Sequential quadratic programming-based non-cooperative target distributed hybrid processing optimization method

The distributed hybrid processing optimization problem of non-cooperative targets is an important research direction for future networked air-defense and anti-missile firepower systems. In this paper, the air-defense anti-missile targets defense problem is abstracted as a nonconvex constrained combinatorial optimization problem with the optimization objective of maximizing the degree of contribution of the processing scheme to non-cooperative targets, and the constraints mainly consider geographical conditions and anti-missile equipment resources. The grid discretization concept is used to partition the defense area into network nodes, and the overall defense strategy scheme is described as a nonlinear programming problem to solve the minimum defense cost within the maximum defense capability of the defense system network. In the solution of the minimum defense cost problem, the processing scheme, equipment coverage capability, constraints and node cost requirements are characterized, then a nonlinear mathematical model of the non-cooperative target distributed hybrid processing optimization problem is established, and a local optimal solution based on the sequential quadratic programming algorithm is constructed, and the optimal firepower processing scheme is given by using the sequential quadratic programming method containing non-convex quadratic equations and inequality constraints. Finally, the effectiveness of the proposed method is verified by simulation examples.

Impedance control of multi-arm space robot for the capture of non-cooperative targets

Robotic systems are expected to play an increasingly important role in future space activities. The robotic on-orbital service, whose key is the capturing technology, becomes a research hot spot in recent years. This paper studies the dynamics modeling and impedance control of a multi-arm free-flying space robotic system capturing a non-cooperative target. Firstly, a control-oriented dynamics model is essential in control algorithm design and code realization. Unlike a numerical algorithm, an analytical approach is suggested. Using a general and a quasi-coordinate Lagrangian formulation, the kinematics and dynamics equations are derived.Then, an impedance control algorithm is developed which allows coordinated control of the multiple manipulators to capture a target.Through enforcing a reference impedance, end-effectors behave like a mass-damper-spring system fixed in inertial space in reaction to any contact force between the capture hands and the target. Meanwhile, the position and the attitude of the base are maintained stably by using gas jet thrusters to work against the manipulators' reaction. Finally, a simulation by using a space robot with two manipulators and a free-floating non-cooperative target is illustrated to verify the effectiveness of the proposed method.

Design of a Non-cooperative Target Capture Mechanism

A passive compliant non-cooperative target capture mechanism is designed to maintain the non-cooperative target on-orbit. When the relative position between capture mechanism and satellite is confirmed,a pair of four-bar linkages lock the docking ring,which is used for connecting the satellite and the rocket. The mathematical model of capture mechanism and capture space is built by the Denavit-Hartenberg(D-H)method,and the torque of each joint is analyzed by the Lagrange dynamic equation. Besides,the capture condition and the torque of every joint under different capture conditions are analyzed by simulation in MSC. Adams. The results indicate that the mechanism can capture the non-cooperative target satellite in a wide range. During the process of capture,the passive compliant mechanism at the bottom can increase capture space,thereby reducing the difficulty and enhance stability of the capture.

Design of a Flexible Capture Mechanism Inspired by Sea Anemone for Non-cooperative Targets

Robotic grippers have been used in industry as end-effectors but are usually limited to operations in pre-defined workspace.However,few devices can capture irregularly shaped dynamic targets in space,underwater and other unstructured environments.In this paper,a novel continuum arm group mechanism inspired by the morphology and motions of sea anemones is proposed.It is able to dissipate and absorb the kinetic energy of a fast moving target in omni-direction and utilize multiple arms to wrap and lock the target without accurate positioning control.Wire-driven actuation systems are implemented in the individual continuum arms,achieving both bending motion and stiffness regulation.Through finite element method,the influence of different configurations of the continuum arm group on the capture performance is analyzed.A robotic prototype is constructed and tested,showing the presented arm group mechanism has high adaptability to capture targets with different sizes,shapes,and incident angles.

