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To address the challenges in tracking complex maneuvering extended targets, an effective maneuvering extended target tracking method was proposed for irregularly shaped star-convex using a Transformer network. Initially, the alpha-shape algorithm was used to model the variations in the star-convex shape. In addition, a recursive approach was proposed to estimate the irregular shape of an extended target by detailed derivation in the Bayesian filtering framework. This approach accurately estimated the shape of a static star convex extended target. Moreover, through the structural redesign of the target state transition matrix and the real-time estimation of the maneuvering extended target’s state transition matrix using a transformer network, the accurate tracking of complex maneuvering targets was achieved. Furthermore, the real-time tracking of star convex maneuvering extended targets was achieved by fusing the estimated shape contours with motion states. This study focused on constructing certain complex maneuvering extended target tracking scenarios to assess the performance of the proposed method and the comprehensive estimation capabilities of the algorithm considering both shapes and motion states using multiple performance indicators.

An airborne bistatic radar working in downward-looking mode confronts two major challenges for low-altitude target detection. One is range cell migration (RCM) and Doppler migration (DM) resulting from the relative motion of the radar and target. The other is the non-stationarity characteristic of clutter due to the radar configuration. To solve these problems, this paper proposes a joint implementation method based on sub-aperture processing to achieve clutter suppression and coherent maneuvering target detection. Specifically, clutter Doppler compensation and sliding window processing are carried out to realize sub-aperture space–time processing, removing the clutter non-stationarity resulting from the bistatic geometric configuration. Thus, the output matrix of clutter suppression in the sub-aperture could be obtained. Then, the elements with the same phase of this matrix are superimposed and rearranged to achieve the reconstructed 2-D range-pluse echo matrix. Next, the aperture division with respect to slow time is conducted and the RCM correction based on modified location rotation transform (MLRT) and coherent integration (CI) are realized within each sub-aperture. Finally, the matched filtering process (MFP) is applied to compensate for the RCM/DM among different sub-apertures to coherently integrate the maneuvering target energy of all sub-apertures. The simulation and measured data processing results prove the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Targets faced by inverse synthetic aperture radar (ISAR) are often non-cooperative, with target maneuvering being the main manifestation of this non-cooperation. Maneuvers cause ISAR imaging results to be severely defocused, which can create huge difficulties in target identification. In addition, as the ISAR bandwidth continues to increase, the impact of migration through resolution cells (MTRC) on imaging results becomes more significant. Target non-cooperation may also result in sparse aperture, leading to the failure of traditional ISAR imaging algorithms. Therefore, this paper proposes an algorithm to realize MTRC correction and sparse aperture ISAR imaging for maneuvering targets simultaneously named whale optimization algorithm–fast iterative shrinkage thresholding algorithm (WOA-FISTA). In this algorithm, FISTA is used to perform MTRC correction and sparse aperture ISAR imaging efficiently and WOA is adopted to estimate the rotational parameter to eliminate the effects of maneuvering on imaging results. Experimental results based on simulation and measured datasets prove that the proposed algorithm implements sparse aperture ISAR imaging and MTRC correction for maneuvering targets simultaneously. The proposed algorithm achieves better results than traditional algorithms under different signal-to-noise ratio conditions. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a fixed‐time cooperative guidance law for leader‐following missiles, comprising one leader missile with the target seeker and several seeker‐less follower missiles. The aim is to achieve a simultaneous attack on a maneuvering target at desired impact angles. First, a guidance law with impact angle control for the leader missile against a maneuvering target is proposed based on nonsingular fast terminal sliding mode (NFTSM) control algorithm. Then, the design of cooperative guidance law for the follower missiles is composed of two parts: along the follower‐to‐leader line of sight (LOS) direction, the guidance command derived from bi‐homogeneous property is designed to ensure that the follower‐leader ranges keep proportional consensus with the range‐to‐go of the leader missile, thus avoiding the estimation of time‐to‐go (tgo$$ {t}_{go} $$); in the normal follower‐to‐leader LOS direction, considering the relative impact angle constraints which is determined by the leader LOS angle, the guidance command is proposed based on predefined‐time sliding mode control method. What's more, a distributed fixed‐time observer is designed for the follower missiles to compensate for unobtainable leader missile information. The fixed‐time stability of the proposed methods is demonstrated using the Lyapunov theory and bi‐homogeneous property. Finally, simulation results confirm the effectiveness and superiority of the proposed fixed‐time cooperative guidance law with leader‐following strategy. [ABSTRACT FROM AUTHOR]

In this paper, by accounting for the angle constraint (AC) and autopilot lag compensation (ALC), a novel fixed-time convergent guidance law is developed based on a fixed-time state observer and bi-limit homogeneous technique. The newly proposed guidance law exhibits three attractive features: (1) unlike existing guidance laws with AC and ALC which can only guarantee asymptotic stability or finite-time stability, the newly proposed guidance scheme can achieve fixed-time stability. Thus, the newly proposed scheme can drive the guidance error to zero within bounded time which is independent of the initial system conditions. (2) To compensate for autopilot lag, existing guidance schemes need the unmeasurable second derivative of the range along line-of-sight (LOS) and second derivative of LOS angle or the derivative of missile's acceleration. Without using these unmeasurable states, the newly proposed guidance law still can guarantee the fixed-time stability. (3) By using the bi-limit homogeneous technique to construct an integral sliding-mode surface, the proposed scheme eliminates the singular problem without using the commonly-used approximate method in recent fixed-time convergent guidance schemes. Finally, the simulation results demonstrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology 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.)

