Finite-Time H∞ Control of Switched Nonlinear Systems under State-Dependent Switching

This paper investigates the finite-time H∞ control problem of switched nonlinear systems via state-dependent switching and state feedback control. Unlike the existing approach based on time-dependent switching strategy, in which the switching instants must be given in advance, the state-dependent switching strategy is used to design switching signals. Based on multiple Lyapunov-like functions method, several criteria for switched nonlinear systems to be finite-time H∞ control are derived. Finally, a numerical example with simulation results is provided to show the validity of the conclusions.

Long-Time Behavior of Solution for Autonomous Suspension Bridge Equations with State-Dependent Delay

This work is devoted to the following suspension bridge with state-dependent delay: . The main goal of this paper is to investigate the long-time behavior of the system. Under suitable hypothesis, the quasi-stability estimates of the system are established, based on which the existence of global attractor with finite fractal dimension is obtained. Furthermore, the existence of exponential attractor is proved.

Persymmetric adaptive polarimetric detection of subspace range-spread targets in compound Gaussian sea clutter

This paper focuses on the adaptive detection of range and Doppler dual-spread targets in non-homogeneous and nonGaussian sea clutter.The sea clutter from two polarimetric channels is modeled as a compound-Gaussian model with different parameters,and the target is modeled as a subspace rangespread target model.The persymmetric structure is used to model the clutter covariance matrix,in order to reduce the reliance on secondary data of the designed detectors.Three adaptive polarimetric persymmetric detectors are designed based on the generalized likelihood ratio test(GLRT),Rao test,and Wald test.All the proposed detectors have constant falsealarm rate property with respect to the clutter texture,the speckle covariance matrix.Experimental results on simulated and measured data show that three adaptive detectors outperform the competitors in different clutter environments,and the proposed GLRT detector has the best detection performance under different parameters.

Kullback-Leibler Divergence Based ISAC Constellation and Beamforming Design in the Presence of Clutter

Integrated sensing and communication(ISAC)is regarded as a pivotal technology for 6G communication.In this paper,we employ Kullback-Leibler divergence(KLD)as the unified performance metric for ISAC systems and investigate constellation and beamforming design in the presence of clutters.In particular,the constellation design problem is solved via the successive convex approximation(SCA)technique,and the optimal beamforming in terms of sensing KLD is proven to be equivalent to maximizing the signal-to-interference-plus-noise ratio(SINR)of echo signals.Numerical results demonstrate the tradeoff between sensing and communication performance under different parameter setups.Additionally,the beampattern generated by the proposed algorithm achieves significant clutter suppression and higher SINR of echo signals compared with the conventional scheme.

EXACT CONTROLLABILITY AND CONTINUOUS DEPENDENCE OF FRACTIONAL NEUTRAL INTEGRO-DIFFERENTIAL EQUATIONS WITH STATE-DEPENDENT DELAY

In the present paper,with the help of the resolvent operator and some analytic methods,the exact controllability and continuous dependence are investigated for a fractional neutral integro-differential equations with state-dependent delay.As an application,we also give one example to demonstrate our results.

Attitude controller for reentry vehicles using state-dependent Riccati equation method

To get better tracking performance of attitude command over the reentry phase of vehicles, the use of state-dependent Riccati equation (SDRE) method for attitude controller design of reentry vehicles was investigated. Guidance commands are generated based on optimal guidance law. SDRE control method employs factorization of the nonlinear dynamics into a state vector and state dependent matrix valued function. State-dependent coefficients are derived based on reentry motion equations in pitch and yaw channels. Unlike constant weighting matrix Q, elements of Q are set as the functions of state error so as to get satisfactory feedback and eliminate state error rapidly, then formulation of SDRE is realized. Riccati equation is solved real-timely with Schur algorithm. State feedback control law u(x) is derived with linear quadratic regulator (LQR) method. Simulation results show that SDRE controller steadily tracks attitude command, and impact point error of reentry vehicle is acceptable. Compared with PID controller, tracking performance of attitude command using SDRE controller is better with smaller control surface deflection. The attitude tracking error with SDRE controller is within 5°, and the control deflection is within 30°.

