara;Chamira U. S. Edussooriya;Len T. Bruton;
      Pages: 3029 - 3038
      Abstract: This paper presents the design, implementation, and the experimental verifications of a 2.4-GHz multibeam array receiver based on two-dimensional (2-D) spatially bandpass (SBP) digital plane wave (PW) filters. The digital array receiver consists of 2.4-GHz 16-element uniform linear array, and quadrature sampling is employed to process the broadband PWs at the baseband. Both 2-D finite impulse response (FIR) and infinite impulse response (IIR) digital filters having multiple trapezoidal-shaped passbands are employed as the 2-D SBP digital PW filters. Both 2-D FIR and IIR trapezoidal filters are implemented on a Xilinx Virtex 6 sx475t field programmable gate array chip that comes with the reconfigurable open architecture computing hardware version-2 (ROACH-2) platform. The 16 in-phase and quadrature-phase downconverted signals are sampled using the ROACH-2 platform and are processed using the digital architectures to form multiple beams. Example radio-frequency beam patterns corresponding to each filter architecture are measured and reported. The main lobes of the measured multibeam patterns are well aligned with the simulated multibeam patterns.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Smooth Interpolation-Based Fixed-Final-Time Command Generation
    • Authors: Haichao Hong;Arnab Maity;Florian Holzapfel;Shengjing Tang;Mengmeng Wang;
      Pages: 3039 - 3049
      Abstract: This paper proposes a command generation approach based on the smooth interpolation without twist constraints and the input-output relation developed by the generalized model predictive static programming. Commands are efficiently generated to achieve the desired terminal condition at a specified final time in an interpolative manner featuring a noniterative nature. The effectiveness of this approach is demonstrated through three different simulation studies including a double integrator benchmark, a soft lunar landing problem, and a cluster missile guidance problem.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Helmholtz Cage Design and Validation for Nanosatellites HWIL Testing
    • Authors: Rodrigo Cardoso da Silva;Igor Seiiti Kinoshita Ishioka;Chantal Cappelletti;Simone Battistini;Renato Alves Borges;
      Pages: 3050 - 3061
      Abstract: This paper deals with the design, realization, and testing of an earth magnetic field simulator, which allows us to validate hardware-in-the-loop algorithms, as well as to test new actuators. The design is driven by typical small satellites functional requirements. The subsystems that compose the simulator are described in detail. The validation of the simulator is performed by assessing its functioning, the uniformity of the recreated magnetic field, and the functionality of a magnetorquer.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Heterogeneous Track-to-Track Fusion in 3-D Using IRST Sensor and Air MTI
    • Authors: Mahendra Mallick;Kuo-Chu Chang;Sanjeev Arulampalam;Yanjun Yan;
      Pages: 3062 - 3079
      Abstract: Only a few publications exist at present on heterogeneous track-to-track fusion (T2TF). A common limitation of the current work on heterogeneous T2TF is that the cross covariance due to common process noise cannot be computed. This is due to the fact that two local trackers use different dynamic models, and hence, it is difficult to account for the common process noise. We consider a heterogeneous T2TF problem in three dimension (3-D) using a passive infrared search and track (IRST) sensor and an active air moving target indicator (AMTI) radar with the nearly constant velocity motion of the target. The active AMTI tracker uses the Cartesian state vector with 3-D position and velocity, and the dynamic model is linear. A passive IRST tracker commonly uses modified spherical coordinates (MSCs) for the state vector, where the dynamic model is nonlinear. In this formulation, the common process noise is explicitly modeled in both dynamic models. Therefore, it is possible to take into account the common process noise. We use the cubature Kalman filter (CKF) in both trackers due to its numerical stability and improved state estimation accuracy over existing nonlinear filters. The passive tracker uses a range-parameterized MSC-based CKF, and the active tracker uses a Cartesian CKF. We perform T2TF using the information filter (IF), where each local tracker sends its information matrix and the corresponding information state estimate to the fusion center. The IF handles the common process noise in an approximate way. Results from Monte Carlo simulations show that the accuracy of the proposed IF-based T2TF is close to that of the centralized fusion with varying levels of process noise and communication data rate.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Improved Multiple Hypothesis Tracker for Joint Multiple Target Tracking
           and Feature Extraction
    • Authors: Le Zheng;Xiaodong Wang;
      Pages: 3080 - 3089
      Abstract: Feature-aided tracking can often yield improved tracking performance over the standard multiple target tracking (MTT) algorithms. However, in many applications, the feature signal of the targets consists of sparse Fourier-domain signals. It changes quickly and nonlinearly in the time domain, and the feature measurements are corrupted by missed detections and misassociations. In this paper, we develop a feature-aided multiple hypothesis tracker for joint MTT and feature extraction in dense target environments. We use the atomic norm constraint to formulate the sparsity of feature signal and use the ℓ1-norm to formulate the sparsity of the corruption induced by misassociations. Based on the sparse representation, the feature signal are estimated by solving a semidefinite program. With the estimated feature signal, refiltering is performed to estimate the kinematic states of the targets, where the association makes use of both kinematic and feature information. Simulation results are presented to illustrate the performance of the proposed algorithm.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Batch Compressive Sensing for Passive Radar Range-Doppler Map Generation
    • Authors: Weike Feng;Jean-Michel Friedt;Grigory Cherniak;Motoyuki Sato;
      Pages: 3090 - 3102
      Abstract: By exploiting the sparsity of the scene containing only a few moving targets, a high-resolution and real-time range-Doppler map generation algorithm for passive bistatic radar is proposed. The proposed algorithm divides the long integration time into multiple short batches, from which a few batches are randomly selected on the basis of compressive sensing theory. A one-dimensional cross correlation is performed for each selected batch to obtain the range-compressed profile. Mean-value subtraction is then performed to suppress the direct path interference and stationary target reflections. Finally, an extended orthogonal matching pursuit algorithm is proposed for the effective estimation of target Doppler frequency. Practical application of this novel algorithm is examined by the detection of airplanes and ships via two synchronized general-purpose software-defined radio receivers. The results show that the proposed algorithm can achieve an improved resolution and a reduced sidelobe level compared to the conventional algorithms.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Angular Superresol for Signal Model in Coherent Scanning Radars