Non-cooperative target pose estimation based on improved iterative closest point algorithm

For localisation of unknown non-cooperative targets in space,the existence of interference points causes inaccuracy of pose estimation while utilizing point cloud registration.To address this issue,this paper proposes a new iterative closest point(ICP)algorithm combined with distributed weights to intensify the dependability and robustness of the non-cooperative target localisation.As interference points in space have not yet been extensively studied,we classify them into two broad categories,far interference points and near interference points.For the former,the statistical outlier elimination algorithm is employed.For the latter,the Gaussian distributed weights,simultaneously valuing with the variation of the Euclidean distance from each point to the centroid,are commingled to the traditional ICP algorithm.In each iteration,the weight matrix W in connection with the overall localisation is obtained,and the singular value decomposition is adopted to accomplish high-precision estimation of the target pose.Finally,the experiments are implemented by shooting the satellite model and setting the position of interference points.The outcomes suggest that the proposed algorithm can effectively suppress interference points and enhance the accuracy of non-cooperative target pose estimation.When the interference point number reaches about 700,the average error of angle is superior to 0.88°.

A Method to Obtain the Moving Speed of Uncooperative Target Based on Only Two Measurements

The existing research results show that a fixed single station must conduct three consecutive frequency shift measurements and obtain the target’s moving speed by constructing two frequency difference equations. This article proposes a new method that requires only two consecutive measurements. While using the azimuth measurement to obtain the angular difference between two radial distances, it also conducts two consecutive Doppler frequency shift measurements at the same target azimuth. On the basis of this measurement, a frequency difference equation is first constructed and solved jointly with the Doppler frequency shift equation. By eliminating the velocity variable and using the measured angular difference to obtain the target’s lead angle, the target’s velocity can be solved by using the Doppler frequency shift equation again. The new method avoids the condition that the target must move equidistantly, which not only provides an achievable method for engineering applications but also lays a good foundation for further exploring the use of steady-state signals to achieve passive positioning.

Analytic optimal pose tracking control in close-range proximity operations with a non-cooperative target

This paper investigates an analytical optimal pose tracking control problem for chaser spacecraft during the close-range proximity operations with a non-cooperative space target subject to attitude tumbling and unknown orbital maneuvering.Firstly,the relative translational motion between the orbital target and the chaser spacecraft is described in the Line-of-Sight(LOS)coordinate frame along with attitude quaternion dynamics.Then,based on the coupled 6-Degree of Freedom(DOF)pose dynamic model,an analytical optimal control action consisting of constrained optimal control value,application time and its duration are proposed via exploring the iterative sequential action control algorithm.Meanwhile,the global closed-loop asymptotic stability of the proposed predictive control action is presented and discussed.Compared with traditional proximity control schemes,the highlighting advantages are that the application time and duration of the devised controller is applied discretely in light of the influence of the instantaneous pose configuration on the pose tracking performance with less energy consumptions rather than at each sample time.Finally,three groups of illustrative examples are organized to validate the effectiveness of the proposed analytical optimal pose tracking control scheme.

Spin-image surface matching based target recognition in laser radar range imagery

We explore the problem of in-plane rotation-invariance existing in the vertical detection of laser radar （Ladar） using the algorithm of spin-image surface matching. The method used to recognize the target in the range imagery of Ladar is time-consuming, owing to its complicated procedure, which violates the requirement of real-time target recognition in practical applications. To simplify the troublesome procedures, we improve the spin-image algorithm by introducing a statistical correlated coeff^cient into target recognition in range imagery of Ladar. The system performance is demonstrated on sixteen simulated noise range images with targets rotated through an arbitrary angle in plane. A high efficiency and an acceptable recognition rate obtained herein testify the validity of the improved algorithm for practical applications. The proposed algorithm not only solves the problem of in-plane rotation-invariance rationally, but also meets the real-time requirement. This paper ends with a comparison of the proposed method and the previous one.

CoFe/NiFe复合自由层对自旋阀磁电阻变化率的影响

研究CoFe/NiFe复合自由层对自旋阀磁电阻变化率的影响。在实验中通过固定溅射功率、时间和气流,调节靶基距(TSD)得到不同厚度及均匀性的复合自由层CoFe/NiFe薄膜,进而达到优化自旋阀结构提高其磁电阻率的目的。实验结果表明:在TSD分别为8.382 cm、8.890 cm时,制备的CoFe和NiFe单层膜性能最优,电阻标准偏差分别为1.33%、0.98%。通过磁性能综合测试平台对优化后的CoFe/NiFe复合自由层的自旋阀结构进行了测试,磁电阻变化率(MR)较优化前提高了约0.84%。该研究可为高性能自旋阀结构的制备提供参考。