In this paper, we propose a nonlinear tracking solution for maneuvering aerial targets based on an adaptive interacting multiple model (IMM) framework and unscented Kalman filters (UKFs), termed as AIMM-UKF. The purpose is to obtain more accurate estimates, better consistency of the tracker, and more robust prediction during sensor outages. The AIMM-UKF framework provides quick switching between two UKFs by adapting the transition probabilities between modes based on a distance function. Two modes are implemented: a uniform motion model and a maneuvering model. The experimental validation is performed with Monte Carlo simulations of three scenarios with ACAS Xa tracking logic as a benchmark, which is the next generation of airborne collision avoidance systems. The two algorithms are compared using hypothesis testing of the root mean square errors. In addition, we determine the normalized estimation error squared (NEES), a new proposed noise reduction factor to compare the estimation errors against the measurement errors, and an estimated maximum error of the tracker during sensor dropouts. The experimental results illustrate the superior performance of the proposed solution with respect to the tracking accuracy, consistency, and expected maximum error. [ABSTRACT FROM AUTHOR]

In order to intercept a high-speed maneuvering target at a specific attack angle, a three dimensional sliding mode terminal guidance law is designed based on finite-time and small-overshoot prescribed performance control, which is a new method in control field. The linear sliding surface is designed based on the angle of sight deviation and angle of sight rate deviation to ensure that the angle of sight and angle of sight rate converge to the expected value in finite time. On reaching law design, guidance instructions for the yaw plane and pitch plane are designed respectively based on the finite-time and small-overshoot prescribed performance control, ensuring that the tracking error can converge at a preset convergence time and the overshoot is constrained to a small range. At the same time, the nonlinear finite-time observer is introduced to estimate the target acceleration term in the guidance instruction to further improve the guidance accuracy. The simulation results show that the proposed guidance law can intercept targets at specific attack angle under different interception conditions. Compared with the existing fast terminal sliding mode guidance law, the proposed guidance law can guarantee the small-overshoot convergence of sliding mode variables in finite time, and can strike the target form the specific angle. When intercepting maneuvering targets, the miss distance can be controlled below 1 m, improving the steady-state performance and transient performance of the system.

This paper presents a low-altitude unmanned aerial vehicle (UAV) attitude detection and tracking algorithm, named UAV-Pose. In the context of low-altitude UAV countermeasure tasks, precise attitude detection and tracking are crucial for achieving laser-guided precision strikes. To meet the varying requirements during the tracking stages, this study designs two capture networks with different resolutions. Firstly, a lightweight bottleneck structure, GhostNeck, is introduced to accelerate detection speed. Secondly, a significant improvement in detection accuracy is achieved by integrating an attention mechanism and SimCC loss. Additionally, a data augmentation method is proposed to adapt to attitude detection under atmospheric turbulence. A self-collected dataset, named UAV-ADT (UAV Attitude Detection and Tracking), is constructed for training and evaluating the target detection algorithm. The algorithm is deployed using the TensorRT tool and tested on the UAV-ADT dataset, demonstrating a detection speed of 300 frames per second (FPS) with a map75 reaching 97.8% and a PCK (Percentage of Correct Keypoints) metric reaching 99.3%. Real-world field experiments further validate the accurate detection and continuous tracking of UAV attitudes, providing essential support for counter-UAV operations.

In order to improve the multiple-missile cooperative attack capability and penetration capability, this paper investigates two three-dimensional impact-angle-constrained cooperative guidance strategies against maneuvering target for controllable thrust missiles. First, a three-dimensional nonlinear guidance model is established that does not assume small missile lead angles in the guidance process. Second, in the line-of-sight (LOS) direction of the cluster cooperative guidance strategy, the proposed guidance algorithm transforms the simultaneous attack problem into a second-order multiagent consensus problem, which effectively solves the practical problem of low guidance precision provoked by the time-to-go estimation. Then, by combining second-order sliding mode control (SMC) and nonsingular terminal SMC theory, the guidance algorithms in the normal and lateral directions to the LOS are designed, respectively, so that the multi-missile can accurately attack a maneuvering target while satisfying the impact angle constraints. Finally, by utilizing the second-order multiagent consensus tracking control in the leader-following cooperative guidance strategy, a novel leader-following time consistency algorithm is investigated to ensure that the leader and followers can attack the maneuvering target simultaneously. Moreover, the stability of the investigated guidance algorithms is proved mathematically. The effectiveness and superiority of the proposed cooperative guidance strategies are verified by numerical simulations. • This paper designs two three-dimensional impact-angle-constrained cooperative guidance strategies against maneuvering target. • This paper utilizes the relative distance and radial relative velocity as consensus variables to improve guidance precision. • This paper combines a nonsingular SMC with a second-order sliding mode control theory to improve guidance performance. • The proposed cooperative guidance algorithm has a simpler form and a more straightforward structure to avoid singularity problems. [ABSTRACT FROM AUTHOR]

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.)

In this paper, a new fixed-time convergence guidance law is proposed against maneuvering targets in the three-dimensional (3-D) engagement scenario. The fixed-time stability theory is used to zero the line-of-sight (LOS) angle rate, which will ensure the collision course and the impact of the target. It is proven that the convergence of the LOS angle rate can be achieved before the final impact time of the guidance process, regardless of the initial conditions. Furthermore, the convergence rate is merely related to control parameters. In theoretical analysis, the convergence rate and upper bound are compared with that of other laws to show the potential advantages of the proposed guidance law. Finally, simulations are carried out to illustrate the effectiveness and robustness of the proposed guidance law. [ABSTRACT FROM AUTHOR]

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.)