    • Authors: Yueli Li;Jianguo Liu;Xiaoqing Jiang;Xiaotao Huang;
      Pages: 3103 - 3116
      Abstract: Noncoherent signal models are widely applied to angular superresolution in forward-looking imaging radars. However, the relative phase influences the resolvability of the model in coherent applications. We reveal the reason why phase shifts affect deconvolution and propose a coherent signal model by replacing the antenna power pattern with the radiation pattern. REGU, TSVD, and IAA are utilized in numerical tests and simulations. Experimental results have demonstrated significant resolution improvements for forward-looking imaging in coherent scanning radars.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Fast Acquisition of Spread Spectrum Signals Using Multiple GPUs
    • Authors: Ying Liu;Hongyuan Cui;Renliang Zhao;
      Pages: 3117 - 3125
      Abstract: Spread spectrum (SS) signal acquisition in satellite communication is a very computation intensive technique, which hinders the development of real-time spread spectrum signal acquisition. In this paper, in order to achieve real-time acquisition, we propose a multi-GPU based SS signal acquisition algorithm. First, sliding correlation, the computation kernel, is formulated and efficiently parallelized by CUDA. Second, a CUDA-enabled SS signal acquisition algorithm is implemented by adopting the CUDA-enabled sliding correlation. Third, a multi-GPU based algorithm is implemented by using multi-GPU programming. The performance is evaluated in a real SS telemetry system. Real-time acquisition is achieved in all cases by using a single K40 GPU. Furthermore, an average of 374.7× speedup (max 473×) in 6 datasets is achieved when using four K40 GPUs. Good scalability is observed when varying the parameters.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Human Path-Planning for Autonomous Spacecraft Guidance at Binary Asteroids
    • Authors: Davide Guzzetti;Hexi Baoyin;
      Pages: 3126 - 3138
      Abstract: Rather than using baseline-oriented approaches, autonomous spacecraft trajectory planning within asteroid systems may be based on human behavior that is learned by demonstration. In this paper, we conducted a numerical experiment to observe a human agent steering in real-time spacecraft motion within simulated binary asteroid environments. The resulting collection of human-planned trajectories demonstrates effective guidance mechanisms and reveals underlying path-planning processes that may serve for more agile and autonomous asteroid exploration.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Robust Adaptive Beamforming via Simplified Interference Power Estimation
    • Authors: Zhi Zheng;Tong Yang;Wen-Qin Wang;Hing Cheung So;
      Pages: 3139 - 3152
      Abstract: Adaptive beamformer is very sensitive to model mismatch, especially when the signal-of-interest is present in the training data. In this paper, we focus on the topic of robust adaptive beamforming (RAB) based on interference-plus-noise covariance matrix (INCM) reconstruction. First, we analyze the effectiveness of several INCM reconstruction schemes, and particularly analyze the impacts of interference power estimation on RAB. Second, according to the analysis results, we develop a simplified algorithm to estimate the interference powers, and a RAB algorithm based on INCM reconstruction is then presented. Compared with some existing methods, the proposed algorithm simplifies the interference power estimation of INCM reconstruction. Aligned with our analysis, simulation results demonstrate that the overestimation of interference powers hardly degrades the performance of adaptive beamforming, and our proposed algorithm achieves nearly optimal performance across a wide range of signal-to-noise ratios.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Linear- and Linear-Matrix-Inequality-Constrained State Estimation for
           Nonlinear Systems
    • Authors: Robin Aucoin;Stephen Alexander Chee;James Richard Forbes;
      Pages: 3153 - 3167
      Abstract: This paper considers nonlinear state estimation subject to inequality constraints in the form of linear and linear-matrix inequalities. Rewriting the standard maximum likelihood objective function used to derive the Kalman filter allows the Kalman gain to be found by solving a constrained optimization problem with a linear objective function subject to a linear-matrix-inequality constraint. Additional constraints, such as weighted-norm- or linear-inequality constraints, that the state estimate must satisfy are easily augmented to the constrained optimization problem. The proposed constrained estimation methodology is applied in the extended Kalman filter (EKF) and sigma point Kalman filter (SPKF) frameworks. Motivated by estimation problems involving a vehicle that can rotate and translate in space, multiplicative versions of the constrained EKF and SPKF formulations are discussed. Simulation results for a ground-based mobile robot operating in a constrained three-dimensional terrain are presented and are compared to results that use the traditional multiplicative EKF and SPKF, as well as filters that enforce inequality constraints by simply projecting the state estimate into the constrained domain along the shortest Euclidean distance.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Novel Classification Algorithm for Ballistic Target Based on HRRP Frame
    • Authors: Adriano Rosario Persico;Christos V. Ilioudis;Carmine Clemente;John J. Soraghan;
      Pages: 3168 - 3189
      Abstract: Nowadays, the identification of ballistic missile warheads in a cloud of decoys and debris is essential for defense systems in order to optimize the use of ammunition resources, avoiding to run out of all the available interceptors in vain. This paper introduces a novel solution for the classification of ballistic targets based on the computation of the inverse Radon transform of the target signatures, represented by a high-resolution range profile frame acquired within an entire period of the main rotation of the target. Namely, the precession for warheads and the tumbling for decoys are taken into account. The pseudo-Zernike moments of the resulting transformation are evaluated as the final feature vector for the classifier. The extracted features guarantee robustness against target's dimensions and rotation velocity, and the initial phase of the target's motion. The classification results on simulated data are shown for different polarizations of the electromagnetic radar waveform and for various operational conditions, confirming the validity of the algorithm.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Fast Range and Motion Parameters Estimation for Maneuvering Targets Using
           Time-Reversal Process
    • Authors: Maozhong Fu;Yixiong Zhang;Risheng Wu;Zhenmiao Deng;Yunjian Zhang;Xiangyu Xiong;
      Pages: 3190 - 3206
      Abstract: For maneuvering targets, their motion during long observing time will deteriorate the integration results and degrade the performance of range and motion parameters estimation. To solve this problem, a computationally efficient method based on the time-reversal (TR) process and maximum likelihood (ML) principle, i.e., TR-MLE is proposed. The proposed method decouples the joint parameter estimation problem into two simpler problems, which not only increases the efficiency but also improves the estimation performance in low signal-noise-ratio. Furthermore, a fast method using Chirp-Z transform and Newton's method is developed for a more efficient implementation. The theoretical analysis of the noise properties after the TR process is carried out. Then, the corresponding Cramér–Rao lower bound that can evaluate the performance loss introduced by the TR process is discussed in detail. Simulated data and real data are used to assess the performance of the proposed method.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Compressive Sensing-Based Joint Range-Doppler and Clutter Estimation
