Sliding Mode Control For Several Classes Of Discrete Uncertain Networked Systems With Time-Delays

Accompanying with the rapid developments of the network techniques,the information of control system can be transmited conveniently via network.In fact,with help of the real-time communication network,all of this system components including the actuator and controller should form the closed loop.This kind of closed loop is usually regarded as the networked control system(NCS).Compared with traditional systems,the NCS exhibits many attractive features,such as the ability to share resources and remote manipulation.Owing to above advantages,the application prospects of NCS to industry fields have been bright once its conception was brought forward.On the other hand,the inconvenience,caused by the introduction of the network into the control system,is also well known,such as time-delays and data packet loss.Therefore,it is of great practical significance on how to decrease undesirable effects of above network-induced phenomena onto the control system performance,and then how to propose effective control schemes.In this thesis,we aim to consider several classes of discrete uncertain networked systems with time-delays,and propose some new robust sliding mode control(SMC)strategies based on the matrix inequality method.The main research contents are displayed as follows:Firstly,the design problem of sliding mode controllers is discussed for a class of uncertain delayed systems with randomly varying nonlinearities.Since the occurrence probabilities of randomly varying nonlinearities could be uncertain,we aim to design a new SMC algorithm.First of all,a linear sliding surface is designed based on the current and previous state information.Subsequently,by properly choosing the Lyapunov functional and using the stability theory,a sufficient criterion is given to guarantee that the sliding mode dynamics is robustly asymptotically stable in the mean square.In addition,the robust sliding mode controller is designed and the reachability of the sliding surface is discussed.Based on above results,we further discuss the robust H_?SMC problem for networked systems with time-varying delay,parameter uncertainties,and randomly varying nonlinearities(RVNs).Also,according to the feasible solution of a minimization problem,the expression of the desired SMC law is given.Finally,numerical simulations are utilized to verify the effectiveness of the proposed control algorithms.Secondly,the robust SMC problem is studied for a class of nonlinear systems with stochastic communication delays(SCDs)and randomly occurring uncertainty(ROU).Here,the occurrence probabilities of SCDs,ROU and RVNs could be uncertain simultaneously.A sliding surface of linear form is constructed.And then,by combining the idea of delay fractioning and Lyapunov stability theory,a delay-dependent criterion is obtained to guarantee the asymptotic stability in the mean square of sliding mode dynamics.In addition,the state feedback sliding mode controller is also constructed.Finally,simulation results clearly show the feasibility of the new control strategy.Thirdly,the robust H_?SMC problem is investigated for a class of Markovian jumping delayed uncertain systems with repeated scalar nonlinearities.Based on the current state information,a sliding surface of linear form is designed.And then,by using Lyapunov theory and inequality processing techniques,sufficient criteria are established to ensure the robust mean-square asymptotic stability of resulted sliding motion with a prescribed H_?performance.In addition,by considering the repeated scalar nonlinearities of the system,the explicit expression of the H_?SMC law is given and the reachability is discussed.Finally,the simulation results are employed to illustrate the effectiveness of the proposed H_?SMC algorithm.Fourthly,the robust SMC strategy with data packet loss is provided for a class of Markovian jumping delayed uncertain systems with repeated scalar nonlinearities.The phenomenon of Markovian packet loss is first modeled.Based on probability of data packet loss and the compensation scheme,a novel sliding surface is designed.In the sequel,according to the stochastic analysis theory,the mean-square asymptotic stability criteria of resulted sliding motion are given.Besides,the expression of the desired robust SMC law is given by using the compensation scheme.Finally,the feasibility and effectiveness of the new strategy are displayed by simulation results.