Research On The Robust L₁ Control And Filtering For Nonlinear Networked Control Systems

Compared with the traditional point-to-point control system,networked control systems have been widely applied in various of control fields because of their many advantages.However,the introduction of communication network also causes the emergence of unfavorable factors.Affected by the constraint conditions such as network bandwidth and transmission rate,random delay and packet loss may exist during the process of signal transmission,which may lead to deterioration of the control performance or even instability of the system.Considering the aging and zero offset of sensors in communication networks,sensor failures are inevitable and the system performance is also affected.The difficulty of modeling is increased because of the nonlinearity,time-variant,uncertainty and so on.Therefore,taking the above points into consideration,and choosing different performances for different external disturbances,this paper concentrates on studying the robust control and filtering problems of nonlinear networked control systems,and the proposed methods have been proved to be effective through numerical examples.The main contents are as follows:Firstly,the robust H? control in discrete-time domain is studied for networked control systems,which contain random time delays and packet dropouts in both forward channel and feedback channel.The random time delays and packet dropouts are described as multiple Bernoulli distributions,thus the closed-loop networked control systems are modeled as stochastic parameter systems.Based on Lyapunov stability theory and augmented state-space method,a H? criterion is obtained of the mean-square exponential stability for the closed-loop networked control systems.By using the LMI technique and the cone complementary linearization algorithm,a design method of the dynamic output feedback controller is presented.Finally,The effectiveness of the proposed method is validated by the simulation.Secondly,the controlling and filtering problem for nonlinear distributed delay systems described by T-S fuzzy model is investigated.On the one hand,this paper concentrates on investigating the robust L1 output tracking control problem for the networked control systems described by Takagi-Sugeno fuzzy model with distributed delays and uncertainties.First,according to the parallel distributed compensation and Lyapunov theory,a fuzzy delay-dependent and basis-dependent Lyapunov-Krasovskii function that contributes to reducing the conservatism is constructed.Second,the L1 performance criterion guaranteeing the asymptotic stability of the corresponding tracking control system and satisfying theprescribed tracking performance is derived.Furthermore,the output tracking control problem is converted into a convex optimisation problem.Finally,the results from simulation certify the effectiveness of the designed controller.On the other hand,the H? filtering problem for nonlinear distributed delay systems described by T-S fuzzy model is also investigated.A proper Lyapunov function is chosen to derived the performance criterion,and furthermore,an effective filtering method is given.Thirdly,the L1 filtering for the distributed delay system under network is studied.On the one hand,considering the influence of distributed delays and sensor fault modes on the system performance in communication network,this paper is concerned with L1 filtering problem for distributed delay systems with multiple sensor fault modes.A set of stochastic variables are used to describe the sensor faults,and the filtering error system with stochastic variables is established.By constructing a delay-dependent Lyapunov-Krasovskii function,according to Lyapunov theory and the integral inequality method,the L1 performance criterion guaranteeing the mean-square asymptotic stability of the filtering error system is formulated,and furthermore,the method for obtaining the filter parameters is given.Finally,a numerical example is presented to demonstrate the effectiveness of the proposed method.On the other hand,the L1 filtering is studied for the nonlinear distributed system described by T-S fuzzy model.A proper Lyapunov-Krasovskii function is chosen to derived the L1 performance criterion to guarantee the asymptotic stability of the filtering error system.Besides,the congruence transformations and variable substitutions are performed to obtain a method of gaining the filter parameters,then the effectiveness of such method is demonstrated.Lastly,this study concentrates on investigating the robust L1 filtering problem for a nonlinear system described by a Takagi-Sugeno fuzzy model with distributed delay and time-varying delay.The stochastic distribution characteristic of the network-induced delay is considered,and the Bernoulli distributed sequence is utilized to represent the probability distribution of the delay appearing in certain intervals.First of all,according to parallel distributed compensation,an augmented system with stochastic variable is established.Next,the L1 performance criterion guaranteeing the mean-square asymptotic stability of the fuzzy filtering error system is formulated,by taking advantage of a novel Lyapunov-Krasovskii function and the integral inequality method.Besides,the robust L1 filtering problem is solved by using the linear matrix inequality technique.