Research On Sliding Mode Controller Of Networked Control System Based On Time Delay Compensation

With the rapid development of computer and communication technology,Networked Control System(NCS)has been widely employed in process control,remote control,teleoperation and other fields,while it has great application potential in robots,vehicles,aircraft and spacecraft at the same time.Recently,some scholars have began to use sliding mode control strategy to design controllers for NCS with time delay,which provides a new idea for improving the stability and dynamic performance of the system.This paper presents a series of design schemes of sliding mode controller for NCS based on time delay compensation.In order to solve the state stabilization problem of NCS,sliding mode controllers are designed which can guarantee the stability of closed-loop systems in different situations according to the characteristics of network delay.Furthermore,aiming at solving the tracking control problem of NCS,two sliding mode tracking control methods are proposed,including a reference model approach and a method for special plant respectively.Advantages of the proposed two methods are analyzed through experiments.Firstly,continuous and discrete NCSs with bilateral fixed-delay are both considered,while model uncertainty and external disturbance are introduced respectively.The design methods of sliding mode controllers are proposed for these systems to ensure systems'state stabilization based on time delay compensation.Secondly,for NCSs with stochastic time-varying delay,the design methods of sliding mode controllers are also discussed.The designed controllers can guarantee the state stabilization of the systems with unilateral delay or bilateral delay where input delay is variable.Further,the influence of delay range on system stability is analyzed,and the maximum allowable delay bound is obtained.Then,the tracking control for NCS is studied.Based on reference model,a design method of sliding mode tracking controller is proposed.In this method,the H_?control theory is used to prove stability and analyse tracking performance of the obtained augmented closed-loop system.The simulation results show that the controller can improve anti-interference ability of the system.Finally,a new design method of sliding mode tracking controller is proposed.The tracking control performance of this controller is analyzed.It is proved that this method can effectively reduce or eliminate the steady-state error for a class of NCS in which plant model has a common and specific form.The effectiveness and practicability of the method are illustrated based on a two-degree-of-freedom robot experimental platform.