Robust stability and stabilization for uncertain discrete-time switched singular systems with time-varying delays

The problems of robust stability and stabilization via memoryless state feedback for a class of discrete-time switched singular systems with time-varying delays and linear fractional uncertainties are investigated.By constructing a novel switched Lyapunov-Krasovskii functional,a delay-dependent criterion for the unforced system to be regular,causal and uniformly asymptotically stable is established in terms of linear matrix inequalities（LMIs）.An explicit expression for the desired memoryless state feedback stabilization controller is also given.The merits of the proposed criteria lie in their less conservativeness and relative simplicity,which are achieved by considering additionally useful terms（ignored in previous methods） when estimating the upper bound of the forward difference of the Lyapunov-Krasovskii functional and by avoiding utilizing any model augmentation transformation.Some numerical examples are provided to illustrate the validity of the proposed methods.

Global Practical Stabilization of Discrete-Time Switched Affine Systems via a General Quadratic Lyapunov Function and a Decentralized Ellipsoid

This paper addresses the problem of global practical stabilization of discrete-time switched affine systems via statedependent switching rules.Several attempts have been made to solve this problem via different types of a common quadratic Lyapunov function and an ellipsoid.These classical results require either the quadratic Lyapunov function or the employed ellipsoid to be of the centralized type.In some cases,the ellipsoids are defined dependently as the level sets of a decentralized Lyapunov function.In this paper,we extend the existing results by the simultaneous use of a general decentralized Lyapunov function and a decentralized ellipsoid parameterized independently.The proposed conditions provide less conservative results than existing works in the sense of the ultimate invariant set of attraction size.Two different approaches are proposed to extract the ultimate invariant set of attraction with a minimum size,i.e.,a purely numerical method and a numerical-analytical one.In the former,both invariant and attractiveness conditions are imposed to extract the final set of matrix inequalities.The latter is established on a principle that the attractiveness of a set implies its invariance.Thus,the stability conditions are derived based on only the attractiveness property as a set of matrix inequalities with a smaller dimension.Illustrative examples are presented to prove the satisfactory operation of the proposed stabilization methods.

Stabilization of a class of discrete-time switched systems via observer-based output feedback

In this paper, observer-based static output feedback control problem for discrete-time uncertain switched systems is investigated under an arbitrary switching rule. The main method used in this note is combining switched Lyapunov function （SLF） method with Finsler＇s Lemma. Based on linear matrix inequality （LMI） a less conservative stability condition is established and this condition allows extra degree of freedom for stability analysis. Finally, a simulation example is given to illustrate the efficiency of the result.

Optimal fault detection for a class of discrete-time switched linear systems

This paper deals with the problem of optimal fault detection filter （FDF） design for a class of discrete-time switched linear systems under arbitrary switching. By using an observer-based FDF as a residual generator, the design of the FDF is formulated into an optimization problem through maximizing the H_/H∞ or H∞/H∞ performance index. With the aid of an operator optimization method, it is shown that a mode-dependent unified optimal solution can be derived by solving a coupled Riccati equation. A numerical example is given to show the effectiveness of the proposed method.

Robust H_∞ output feedback controller design for linear uncertain discrete-time switched systems via state reset

This paper studies the problem of robust H∞ output feedback controller via state-reset for linear uncertain discrete-time switched systems. Using multiple Lyapunov functions,we address an output feedback controller under arbitrary switching signals,in which an H∞ performance is required. The condition is shown in the form of linear matrix inequalities (LMI). Finally,a numerical example shows the feasibility of the designed controller and illustrates that the new sufficient condition has lower conservation and more optimized H∞ tfperformance.

Attitude sensor fault diagnosis based on Kalman filter of discrete-time descriptor system

To diagnose the fault of attitude sensors in satellites, this paper proposes a novel approach based on the Kalman filter of the discrete-time descriptor system. By regarding the sensor fault term as the auxiliary state vector, the attitude measurement system subjected to the attitude sensor fault is modeled by the discrete-time descriptor system. The condition of estimability of such systems is given. And then a Kalman filter of the discrete-time descriptor system is established based on the methodology of the maximum likelihood estimation. With the descriptor Kalman filter, the state vector of the original system and sensor fault can be estimated simultaneously. The proposed method is able to esti-mate an abrupt sensor fault as well as the incipient one. Moreover, it is also effective in the multiple faults scenario. Simulations are conducted to confirm the effectiveness of the proposed method.

