Study On Sliding-Mode Control For Discrete-Time Uncertain System

Variable structure control(VSC)is a kind of nonlinear control method.The nonlinear reflected in the switch of controller.In the case of parametric perturbation and external disturbance,the variable structure system has the invariance ch aracteristics,and its strong robustness has aroused great interest from domestic and foreign scholars.In discrete systems,due to the existence of buffeting problems,the practical application of sliding mode control is hindered.In this paper,a variety of sliding mode controllers are designed for discrete time uncertain systems,which greatly attenuates system buffeting and has excellent dynamic performance.The main works in this study are following:Firstly,the research results of sliding mode contro l in each stage are expounded.The mechanism of chattering of discrete sliding mode variable structure is discussed in detail,and the solutions given by scholars from different countries are studied.Secondly,the definition,basic principle and propertie s of variable structure control are studied.The design of discrete sliding mode,including the design of sliding surface,the condition of sliding mode and the existence condition are studied emphatically.The existence condition and stability of quasi-sliding mode are studied,and the research status of current discrete sliding mode control and the causes of chattering are analyzed.Thirdly,the advantages and disadvantages of the variable speed approaching law are analyzed,and the design scheme of the new discrete sliding mode control is given to improve the dynamic quality of the system.The stability of the system is analyzed,and the system performance is analyzed in detail.Especially,the influence law of the convergence law parameter on the dynamic quality of the system is studied in detail.The simulation results show that the approximation law can improve the approximation rate and weaken the buffeting,thus verifying the validity of the approximation law.Fourthly,a simple and effective slidin g mode optimization scheme based on fuzzy control is presented.The scheme does not rely on expert experience,but based on the results of theoretical analysis,a fuzzy control optimization scheme with single input,dual output and simple rules is designed,which reduces the complexity of fuzzy control,but maintains a good optimization effect The correctness of the result of parameter analysis is verified by numerical simulation,and it is proved that the fuzzy optimization scheme is simple and effective.Finally,according to the decay control design principle,the convergence time exponential exponential law is given,which can ensure that the system state approaches the origin at a faster rate,and draws some conclusions.The theoretical analysis and num erical simulation show that the scheme can make the motion move quickly and converge to the origin.