An airborne bistatic radar working in downward-looking mode confronts two major challenges for low-altitude target detection. One is range cell migration (RCM) and Doppler migration (DM) resulting from the relative motion of the radar and target. The other is the non-stationarity characteristic of clutter due to the radar configuration. To solve these problems, this paper proposes a joint implementation method based on sub-aperture processing to achieve clutter suppression and coherent maneuvering target detection. Specifically, clutter Doppler compensation and sliding window processing are carried out to realize sub-aperture space–time processing, removing the clutter non-stationarity resulting from the bistatic geometric configuration. Thus, the output matrix of clutter suppression in the sub-aperture could be obtained. Then, the elements with the same phase of this matrix are superimposed and rearranged to achieve the reconstructed 2-D range-pluse echo matrix. Next, the aperture division with respect to slow time is conducted and the RCM correction based on modified location rotation transform (MLRT) and coherent integration (CI) are realized within each sub-aperture. Finally, the matched filtering process (MFP) is applied to compensate for the RCM/DM among different sub-apertures to coherently integrate the maneuvering target energy of all sub-apertures. The simulation and measured data processing results prove the validity of the proposed method.

Targets faced by inverse synthetic aperture radar (ISAR) are often non-cooperative, with target maneuvering being the main manifestation of this non-cooperation. Maneuvers cause ISAR imaging results to be severely defocused, which can create huge difficulties in target identification. In addition, as the ISAR bandwidth continues to increase, the impact of migration through resolution cells (MTRC) on imaging results becomes more significant. Target non-cooperation may also result in sparse aperture, leading to the failure of traditional ISAR imaging algorithms. Therefore, this paper proposes an algorithm to realize MTRC correction and sparse aperture ISAR imaging for maneuvering targets simultaneously named whale optimization algorithm–fast iterative shrinkage thresholding algorithm (WOA-FISTA). In this algorithm, FISTA is used to perform MTRC correction and sparse aperture ISAR imaging efficiently and WOA is adopted to estimate the rotational parameter to eliminate the effects of maneuvering on imaging results. Experimental results based on simulation and measured datasets prove that the proposed algorithm implements sparse aperture ISAR imaging and MTRC correction for maneuvering targets simultaneously. The proposed algorithm achieves better results than traditional algorithms under different signal-to-noise ratio conditions.

For bistatic inverse synthetic aperture radar (Bi-ISAR), the non-uniform motion state of maneuvering target and the time-varying bistatic angle make the traditional imaging method of moving target face the problem of translation compensation, and the traditional translation compensation method is not suitable for the return wave in the case of sparse aperture. In this paper, a compensation imaging method combining two-dimension joint linearized Bregman iteration and image contrast search is proposed. The translation compensation problem can be transformed into two-dimension joint compressed sensing sparse reconstruction and moving target motion parameter estimation. The proposed algorithm makes use of the gain of echo two-dimension compression, greatly improves the accuracy of translation compensation and the quality of target image and has strong robustness to noise. The processing results of simulation data verify the effectiveness and superiority of the algorithm.

Long-time coherent integration works to significantly increase the detection probability for maneuvering targets. However, during the observation time, the problems that often tend to occur are range cell migration (RCM) and Doppler frequency cell migration (DFCM), due to the high velocity and acceleration of the maneuvering target, which can reduce the detection of the maneuvering targets. In this regard, we propose a new coherent integration approach, based on the product scale zoom discrete chirp Fourier transform (PSZDCFT). Specifically, by introducing the zoom operation into the modified discrete chirp Fourier transform (MDCFT), the zoom discrete chirp Fourier transform (ZDCFT) can correctly estimate the centroid frequency and chirp rate of the linear frequency-modulated signal (LFM), regardless of whether the parameters of the LFM signal are outside the estimation scopes. Then, the scale operation, combined with ZDCFT, is performed on the radar echo signal in the range frequency slow time domain, to remove the coupling. Thereafter, a product operation is executed along the range frequency to inhibit spurious peaks and reinforce the true peak. Finally, the velocity and acceleration of the target estimated from the true peak position, are used to construct a phase compensation function to eliminate the RCM and DFCM, thus achieving coherent integration. The method is a linear transform without energy loss, and is suitable for low signal-to-noise (SNR) environments. Moreover, the method can be effectively fulfilled based on the chirp-z transform (CZT), which prevents the brute-force search. Thus, the method reaches a favorable tradeoff between anti-noise performance and computational load. Intensive simulations demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office 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.)