A novel extended Tsypkin criterion for discrete-time descriptor systems with ferromagnetic hysteresis nonlinear physical phenomenon

This paper concerns the absolute stability problem of discrete-time descriptor systems with feedback connected ferromagnetic hysteresis nonlinearities. The ferromagnetic hysteresis model satisfies the passivity conditions of hysteresis operator, that is the input-output relation of the transformed operator is passive. The bound condition of the solution of the ferromagnetic hysteresis model is given. Through the framework of loop transformation, an augmented discrete-time descriptor system model is established for the stability analysis. A new extended Tsypkin criterion for the absolute stability of discrete-time descriptor systems with hysteresis is presented based on the linear matrix inequalities technique. A numerical example is given to illustrate the effectiveness of the extended criterion.

Observer-based robust H-infinity control for uncertain switched systems

The problem of observer-based robust H-infinity control is addressed for a class of linear discrete-time switched systems with time-varying norm-bounded uncertainties by using switched Lyapunov function method. None of the individual subsystems is assumed to be robustly H-infinity solvable. A novel switched Lypunov function matrix with diagonal-block form is devised to overcome the difficulties in designing switching laws. For robust H-infinity stability analysis, two linear-matrix-inequality-based sufficient conditions are derived by only using the smallest region function strategy if some parameters are preselected. Then, the robust H-infinity control synthesis is studied using a switching state feedback and an observer-based switching dynamical output feedback. All the switching laws are simultaneously constructively designed. Finally, a simulation example is given to illustrate the validity of the results.

On the leader-following exponential consensus of discrete-time linear multi-agent systems over jointly connected switching networks

The leader-following asymptotic consensus problem for general discrete-time linear multi-agent systems over jointly con-nected switching networks was solved about a decade ago.Recently,the leader-following exponential consensus was further established using the so-called Krasovskii-LaSalle theorem for a class of discrete-time linear switched systems.But this method involves some advanced concepts such as the weak zero-state detectability of some limiting system.In this paper,we offer a simpler solution to the leader-following exponential consensus problem for general discrete-time linear multi-agent systems over jointly connected switching networks.After converting the solvability of the problem to the establishment of the exponential stability for a class of discrete-time linear switched systems,we first show that this class of linear switched systems is uniformly completely observable.Then,we further conclude that the uniform complete observability for this class of linear switched systems implies the exponential stability for the same class of linear switched systems,thus leading to the solution of the leader-following exponential consensus problem.Moreover,our approach also gives rise to an explicit characterization of the exponential convergence rate of the leader-following consensus problem.

Stabilization for a Class of Discrete-time Switched Large-scale Systems with Parameter Uncertainties

The problem of robust stabilization for a class of discrete-time switched large-scale systems with parameter uncertainties and nonlinear interconnected terms is considered. By using state feedback and Lyapunov function technique, a decentralized switching control approach is put forward to guarantee the solutions of large-scale systems converge to the origin globally. A numerical example and a corresponding simulation result are utilized to verify the effectiveness of the presented approach.

New Delay-Dependent Stability of Uncertain Discrete-Time Switched Systems with Time-Varying Delays

This paper deals with the issues of robust stability for uncertain discrete-time switched systems with mode-dependent time delays.Based on a novel difference inequality and a switched Lyapunov function,new delay-dependent stability criteria are formulated in terms of linear matrix inequalities （LMIs） which are not contained in known literature.A numerical example is given to demonstrate that the proposed criteria improves some existing results significantly with much less computational effort.

Stationary Analysis of Geo/Geo/1 Queue with Two-Speed Service and the Optimal Switching Threshold for the Service Rate

This paper considers a Geo/Geo/1 queueing system with infinite capacity, in which the service rate changes depending on the workload. Initially, when the number of customers in the system is less than a certain threshold L, low service rate is provided for cost saving. On the other hand, the high service rate is activated as soon as L customers accumulate in the system and such service rate is preserved until the system becomes completely empty even if the number of customers falls below L. The steady-state probability distribution and the expected number of customers in the system are derived. Through the first-step argument, a recursive algorithm for computing the first moment of the conditional sojourn time is obtained. Furthermore, employing the results of regeneration cycle analysis, the direct search method is also implemented to determine the optimal value of L for minimizing the long-run average cost rate function.

Stability of Switched Positive Descriptor Systems with Average Dwell Time Switching

In this paper, the problems of stability for a class of switched positive descriptor systems(SPDSs)with average dwell time(ADT) switching are investigated. First, based on the equivalent switched system and the properties of the projector matrix, sufficient stabilities are given for the underlying systems in both continuoustime and discrete-time contexts. Then, a sufficient stability condition for the SPDS with both stable and unstable subsystems is obtained. The stability results for the SPDSs are represented in terms of a set of linear programmings(LPs) by the multiple linear co-positive Lyapunov function(MLCLF) approach. Finally, three numerical examples are given to illustrate the effectiveness of the obtained theoretical results.

