基于网络的离散切换时滞系统故障检测和控制器协同设计

针对带有时变时滞和数据包丢失的离散网络切换控制系统,提出在任意切换信号下的闭环故障检测和控制器协同设计策略;基于平均驻留时间和李雅普诺夫(LKF)方法,给出并证明离散切换时滞动态系统指数均方稳定且具有满意的H_∞性能指标的充分条件;将离散网络切换时滞系统的控制器和故障检测滤波器的参数求解转化为可行的凸优化问题,确保残差和故障估计误差尽可能小.仿真实验结果验证了所提出方法的有效性.     

具有时变时滞的离散切换系统基于观测器的H∞控制

利用多Lyapunov函数方法，研究一类具有时变时滞的线性离散切换系统基于观测器的H∞控制问题．通过设计对角分块形式的多Lyapunov函数矩阵．使切换律只依赖于观测状态．在基于观测器的切换反馈控制策略下,给出了系统实现H∞控制的充分条件，且条件可以表示为与时滞界相关的线性矩阵不等式（LMI）的形式．同时还给出了切换律、观测器和控制器的设计方案．最后用一个仿真例子表明了结论的有效性．     

New results on robust H-infinity control for discrete-time systems with interval time-varying delays

This paper deals with delay-dependent robust H-infinity control for uncertain discrete-time systems with interval time-varying delay. By using a new Lyapunov functional and the convex combination method, a new delay-dependent stability criterion is established. Some redundant variable matrices are removed in the new conditions, which makes the obtained results more efficient. Then, an iterative algorithm based on the cone complementarity Linearization method is proposed to obtain the delay-dependent robust H-infinity controller. Numerical examples are given to show the effectiveness of the proposed method.     

具有区间时滞的离散时间基因调控网络稳定性研究

针对具有随机干扰和区间时滞的离散时间基因调控网络(GRNs),基于Lyapunov稳定性定理,利用改进型自由权矩阵方法研究其时滞相关稳定问题.通过考虑时变时滞、时滞上界及它们的差三者之间的关系,同时保留增广Lyapunov-Krasovskii泛函差分中的所有有用项,获得一种更低保守性的时滞相关渐近稳定新判据.最后,给出仿真实例验证本文方法的有效性及相比已有方法的优越性.     

Consensus protocols for discrete-time multi-agent systems with time-varying delays

This paper addresses consensus problems for discrete-time multi-agent systems with time-varying delays and switching interaction topologies and provides a class of effective consensus protocols that are built on repeatedly using the same state information at two time-steps. We show that those protocols can solve consensus problems under milder conditions than the popular consensus algorithm proposed by Jadbabaie et al., specifically, the presented protocols allow for the case that agents can only use delayed information of themselves, whereas the popular one is invalid. It is proved that if the union of the interaction topologies across the time interval with some given length always has a spanning tree, then in the presence of bounded time-varying delays, those protocols solve consensus problems.     

Fault detection for discrete-time LPV systems using interval observers

This paper is concerned with the fault detection (FD) problem for discrete-time linear parameter-varying systems subject to bounded disturbances. A parameter-dependent FD interval observer is designed based on parameter-dependent Lyapunov and slack matrices. The design method is presented by translating the parameter-dependent linear matrix inequalities (LMIs) into finite ones. In contrast to the existing results based on parameter-independent and diagonal Lyapunov matrices, the derived disturbance attenuation, fault sensitivity and nonnegative conditions lead to less conservative LMI characterisations. Furthermore, without the need to design the residual evaluation functions and thresholds, the residual intervals generated by the interval observers are used directly for FD decision. Finally, simulation results are presented for showing the effectiveness and superiority of the proposed method.     

离散区间线性切换正系统的镇定

这里同时考虑了快切换和慢切换两类切换情形, 即任意切换和平均驻留时间切换情形. 在这两种情形下, 均给出了系统状态反馈镇定控制器的存在条件, 所设计的控制器能够在原系统不必为正的情况下保证相应的闭环系统对于所有给定的区间不确定性不但为正而且渐近稳定. 由于所获得的控制器存在条件均被描述为了线性不等式的形式, 因此通过求解简单的线性规划问题很容易确定出所期望的控制器参数. 最后, 通过数值算例说明了本文所提出的镇定控制器设计方法的有效性.     

