Stability of digital filters subject to external interference and state-delay

This paper presents passivity-based results to address stability of interfered digital filters with state-delay and saturation nonlinearities. A very-strict passivity condition is proposed for the digital filters by using an appropriate Lyapunov-Krasovskii functional. The established criterion ensures limit-cycle free realization of state-delayed interfered digital filters using saturation arithmetic. Conditions for passivity, input-strict passivity and output-strict passivity of the digital filters are obtained as special cases of the proposed result. In addition, an asymptotic stability condition for the digital filters with zero external interference is presented. It is also demonstrated that a stability condition reported in a recent work may be recovered from the established criterion. Numerical simulations are given to demonstrate worthiness of the proposed results.

Output Feedback Control of NCS with Communication Constraints

Considering the influence of communication constraints and uncertain short delay, this paper models NCS with communication sequence as a discrete periodical switching system with uncertainty, which integrates information scheduling and control. Using the method of piecewise Lyapunov function and the switching system theory, the asymptotic stability condition of the system with periodical information scheduling is derived in the form of matrix inequalities, and a output feedback controller design method is derived.

Design of Robust Modified Repetitive-Control System for Linear Periodic Plants

This paper concerns a linear-matrix-inequality (LMI)-based method of designing a robust modified repetitive-control system (MRCS) for a class of strictly proper plants with periodic uncertainties. It exploits the nature of control and learning and the periodicity and continuity of repetitive control to convert the design problem into a robust stabilization problem for a continuous-discrete 2D system. The LMI technique and Lyapunov stability theory are used to derive an LMI-based asymptotic stability condition that can be used directly in the design of the gains of the repetitive controller. Two tuning parameters in the condition enable preferential adjustment of control and learning. A numerical example illustrates the tuning procedure and demonstrates the effectiveness of the method.

Controller Design and Analysis of Networked Control Systems with Time Varying Uncertainty

A class of networked control systems (NCSs) with time varying uncertainty in the plant was investigated. A new kind of stochastic communication logic based on the current value of the estimation error was proposed. Some new criteria for the asymptotical stabilization of such systems have been established. The asymptotic stability condition of the systems was established by Lyapunov theory. A numerical example was demonstrated the efficiency of the obtained result.