A generic Bayesian framework is presented to track lost-in-space noncooperative maneuvering satellites. The developed framework predicts the reachability set for a lost-in-space satellite given bounds on maneuver parameters such as maneuver time and maneuver magnitude. Reachability sets are represented as a desired order polynomial series as a function of maneuver parameters. Recent advances in non-product quadrature methods are utilized to compute coefficients of this polynomial series in a computationally efficient manner. A major contribution of this work is to develop quadrature methods to generate samples for spherically uniform distribution for bounded magnitude maneuvers. Samples generated from this polynomial series are used for direct particle propagation in a traditional Bayesian filter rather than solving governing equations of motion for each sample point. An important component of the developed framework is a search strategy which exploits the reachability set calculations to task the sensor to increase the detection probability of the satellite. The samples generated from initial reachability sets are updated to systematically reduce the target search region based on actual detection of the target in a Bayesian framework. Numerical simulations are performed to show the efficacy of the developed ideas for tracking a lost-in-space satellite with the help of space based sensor. Performance of the proposed method varies widely based on factors such as the reachability set polynomial order, maneuver uncertainty bounds, sensor parameters (Field of view, measurement frequency, and detection probability), and initial conditions. For numerical experiments performed, the observer gained the custody of the maneuvering target in 100 % and 96 % of Monte Carlo (MC) simulations for the single maneuver and two maneuver cases, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a novel cooperative and predictive guidance law is proposed to intercept high-speed and high-maneuverability targets with inferior interceptors. The purpose of guidance is cooperatively covering the most-probable locations where the target may be in the future. To fulfill this purpose, predicted target states in the form of a probability density function were obtained using limited target information, i.e., noisy position data for one case and maneuverability limits for the second case, at first. Next, the likelihood of the reachable set of interceptors was computed over the predicted target state. Then, to increase the probability of interception in a finite time, the interceptors' trajectories were adjusted collaboratively depending on the likelihood values. An extensive Monte Carlo study, with practically applicable simulation parameters, was used to demonstrate the effectiveness of the proposed methods against targets in challenging maneuvering modes. [ABSTRACT FROM AUTHOR]

This research introduces a new approach to address the challenges related to inaccuracies in shape estimation and motion state tracking during the tracking of maneuvering extended targets. The method combines a novel neural network model with a cubature Kalman filter. Initially, the target's shape variation is represented using a second-order autoregressive model, and Bayesian filtering is employed for target contour estimation in static environments. Subsequently, the kinematic state tracking of maneuvering targets is enhanced by modifying a neural network model based on Transformer architecture. Through the effective integration of these techniques, precise tracking of maneuvering extended targets is achieved, facilitating accurate estimation of irregular contour information while tracking the targets' motion state in real-time. The efficacy of the proposed approach is further confirmed through various simulation scenarios, underscoring its suitability for tracking maneuvering extended targets. • Modeling target shape with 2nd-order AR model, initial contour via alpha-shape algorithm, refining shape with Bayesian filtering. • State transfer matrix parameter estimation via neural network model and Cubature Kalman Filter for maneuvering target kinematic state estimation. • Integration of shape estimation and kinematic state method enables real-time tracking for Maneuvering Extended Target Tracking. [ABSTRACT FROM AUTHOR]

• A novel DRL-based decision approach for simultaneously conducting the coordinated attack of the maneuvering target and the evasion of interceptors. • A MOMDP containing multi-step history states is constructed and further transformed into a first-order MDP with memory extraction, which integrates the spatio-temporal coupling properties among missiles, interceptors, and targets while supporting efficient sequential decision-making. • Domain-knowledge-assisted pre-training and reward functions are constructed to speed up the convergence of the training process. This paper presents an open and interesting issue for missiles, i.e., achieving collaborative parameters constrained cooperative guidance, despite the interference of pursing interceptors (INTs) and the maneuvering target, by the fact that the target-missile-interceptor (TMI) engagement induces their complex and time-varying relationships. The Memory-Extraction-based Soft-Actor-Critic (ME-SAC) approach is proposed, which enhances the collaborative performance of missiles by implicitly extracting coupling motion characteristics among TMI from historical state, achieving the joint optimization of situation awareness and strategy. Firstly, the cooperative guidance task is formulated as a multi-order Markov decision process (MOMDP) to better represent the dynamic evolution of engagement, and a memory-extraction process is introduced to alleviate the curse of dimensionality. Secondly, a memory-decision-oriented maximum entropy framework combined with memory update modules is designed for enhancing strategy search ability. Then, a domain-knowledge-based pre-training is implemented to improve convergence speed. Finally, in simulation evaluation with various scenarios, the proposed ME-SAC shows more promising than the typical DRL-based and model-based algorithms in task success rate, learning efficiency, and adaptability. [ABSTRACT FROM AUTHOR]

In this paper, by accounting for the angle constraint (AC) and autopilot lag compensation (ALC), a novel fixed-time convergent guidance law is developed based on a fixed-time state observer and bi-limit homogeneous technique. The newly proposed guidance law exhibits three attractive features: (1) unlike existing guidance laws with AC and ALC which can only guarantee asymptotic stability or finite-time stability, the newly proposed guidance scheme can achieve fixed-time stability. Thus, the newly proposed scheme can drive the guidance error to zero within bounded time which is independent of the initial system conditions. (2) To compensate for autopilot lag, existing guidance schemes need the unmeasurable second derivative of the range along line-of-sight (LOS) and second derivative of LOS angle or the derivative of missile’s acceleration. Without using these unmeasurable states, the newly proposed guidance law still can guarantee the fixed-time stability. (3) By using the bi-limit homogeneous technique to construct an integral sliding-mode surface, the proposed scheme eliminates the singular problem without using the commonly-used approximate method in recent fixed-time convergent guidance schemes. Finally, the simulation results demonstrate the effectiveness of the proposed scheme.

According to the actual situation of gun-launched UAV intercepting "Low-slow-small" target and the specific maneuverability of gun-launched UAV, an enhanced real proportion guidance law (RTPN) guidance interception method is designed. The traditional RTPN method does not consider the saturation overload limit and the capture region of arbitrary maneuvering target. In addition, aiming at the measurement error and the dynamic response delay of the gun-launched UAV during the interception, the EKF data fusion track prediction algorithm is proposed. Simulation results show that the proposed method can effectively solve the problem.

