Delayed Observers for Linear Systems With Unknown Inputs

We present a method for constructing reduced-order state observers for linear systems with unknown inputs. Our approach provides a characterization of observers with delay, which eases the established necessary conditions for existence of unknown input observers with zero-delay. We develop a parameterization of the observer gain that decouples the unknown inputs from the estimation error, and we use the remaining freedom to ensure stability of the error dynamics. Our procedure is quite general in that it encompasses the design of full-order observers via appropriate choices of design matrices     

Bounding the Parameters of Linear Systems With Input Backlash

In this note we present a two-stage procedure for deriving parameters bounds of linear systems with input backlash when the output measurement errors are bounded. First, using steady-state input-output data, parameters of the nonlinear dynamic block are tightly bounded. Then, given a suitable PRBS input sequence we evaluate tight bounds on the unmeasurable inner signal which, together with noisy output measurements are employed for bounding the parameters of the linear dynamic system     

Detectability and Stabilizability of Discrete-Time Switched Linear Systems

For discrete-time switched linear systems under nondeterministic autonomous switching, the existence of causal finite-path-dependent stabilizing output injection and state feedback laws are characterized by increasing unions of linear matrix inequality conditions. These convex characterizations lead to the notions of causal finite-path-dependent detectability and stabilizability, which in turn yield a separation result for dynamic output feedback stabilization. By generalizing the standard duality concept to switched systems under arbitrary switching path constraints, we relate these notions to direct extensions of time-varying detectability and stabilizability requirements.      

Switching Stabilizability for Continuous-Time Uncertain Switched Linear Systems

This paper investigates the switching stabilizability problem for a class of continuous-time switched linear systems with time-variant parametric uncertainties. First, a necessary and sufficient condition for the asymptotic stabilizability of such uncertain switched linear system is derived, under the assumption that the closed-loop switched system does not generate sliding motions. Then, an additional condition is introduced to exclude the possibility of unstable sliding motions. Finally, a necessary and sufficient for the asymptotic stabilizability of such continuous-time uncertain switched linear systems is presented. This result improves upon conditions found in the literature which are either sufficient only or necessary only     

Self-triggered Consensus Control for Linear Multi-agent Systems With Input Saturation

In this paper, we study the consensus problem for a class of linear multi-agent systems (MASs) with consideration of input saturation under the self-triggered mechanism. In the context of discrete-time systems, a self-triggered strategy is developed to determine the time interval between the adjacent triggers. The triggering condition is designed by using the current sampled consensus error. Furthermore, the consensus control protocol is designed by means of a state feedback approach. It is shown that the considered multi-agent systems can reach consensus with the presented algorithm. Some sufficient conditions are proposed in the form of linear matrix inequalities (LMIs) to show the positively invariant property of the domain of attraction (DOA). Moreover, some sufficient conditions of controller synthesis are provided to enlarge the volume of the DOA and obtain the control gain matrix. A numerical example is simulated to demonstrate the effectiveness of the theoretical analysis results.      

Finite-Time Stabilization of Linear Systems With Input Constraints by Event-Triggered Control

<正>Dear editor,This letter designs the event-triggered control(ETC) to achieve finite-time stabilization(FTS) of linear systems with input constraints. The key idea of the established algorithm is that the designed time-varying high-gain is only scheduled on a specified time determined by an event-triggered mechanism.     

Linear Systems Subject to Input Saturation and Time Delay: Global Asymptotic Stabilization

This note deals with the problem of global asymptotic stabilization of linear systems by bounded static feedbacks subject to time delay. Under standard necessary conditions, we provide two constructions of controllers of nested saturation type which extends to the general case partial results of previous papers for arbitrary small bound on the control and large (constant) delay. To validate the approach, a third-order integrator and oscillator with multiplicity two example is presented     

不确定变时滞线性系统的镇定条件

研究含时变非结构不确定性的变时滞线性系统的镇定控制器设计问题，基于代数Riccati方程的处理方法，提出了使其闭环系统渐近稳定的无记忆反馈控制器的设计方案．此外，还导出了两组直接由系统参数表示的鲁棒镇定条件．文末给出了用以阐明所得结果的数值算例，并与已有的结果进行了比较．     

On Asymptotic Stabilization of Linear Discrete-time Systems with Saturated State Feedback

As saturation is involved in the stabilizing feedback control of a linear discrete-time system, the original global-asymptotic stabilization (GAS) may drop to region-asymptotic stabilization (RAS). How to test if the saturated feedback system is GAS or RAS? The paper presents a criterion to answer this question, and describes an algorithm to calculate an invariant attractive ellipsoid for the RAS case. At last, the effectiveness of the approach is shown with examples.     

含饱和状态反馈线性离散时间系统渐近稳定性

As saturation is involved in the stabilizing feedback control of a linear discrete-time system, the original global-asymptotic stabilization (GAS) may drop to region-asymptotic stabilization (RAS). How to test if the saturated feedback system is GAS or RAS? The paper presents a criterion to answer this question, and describes an algorithm to calculate an invariant attractive ellipsoid for the RAS case. At last, the effectiveness of the approach is shown with examples.     

