Search

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamic task allocation of unmanned aerial vehicle swarms for ground targets is an important part of unmanned aerial vehicle (UAV) swarms task planning and the key technology to improve autonomy. The realization of dynamic task allocation in UAV swarms for ground targets is very difficult because of the large uncertainty of swarms, the target and environment state, and the high real-time allocation requirements. Hence, dynamic task allocation of UAV swarms oriented to ground targets has become a key and difficult problem in the field of mission planning. In this work, a dynamic task allocation method for UAV swarms oriented to ground targets is comprehensively and systematically summarized from two aspects: the establishment of an allocation model and the solution of the allocation model. First, the basic concept and trigger scenario are introduced. Second, the research status and the advantages and disadvantages of the two allocation models are analyzed. Third, the research status and the advantages and disadvantages of several common dynamic task allocation algorithms, such as the algorithm based on market mechanisms, intelligent optimization algorithm, and clustering algorithm, are evaluated. Finally, the specific problems of the current UAV swarm dynamic task allocation method for ground targets are highlighted, and future research directions are established. This work offers important reference significance for fully understanding the current situation of UAV swarm dynamic task allocation technology.

This study proposes a near-optimal, impulsive control method for overflying ground targets. A set of impulses, which adjusts the satellite ground trajectory to enable the overflight, is derived. The proposed impulsive solution is expressed in closed-form which only consists of orbital revolution numbers and target overflight errors. It allows not only simplifying the search for a minimum delta-v solution but also facilitating its extension to the multiple-target overflight problem. It is also provided in this paper an insight connecting the overflight problem to a relative orbit transfer problem controlling a phase angle or mean anomaly. Numerical examples for single-, two-, and three-target overflight verify that the controlled trajectory with the proposed impulsive solution successfully overflies the designated targets within a prescribed time. It is also demonstrated that the total delta-v required for the proposed method is near-optimal based on the performance comparison with a numerical optimization-based method which employs a very large set of initial guesses. [ABSTRACT FROM AUTHOR]

This article deals with cooperative target circumnavigation control strategy for a team of unmanned aerial vehicles (UAVs) when only range measurements are available. First, we propose novel guidance laws based solely on range measurements for tracking and cooperation. Then, convergence and stability of the proposed guidance laws are proved by a rigorous inference of mathematics. Moreover, an illustrative simulation shows that the controlled UAVs orbit around a target and maintain even spacing along the common circle, which confirms the performance of the proposed guidance algorithms. [ABSTRACT FROM AUTHOR]

Global Positioning System (GPS) satellites offer promising opportunity for Passive Radar systems due to their global coverage and the availability of multiple satellites throughout the world. However, their low power at ground level limits system coverage. In this paper, a GPS based Passive Radar which exploits a single illumination source, and uses digital array processing for ground targets localization is presented. To face signal power problems, a processing scheme combining reconstructed reference signals, adaptive filtering techniques and spatial filtering is implemented. Conventional beamforming techniques are used to increase the level of the target echo before the detection stage, and high resolution DoA estimation techniques are applied to estimate targets azimuth. Ground target localization in local Cartesian space is performed taking into account the system geometry, range and azimuth information. Both synthetic and real radar data are used to analyse system operation. During the measurement campaign, a cooperative vehicle was used for validation purposes. Results confirm that ground targets detection and localization are feasible using a single GPS transmitter.

Over-flight and standoff tracking are the two typical modes of fixed wing unmanned aerial vehicle tracking ground targets. The guidance law of each mode is usually designed independently and thus shows different forms. In this paper, based on the constraints on unmanned aerial vehicle flight, a novel unitized guidance law, which is compatible with these two modes, is proposed. The stability of the guidance law is rigorously proved by a Lyapunov function, and the design of guidance parameters is discussed. Numerical simulation results show that the proposed guidance law can be used for automatically tracking the stationary and moving ground targets well, and also can switch between the two tracking modes smoothly. [ABSTRACT FROM AUTHOR]

In this paper, a new guidance law using range-based measurements is proposed. Firstly, the new guidance law is designed for circumnavigating a ground target using range and range-rate measurements; Secondly, a Lyapunov function is designed to prove the stability of the proposed guidance law. Compared with the existing ones, this guidance law is more compact. Simulation results show that the guidance law can achieve the circumnavigating task well for the stationary ground target. [ABSTRACT FROM AUTHOR]

