基于无记忆降阶观测器的网络化控制系统故障检测方法

网络化控制系统(Networked Control System,简称NCS)研究的是如何通过网络实现闭 环控制,是涉及控制科学和计算机网络等多个学科知识的跨学科研究领域.本文将网络化控制系 统视为带有时延的采样控制系统,构造了一个无记忆的降阶状态观测器,通过比较观测器输出和 系统实际输出来产生残差,从而对网络化系统的控制故障进行了检测.仿真结果表明此方法是可 行的.  

保代价采样控制在打浆过程中的应用

针对打浆过程计算机控制系统提出了保代价采样控制，当系统存在结构不确定时，该方法能使系统闭环鲁棒稳定，且系统的性能指标达到一定的要求，理论分析和仿真结果表明，保代价采样控制是打浆过程一种有效可行的控制方案。  

A bound of conservativeness in sampled-data robust stabilization and its dependence on sampling periods

This paper investigates conservativeness of the ²-induced norm in a sampled-data robust stabilization problem. Namely, it is shown that possible conservativeness of the ²-induced norm can be bounded by difference between the best achievable performance of time-invariant continuous-time controllers and that of sampled-data controllers. Moreover, this difference is proven to approach zero as a sampling period tends to zero, which means the conservativeness above loses importance when a sampling period is small. These results are important because robust stabilization based on the ²-induced norm is computationally inexpensive compared with robust stabilization based on the non-conservative robust stability index. One key lemma plays an essential role in this paper and it should be interesting independently.  

A refined input delay approach to sampled-data control

This paper considers sampled-data control of linear systems under uncertain sampling with the known upper bound on the sampling intervals. Recently a discontinuous Lyapunov function method was introduced by using impulsive system representation of the sampled-data systems (Naghshtabrizi, Hespanha, & Teel, 2008). The latter method improved the existing results, based on the input delay approach via time-independent Lyapunov functionals. The present paper introduces novel time-dependent Lyapunov functionals in the framework of the input delay approach, which essentially improve the existing results. These Lyapunov functionals do not grow after the sampling times. For the first time, for systems with time-varying delays, the introduced Lyapunov functionals can guarantee the stability under the sampling which may be greater than the analytical upper bound on the constant delay that preserves the stability. We show also that the term of the Lyapunov function, which was introduced in the above mentioned reference for the analysis of systems with constant sampling, is applicable to systems with variable sampling.  

Stability and stabilization of nonuniform sampling systems

This paper is concerned with nonuniform sampling systems, where the sampling interval is time-varying within a certain known bound. The system is transformed into a time-varying discrete time system, where time-varying parts due to the sampling interval variation are treated as norm bounded uncertainties using robust control techniques. To reduce conservatism arising from modeling time-varying parts as a single uncertainty, the time-varying parts are modeled as N uncertainties. With larger N, a less conservative stability condition is derived at sacrifice of more computation. It is shown through a numerical example that the proposed stability condition is better than existing stability conditions.  

Controller synthesis for networked control systems

This paper presents a discrete-time model for networked control systems (NCSs) that incorporates all network phenomena: time-varying sampling intervals, packet dropouts and time-varying delays that may be both smaller and larger than the sampling interval. Based on this model, constructive LMI conditions for controller synthesis are derived, such that stabilizing state-feedback controllers can be designed. Besides the proposed controller synthesis conditions a comparison is made between the use of parameter-dependent Lyapunov functions and Lyapunov-Krasovskii functions for stability analysis. Several examples illustrate the effectiveness of the developed theory.  

Dual-mode structure digital repetitive control

A flexible repetitive control (RC) scheme named “dual-mode structure repetitive control” (DMRC) is presented in this article. A robust stability criterion for DMRC systems is derived in terms of two parameters: odd-harmonic RC gain and even-harmonic RC gain. Several useful corollaries for the stability are addressed to reveal the compatibility of DMRC. The general framework of DMRC offers the flexibility in the development of various RC controllers. Without additional complexity and loss of tracking accuracy, DMRC can achieve faster error convergence rate than conventional RCs. DMRC requires the same data memory size as that of conventional RC one. An application example of DMRC controlled PWM inverter illustrates the validity of our proposed DMRC scheme. Comparisons of DMRC, conventional RC and odd-harmonic RC highlight the advantages of the presented DMRC approach.  

离散时间系统零动态的研究现状和未来挑战

在数字控制系统的分析与设计中, 零动态是一个被广泛关注的重要概念, 近年来取得了诸多新的理论与方法进展. 本文首先描述了离散时间系统零动态理论的研究背景和研究意义, 同时简要介绍了离散时间系统零动态理论所涉及到的3个相关问题, 如: 信号的采样与重建、连续时间系统的等价离散时间系统模型以及在离散连续时间系统过程中所需要的工具(q算子和±算子). 其次, 立足现有文献, 针对离散零动态的特点, 从线性离散时间系统和非线性离散时间系统两个方面全面而深入地介绍了近年来离散零动态研究工作的进展. 最后分析了零动态在数字控制系统分析与设计中的局限性以及出现的挑战性课题, 并指明未来工作的研究方向.  

Synchronization for general complex dynamical networks with sampled-data

In this paper, the sampled-data synchronization control problem is investigated for a class of general complex networks with time-varying coupling delays. A rather general sector-like nonlinear function is used to describe the nonlinearities existing in the network. By using the method of converting the sampling period into a bounded time-varying delay, the addressed problem is first transformed to the problem of stability analysis for a differential equation with multiple time-varying delays. Then, by constructing a Lyapunov functional and using Jensen's inequality, a sufficient condition is derived to ensure the exponential stability of the resulting delayed differential equation. Based on that, the desired sampled-data feedback controllers are designed in terms of the solution to certain linear matrix inequalities (LMIs) that can be solved effectively by using available software. Finally, a numerical simulation example is exploited to demonstrate the effectiveness of the proposed sampled-data control scheme.