This paper addresses the issue of a complex three-dimension (3-D) terminal guidance process that is used against maneuvering targets while considering both the terminal impact angle (TIA) and field-of-view (FOV) angle constraints. According to the highly coupled and nonlinear 3-D terminal guidance model, an adaptive back-stepping sliding-mode guidance law algorithm is proposed in order to guarantee the stability and robustness of the guidance system. Considering the explicit expression of the line-of-sight (LOS) angle in the kinematics and dynamics of the terminal guidance process, the TIA constraint is transformed into an LOS constraint based on their well-known relationship. In view of the challenges in obtaining the motion information of maneuvering targets, an adaptive law design is introduced in order to estimate and compensate for external disturbances caused by the maneuvering of the target and modeling uncertainty. In addition, because the FOV angle represented by the overall leading angle is not a state variable in the sliding-mode guidance system, it is decoupled into two partial leading angles based on a specific transformation relation, so the 3-D terminal guidance control problem is converted into separate tracking system control issues in the pitch and yaw planes. Then, the Lyapunov stability theory is utilized to substantiate the stability of the guidance system, where the Lyapunov functions in both of the subsystems consist of the LOS and partial FOV state error terms. Finally, a series of simulations of various motion states of maneuvering targets under different terminal cases were carried out. It was proved that the terminal guidance design based on the strategies presented above was able to obtain the desired LOS constraints with satisfying the FOV limitation, and the simulation results verified the effectiveness, universality, and significance for practical applications of the proposed guidance design method. [ABSTRACT FROM AUTHOR]

Aiming at the problem of multi-missile cooperative interception of maneuvering targets, two different cooperative guidance laws are designed based on the time-to-go. For the scenario of multi-missile distributed communication, a distributed cooperative proportional guidance law with time-varying navigation coefficients is designed based on the idea of biased proportional guidance. For the scenario of specified attack time, based on the form of time-to-go under constant lead angle, a sliding mode guidance law with a specified attack time is designed by using sliding mode control and nonlinear disturbance observer. Simulation results show that the two guidance laws proposed in this paper can effectively carry out cooperative attack or sequential attack against maneuvering targets.

In this paper, a filtering algorithm for tracking strong maneuvering targets is proposed to improve the attack ability of air-to-air missiles in air combat. Firstly, by analyzing the filtering algorithm of strong maneuvering targets, a hybrid grid multiple model(HGMM)framework based on interacting multiple model algorithm is constructed. Then, the hybrid grid multiple model algorithm is designed in detail. Finally, numerical simulation shows that the proposed method is feasible and has good tracking effect, the tracking accuracy is improved abaut 20%.

In this paper, we propose a nonlinear tracking solution for maneuvering aerial targets based on an adaptive interacting multiple model (IMM) framework and unscented Kalman filters (UKFs), termed as AIMM-UKF. The purpose is to obtain more accurate estimates, better consistency of the tracker, and more robust prediction during sensor outages. The AIMM-UKF framework provides quick switching between two UKFs by adapting the transition probabilities between modes based on a distance function. Two modes are implemented: a uniform motion model and a maneuvering model. The experimental validation is performed with Monte Carlo simulations of three scenarios with ACAS Xa tracking logic as a benchmark, which is the next generation of airborne collision avoidance systems. The two algorithms are compared using hypothesis testing of the root mean square errors. In addition, we determine the normalized estimation error squared (NEES), a new proposed noise reduction factor to compare the estimation errors against the measurement errors, and an estimated maximum error of the tracker during sensor dropouts. The experimental results illustrate the superior performance of the proposed solution with respect to the tracking accuracy, consistency, and expected maximum error.

This paper proposes a prescribed-time cooperative guidance law (PTCGL) against maneuvering target with variable line-of-sight (LOS) angle constraint for leader-following missiles, where the convergence times of the state errors can be arbitrarily set. The leader missile against the maneuvering target is provided as the modified proportional navigation (MPN) guidance law. The proposed PTCGL for follower missiles consist of two parts, in LOS direction, the range-to-go (Rgo) is selected as a co-variable, avoiding the estimation of time-to-go (Tgo), and a novel second-order nonlinear consensus protocol is developed to design the PTCGL; in normal LOS direction, considering the variable LOS angle constraint, the cooperative guidance law is designed with the proposed prescribed-time sliding model control (PTSMC) method. Besides, the prescribed-time convergence of Rgo and LOS errors are proved. Finally, the effectiveness and superiority of the proposed PTCGL with leader-following strategy is illustrated by numerical simulation results. • The convergence time of the cooperative guidance law can be set arbitrarily. • The multi-missile surrounding attack was achieved without pre-setting the desired LOS angle. • The Range-to-go was selected as a co-variable to design the cooperative guidance law. • A prescribed time convergence sliding mode method was developed to design the cooperative guidance law. [ABSTRACT FROM AUTHOR]

For bistatic inverse synthetic aperture radar (Bi-ISAR), the non-uniform motion state of maneuvering target and the time-varying bistatic angle make the traditional imaging method of moving target face the problem of translation compensation, and the traditional translation compensation method is not suitable for the return wave in the case of sparse aperture. In this paper, a compensation imaging method combining two-dimension joint linearized Bregman iteration and image contrast search is proposed. The translation compensation problem can be transformed into two-dimension joint compressed sensing sparse reconstruction and moving target motion parameter estimation. The proposed algorithm makes use of the gain of echo twodimension compression, greatly improves the accuracy of translation compensation and the quality of target image and has stronger robustness to noise. The processing results of simulation data verify the effectiveness and superiority of the algorithm. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation 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.)