    • Authors: Soheil Salari;Francois Chan;Yiu-Tong Chan;Rudy Guay;
      Pages: 3207 - 3217
      Abstract: In this paper, we address the problem of radar range-Doppler imaging in the presence of clutter. Specifically, we formulate the range-Doppler imaging problem as that of recovery of a sparse vector contaminated by clutter in addition to noise. We propose a sparse Bayesian learning (SBL)-based algorithm to jointly obtain the range-Doppler image, variance of the noise, and covariance matrix of the clutter. Furthermore, we adapt a simple pruning mechanism that reduces the computational cost and improves the convergence speed.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Optimal 3-D Aerial Relay Placement for Multi-User MIMO Communications
    • Authors: Emmanouel T. Michailidis;Nikolaos Nomikos;Petros S. Bithas;Demosthenes Vouyioukas;Athanasios G. Kanatas;
      Pages: 3218 - 3229
      Abstract: In this paper, an airborne multi-user (MU) multiple-input multiple-output (MIMO) communication system is investigated, consisting of multiple users sources, multiple users destinations, and an aerial platform acting as a decode-and-forward (DF) relay. In this context, a novel three-dimensional (3-D) geometry-based optimization method for the relay location is proposed and expressions for the outage probability are presented. The results highlight the impact of the relay position, power allocation, fading severity, and number of antennas on the system performance.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Capacity of Interference Exploitation Schemes in Multibeam Satellite
    • Authors: Alessandro Ugolini;Giulio Colavolpe;Martina Angelone;Alessandro Vanelli-Coralli;Alberto Ginesi;
      Pages: 3230 - 3245
      Abstract: In this paper, we propose a framework, based on the combined use of single- and multiuser detection, to jointly optimize the achievable rates of two signals sharing the same frequency in the forward link of a multibeam satellite system. We then propose the application of the described framework to two different scenarios of interest. First, we consider a uniform coverage scenario, aimed at maximizing the average throughput per beam in a realistic coverage condition. We compare different solutions based on alternative frequency reuse (FR) schemes and different receiver strategies. We demonstrate that the use of multiuser detection can achieve significant gains over a reference strategy based on single-user detection. Next, we analyze a “hotspot” case, where resources are pulled from empty beams to serve a beam with a high service demand. Also in this case, we compare several strategies and FR schemes. We show that the best performance is achieved by a scheme adopting three colors and single-user detection.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Spacecraft Hovering Flight in a Binary Asteroid System by Using Fuzzy
           Logic Control
    • Authors: Yonglong Zhang;Xiangyuan Zeng;Fengdi Zhang;
      Pages: 3246 - 3258
      Abstract: Fuzzy logic controllers are designed for spacecraft hovering flight in a binary asteroid system. The binary asteroid system is modeled as an ellipsoid-sphere system where the spherical harmonics method is adopted to represent the gravitational field of the asteroids. The method to design the fuzzy logic controllers is introduced in detail. Hovering flight about the inner collinear equilibrium point L1 of binary asteroid Didymos is numerically presented. Detailed steps on roughly estimating the scaling gains of fuzzy logic controllers are also summarized. Numerical simulations are performed to show the effectiveness of the proposed method. Moreover, the aforementioned fuzzy logic controllers can be used for both continuous and impulsive thrusters. The fuzzy controllers with continuous thrust, the fuzzy controllers with fixed thrust, and the other two kinds of sliding-mode controllers are optimized in the same way and compared in the same simulation environment together, to show tremendous advantages of fuzzy logic controllers and continuous thrusters on both control performance and propellant consumption.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Adaptive Finite-Time 6-DOF Tracking Control for Spacecraft Fly Around With
           Input Saturation and State Constraints
    • Authors: Yi Huang;Yingmin Jia;
      Pages: 3259 - 3272
      Abstract: An adaptive finite-time control scheme is developed for noncooperative spacecraft fly-around subject to input saturation, full-state constraints, dynamic couplings, parameter uncertainties, and disturbances. Different from traditional fly-around model based on C-W equation, the derived 6-DOF spacecraft fly-around model can be suitable for noncooperative case in close proximity. By using the backstepping control technique, an integrated adaptive finite-time control law is designed, in which the tan-type barrier Lyapunov function (BLF) is incorporated to handle the full-state constraints. Meanwhile, the unknown dynamic couplings, parameter uncertainties, and disturbances are attenuated effectively by using adaptive estimation technique and the adverse effects raised from input saturation are reduced by the designed saturation compensator. Based on the constructed BLF, it is shown that the designed adaptive finite-time controller can guarantee that full-state constraints are not breached, but also can drive relative position and attitude tracking errors into the accurate convergent regions with finite-time convergence. Finally, the performance and advantage of the designed adaptive finite-time control scheme are demonstrated by numerical simulations.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Integrated Control and Magnetic Suspension for Fast Attitude Maneuvering
           and Stabilization
    • Authors: Liang Tang;Zixi Guo;
      Pages: 3273 - 3283
      Abstract: This paper presents a method for spacecraft to achieve the task of fast maneuvering and fast stabilization. To realize this task, a new type of vibration isolation platform whose actuators are based on magnetic suspension techniques and an attitude controller to suit the spacecraft with this new vibration isolation platform are presented. High-frequency vibrations would reduce the stability of the attitude control, and low-frequency vibrations would reduce the maneuvering time of the attitude control. The vibration isolation platform presented in this paper is assembled between the spacecraft bus and the attitude control actuators and acts to reduce the high-frequency vibrations. The vibration isolation platform, which consists of the vibration isolation strut with magnetic suspension, has better performance in the region of high frequency according to the frequency-domain analysis. An appropriate controller for the vibration isolation strut is designed based on the frequency-domain analysis. Then, the attitude controller of the spacecraft bus is designed using the finite-time control theory to reduce the low-frequency vibrations, thus reducing the maneuvering time. Finally, the numerical simulations show that the vibration isolation platform and the attitude controller do work and cooperate well.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Characterization of Rotating Objects With Tomographic Reconstruction of