This paper proposes a compact K-band radar applied to a miniature proximity fuze for the active defense system. In this terrestrial environment, it is not easy to detect approaching small targets because the clutter is scattered. In addition, it is difficult to miniaturize the radar for the small proximity fuze while improving the target accuracy of the radar in such environments. To solve these difficulties, this study presents system analysis and design, antenna design, and transceiver and signal processor design of the compact K-band radar. Some test results are presented and the results are analyzed, the validity of the proposed study is examined. [ABSTRACT FROM AUTHOR]

For operationally responsive space missions, traditional orbit design problems are only for a single type of targets, i.e., only ground targets or only space targets. This paper studies the hybrid ground and space targets of interest by considering J 2 perturbation. The ground-target visit problem needs the ground track of the designed orbit to pass through the ground target, and one ground target corresponds to one equality constraint. The space-target visit problem is viewed as the orbit flyby problem, and one space target corresponds to two equality constraints. According to the numbers of designed variables and equality constraints, there are two cases for the maximum number of hybrid targets: (1) two ground targets and two space targets; (2) four ground targets and one space target. For given orbital inclination and right ascension of ascending node, the other orbital elements of the designed orbit are obtained by numerical methods. Then, the problem is transformed into solving nonlinear equations only of two variables. Newton-Raphson iterations are adopted to solve the problem, and the initial guesses are obtained by the grid search method. Several numerical examples are presented to validate the proposed orbit design approach for hybrid ground-space targets. [ABSTRACT FROM AUTHOR]

Global Positioning System (GPS) satellites offer promising opportunity for Passive Radar systems due to their global coverage and the availability of multiple satellites throughout the world. However, their low power at ground level limits system coverage. In this paper, a GPS based Passive Radar which exploits a single illumination source, and uses digital array processing for ground targets localization is presented. To face signal power problems, a processing scheme combining reconstructed reference signals, adaptive filtering techniques and spatial filtering is implemented. Conventional beamforming techniques are used to increase the level of the target echo before the detection stage, and high resolution DoA estimation techniques are applied to estimate targets azimuth. Ground target localization in local Cartesian space is performed taking into account the system geometry, range and azimuth information. Both synthetic and real radar data are used to analyse system operation. During the measurement campaign, a cooperative vehicle was used for validation purposes. Results confirm that ground targets detection and localization are feasible using a single GPS transmitter. [ABSTRACT FROM AUTHOR]

This paper proposes a synthetic aperture radar (SAR) automatic target recognition approach based on a global scattering center model. The scattering center model is established offline using range profiles at multiple viewing angles, so the original data amount is much less than that required for establishing SAR image templates. Scattering center features at different target poses can be conveniently predicted by this model. Moreover, the model can be modified to predict features for various target configurations. For the SAR image to be classified, regional features in different levels are extracted by thresholding and morphological operations. The regional features will be matched to the predicted scattering center features of different targets to arrive at a decision. This region-to-point matching is much easier to implement and is less sensitive to nonideal factors such as noise and pose estimation error than point-to-point matching. A matching scheme going through from coarse to fine regional features in the inner cycle and going through different pose hypotheses in the outer cycle is designed to improve the efficiency and robustness of the classifier. Experiments using both data predicted by a high-frequency electromagnetic (EM) code and data measured in the MSTAR program verify the validity of the method. [ABSTRACT FROM AUTHOR]

Drone platform for synthetic aperture radar (SAR) operation has been little publicised due to the technical constraint of the payload implementation. Multi‐rotor drone based SAR is distinguished from the conventional airborne system by the increased sensitivity to turbulences and poor motion stability. Extremely limited power and mass budgets may prevent the use of extra hardware for motion compensation and the difficulty of SAR focusing is aggravated. Feasibility of micro‐SAR drone operation is investigated through field tests, where experimental SAR images are acquired over ground targets. Attempts have been made to implement near‐real‐time compensation for non‐uniform motion disturbance. Finally, experimental drone SAR operation is validated through calibrated SAR images. [ABSTRACT FROM AUTHOR]