一类带有时滞的不确定广义系统的切换渐近稳定性

研究了一类带有时滞的切换不确定广义系统的鲁棒渐近稳定问题.利用Lyapunov稳定性定理和线性矩阵不等式(Linear matrix inequality,LMI)工具,采用多Lyapunov函数技术,在设定的切换律下,得到切换不确定广义时滞系统鲁棒渐近稳定的时滞相关充分条件.进一步,建立了一个具有线性矩阵不等式约束的凸优化问题,利用Matlab软件中的LMI工具箱求解,得到保证切换广义系统鲁棒渐近稳定的最大可允许时滞上界.最后示例表明了该方法的有效性.

非线性切换广义系统的输入-状态稳定性

针对一类非线性切换广义系统,分两种情况对其输入–状态稳定性问题进行了研究.采用平均驻留时间方法,通过设计适当的切换规则,给出了非线性切换广义系统整体输入–状态稳定的充分条件.相较于已有的控制方法,该方法无需构造输入–状态稳定的Lyapunov函数以及无需设计控制器的具体结构,这在一定程度上方便了控制器的设计.最后,两个仿真算例表明了所提方法的有效性.

模糊广义离散系统的稳定与镇定

本文利用Lyapunov方法研究了T-S模糊广义离散系统稳定与镇定问题.针对该系统的开环情况,给出了其渐近稳定的充分条件.在此基础上,设计了模糊状态控制器,给出了该类系统的闭环系统是全局渐近稳定的充分条件,并将此条件用线性矩阵不等式(LMI)表示.最后,引入一种新的受限等价分解,将所考虑的系统分解成两个低维的子系统,设计了准切换面和离散滑模控制律,使得在控制的作用下,系统解的轨迹沿着准切换流形收敛到原点.

一类不确定离散切换广义系统的二次保性能控制

针对一类具有范数有界时变参数不确定性的线性切换广义系统,研究了其在任意切换策略下的二次稳定保性能状态反馈控制器的设计问题.结合一个二次型性能指标,利用Lyapunov稳定性理论和线性矩阵不等式技术,给出了此类离散切换广义系统的保性能控制器存在的一个充分条件,使得闭环切换广义系统是二次稳定的,且闭环性能指标值不超过某个确定上界.给出的保性能控制器存在的充分条件可以通过Matlab的LMI工具箱求解,适合在工程中应用.数值仿真例子说明了该方法的有效性.

连续切换非方广义线性系统的观测器设计

针对一类连续切换非方广义线性系统,设计了广义状态观测器,并分析了状态估计误差的稳定性。首先通过矩阵的初等变换将连续切换非方广义线性系统的观测器设计问题转换为连续切换广义线性系统的观测器设计问题,之后设计第i个子系统的子观测器,可根据第i个子观测器构造这个广义切换系统的观测器。当观测器是全维观测器,且每个子系统都可检测时,状态估计误差甚至可以在任意切换下指数收敛到零。最后,通过数值实例和Matlab仿真分析说明了观测器设计方法简单可行,观测误差较其他方法的收敛速度快,证实了该方法的有效性和正确性。

切换广义系统的一类统一Lyapunov函数初探

切换系统作为混杂系统中的重要一类,已经进行了深入广泛的研究.本文通过构造一类统一Lyapunov函数的方法,研究切换线性广义系统的稳定性.首先构造了i∈{1,2}时的一个Lyapunov函数;并证明此Lyapunov函数是切换广义系统的一个统一Lyapunov函数;其次利用相似的构造方法推广到i∈{1,2,…,N}的情况,其中A_i,i∈{1,2,…,N}是状态矩阵且是可交换的;最后,给出了在任意切换律下使得该切换广义系统渐近稳定的充分条件.

参数不确定离散切换奇异系统的鲁棒H_∞滤波

研究了参数不确定离散切换奇异系统的鲁棒H∞滤波问题.基于受限系统等价(r.s.e.)变换,并引入新的状态变量,将滤波误差系统转换为切换标准线性系统,然后根据线性矩阵不等式,设计了一个切换滤波器,保证了滤波错误系统对所有容许的不确定性是正则、因果、稳定的,并满足H∞性能.该H∞滤波器既可以是全阶的也可以是降阶的.数值实例说明了方法的有效性.