           Multiaspect Scattered Signals
    • Authors: Javier Martínez García;Karsten Thurn;Martin Vossiek;
      Pages: 3284 - 3291
      Abstract: The backscattered signals of objects under spinning motion or with rotating parts provide very rich information that can be used for classification tasks, parameter extraction, etc. Obtaining such information from noncooperative objects with an unknown target-aspect is often a complicated task with a monostatic configuration. A multistatic radar on the other hand, can exploit the spatial diversity to extract the information from the time-frequency representations obtained from multiple aspect-angles. In this paper, we propose a tomographic approach for characterizing spinning objects in terms of their shape, size, and rotation parameters using a narrow-band multistatic radar. A two-dimensional image is reconstructed after a full rotation period using tomographic methods that allows not only to estimate the shape of the target but also the rotation parameters and the dimensions of the object. This is done very efficiently by combining the tomographic images from different aspect-angles on the transformed log-polar space, instead of the time-frequency representations. Simulations and measurements were conducted for the proof of concept. The measurement results with a simple target and a continuous wave K-band radar show errors below 3° for the orientation estimation and below 5% for the estimation of the object's diameter.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • On the Impulsive Formation Control of Spacecraft Under Path Constraints
    • Authors: Amir Shakouri;
      Pages: 3292 - 3302
      Abstract: This paper deals with the impulsive formation control of spacecraft in the presence of constraints on the position vector and time. Determining a set of path constraints can increase the safety and reliability in an impulsive relative motion of spacecraft. Specially, the feasibility problem of the position norm constraints is considered in this paper. Under assumptions, it is proved that if a position vector be reachable, then the reach time and the corresponding time of impulses are unique. The trajectory boundedness of the spacecraft between adjacent impulses are analyzed using the Gerschgorin and the Rayleigh-Ritz theorems as well as a finite form of the Jensen's inequality. Some boundaries are introduced regarding the Jordan-Brouwer separation theorem which are useful in checking the satisfaction of a constraint. Two numerical examples (approximate circular formation keeping and collision-free maneuver) are solved in order to show the applications and visualize the results.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • A Bearings-Only Trajectory Shaping Guidance Law With Look-Angle Constraint
    • Authors: Yash Raj Sharma;Ashwini Ratnoo;
      Pages: 3303 - 3315
      Abstract: This paper addresses the problem of achieving a desired impact angle against a stationary target with seeker's field-of-view limits. A bearings-only information based guidance law is investigated as a prospective solution. Analyzing the look-angle and the line-of-sight angle relationship, closed-form expressions of the guidance gains are derived for the desired impact angle and maximum look-angle constraints. A detailed analysis is carried out for lateral acceleration boundedness resulting in a design solution expressed in impact angle-maximum look angle space. Validating the guidance law, numerical simulations are performed using a kinematic vehicle model and a realistic model with given thrust and aerodynamic characteristics. Overall, the work offers an easily implementable guidance method with simple structure and closed-form guidance gains.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Frequency-Hopped Signal Source Identification in Frequency-Selective
    • Authors: Joseph L. Loof;Thomas G. Pratt;
      Pages: 3316 - 3329
      Abstract: Blind source separation of frequency-hopped signals is a challenging problem for cases involving multipath exhibiting temporal and angular spread. A novel solution is proposed that exploits polarization-frequency correlation to separate signals, enabling association of hopped signal in these adverse conditions. Performance depends upon signal-to-noise ratios and channel-induced signal feature differences. The method has the advantage of not requiring model order estimation of multipath. The efficacy of the approach is demonstrated in experiments and numerical analyses.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Formal Intent-Based Trajectory Description Languages for Quadrotor
    • Authors: Guillermo Frontera;Ivan Campaña;Ana M. Bernardos;Juan A. Besada;
      Pages: 3330 - 3346
      Abstract: This paper describes a formal language for describing intent of quadrotor aircraft. The aim of this language is to support the prediction of quadrotor trajectories modeling guidance instructions in a compact and univocal manner, enabling to efficiently share trajectory information by several actors. A trajectory computation engine, translating from sentences of this language into a common trajectory is also described. Its use is demonstrated for a complex flight and in real-flight operations.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Theoretical Performance of Low Rank Adaptive Filters in the Large
           Dimensional Regime
    • Authors: Alice Combernoux;Frédéric Pascal;Guillaume Ginolhac;Marc Lesturgie;
      Pages: 3347 - 3364
      Abstract: This paper proposes a new approximation of the theoretical signal to interference plus noise ratio (SINR) loss of the low-rank (LR) adaptive filter built on the eigenvalue decomposition of the sample covariance matrix. This new result is based on an analysis in the large dimensional regime, i.e., when the size and the number of data tend to infinity at the same rate. Compared to previous works, this new derivation allows us to measure the quality of the adaptive filter near the LR contribution. Moreover, we propose a new LR adaptive filter and we also derive its SINR loss approximation in a large dimensional regime. We validate these results on a jamming application and test their robustness in a multiple input multiple output space time adaptive processing application where the data size is large.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Deception Against Near-Field Synthetic Aperture Radar Using Networked
    • Authors: Feng Zhou;Tian Tian;Bo Zhao;Xueru Bai;Weiwei Fan;
      Pages: 3365 - 3377
      Abstract: We propose a new deceptive jamming method using networked receivers to perform deceptive jamming against multimode synthetic aperture radar. Using multiple receivers to measure the time difference of beam arrival, we solve the instantaneous modulation parameters precisely via linear equations. We then solve the time delays and frequency offsets of the deceptive signal without approximation to avoid accumulating electronic reconnaissance errors with traditional deceptive methods. Additionally, we design the distribution of receivers to minimize the condition number, reducing our method's sensitivity to measurement error. Simulation results prove the effectiveness of the proposed method.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Multi-CubeSat Relative Position and Attitude Determination Based on