Stability analysis of discrete-time systems with additive time-varying delays

In this paper, the problem of stability analysis of discrete-time delay systems with two additive time-varying delays is considered. A new stability result is derived for a general class of delay systems which has practical application background in networked control systems . The stability criterion is expressed in the form of linear matrix inequalities (LMIs), which can be readily solved by using standard numerical software. An illustrative example is provided to show the advantage of the proposed stability condition.     

DDI-based finite-time stability analysis for nonlinear switched systems with time-varying delays

This paper investigates the finite-time stability (FTS) analysis problem for switched systems with both nonlinear perturbation and time-varying delays. For the system to be finite-time stable, a sufficient condition is proposed based on some delay differential inequalities (DDIs), rather than the Lyapunov-like functions which are commonly used in the FTS analysis of switched systems. Compared with the Lyapunov-like function method, the FTS conditions based on the DDI method are easier for checking and do not require FTS of each subsystem. Two examples are given to illustrate the effectiveness of the developed theory.     

Input-to-state stability for discrete-time time-varying impulsive switched delayed systems with asynchronous phenomena

This paper studies the input-to-state stability (ISS) for a class of discrete-time time-varying impulsive switched delayed systems, in which the asynchronous phenomena are considered. Asynchronous phenomena here include two implications: asynchronous impulses and switches and asynchronous switching. The former means that the events, that is, impulses and switches, are not necessary to occur simultaneously, while the latter indicates that the actual switching modes and related controllers or specified modes do not coincide. Applying the mode-dependent concept to impulses and switches, both the improved Krasovskii-type and Razumikhin-type ISS criteria are provided. The time differences of Lyapunov functionals or functions here are sign-changing and time-varying, releasing from the traditional assumption that always requires negative definiteness. Meanwhile, in this paper, ISS or non-ISS subsystems and stabilizing or destabilizing impulses are taken into account. Finally, three numerical examples are given to illustrate the effectiveness of the proposed results.     

Fault estimation and accommodation for switched systems with time-varying delay

This paper considers the problem of fault estimation and accommodation for a class of switched systems with time-varying delay. An adaptive fault estimation algorithm is proposed to estimate the fault, moreover, constant or time-varying fault can be estimated. Meanwhile, a delay-dependent criteria is obtained with the purpose of reducing the conservatism of the fault estimation algorithm design. On the basis of fault estimation, an observer-based fault tolerant controller is designed to guarantee the stability of the closed-loop system. Additionally, simulation results are presented to illustrate the efficiency of the proposed results.     

Delay-dependent robust H-infinity control for discrete-time uncertain systems with time-varying state delays

1 Introduction The analysis and synthesis of dynamic control systems with time delays is a subject of great practical and theo- retical importance, and has received considerable attention for decades (see [1,2] and references therein). Stability cri- teria can be classified roughly into two categories: delay- independent and delay-dependent [3]. Delay-independent criteria contains no information on the delay size, which, as might be expected, is generally conservative, especially when the dela…     

Enhancement on stability criteria for linear systems with interval time-varying delays

In this paper, the problem of stability for linear systems with interval time-varying delays is investigated. By constructing a suitable augmented Lyapunov-Krasovskii functional and utilizing Wirtinger-based integral inequality, two sufficient conditions for guaranteeing the asymptotic stability of the concerned systems are derived within the framework of linear matrix inequalities (LMIs). The superiority and validity of the proposed criteria are verified by comparing maximum delay bounds under various conditions via two numerical examples.     

Fault detection for singular switched linear systems with multiple time-varying delay in finite frequency domain

This paper deals with the problem of the fault detection (FD) for continuous-time singular switched linear systems with multiple time-varying delay. In this paper, the actuator fault is considered. Besides, the systems faults and unknown disturbances are assumed in known frequency domains. Some finite frequency performance indices are initially introduced to design the switched FD filters which ensure that the filtering augmented systems under switching signal with average dwell time are exponentially admissible and guarantee the fault input sensitivity and disturbance robustness. By developing generalised Kalman–Yakubovic–Popov lemma and using Parseval's theorem and Fourier transform, finite frequency delay-dependent sufficient conditions for the existence of such a filter which can guarantee the finite-frequency H_? and H_∞ performance are derived and formulated in terms of linear matrix inequalities. Four examples are provided to illustrate the effectiveness of the proposed finite frequency method.     