改进YOLOv5s的弱光水下生物目标检测算法

针对水下光学图像目标检测过程中由于水中光线衰弱严重、图像环境复杂和拍摄设备移动等造成的生物识别精度低的问题,提出了基于改进YOLOv5s的弱光水下生物目标实时检测算法YOLOv5s-underwater。针对弱光水下光线衰弱的问题,引入了限制对比度自适应直方图均衡(CLAHE)算法对输入图像进行预处理,解决了颜色失真和图像毛糙的问题。针对复杂的弱光水下图像环境,提出了快速空间金字塔池化(SPPF)模块,解决了水下物体区分度低和特征损失严重的问题。针对拍摄设备移动带来的场景和形态变化问题,提出了一种基于旋转窗口的Swin-Transformer模块,提高了模型的泛化能力。针对水下小目标,修改了网络模型结构,提高了小目标的检测能力。仿真和实验结果表明:所提算法相较于YOLOv5s检测精度提高30.7%,证明了算法的有效性。

A grasp planning algorithm under uneven contact point distribution scenario for space non-cooperative target capture

The contact point configuration should be carefully chosen to ensure a stable capture,especially for the non-cooperative target capture mission using multi-armed spacecraft.In this work scenario,the contact points on the base and on the arms are distributed on the opposite side of the target.Otherwise,large forces will be needed.To cope with this problem,an uneven-oriented distribution union criterion is proposed.The union criterion contains a virtual symmetrical criterion and a geometry criterion.The virtual symmetrical contact point criterion is derived from the proof of the force closure principle using computational geometry to ensure a stable grasp,and the geometry criterion is calculated by the volume of the minimum polyhedron formed by the contact points to get a wide-range distribution.To further accelerate the optimization rate and enhance the global search ability,a line array modeling method and a continuous-discrete global search algorithm are proposed.The line array modeling method reduces the workload of calculating the descent direction and the gradient available,while the continuous-discrete global search algorithm reducing the optimization dimension.Then a highly efficient grasping is achieved and the corresponding contact point is calculated.Finally,an exhaustive verification is conducted to numerically analyze the disturbance resistance ability,and simulation results demonstrate the effectiveness of the proposed algorithms.

自旋对弹体侵彻效应的影响

为解释带有自旋角速度的侵彻弹体在试验和仿真中的更好表现,开发了考虑自旋角速度的弹体侵彻模型。姿态动力学分析表明了一般侵彻情况下自旋角速度引起弹体非平面运动,正侵彻情况下则出现自旋弹体保持平面运动的特殊情况。基于空腔膨胀模型的推导表明,弹靶接触处的切应力方向改变是自旋弹体侵彻阻力减小的原因之一,与剪切效应导致的空腔表面正应力衰减共同构成了侵彻深度增加的机制。刚体运动学推导表明,多层间隔靶侵彻情况下,靶间进动导致弹体轴线与靶面法向夹角增速减缓甚至减小,是弹道稳定性增加的重要原因。自旋角速度改变了弹体侵彻过程的受力和运动形式,导致其侵彻深度和弹道稳定性增加,总体上对弹体侵彻效应起积极作用。

Non-cooperative spacecraft proximity control considering target behavior uncertainty

The significant characteristics of space non-cooperative targets include the uncertainties of dynamic parameters and behaviors.Herein,a hybrid proximity control strategy adapted to the behavior uncertainty of a non-cooperative target is presented.First,the relative motion dynamics between the chaser and target is established in the geocentric inertial coordinate system and transcribed based on the chaser spacecraft body coordinate system.Subsequently,to facilitate proximity control under uncertain conditions,an extended state observer is designed to estimate and compensate for the total uncertainty in the relative motion dynamics.Finally,an event-triggered sliding mode control law is designed to track the target with behavior uncertainty and realize synchronization.Numerical simulations demonstrate the effectiveness of the proposed proximity control strategy for both tumbling and maneuvering targets.