A numerical study of comparison of two one-state-variable,rate-and state-dependent friction evolution laws

The two one-state-variable, rate- and state-dependent friction laws, i.e., the slip and slowness laws, are com- pared on the basis of dynamical behavior of a one-degree-of-freedom spring-slider model through numerical simulations. Results show that two （normalized） model parameters, i.e., A （the normalized characteristic slip distance） and β-α （the difference in two normalized parameters of friction laws）, control the solutions. From given values of △, β, and α, for the slowness laws, the solution exists and the unique non-zero fixed point is stable when △〉（β-α）, yet not when △ 〈（β-α）. For the slip law, the solution exists for large ranges of model parameters and the number and stability of the non-zero fixed points change from one case to another. Results suggest that the slip law is more appropriate for controlling earthquake dynamics than the slowness law.

Solution of the HJI equations for nonlinear H_∞ control design by state-dependent Riccati equations approach

The relationship between the technique by state- dependent Riccati equations （SDRE） and Hamilton-Jacobi-lsaacs （HJI） equations for nonlinear H∞ control design is investigated. By establishing the Lyapunov matrix equations for partial derivates of the solution of the SDREs and introducing symmetry measure for some related matrices, a method is proposed for examining whether the SDRE method admits a global optimal control equiva- lent to that solved by the HJI equation method. Two examples with simulation are given to illustrate the method is effective.

Discontinuous event-trigger scheme for global stabilization of state-dependent switching neural networks with communication delay

This paper is concerned with the global stabilization of state-dependent switching neural networks(SDSNNs)viadiscontinuous event-triggered control with network-induced communication delay.Aiming at decreasing triggering times,a discontinuous event-trigger scheme is utilized to determine whether the sampling information is required to be sent outor not.Meanwhile,under the effect of communication delay,the trigger condition and SDSNNs are transformed into twotractable models by designing a fictitious delay function.Then,using the Lyapunov–Krasovskii stability theory,someinequality estimation techniques,and extended reciprocally convex combination method,two sufficient criteria are established for ensuring the global stabilization of the resulting closed-loop SDSNNs,respectively.A unified framework isderived that has the ability to handle the simultaneous existence of the communication delay,the properties of discontinuousevent-trigger scheme,as well as feedback controller design.Additionally,the developed results demonstrate a quantitativerelationship among the event trigger parameter,communication delay,and triggering times.Finally,two numerical examples are presented to illustrate the usefulness of the developed stabilization scheme.

Suggested New Terms for Describing Chiral States and the State-Dependent Behavior of Chiral Systems

Deficiencies in the terminology used to describe chiral systems exist for behaviors under various processes and thus a more general, robust terminology is considered. For example, the descriptions for characterizing melting point, solubility, and recrystallization behaviors were adopted well before it was realized that perturbation of the enantiomeric com-position (ec) due to self-disproportionation could be effected by processes other than recrystallization such as sublimation, chromatography over achiral substrates, and even distillation. Thus, an endeavor has been made to address the question of universally describing behaviors under processes that effect, or are dependent on, the ec. The main terms that have been defined with respect to behavior are homomate (analogous to a conglomerate), heteromate, bimate (analogous to a racemic compound), and unimate (analogous to a solid solution) and they apply to melting point, solubility, recrystallization, sublimation, distillation, and chromatographic processes. Additionally, suggestions for improving the terminology for describing the states of chiral systems are also considered and the defined terms are: holemate (hol, ec = 100%), scalemate (scl, 50% ec eqm, ec = 50%).

EXISTENCE,UNIQUENESS AND APPROXIMATION OF THE SOLUTION OF AN ODE WITH (INFINITELY MANY) STATE-DEPENDENT IMPULSES VIA FIXED MESH GALERKIN FORMULATION

A fixed mesh variational formulation is used to establish existence and uniqueness of the solution of ordinary differential equations with (in finitely many) state-dependent in pulses on the right-hand side. This approach gives a natural numerical scheme to approximate the solution.The convergence of the approximation is proved and its asymptatic order obtained.