Event-triggered H∞ control of discrete-time switched linear systems with delays

This paper studies the $H_{\infty }$ control problem of discrete-time delayed switched systems with average dwell time switching signals using event-triggered mechanism. The event-triggered mechanism can reduce redundant information transmission. First, employing state-feedback controller, two sufficient conditions are proposed to guaranteeing (i) exponential stability of the disturbance-free closed-loop system and (ii) $H_{\infty }$ performance of the closed-loop system with disturbance. Moreover, the controller gain is explicitly computed by solving a set of linear matrix inequalities. Second, results obtained for state-feedback controller are extended to those for observer-based state-feedback controller, and both the controller and observer gains are explicitly computed. All conditions are derived by utilizing a properly constructed decay-rate-dependent Lyapunov functional. Finally, a numerical example illustrates the validity of the obtained theoretical results.     

Control discrete-time switched singular systems with state delays under asynchronous switching

This article is concerned with the problem of state feedback control for a class of discrete-time switched singular systems with time-varying state delays under asynchronous switching. The asynchronous switching considered here means that the switching instants of the candidate controllers lag behind those of the system modes. The concept of mismatched control rate is introduced. By using the multiple Lyapunov function approach and the average dwell time technique, a sufficient condition for the existence a stabilising switching law is first derived to guarantee the regularity, causality and exponential stability of the closed-loop system in the presence of asynchronous switching. The stabilising switching law is characterised by a upper bound on the mismatched control rate and a lower bound on the average dwell time. Then, the corresponding solvability condition for a set of mode-dependent state feedback controllers is established by using the linear matrix inequality (LMI) technique. Finally, a numerical example is provided to illustrate the effectiveness of the proposed method.     

Improved results for linear discrete-time systems with an interval time-varying input delay

This paper addresses the problem of delay-dependent stability analysis and controller synthesis for a discrete-time system with an interval time-varying input delay. By dividing delay interval into multiple parts and constructing a novel piecewise Lyapunov–Krasovskii functional, an improved delay-partitioning-dependent stability criterion and a stabilisation criterion are obtained in terms of matrix inequalities. Compared with some existing results, since a tighter bounding inequality is employed to deal with the integral items, our results depend on less number of linear matrix inequality scalar decision variables while obtaining same or better allowable upper delay bound. Numerical examples show the effectiveness of the proposed method.     

Improved stability criteria on discrete-time systems with time-varying and distributed delays

In this paper, through constructing some novel Lyapunov-Krasovskii functional (LKF) terms and using some effective techniques, two sufficient conditions are derived to guarantee a class of discrete-time time-delay systems with distributed delay to be asymptotically and robustly stable, in which the linear fractional uncertainties are involved and the information on the time-delays is fully utilized. By employing the improved reciprocal convex technique, some important terms can be reconsidered when estimating the time difference of LKF, and the criteria can be presented in terms of linear matrix inequalities (LMIs). Especially, these derived conditions heavily depend on the information of time-delay of addressed systems. Finally, three numerical examples demonstrate that our methods can reduce the conservatism more efficiently than some existing ones.     

A new admissibility condition of discrete-time singular systems with time-varying delays

This paper gives a novel delay-dependent admissibility condition of discrete-time singular systems with time-varying delays. For convenience, the time-varying delay is assumed to be the sum of delay lower bound and the integral multiples of a constant delay. Specially, if the constant delay is of unit length, the delay is an interval-like time-varying delay. The proposed admissibility condition is presented and expressed in terms of linear matrix inequality (LMI) by Lyapunov approach. Generally, the uncertainty of time-varying delay would lead to conservatism. In this paper, this critical issue is tackled by accurately estimating the time-varying delay. Consequently, the proposed admissibility condition is less conservative than the existing results, which is demonstrated by a numerical example.     

Stabilization of positive switched systems with time-varying delays under asynchronous switching

This paper investigates the state feedback stabilization problem for a class of positive switched systems with time-varying delays under asynchronous switching in the frameworks of continuous-time and discrete-time dynamics. The so-called asynchronous switching means that the switches between the candidate controllers and system modes are asynchronous. By constructing an appropriate co-positive type Lyapunov-Krasovskii functional and further allowing the functional to increase during the running time of active subsystems, sufficient conditions are provided to guarantee the exponential stability of the resulting closed-loop systems, and the corresponding controller gain matrices and admissible switching signals are presented. Finally, two illustrative examples are given to show the effectiveness of the proposed methods.