           Array Signal Detection in Formation Flying
    • Authors: Jiao Wang;Ruonan Zhang;Jianping Yuan;Jianjun Luo;
      Pages: 3378 - 3393
      Abstract: High-precision relative position and attitude measurement is crucial for consensus control and collision avoidance in multi-CubeSat formation flying. However, the traditional relative navigation systems comprise many sensors and are not suitable for CubeSats due to large volume, complexity, and cost. In this paper, we propose a new approach, called Multi-CubeSat relative State determination by Array Signal detection (MUSAS). The approach utilizes the existing communication systems and antenna arrays on CubeSats without the need of extra components. In MUSAS, deputy vehicle (DV) CubeSats in a formation broadcast orthogonal spread spectrum signals simultaneously. Two chief vehicle (CV) CubeSats receive and separate the signals and extract the multiple-input multiple-output channel response of each DV CubeSat. Then, by utilizing the bi-directional spatial spectrum estimation, the angles-of-arrival and angles-of-departure of the propagation paths from each DV CubeSat to the CV CubeSats are estimated. Finally, the attitudes and positions of all DV CubeSats relative to the CV CubeSats are determined using the derived rotation matrices. We have theoretically proved the proposed MUSAS algorithm and performed extensive simulations to compare its performance with existing methods. Furthermore, we also developed the testbed of MUSAS and conducted field experiments. The simulation and experiment results have verified that, by exploiting the spread spectrum gain and antenna array gain, MUSAS can achieve high accuracy in relative state determination, even using small antenna arrays and low transmission power.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • A Pseudo-Spectrum Approach for Weak Target Detection and Tracking
    • Authors: Gongjian Zhou;Liangliang Wang;Thiagalingam Kirubarajan;
      Pages: 3394 - 3412
      Abstract: Conventional velocity-filtering-based track-before-detect (VF-TBD) methods integrate the energy of a cell in a frame with that of the cell closest to the predicted target position in the last frame of the processing batch, assuming a certain target velocity. However, the target may not exactly be on the quantized cell and its echo envelope may occupy multiple adjacent cells. This often leads to significant energy loss and echo envelope degradation. In this paper, a novel VF-TBD method based on pseudo-spectrum (PS-VF-TBD) is presented to address this problem. For every cell, a pseudo-spectrum is constructed around the predicted position according to the assumed velocity using a truncated point spread function. Samples of the pseudo-spectrum on the cells that are located in the truncated spread area are added onto the last frame of the processing batch to integrate the target energy within multiple cells. Due to the use of the point spread model and the accurate sampling of the predicted spectrum, energy loss can be mitigated and the echo envelope is well maintained. This approach simultaneously maximizes the signal-to-noise ratio (SNR) gain and enables improved parameter estimation utilizing the envelope characteristics. The procedure for pseudo-spectrum construction and multiframe accumulation is derived in detail and the output SNR is analyzed theoretically. It is found that the proposed PS-VF-TBD can achieve an SNR gain greater than that by the conventional VF-TBD method. To deal with a target with unknown velocity, a bank of pseudo-spectrum-based velocity filters is proposed. The signal gain loss resulting from velocity mismatch is investigated and the μ-width of the envelope in the velocity domain is analyzed. Finally, a method for improved position and velocity estimation is presented. Simulation results demonstrate the superiority of the proposed method in terms of SNR gain, detection probability, and estimation accuracy at the expense of i-creased computational complexity.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Dynamic Exhaustive Mobile Target Search Using Unmanned Aerial Vehicles
    • Authors: Douglas Brown;Liang Sun;
      Pages: 3413 - 3423
      Abstract: This paper presents a novel dynamic progressively spiral-out (PSO) formation for a team of unmanned aerial vehicles (UAVs) to perform an exhaustive search of mobile ground targets. Two novel procedures are designed for a UAV to be inserted to and removed from an established PSO formation without discontinuing the confidence area. A comparison study in simulation was conducted using both randomly moving and smart avoidance targets. The results show the effectiveness of the proposed approaches.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Large-Scale Model-Based Avionics Architecture Optimization Methods and
           Case Study
    • Authors: Björn Annighöfer;Ernst Kleemann;
      Pages: 3424 - 3441
      Abstract: This paper presents a model-driven multiobjective avionics system optimization method developed over six years at its final destination, the application in real-world integrated modular avionics systems. It documents the methods, the application scenario, and the results of large-scale optimization studies carried out for the Airbus A350 peripheral acquisition system. The results predict that a significantly lighter system could be possible.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Flow Field Image Based Attitude Control for Small Unmanned Aerial Vehicles
    • Authors: Kenneth Thompson;Yunjun Xu;Benjamin T. Dickinson;
      Pages: 3442 - 3453
      Abstract: In recent years, microscale flow sensors have been extensively studied and developed, which can measure local flow information such as pressure or wall-shear stress over aerial vehicle surfaces in real-time. It is expected that with those sensors onboard, SUAVs can potentially mimic birds or bats in achieving more stable and agile flights than purely relying on rigid body sensors. However, it is challenging to utilize such a rich amount of surface airflow information to enable agile SUAV flights, which could be in the form of 2-D or 3-D images. In this paper, a flow field image based approach is developed for SUAV attitude control. The proposed robust controllers work directly on flow field images through defined image operators. The asymptotically stability of controllers are proven for the closed-loop systems under bounded uncertainties. The effectiveness of the controllers are demonstrated in simulations for both pitching motion and three-axis attitude motion even under gust wind conditions.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Remote Sensing for Vital Information Based on Spectral-Domain Harmonic
    • Authors: Yu Rong;Daniel W. Bliss;
      Pages: 3454 - 3465
