Intelligent Tracking Control For Nonlinear Networked Systems Based On Event-triggered Strategy

Nowadays,networked control systems(NCS)attract widely considerations and studies for its remarkable advantages of communication resource sharing and remote control between system components(such as supervise computer,sensors,controllers and actuators).However,on the one hand,with the expanding demand of control tasks and increasing information traffic,existing communication channel bandwidth and computing capacity are difficult to bear its weight,which urges us to find out a long-distance,high efficiency and low cost transmission solving method.On the other hand,nonlinear characteristic constraints existing in system components are also worthy to be investigated,since such constraints(such as dead-zone effect,hysteresis phenomenon,actuator failure,etc.)will cause severe system performance deterioration and sometimes lead to instability.Specially,it is an important control problem in the vital areas.To be concluded,it is both of theoretical importance and practical significance to investigate how to handle communication constraints and nonlinear characteristic constraints for NCS simultaneously.The thesis takes nonlinear networked control systems into account,and synthesizes the technologies of event-triggered strategy,intelligent control,robust control,adaptive control,etc.The control objective is to establish adaptive controller and update laws following Backstepping framework to handle the considered problem,and finally gives the corresponding stability analysis based on Lyapunov functional theory.This thesis proposes kinds of novel compensation methods in a step-by-step and in-depth research sequence.The main researches are summarized as below:1.A new tuning function backstepping control scheme is proposed for a class of parametric strict feedback nonlinear systems to accommodate actuator failures/faults and dead-zone constraints.Roughly speaking,such a scheme is developed in two steps.First,by using an adaptive smooth inverse function to compensate for the dead-zone nonlinearity,we separate the coupling actuator dynamics into two parts,i.e.,the dead-zone compensation errors and the nominal failure dynamics.Afterward,we further handle these two parts based on the techniques of robust adaptive approach and parametrization method.With our scheme,the global boundedness of the signals in the closed-loop system are ensured,and the tracking error is steered to zero asymptotically.2.The problem of event-triggered adaptive tracking control for parametric strict feedback system subject to actuator dead-zone is investigated,which aims at reducing communication rate and compensating actuator nonlinearity simultaneously.The challenges of this work can be roughly classified into two categories:how to compensate the nonsmooth dead-zone nonlinearity and how to eliminate the quantization signal effects caused by event-triggered strategy.To resolve the first challenge,a new decomposition of dead-zone mathematical model is employed so that dead-zone nonlinearity can be successively compensated by using robust approach.In addition,an adaptive controller and its triggering event are co-designed based on the relative threshold strategy,such that an asymptotic tracking performance can be ensured.The proposed scheme is proved to guarantee the globally bounded of all closed-loop signals and the asymptotic convergence performance of tracking error toward zero.3.The problem of guaranteeing transient performance in adaptive tracking control of uncertain strict-feedback nonlinear systems within the framework of event-triggered control.The unparametrizable uncertainties are successfully resolved by using the fuzzy logic systems to approximate real-time value of the unknown functions,and the square of the norm of fuzzy weight vector is applied to the backstepping recursive design.Furthermore,by constructing a class of new Lyapunov candidates,the chattering phenomenon caused by sign function can be avoided,while the transient performance in terms of the tracking error can also be achieved to be an explicit function with the user-defined parameters.It is further proved that our proposed scheme ensures the global boundedness of all the closed-loop signals.4.The problem of event-triggered tracking control for a class of uncertain nonlinear systems with unknown Prandtl-Ishlinskii(PI)hysteresis is investigated.To solve this problem,two control schemes are proposed.The first basic design scheme applies an effective method to keep balance between communication constraints and system performance under the influence of actuator PI hysteresis,while Zeno-behavior can be avoided.Furthermore,the basic design scheme not only guarantees the tracking error asymptotically converges to zero,but establishes a preserved transient performance.Nevertheless,note that the inclusive sign functions of the basic design scheme will cause possible chattering phenomenon,an alternative event-triggered adaptive control approach is then proposed.Unlike the previous control scheme,the second chattering-avoidance design approach ensures asymptotic convergence of tracking error within a prescribed boundary ?,and finally L2-norm transient performance of tracking error is constructed.