For the guidance problem of multiple missiles attacking a maneuvering target simultaneously in plane, a novel fixed-time distributed cooperative guidance law with impact angle constraint is designed in this paper. The design process of distributed cooperative guidance law can be roughly divided into two parts. First, based on the nonsingular terminal sliding mode control, a cooperative guidance law on the line-of-sight (LOS) direction is developed, which can guarantee that all missiles hit the maneuvering target simultaneously. Second, another guidance law in normal direction of the LOS direction is designed to achieve the fixed-time convergence of LOS angular rate and LOS angle. Finally, numerical simulations verify the effectiveness of the proposed cooperative guidance law for different engagement scenarios. [ABSTRACT FROM AUTHOR]

Moving target detection (MTD) is a research hotspot in radar signal processing. Generally, the time information of non-cooperative moving targets entering and leaving a radar coverage area is unknown, which would lead to severe performance loss for target parameter estimation, detection, and imaging. Unlike our previous research work, this paper addresses the motion parameters estimation and refocusing problem for a radar maneuvering target with unknown entry and departure time. A computationally efficient method that utilizes extended Kalman filtering (EKF) for phase tracking is proposed to estimate the entry and departure times. The proposed method first performs range cell migration correction (RCMC) on the pulse compression echo signal. Then, the maneuvering target signal is modeled as a polynomial phase signal (PPS) and utilizes the EKF to construct a binary state-space equation for polynomial phase tracking. Finally, by comparing the phase tracking results of the noise cell and the signal cell, one can derive estimates for the entry/departure time and motion parameters. Compared with existing methods, the proposed method avoids multi-dimension searching on the parameter space, so it has a prominent advantage in computational complexity. Moreover, the core of the proposed method lies in tracking the polynomial phase, which is not constrained by the order of target motion, and has wider applicability in practice. Both simulated and public radar data are used to validate the effectiveness of the proposed method. • A method for estimating motion parameters under unknown time information is proposed. • The devised estimator can provide satisfactory time information estimation accuracy. • Our method avoids the high-dimensional search, which has low computational cost. • The proposed method further enriches and perfects the phase tracking theory. [ABSTRACT FROM AUTHOR]

Although there have been numerous studies on maneuvering target tracking, few studies have focused on the distinction between unknown maneuvers and inaccurate measurements, leading to low accuracy, poor robustness, or even divergence. To this end, a noise-adaption extended Kalman filter is proposed to track maneuvering targets with multiple synchronous sensors. This filter avoids the simultaneous adjustment of the process model and measurement model without distinction. Instead, the maneuver detection based on the Dempster-Shafer evidence theory is constructed to achieve the reliable distinction between unknown maneuvers and inaccurate measurements by fusing multi-sensor information, which effectively improves the robustness of the filter. Moreover, the adaptive estimation of the process noise covariance is modeled by a Markovian decision process with a proper reward function. Deep deterministic policy gradient is designed to obtain the optimal process noise covariance by taking the innovation as the state and the compensation factor as the action. Furthermore, the recursive estimation of the measurement noise covariance is applied to modify a priori measurement noise covariance of the corresponding sensor. Finally, the fusion algorithm is developed for the global estimation. Simulation experiments are carried out in two scenarios, and simulation results illustrate the feasibility and superiority of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Multiple radar systems represent an attractive option for target tracking because they can significantly enlarge the area coverage and improve both the probability of trajectory detection and the localization accuracy. The presence of multiple extended targets or weak targets is a challenge for multiple radar systems. Moreover, their performance may be severely deteriorated by regions characterized by a high clutter density. In this article, an algorithm for detection and tracking of multiple targets, extended or weak, based on measurements provided by multiple radars in an environment with heavily cluttered regions, is proposed. The proposed method features three stages. In the first stage, past measurements are exploited to build a spatiotemporal clutter map in each radar; a weight is then assigned to each measurement to assess its significance. In the second stage, a track-before-detect algorithm, based on a weighted 3-D Hough transform, is applied to obtain target tracklets. In the third stage, a low-complexity tracklet association method, exploiting a lion reproduction model, is applied to associate tracklets of the same target. Three experiments are presented to illustrate the effectiveness of the proposed approach. The first experiment is based on synthetic data, the second one is based on actual data from a radar network with two homogeneous air surveillance radars, and the third one is based on actual data from a radar network with four different marine surveillance radars. The results reveal that the proposed method can outperform competing approaches. [ABSTRACT FROM AUTHOR]

This article proposes a new terminal cooperative guidance law to control both impact time and impact angle in three-dimensional engagement. The presented guidance law employs on and normal line-of-sight accelerations to control the impact time and angle together. Two parts are included in this guidance law, that is, the guidance laws with impact time constraint and impact angle constraint. The first is designed based on fixed-time consensus theory to fulfill the salvo attack of the target, and the second is developed based on fixed-time nonsingular fast terminal sliding mode control method to achieve the desired impact angles. The stability analysis of this guidance law based on Lyapunov theory is also presented in detail. Moreover, the maneuvering target can be intercepted successfully with the presented guidance law, and the fixed-time stability and less control energy are well ensured. Additionally, the effectiveness and applicability of the proposed guidance scheme are explicitly verified through simulation tests. [ABSTRACT FROM AUTHOR]