      Abstract: In this paper, we propose an efficient and robust non-contact heart rate estimation algorithm. The key idea is to recover the fundamental heartbeat frequency from its higher-order spectral features. Our contributions are threefold: 1) carefully review and examine possible approaches in vital signs detection with ultra-wide band (UWB) impulse radar; 2) numerically and experimentally show an important result that, in the spectral domain, the fundamental heartbeat signal is respiration-interference-limited, whereas its higher-order harmonics are noise-limited; and 3) implement an adaptive heart rate monitoring algorithm based on the proposed theory, which is feasible with continuous monitoring. To justify the proposed theory, we perform a spectral analysis of the harmonics of vital signs signal. We validate the proposed algorithm using a controlled vital sign simulator. We experimentally demonstrate the effectiveness of the harmonics-based heart rate estimation algorithm and compare it against existing methods. For completeness, we also provide a limitation analysis of the proposed algorithm.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Estimation of a Random Feedback Control System With Unknown Input
    • Authors: Radu Visina;Yaakov Bar-Shalom;Peter Willett;
      Pages: 3466 - 3478
      Abstract: A method to estimate/track the state of a high-speed target that can be modeled as a feedback control system in three-dimensional (3-D) space is presented in this paper. The target's lateral acceleration input is not known, but it is known that the target will probably reach a destination position at a future time. The trajectory may involve random maneuvers. If the parameters of the modeled control loop are observable, the proposed model reduces the prediction and estimation errors. If the target's destination is known, then the accuracy can be increased further. The model, based on proportional navigation (PN), is nonlinear and can be used in a multiple-model estimator if the target can also perform random maneuvers along its route to the final destination. It is applied to a 3-D maneuvering aerial target state estimation problem with a target capable of high-magnitude, random lateral accelerations under a PN control policy. It is shown that due to the observability of the feedback control parameters, the filter significantly reduces the error of estimated position/velocity and provides a flexible estimation model for laterally maneuvering point targets in a 3-D fluid.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Modeling and Stability Analysis of a Fixture-Centric Airfield Lighting
    • Authors: Yimajian Yan;Scott D. Sudhoff;Jess Nadel;Donald W. Gallagher;
      Pages: 3479 - 3491
      Abstract: With the rapid development of the LED lighting and power electronics, LED based airfield lighting systems are currently being deployed. For better optical performance of LEDs, fixture-centric airfield lighting system architectures are being investigated. In these systems each lighting fixture includes a power electronic converter which regulates LED brightness. Since tightly regulated power converters behave as constant-power loads which may introduce instability in power electronics-based power systems, the stability assessment of the fixture-centric airfield lighting system becomes prudent. In this paper, the system-level analysis of a notional single-phase ac power-electronics-based airfield lighting system is carried out, and a stability criterion involving the number of fixtures which can be driven is developed. The system qd-axis average-value model is first derived and linearized to generate a small-signal model. Next, the application of the generalized Nyquist stability criterion predicts the small-signal stability about a given operating point. Finally, the proposed model and analysis is experimentally verified with using a proposed qd impedance measurement method. In summary, this paper develops methodologies for single-phase system analysis from both design and field application perspectives.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Particle Filtering With Soft State Constraints for Target Tracking
    • Authors: Cunjia Liu;Baibing Li;Wen-Hua Chen;
      Pages: 3492 - 3504
      Abstract: In practice, additional knowledge about the target to be tracked, other than its fundamental dynamics, can often be modeled as a set of soft constraints and utilized in a filtering process to improve the tracking performance. This paper develops a general approach to the modeling of soft inequality constraints, and investigates particle filtering (PF) with soft state constraints for target tracking. We develop two PF algorithms with soft inequality constraints, i.e., a sequential-importance-resampling particle filter and an auxiliary sampling mechanism. The latter probabilistically selects the candidate particles from the soft inequality constraints of the state variables so that they are more likely to comply with the soft constraints. The performances of the proposed algorithms are evaluated using Monte Carlo simulations in a target tracking scenario.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Determination of Fault Probabilities for ARAIM
    • Authors: Todd Walter;Juan Blanch;Kazuma Gunning;Mathieu Joerger;Boris Pervan;
      Pages: 3505 - 3516
      Abstract: Two critical parameters for advanced receiver autonomous integrity monitoring are the probability of satellite fault and the probability of constellation fault. This paper provides specific definitions for each of these fault types. We describe how these faults are evaluated and how to estimate their probability occurrence. Providing a precise definition of what constitutes a fault is essential so that all observers are able to agree on whether or not one has occurred.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Threshold Region Performance of Multicarrier Maximum Likelihood Direction
           of Arrival Estimator
    • Authors: Francesca Filippini;Fabiola Colone;Antonio De Maio;
      Pages: 3517 - 3530
      Abstract: This paper addresses the performance characterization of a direction of arrival (DoA) estimator in the low signal-to-noise-ratio (SNR) region. The case of a sensor array simultaneously collecting signals emitted at multiple carrier frequencies by a single source is considered. A maximum likelihood (ML) approach is used as a reference method for DoA estimation and its accuracy is characterized in terms of mean square error (MSE). It is well known that for SNR values included in the so-called threshold region, the DoA estimation accuracy decreases rapidly, due to the presence of outliers. This effect can be possibly mitigated when multiple frequency channels are jointly exploited. However, the capability to predict this performance degradation is fundamental either for assessing the robustness of an existing sensor or for supporting its design. Therefore, the scope of this paper is to introduce appropriate approximations to the MSE of a multifrequency ML DoA estimator in order to provide a reliable characterization of its performance in the threshold region. Two models for the source signals are considered and separately discussed, namely the deterministic (or conditional) and stochastic (or unconditional). An extensive simulated analysis is reported to prove the tightness of the approximations and to characterize the benefits steming from the exploitation of signals emitted at multiple carriers.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Range Estimation and Range-Doppler Imaging Using Signed Measurements in
           LFMCW Radar
    • Authors: Rong Zhang;Changheng Li;Jian Li;Gang Wang;
      Pages: 3531 - 3550
