Research On Some Problems Of Adaptive Fuzzy Control For Stochastic Nonlinear Systems

In recent years,with the improvement of people's demand for system control performance,a growing number of practical engineering system began to consider the influences of stochastic disturbance to the system control performance,and most of these practical engineering systems with stochastic disturbance can be modeled as the stochastic nonlinear systems,such as electric power systems,mechanical arm systems and missile systems,etc.Therefore,the problem of adaptive control for stochastic nonlinear systems has received extensive attention in recent years.Different from deterministic nonlinear systems,the existence of stochastic disturbance makes it more difficult to deal with the nonlinear terms in the system,and it is necessary to consider the influence of stochastic disturbance and the processing difficulty when dealing with the unknown nonlinear in the system.However,the application of adaptive control method brings a new idea to solve the above control problems of the stochastic nonlinear systems.As a widely used control method in the control field,adaptive control method has made a lot of effective results in the control problems of stochastic nonlinear systems,but there are still many important control problems to be solved.Based on the relevant development and research of domestic and foreign,by combining the adaptive fuzzy control method and the backstepping method,this paper has carried out the following work and research for some control problems of stochastic nonlinear systems:Firstly,the tracking control problem is studied for the single-input single-output stochastic nonlinear systems with unknown hysteresis.A novel adaptive fuzzy event-triggered control scheme is designed based on the framework of backstepping method by combining the event-triggering technique and the Lyapunov function,which solves the influences of unknown hysteresis on the control performance of stochastic nonlinear system under the condition of unmeasured state.Moreover,the proposed control scheme can guarantee the boundedness of all signals and the stability of the system.The simulation example shows the effectiveness of the proposed control scheme.Then,the command filtered tracking control problem is investigated for a single-input single-output stochastic nonlinear system with multiple time-delay.In the process of controller design,the command filter technique is introduced to avoid the problem of complexity of explosion inherent in the backstepping method.In addition,by combining the command filter technique with the variable separation technique,the algebraic loop problem existing in the non-strict feedback system is solved.Then,the stability of the system is proved by the Lyapunov stochastic stability criterion.The effectiveness of the proposed control scheme is showed by the simulation result.At last,the adaptive fuzzy event-triggered control problem is studied for multi-input multi-output stochastic nonlinear systems with unmeasurable states and multiple time delays.In order to solve the interconnection effects caused by multiple time-delays in multi-input multi-output stochastic nonlinear systems,a new variable separation method based on command filter is proposed.In addition,in order to reduce the waste of communication resources in the system,a new adaptive fuzzy event-triggered control scheme is designed.It can be guaranteed that all the signals in the system are semi-global uniformly ultimately bounded in probability by Lyapunov stability theory.Simulation results are given to prove the effectiveness of the control scheme.