The Effect of State-Dependent Control for an SIRS Epidemic Model with Varying Total Population

Based on the mechanism of prevention and control of infectious disease, we propose, in this paper, an SIRS epidemic model with varying total population size and state-dependent control, where the fraction of susceptible individuals in population is as the detection threshold value. By the Poincaré map, theory of differential inequalities and differential equation geometry, the existence and orbital stability of the disease-free periodic solution are discussed. Theoretical results show that by state-dependent pulse vaccination we can make the proportion of infected individuals tend to zero, and control the transmission of disease in population.

A general evaluation system for optimal selection performance of radar clutter model

The optimal selection of radar clutter model is the premise of target detection,tracking,recognition,and cognitive waveform design in clutter background.Clutter characterization models are usually derived by mathematical simplification or empirical data fitting.However,the lack of standard model labels is a challenge in the optimal selection process.To solve this problem,a general three-level evaluation system for the model selection performance is proposed,including model selection accuracy index based on simulation data,fit goodness indexs based on the optimally selected model,and evaluation index based on the supporting performance to its third-party.The three-level evaluation system can more comprehensively and accurately describe the selection performance of the radar clutter model in different ways,and can be popularized and applied to the evaluation of other similar characterization model selection.

Wind turbine clutter mitigation using morphological component analysis with group sparsity

To address the problem that dynamic wind turbine clutter(WTC)significantly degrades the performance of weather radar,a WTC mitigation algorithm using morphological component analysis(MCA)with group sparsity is studied in this paper.The ground clutter is suppressed firstly to reduce the morphological compositions of radar echo.After that,the MCA algorithm is applied and the window used in the short-time Fourier transform(STFT)is optimized to lessen the spectrum leakage of WTC.Finally,the group sparsity structure of WTC in the STFT domain can be utilized to decrease the degrees of freedom in the solution,thus contributing to better estimation performance of weather signals.The effectiveness and feasibility of the proposed method are demonstrated by numerical simulations.

高灵敏微波载荷卫星出舱电缆及舱体屏蔽的EMC设计

针对高灵敏微波载荷卫星对舱板电磁屏蔽效能的高需求与出舱电缆对舱体屏蔽效能巨大破坏性之间的矛盾,文章首先提出航天器理想舱板(无出舱电缆)的电磁屏蔽效能分析方法,给出提高对于1 GHz以上干扰电磁波屏蔽效能的设计原则;然后分析出舱电缆成为影响航天器外舱板对P波段(150 MHz~1 GHz)电磁波屏蔽效能主要因素的机理,给出干扰电流与干扰场强关系计算公式;最后给出出舱电缆及舱体屏蔽的电磁兼容(EMC)设计方法,提出用接地电阻测量法验证出舱电缆屏蔽皮接地的有效性,为总体总装EMC实施找到关键控制手段,并通过整星试验数据确认此方法能有效提升整星EMC试验效率。

基于绝对多普勒的多预警机协同补盲方法

为了实现对责任区全区域、大视角来袭目标的严密预警探测,提出一种基于绝对多普勒的多预警机协同补盲方法。首先,分析目标径向速度的影响因素及其变化规律,推导绝对多普勒的数学表达式,将影响多普勒盲区的复杂多变因素优化调整为目标速度及目标与预警机间的相对位置。其次,运用仿真建模方法,基于绝对多普勒杂波凹口表达式,设计一种以检测点数表征的单预警机多普勒盲区地图绘制方法。然后,在“使得协同中的各预警机或至少有一架预警机的径向速度盲区不落在或尽量少落在重点方向上”的准则牵引下,提出一种图上作业式的多预警机相对位置关系解算方法,完成多预警机的协同部署。最后,通过双预警机圆环拱卫阵形的协同部署实验,验证该方法的有效性和实用性。