具有滞后输入的不确定系统的鲁棒镇定

本文研究具有滞后输入的不确定系统的鲁棒镇定问题，导出了系统可以用一个无记忆状态反馈控制律鲁棒镇定的条件，据此，提出了一个鲁棒稳定化控制器的设计方法．     

一类单输入线性切换系统的可镇定性研究

考虑一类单输入线性切换系统的可镇定性问题,利用变结构控制对系统进行降维．通过对系统滑动模态的研究,得出了系统一致可镇定的充分条件和系统存在容许镇定策略的充分条件．给出了具体的容许镇定策略集合,并对二阶切换系统给出了详细的容许镇定策略．仿真实例验证了所提出结论的有效性．     

线性定常系统的δ－算子描述──能控性与能稳性*

本文讨论了δ－算子描述下的线性定常系统的能控性与能稳性问题。研究结果表明：虽然两种描述（即传统的ｑ－算子描述和本文讨论的δ－算子描述）方法下的能控性定义及判据形式上并无二致，然而在高速采样的条件下，两种描述方法下的系统的能控度与能稳度呈现出完全相反的特性，一般而言，δ－算子描述方法更加适合高速采样情形。     

Quadratic Stabilizability for Polytopic Uncertain Switched Linear Systems via Switched Observer

In this paper, we study a quadratic stabilizability problem via switched observer for uncertain continuous‐time switched linear systems in the sense that the subsystem's matrices are represented as a polytopic linear combination of vertex matrices. Firstly, sufficient conditions for polytopic uncertain continuous‐time switched linear systems to be quadratically stabilizable via state feedback are summarized. Next, sufficient conditions for polytopic uncertain switched linear systems to be quadratically stabilizable via switched observer are given under the assumption that output matrices of subsystems have no uncertainties. Further, a numerical example is also investigated.     

线性定常系统的δ－算子描述──能控性与能稳性

本文讨论了δ－算子描述下的线性定常系统的能控性与能稳性问题．研究结果表明：虽然两种描述（即传统的ｑ－算子描述和本文讨论的δ－算子描述）方法下的能控性定义及判据形式上并无二致，然而在高速采样的条件下，两种描述方法下的系统的能控度与能稳度呈现出完全相反的特性，一般而言，δ－算子描述方法更加适合高速采样情形．     

Identification Input Design for Consistent Parameter Estimation of Linear Systems With Binary-Valued Output Observations

Input design is of essential importance in system identification for providing sufficient probing capabilities to guarantee convergence of parameter estimates to their true values. This paper presents conditions on input signals that characterize their probing richness for strongly consistent parameter estimation of linear systems with binary-valued output observations. Necessary and sufficient conditions on periodic signals are derived for sufficient richness. These conditions are further studied under different system configurations including open-loop and feedback systems, and different scenarios of noises including actuator noise, input measurement noise, and output measurement noise. In addition to system parameter estimation, essential properties of identifiability and input conditions are also derived when sensor thresholds or noise distribution functions are unknown. The findings of this paper provide a foundation to study identification of systems that either use binary-valued or quantized sensors or involve communication channels, which mandate quantization of signals.     

不确定线性系统输出反馈鲁棒镇定的充要条件

研究不确定性线性系统的输出反馈鲁棒镇定问题，给出了具有范数有界参数不确定线性系统静态输出反馈鲁棒镇定的充要条件。所给方法的设计过程只需解一个特殊的代数Ｒｉｃｃａｔｉ不等式或代数Ｒｉｃｃａｔｉ方程算法实现简便。最后通过实例验证了本方法的有效性。     

Stability and Stabilizability of Switched Linear Systems: A Survey of Recent Results

During the past several years, there have been increasing research activities in the field of stability analysis and switching stabilization for switched systems. This paper aims to briefly survey recent results in this field. First, the stability analysis for switched systems is reviewed. We focus on the stability analysis for switched linear systems under arbitrary switching, and we highlight necessary and sufficient conditions for asymptotic stability. After a brief review of the stability analysis under restricted switching and the multiple Lyapunov function theory, the switching stabilization problem is studied, and a variety of switching stabilization methods found in the literature are outlined. Then the switching stabilizability problem is investigated, that is under what condition it is possible to stabilize a switched system by properly designing switching control laws. Note that the switching stabilizability problem has been one of the most elusive problems in the switched systems literature. A necessary and sufficient condition for asymptotic stabilizability of switched linear systems is described here.      

线性开关系统的饱和控制

利用开关系统切换的特点研究了线性开关系统的饱和控制问题,在较弱的条件下,得到了开关系统饱和镇定的结果,即构成开关系统的每个子系统可以是非稳定的,但假定由开关系统构成的某个凸组合系统是可稳的.借助于Lyapunov函数设计饱和控制器,基于凸组合系统的稳定性设计切换规律,引入设计参数满足控制器实现的条件,使开关系统局部渐近稳定.