In this article, fixed-time cooperative guidance laws are designed for multiple missiles to simultaneously attack a maneuvering target at desired terminal angles. The 3-D guidance commands consist of tangential acceleration along line-of-sight (LOS) direction to achieve a salvo attack and normal acceleration perpendicular to the LOS direction to realize a terminal angle-constrained interception. First, the tangential acceleration is derived from a distributed cooperative protocol to guarantee the fixed-time consensus of impact times for multiple missiles. Second, based on the integral sliding manifold and fixed-time reaching law, the normal acceleration is developed for each missile to converge the LOS angle to the desired value within a fixed time. In particular, the unknown target acceleration components are estimated by fixed-time observers and compensated in the guidance commands. The fixed-time stability of the proposed cooperative guidance law is rigorously proved and the explicit estimate for the convergence time is theoretically provided. Then, the proposed methods are utilized to realize the cooperative mission in the planar guidance scenario. Finally, the effectiveness and advantages of the proposed cooperative guidance laws are demonstrated through numerical simulations with comparative studies. [ABSTRACT FROM AUTHOR]

A distributed multi-missile cooperative guidance law based on the finite time theory is proposed to solve the terminal guidance problem of three-dimensional multi-missiles cooperative interception of large maneuvering target. According to the finite time consistency theory, an adaptive guidance law based on the integral sliding mode is designed to ensure that all missiles can reach the target at the same time in the terminal guidance process. The longitudinal and lateral acceleration of the line of sight are based on the guidance law of the fast terminal sliding mode surface. The terminal attack angle is constrained, so that the terminal attack Angle can reach the expected value in finite time. The simulation results show that the designed guidance law can achieve the cooperative attack on the maneuvering targets.

In this paper, we estimate Doppler frequency of a maneuvering target being tracked by passive radar using two types of particle filter, the first is “Maximum Likelihood Particle Filter” (MLPF) and the second is “Minimum Variance Particle filter” (MVPF). By simulating the passive radar system that has the bistatic geometry “Digital Video Broadcasting-Terrestrial (DVB-T) transmitter / receiver” with these two types, we can estimate the Doppler frequency of the maneuvering target and compare the simulation results for deciding which type gives better performance.

Introduction. The concepts of constructing promising radar systems (radars) show that these will be integral type complexes. The creation of such systems implies the presence in their composition of an information system consisting of channels that produce a functionally completed procedure for processing signals and information to solve a definite task.Aim. Development of a target coordinate correction algorithm based on spatial orientation information.Materials and methods. The tasks were solved by methods of mathematical analysis and numerical modeling. To justify reliability and performance of the proposed algorithm, a model was developed. The model allowed one to obtain accuracy characteristics of the algorithm.Results. As a result of the simulation, the accuracy characteristics of the target coordinate correction algorithm based on spatial orientation information were investigated. It determines the quality of building of the target trajectory and the quality of the target tracking system. The structure and the description of the developed algorithm were given, an implementation option was shown. The results of estimation of the accuracy of the algorithm were presented.Conclusion. As a result of the analysis of the target coordinate correction algorithm based on information about the target’s spatial orientation, as well as modeling of its operation, a conclusion about the reliability and the performance of the proposed algorithm was drawn The presented data of experimental studies on the accuracy characteristics of the proposed algorithm showed the feasibility of the decisions made. The presented results allow one to determine the most appropriate and effective way to develop simplified versions of the algorithm.

In this paper, a new fixed-time convergence guidance law is proposed against maneuvering targets in the three-dimensional (3-D) engagement scenario. The fixed-time stability theory is used to zero the line-of-sight (LOS) angle rate, which will ensure the collision course and the impact of the target. It is proven that the convergence of the LOS angle rate can be achieved before the final impact time of the guidance process, regardless of the initial conditions. Furthermore, the convergence rate is merely related to control parameters. In theoretical analysis, the convergence rate and upper bound are compared with that of other laws to show the potential advantages of the proposed guidance law. Finally, simulations are carried out to illustrate the effectiveness and robustness of the proposed guidance law.

Long-time coherent integration works to significantly increase the detection probability for maneuvering targets. However, during the observation time, the problems that often tend to occur are range cell migration (RCM) and Doppler frequency cell migration (DFCM), due to the high velocity and acceleration of the maneuvering target, which can reduce the detection of the maneuvering targets. In this regard, we propose a new coherent integration approach, based on the product scale zoom discrete chirp Fourier transform (PSZDCFT). Specifically, by introducing the zoom operation into the modified discrete chirp Fourier transform (MDCFT), the zoom discrete chirp Fourier transform (ZDCFT) can correctly estimate the centroid frequency and chirp rate of the linear frequency-modulated signal (LFM), regardless of whether the parameters of the LFM signal are outside the estimation scopes. Then, the scale operation, combined with ZDCFT, is performed on the radar echo signal in the range frequency slow time domain, to remove the coupling. Thereafter, a product operation is executed along the range frequency to inhibit spurious peaks and reinforce the true peak. Finally, the velocity and acceleration of the target estimated from the true peak position, are used to construct a phase compensation function to eliminate the RCM and DFCM, thus achieving coherent integration. The method is a linear transform without energy loss, and is suitable for low signal-to-noise (SNR) environments. Moreover, the method can be effectively fulfilled based on the chirp-z transform (CZT), which prevents the brute-force search. Thus, the method reaches a favorable tradeoff between anti-noise performance and computational load. Intensive simulations demonstrate the effectiveness of the proposed method.

