Zhou Gu

A delay distribution based stability analysis and synthesis approach for networked control systems

Communication delays in networked control systems (NCSs) has been shown to have non-uniform distribution and multifractal nature. This paper proposes a delay distribution based stability analysis and synthesis approach for NCSs with non-uniform distribution characteristics of network communication delays. A stochastic control model related with the characteristics of communication networks is established to describe the NCSs. Then, delay distribution-dependent NCS stability criteria are derived in the form of linear matrix inequalities (LMIs). Also, the maximum allowable upper delay bound and controller feedback gain can be obtained simultaneously from the developed approach by solving a constrained convex optimization problem. Numerical examples showed that the results derived from the proposed method are less conservativeness than those derived from the existing methods.

T–S Fuzzy Model-Based Robust Stabilization for Networked Control Systems With Probabilistic Sensor and Actuator Failure

The system studied in this paper has four main features: 1) It is a networked controlled system (NCS), and therefore, the signal transfer is subject to random delay and/or loss; 2) it is a nonlinear system approximated by a Takegi--Sugeno (T-S) fuzzy model; 3) its multisensors and multiactuators are subject to various possible faults/failures; and 4) there are uncertainties in the plant model parameters. A comprehensive model is first developed in this paper to cover these features for a class of NCS nonlinear systems. This model has removed some limitations of similar models in the published literature. Then, the Lyapunov functional and the linear matrix inequality (LMI) are applied to develop two new stability conditions (Theorems 1 and 2). These conditions and an algorithm are used to design a controller to achieve robust mean square stability of the system. Finally, two examples are used to demonstrate the application of the modeling and the controller design method developed.

Sampling period scheduling of networked control systems with multiple-control loops

This paper addresses the sampling period scheduling of Networked Control Systems (NCSs) with multiple control loops. The generalized exponential function is employed to describe Integral Absolute Error (IAE) performance versus sampling period by Truetime toolbox under Matlab environment, and the sampling periods are scheduled to obtain the optimal integrated performance based on Kuhn-Tucker Theorem, which are subject to the stability of every control loop and the bandwidth on available network resource. Numerical examples are given to show the effectiveness of our method.

New results on H ∞ filter design for nonlinear systems with time-delay through a T-S fuzzy model approach

H ∞ filter design for nonlinear systems with time-delay via a T-S fuzzy model approach is investigated based on a piecewise analysis method. Two cases of time-varying delays are fully considered: one is the time-varying delay being continuous uniformly bounded while the other is the time-varying delay being differentiable uniformly bounded with delay-derivative bounded by a constant. Based on a piecewise analysis method, the variation interval of the time delay is first divided into several subintervals, then the convexity property of the matrix inequality and the free weighting matrix method are fully used in this article. Some novel delay-dependent H ∞ filtering criteria are expressed as a set of linear matrix inequalities, which can lead to much less conservative analysis results. Finally, a numerical example is given to illustrate that the results in this article are more effective and less conservative than some existing ones.

A new approach to H∞ filtering for linear time-delay systems

Abstract This paper proposes a class of H ∞ filter design for continue-time systems with time-varying delay. Firstly, by exploiting a new Lyapunov function and using the convexity property of the matrix inequality, some delay-dependent stability conditions can be obtained for the asymptotical stability of the filtering-error system, which can lead to much less conservative analysis results. Secondly, based on the obtained conditions, the filter parameter matrixes can be obtained in terms of linear matrix inequalities (LMIs). Finally, two examples are given to demonstrate the effectiveness and the merit of the proposed method.

Fault-distribution-dependent reliable fuzzy control for T-S fuzzy systems with interval time-varying delay

A new practical actuator-fault model is proposed by assuming that the actuator fault obeys a certain probabilistic distribution. This article addresses the problem of a reliable fuzzy control for Takagi–Sugeno (T-S) fuzzy systems with interval time-varying delays. By using a Lyapunov–Krasovskii approach, a sufficient condition for the existence of a reliable controller is expressed by a set of linear matrix inequalities. Illustrative examples show the effectiveness of the proposed design procedures.

Robust H ∞ Control for linear systems with delay in state or input

A Piecewise analysis method technique is proposed to investigate the H∞ control of uncertain systems with time delay in state or input. Firstly, the variation interval of the time-varying delay is divided into several subintervals with equal length. By checking the variation of derivative of the Lyapunov functional in every subinterval, some new criteria on H∞ performance analysis of the systems are derived in terms of the convexity properties of a matrix inequality and some other new analysis techniques. Then, criteria for the H∞ control design are presented, which are concluded from the H∞ performance analysis results. As applications of the derived results, H∞ performance analysis and H∞ control design are carried out for some systems, including a numerical systems and linearized truck trailer system. Discussions show that, the proposed method is effective for these systems and appears much less conservativeness than those given in the existing references.

Reliable output feedback control for systems with control input delay and stochastic actuator failure

This paper is concerned with the design of reliable static output feedback controllers (RSOFC) for systems with stochastic actuators failure. A sufficient condition for the existence of reliable RSOFC is presented in terms of a set of linear matrix inequalities (LMIs), which guarantees that the closed-loop system, with consideration of actuators failure, satisfies a desired H∞ disturbance attenuation γ. A numerical example is presented to illustrate the effectiveness of the proposed design method.

Improved robust H ∞ control for delay systems with uncertainties

Addressing time-delay systems, this paper proposes an innovative approach to significantly improve the stability performance while reducing the computing demand considerably. The key features of the approach include the removal of the redundant information from the augmented matrix and the use of a tighter bounding technology. With the proposed approach, a new delay-dependent bounded real lemma for uncertain systems with interval time-varying delay are derived. Numerical examples are given to demonstrate the effectiveness of the proposed approach.