基于飞行时间相机的非合作慢旋卫星稠密重建研究

针对非合作慢旋卫星的模型重建问题,提出基于飞行时间(time-of-flight,TOF)相机和同时定位与制图(simultaneous localization and mapping,SLAM)的稠密重建方法。基于预先检测与自适应阈值方法提高旋转提取与描述(oriented fast and rotated brief,ORB)的特征尺度适应性。利用运动度量方法选取关键帧。利用子模型拼接方法加快重建效率。利用仿真环境制作非合作慢旋卫星的数据集。仿真实验结果表明:该方法能够实现长时间稳定地工作,可在3 min内重建出卫星模型的稠密点云,点云密度大于5000,重建误差小于5 cm。利用机械臂、卫星模型及光学暗室搭建半物理实验系统,表明算法的精度及抗噪声能力基本满足非合作目标感知的任务的需求。

空间锥体目标微动特性分析与识别方法

空间锥体目标在大气层外飞行过程中存在不同的微动,目标的微动为进动,诱饵的微动为摆动或自旋.根据目标与诱饵的微动差异,提出了应用特征谱作为识别特征的分类方法.基于多散射中心信号模型,分析了进动、摆动以及自旋调制信号的微多普勒特性.分析结果表明,进动、摆动与自旋目标的微多普勒谱虽然均可以近似为线谱,但是存在明显差异.应用谐波和的形式描述回波信号,并采用特征值分解提取特征谱作为识别特征.仿真结果表明,该方法能够有效地识别目标与诱饵.

旋转涂层法制备聚酰亚胺薄膜

研究了采用二酐和二胺合成聚酰胺酸溶液，利用旋转涂层法制备聚酰亚胺薄膜的方法并对成膜机理进行了初步探讨。研究表明：在固定旋转时间时，通过控制合成聚酰胺酸的浓度和旋转速度可基本上控制薄膜的厚度，旋转涂膜法制备的聚酰亚胺薄膜厚度起伏小于5％，薄膜表面光洁度达到0．3～0．4nm，0．3μm厚聚酰亚胺薄膜的弹性模量为50～80MPa。

基于自旋图的三维自动目标识别

将三维表面匹配领域的自旋图(spin-images)方法运用于扫描激光雷达自动目标识别中,基于自旋图特征,提出了平均最大相似性度量、候选对应关系数目、几何一致性筛选后对应关系数目、分组筛选后最大组的对应关系数目这4个识别指标,并将其组合构成组合识别准则,从而进行三维目标识别。同时针对实际应用需求,进一步研究了点云空间分辨率、激光雷达测距误差以及遮挡对目标识别率的影响,为激光雷达三维目标识别系统的设计提供了参考。

基于微多普勒特征的空间锥体目标识别

空间锥体目标在大气层外飞行过程中存在不同的微动,目标的微动为进动,诱饵的微动为摆动或自旋。根据真假目标的微动差异,提出了低分辨雷达的目标识别方法。在多散射中心信号模型下分析了真假目标的微多普勒特性,指出目标回波信号微多普勒谱与其进动参数密切相关,而诱饵回波信号微多普勒谱与其摆动\自旋频率密切相关。应用低分辨雷达多次回波信号抽取微多普勒域熵与波形标准差作为识别特征,并采用两种分类器进行分类识别。仿真结果表明:所提方法可以有效地实现真假目标的分类。

高速旋转目标旋转速度估计方法

旋转速度估计是高速旋转目标成像的基础,论文提出一种新的旋转速度估计方法,该算法基于旋转目标在距离时间域所具有的特性,在利用傅里叶变换粗略估计旋转速度的基础上,利用计算图像熵的方法在特定范围内对角速度估计值进行调整,以获得很高的估计精度。该方法直接计算整幅图像的熵值,从而不依赖单个的散射点。使用仿真数据演示了算法的性能,证明了算法的有效性。

基于压缩感知的窄带高速自旋目标超分辨成像物理机理分析

常规窄带雷达系统对高速自旋的空天目标成像时,方位脉冲重复频率通常难以满足采样率要求.而基于压缩感知(compressive sensing,CS)理论则可实现欠采样条件下窄带高速自旋目标的成像.本文对这一成像的物理机理进行分析和讨论.首先,构建方位欠采样回波模型,分析了该模型与CS理论的关系;其次,从物理角度分析基于CS理论可以保证欠采样条件下散射点准确重构的机理,给出欠采样倍数的理论下限值.仿真结果表明,欠采样条件下窄带雷达系统可实现对高速自旋目标二维成像,同时验证了基于CS的欠采样成像性能与欠采样倍数、等效强散射点个数以及波长等有关,与信号带宽无关等结论.