      Abstract: We consider range estimation and range-Doppler imaging using signed measurements of a radar system. Known time-varying thresholds are investigated for taking the signed measurements through one-bit sampling, and are compared with unknown dithering with known probability density function. The maximum likelihood (ML) approach is considered for signal parameter estimation. Since the ML algorithm is computationally prohibitive, a relaxation-based approach, referred to as the One-Bit RELAX algorithm, is used for signal parameter estimation. The conventional RELAX algorithm proposed for high-resolution sampling is also considered for comparison purposes. Moreover, a model-order selection tool, namely the Bayesian information criterion, is used to determine the number of scatterers within the scene of interest. Both numerical and experimental examples are provided to demonstrate the performance of the proposed approaches.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • An Adaptive Estimator-Based Sliding Mode Control Scheme for Uncertain
           POESLL Converter
    • Authors: Meysam Mahdavi;Maryam Shahriari-kahkeshi;Navid Reza Abjadi;
      Pages: 3551 - 3560
      Abstract: The positive output elementary super lift Luo (POESLL) converter is a dc-dc converter with a simple structure, which can increase input voltage with low ripples and high voltage gain. This study proposes an adaptive estimator-based sliding mode control scheme for the POSELL converter considering a reduced-order model of the converter with an unknown load and unknown input voltage. The proposed controller is composed of two parts: 1) an adaptive estimator, and 2) the sliding mode controller. At first, it is assumed that the state variables of the converter are available and adaptive estimator is proposed to facilitate the design of adaptive laws for estimating unknown parameters. Then, the sliding mode control input is designed based on the estimation of unknown parameters. Stability analysis of the proposed scheme is provided and σ-modification type robust adaptive laws for estimating the uncertain parameters are derived based on the Lyapunov direct method. Furthermore, one modification term is proposed to satisfy the sliding condition. Finally, the proposed scheme is experimentally implemented in real time using STM32F407VG discrete signal processor board interfaced with MATLAB. In addition, in order to compare and highlight the effective performance of the proposed scheme, the proportional-integral (PI) controller is designed and implemented. Experimental results are presented for both of the proposed approach and the PI one. The results verify the ability of the proposed scheme for voltage regulation as well as its robustness against parameter uncertainties. Additionally, comparison results demonstrate that the proposed controller has superior performance than the PI controller.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Parameter-Refined OMP for Compressive Radar Imaging of Rotating Targets
    • Authors: Ngoc Hung Nguyen;Kutluyıl Doğançay;Hai-Tan Tran;Paul E. Berry;
      Pages: 3561 - 3577
      Abstract: This paper presents a new parameter-refined orthogonal matching pursuit method to tackle the dictionary mismatch problem arising in compressive radar imaging of a rotating target with off-grid scatterers. The main idea is to replace the linear least-squares projection step of the conventional orthogonal matching pursuit (OMP) method with a nonlinear least-squares procedure which jointly estimates the off-grid positions and reflectivities of true scatterers. Simulations are presented to corroborate the performance advantages of the proposed method.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Shared-Autocorrelation Binary Codes Found by Exhaustive Search
    • Authors: Gregory Emmett Coxson;Jon Carmelo Russo;
      Pages: 3578 - 3586
      Abstract: Binary code negation and reversal are known to leave the autocorrelation sequence (ACS) unchanged. However, for some code lengths, there exist “shared-autocorrelation” code pairs for which the mechanism behind shared autocorrelation is not so simple. In this paper, exhaustive search is used to find representatives for all such code pairs for lengths 2 to 39. The resulting code pairs are used to discover code structures associated with the shared autocorrelation property. Some of the code pairs discovered exhibit either Golay skew-symmetry or are found to be Kronecker products of smaller shared-autocorrelation pairs. All four-code sets (or quads) for length N ≤ 36 having the shared-ACS property were also found.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Reception of LoRa Signals From LEO Satellites
    • Authors: Giulio Colavolpe;Tommaso Foggi;Michelangelo Ricciulli;Yuri Zanettini;Juan-Pedro Mediano-Alameda;
      Pages: 3587 - 3602
      Abstract: In this paper, the detection of LoRa signals from a low-earth orbit (LEO) satellite is considered. The use of a LEO satellite to collect messages from the terminals, as an alternative to terrestrial base stations in rural areas, represents a major challenge due to the specific impairments of this scenario, e.g., Doppler effects and interfering signals. A redesign, whose validation is assessed through a system simulator operating in a realistic scenario, is thus required.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • DOA Estimation in Impulsive Noise via Low-Rank Matrix Approximation and
           Weakly Convex Optimization
    • Authors: Qi Liu;Yuantao Gu;Hing Cheung So;
      Pages: 3603 - 3616
      Abstract: Conventional direction-of-arrival (DOA) estimators are vulnerable to impulsive noise. In this paper, to tackle this issue, a class of weakly convex-inducing penalties is introduced for robust DOA estimation via low-rank matrix approximation, where ℓ2,1-norm is adopted as the metric for suppressing the outliers. Two iterative algorithms are developed to construct the noise-free data matrix. To avoid determining the number of sources, the DOAs are estimated by exploiting the special joint diagonalization structure of the constructed signal covariance matrix. Compared with several existing algorithms, the proposed methods enjoy faster computation, similar DOA estimation performance against impulsive noise and requiring no a priori information of the source number. Numerical experiments are included to demonstrate the outlier-resistance of our solutions.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Radar Data Cube Processing for Human Activity Recognition Using
           Multisubspace Learning
    • Authors: Baris Erol;Moeness G. Amin;
      Pages: 3617 - 3628
      Abstract: In recent years, radar has been employed as a fall detector because of its effective sensing capabilities and penetration through walls. In this paper, we introduce a multilinear subspace human activity recognition scheme that exploits the three radar signal variables: slow-time, fast-time, and Doppler frequency. The proposed approach attempts to find the optimum subspaces that minimize the reconstruction error for different modes of the radar data cube. A comprehensive analysis of the optimization considerations is performed, such as initialization, number of projections, and convergence of the algorithms. Finally, a boosting scheme is proposed combining the unsupervised multilinear principal component analysis (PCA) with the supervised methods of linear discriminant analysis and shallow neural networks. Experimental results based on real radar data obtained from multiple subjects, different locations, and aspect angles (0°, 30°, 45°, 60°, and 90°) demonstrate that the proposed algorithm yields the highest overall classification accuracy among spectrogram-based methods including predefined physical features, one- and two-dimensional PCA and convolutional neural networks.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Attitude Reconstruction From Inertial Measurements: QuatFIter and Its