In this paper, a novel cooperative and predictive guidance law is proposed to intercept high-speed and high-maneuverability targets with inferior interceptors. The purpose of guidance is cooperatively covering the most-probable locations where the target may be in the future. To fulfill this purpose, predicted target states in the form of a probability density function were obtained using limited target information, i.e., noisy position data for one case and maneuverability limits for the second case, at first. Next, the likelihood of the reachable set of interceptors was computed over the predicted target state. Then, to increase the probability of interception in a finite time, the interceptors’ trajectories were adjusted collaboratively depending on the likelihood values. An extensive Monte Carlo study, with practically applicable simulation parameters, was used to demonstrate the effectiveness of the proposed methods against targets in challenging maneuvering modes.

This article proposes a new terminal cooperative guidance law with impact time constraint in three-dimensional (3D) engagement. Two parts are comprised by this guidance scheme to control the impact time and fulfill the interception. The guidance law along the line-of-sight (LOS) direction is first designed based on finite time consensus protocol to share time-to-go values among missiles and reach the consensus. Meanwhile, the guidance law on the LOS normal direction is developed based on the fast finite time control method to achieve the interception. The stability analysis of the proposed guidance law based on the Lyapunov theory is also demonstrated in detail. Moreover, the maneuvering target can be intercepted successfully under the presented control algorithm, and the guidance system can fulfill stability within finite time. Additionally, the effectiveness and applicability of the proposed guidance scheme are explicitly verified through simulation tests. [ABSTRACT FROM AUTHOR]

The existing generalized Radon–Fourier transform (GRFT) algorithm can achieve coherent integration of high-order maneuvering targets by jointly searching in multiple dimensions, but it has high computational complexity. This article proposes a fast algorithm for the GRFT. We consider a maneuvering target with complex motions, where the jerk results in the third-order range migration (TRM) and the third-order Doppler migration (TDM). The echo data are segmented to allow the TRM, and the TDM of each segment is ignorable. In doing so, the jerk in each segment can be estimated by the second-order Radon–Fourier transform, which is used to compensate for the gain loss due to the ignoring of jerk. The final integration result can then be obtained by accumulating the results in all segments. Since the jerk does not need to be searched in the proposed algorithm, the computational complexity of the proposed algorithm is much lower than that of the standard GRFT. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of a complex three-dimension (3-D) terminal guidance process that is used against maneuvering targets while considering both the terminal impact angle (TIA) and field-of-view (FOV) angle constraints. According to the highly coupled and nonlinear 3-D terminal guidance model, an adaptive back-stepping sliding-mode guidance law algorithm is proposed in order to guarantee the stability and robustness of the guidance system. Considering the explicit expression of the line-of-sight (LOS) angle in the kinematics and dynamics of the terminal guidance process, the TIA constraint is transformed into an LOS constraint based on their well-known relationship. In view of the challenges in obtaining the motion information of maneuvering targets, an adaptive law design is introduced in order to estimate and compensate for external disturbances caused by the maneuvering of the target and modeling uncertainty. In addition, because the FOV angle represented by the overall leading angle is not a state variable in the sliding-mode guidance system, it is decoupled into two partial leading angles based on a specific transformation relation, so the 3-D terminal guidance control problem is converted into separate tracking system control issues in the pitch and yaw planes. Then, the Lyapunov stability theory is utilized to substantiate the stability of the guidance system, where the Lyapunov functions in both of the subsystems consist of the LOS and partial FOV state error terms. Finally, a series of simulations of various motion states of maneuvering targets under different terminal cases were carried out. It was proved that the terminal guidance design based on the strategies presented above was able to obtain the desired LOS constraints with satisfying the FOV limitation, and the simulation results verified the effectiveness, universality, and significance for practical applications of the proposed guidance design method.

This paper introduces a fast fixed-time guidance law with terminal angle constraint for interception of maneuvering targets, which is based on the structure of singularity-free fast terminal sliding mode and the fixed-time stability theory. Different from the finite-time stability, the fixed-time stability can predefine the maximum stabilization time of system states which is independent on the initial value of system states. Under the proposed guidance law, the guidance system can achieve stabilization within settling time which decides by the parameters of controller. In addition, an adaptive law is proposed which alleviate the chattering of sliding mode and smooths the guidance law. Meanwhile, the proof of the sliding mode manifold and system states fixed-time convergence is given by Lyapunov stability theory. Finally, numerical simulations demonstrate the performance of the proposed guidance law is satisfying. [ABSTRACT FROM AUTHOR]

Long time coherent integration technique is one of the most important methods to improve the radar detection ability of a weak maneuvering target. However, the integration performance may be greatly influenced by the range migration and Doppler migration effects caused by the complex motions of maneuvering targets when long time integration is applied. Besides, the frequency hopping characteristic of the transmitted signal will also result in Doppler migration which cannot be eliminated by the conventional coherent integration method. To deal with this problem, a novel coherent integration method based on phase compensation is proposed. By using the frequency hopping pattern, the Doppler migration is eliminated by adding an extra phase in the twiddle factor of Fourier Transform in this proposed method. Since the phase error is compensated, long time coherent integration can be achieved. The effectiveness of the proposed method is verified by the simulation results and the performance analysis.