初相捷变波形优化设计与信号处理方法研究

捷变波形具备一定的距离和速度模糊抑制能力,同时兼具优良的低截获和抗干扰性能,为雷达系统提供了新的信号处理维度。初相捷变波形相对简单,工程实现难度小,为实现波形设计和信号处理闭环,本文开展了初相捷变波形优化设计与信号处理方法研究。首先,介绍了初相捷变波形的距离选通特性,进而构建了基于距离选通特性的初相捷变波形优化设计模型,并通过Majorization-Minimization算法和牛顿法进行求解。所提算法可采用平方迭代法加快收敛速度,经仿真验证,与随机产生的初相捷变波形相比,所提算法可以显著改善优化后初相捷变波形的距离选通特性。其次,基于初相捷变波形的抗折叠杂波性能,探讨了基于距离选通特性的自适应杂波抑制算法,即利用初相捷变波形空时维导向矢量的距离选通特点,实现分距离段杂波抑制,使得近距主副瓣杂波不会折叠到远距离段,经仿真与实测数据验证,所提算法在强杂波环境下具备良好的远距低速目标探测能力。最后,研究了基于距离选通和交替反演的干扰抑制算法,利用远距支援干扰滞后于目标回波的特点,并基于初相捷变波形的距离选通特性,通过距离段间交替投影实现干扰与目标回波的分距离段重构,经仿真验证,所提算法可以实现对远距支援干扰的有效抑制。

基于杂波拖尾分布的雷达无人机检测性能分析

固定翼无人机(unmanned aerial vehicle,UAV)给雷达低空监视提出了严峻挑战。分析雷达对固定翼UAV的检测性能,可为雷达UAV检测能力评估和技术升级提供重要参考。本文结合雷达探测低空固定翼UAV外场实测数据,首先分析了低空固定翼UAV雷达接收信号幅度统计分布,采用多项式对杂波拖尾导致的虚警概率进行拟合建模;然后,根据虚警概率分布得到雷达检测门限;进而根据UAV回波+杂波幅度分布理论推导得到雷达检测概率;最后,将理论分析性能与传统性能分析结果、雷达实际检测性能进行对比。结果表明,采用多项式对杂波拖尾导致的虚警概率进行单独建模,由此获得的雷达检测门限精度更高,从而使雷达UAV检测性能分析结果较传统性能分析结果更准确。

基于残差单元与注意力门的非对称编解码海杂波抑制网络

针对非均匀海杂波环境下弱小目标检测困难的问题,本文基于复值残差单元和注意力门机制,提出一种用于海杂波抑制的非对称编解码网络(Asymmetric Encoder-Decoder Network,AED-Net).该网络以雷达回波经匹配滤波后得到的复值信号为输入,利用复值残差单元取代常规卷积单元进行弱小目标和海杂波特征的提取,增强网络特征提取能力的同时避免特征信息退化.然后采用注意力门模块将编码路径各模块提取的特征信息分别送入到解码路径对应的模块.最终输出海杂波抑制后的复值信号.由于各注意力门的输入和输出维度可根据网络结构自主选择,该网络设计是一种非对称编解码结构.与典型对称编解码网络UNet相比,复值残差单元与注意力门的引入显著降低了特征信息的冗余度,增强特征信息的提取与传递,提升了海杂波抑制性能.与此同时,复值残差单元的参数规模远小于卷积单元,而注意力门的引入也有效减少解码路径单元的数量,整个网络的参数规模显著减小.基于海杂波实测数据的实验结果表明,与典型复值UNet(Complex Value-UNet,CV-UNet)网络相比,AED-Net的输出信杂比平均提升9 dB,有效工作的最低信杂比降低了3 dB,模型参数量和计算量分别减少57.8%、50%.

矿井探地雷达背景杂波抑制方法综述

随着中国煤炭安全高效智能开采需求的不断提升,矿井探地雷达(ground-penetrating radar, GPR)作为一种高精度物探方法,在煤矿井下探测中有广阔的应用前景。由于探地雷达目标回波信号受系统内部噪声、外部电磁干扰、巷道回波、地下介质不均匀等干扰影响,虚警率较高。尤其对于小尺寸目标,其回波信号为弱信号,容易淹没在强烈的背景杂波中,成为目前制约探地雷达探测性能的主要因素之一,进一步实现井下煤层、构造探测、提高探测精度的关键在于对背景杂波的抑制。从对消法、滤波法、分解法和网络法出发,综述这些杂波抑制方法的基本原理、优缺点及其在探地雷达干扰抑制领域的研究进展,并探讨各种方法的适用范围和发展潜力。杂波抑制技术的不断创新将进一步提高探地雷达的信噪比与灵敏度,使其在煤矿井下探测中发挥更大的应用价值。