           Comparison with RodFIter
    • Authors: Yuanxin Wu;Gongmin Yan;
      Pages: 3629 - 3639
      Abstract: RodFIter is a promising method of attitude reconstruction from inertial measurements based on the functional iterative integration of Rodrigues vector. The Rodrigues vector is used to encode the attitude in place of the popular rotation vector because it has a polynomial-like rate equation and could be cast into theoretically sound and exact integration. This paper further applies the approach of RodFIter to the unity-norm quaternion for attitude reconstruction, named QuatFIter, and shows that it is identical to the previous Picard-type quaternion method. The Chebyshev polynomial approximation and truncation techniques from the RodFIter are exploited to speed up its implementation. Numerical results demonstrate that the QuatFIter is comparable in accuracy to the RodFIter, although its convergence rate is relatively slower with respect to the number of iterations. Notably, the QuatFIter has about two times better computational efficiency, thanks to the linear quaternion kinematic equation.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Scaling Transform Based Information Geometry Method for DOA Estimation
    • Authors: Yang-Yang Dong;Chun-Xi Dong;Wei Liu;Ming-Ming Liu;Zheng-Zhao Tang;
      Pages: 3640 - 3650
      Abstract: By exploiting the relationship between probability density and the differential geometry structure of received data and geodesic distance, the recently proposed information geometry (IG) method can provide higher accuracy and resolution ability for direction of arrival (DOA) estimation than many existing methods. However, its performance is not robust even for high signal-to-noise ratio. To have a deep understanding of its unstable performance, a theoretical analysis of the IG method is presented by deriving the relationship between the cost function and the number of array elements, powers and DOAs of source signals, and noise power. Then, to make better use of the nonlinear and super resolution property of the cost function, a Scaling TRansform based INformation Geometry (STRING) method is proposed, which simply scales the array received data or its covariance matrix by a real number. However, the expression for the optimum value of the scalar is complicated and related to the unknown signal DOAs and powers. Hence, a decision criterion and a simple search based procedure are developed, guaranteeing a robust performance. As demonstrated by computer simulations, the proposed STRING method has the best and robust angle resolution performance compared with many existing high resolution methods and even outperforms the classic Cramer-Rao bound, although at the cost of a bias in the estimation results.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Resilient Attitude Alignment in Multispacecraft Systems
    • Authors: Hamed Rezaee;Farzaneh Abdollahi;
      Pages: 3651 - 3657
      Abstract: Resilient attitude alignment of leaderless multispacecraft systems (MSSs) in the presence of cyberattacks is investigated. The main problem of resilient cooperative control schemes existing in the literature is their limitation to integrator linear systems. However, since real spacecraft are prone to uncertainties in model parameters, they may not be feedback linearizable to integrator models. Thus, the main contribution of the current study is to guarantee attitude alignment in MSSs in the presence of cyberattacks when the model parameters of the spacecraft are unknown. We propose a cooperative adaptive control scheme for a network of spacecraft, and based on the concept of robust graphs, we show that if the network connectivity is sufficiently robust with respect to the number of possible malicious spacecraft (spacecraft under cyberattacks), attitude alignment among the normal spacecraft can be guaranteed. The accuracy of the proposed control strategy is validated via a simulation example.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • A Sparsity-Based Passive Multistatic Detector
    • Authors: Xin Zhang;Johan Swärd;Hongbin Li;Andreas Jakobsson;Braham Himed;
      Pages: 3658 - 3666
      Abstract: In this paper, we examine the problem of target detection for the multistatic passive radar. Passive radar systems leverage the existing wireless sources, such as radio/TV stations and cellular signals that are referred to as illuminators of opportunity (IOs), to illuminate the environment and provide surveillance functions. Usually, these IO source signals are sparse or locally sparse in the frequency domain. We develop a passive multistatic detector by exploiting the sparsity or local sparsity of the IO signals. To improve the computational efficiency, two fast implementations of the proposed detector are also introduced. Simulation results show that the proposed approaches outperform the conventional passive detection methods that model the IO signals as unknown without any specific structures.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Improving the Doppler Resolution of Ground-Based Surveillance Radar for
           Drone Detection
    • Authors: Hongbo Sun;Beom-Seok Oh;Xin Guo;Zhiping Lin;
      Pages: 3667 - 3673
      Abstract: In this paper, we propose to use an iterative adaptive approach to perform the Doppler processing in ground-based surveillance radar for drone detection. It overcomes the limited dwell time and improves the Doppler resolution, and therefore significantly enhances the discrimination of micro-Doppler signature and the correct classification of drones. In addition, the target detectability is also improved. This approach is validated in the field experiments conducted with a commercial portable ground-based surveillance radar.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
  • Initial Trajectory Design of Electric Solar Wind Sail Based on Finite
           Fourier Series Shape-Based Method
    • Authors: Mingying Huo;Gang Zhang;Naiming Qi;Yufei Liu;Xin Shi;
      Pages: 3674 - 3683
      Abstract: Electric solar wind sail (E-sail) is an innovative propulsion system, which can generate low and continuous thrust without any propellant by reflecting ions from the solar wind. Because the propulsive acceleration of E-sail is low and continuous, its trajectory is usually characterized by long flight time. In order to explore more flight plans, rapid trajectory design is useful for preliminary mission analysis and design. This paper presents a method for rapid generation of minimum-time, three-dimensional trajectories for an E-sail using the finite Fourier series shape-based method. Unlike the more conventional electric thruster, the thrust vector of an E-sail is constrained. In order to consider the characteristics of the E-sail thrust, inequality constraints of thrust acceleration are investigated based on a recent thrust model. The numerical simulation results show that the proposed method is useful to quickly design the flight trajectory of the E-sail by considering the actual characteristics of the thrust vector.
      PubDate: Dec. 2019
      Issue No: Vol. 55, No. 6 (2019)
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