Research On Adaptive Control Method For Nonlinear Systems Based On Multiple Constraints

The vast majority of control problems can be divided into three categories: stabilization problems,regulation problems,and tracking problems.They all belong to trajectory tracking problems.The tracking performance is one of the important criteria for judging the control algorithm.The traditional performance problem in nonlinear adaptive control is limited to ensure that the system tracking error converges to a certain residual set,and the size of the residual set depends on the size of design parameters and some unknown items,there is no systematic method to determine the required boundaries.However,it must be pointed out that many control problems have clear requirements on performance issues(transient performance,steady-state performance).Therefore,it is of great theoretical and practical significance to study the trajectory tracking control problem that guarantees the pre-performance bounded.In addition,constraints such as nonlinearity,parameter uncertainty,external disturbance,actuator failure,and input saturation are widely considered in practical engineering problems.The primary objective of this work is to investigate the adaptive control of nonlinear systems based on multiple constraints.Firstly,the fault-tolerant tracking problems of a class of perturbed nonlinear systems with performance constraints are studied.By introducing the performance function,the traditional tracking error is converted into generalized tracking error.The generalized tracking error is used to design controller,and the performance constraint problem is solved skillfully.The idea of extracting the core function is used to deal with the uncertain nonlinear part in the system.In the process of controller design,by introducing a firstorder filter and boundary layer error,combined with dynamic surface control technology and adaptive backstepping controller design method,the adaptive control rate and update rate are designed.Then,the impact of actuator failure and external disturbances in the system are resolved successfully.The designed control algorithm can achieve the stable tracking of the target trajectory with guaranteed the pre-specified performance bounded(transient performance,steady-state performance)under the above constraints,and ensure that the internal signals of the closed-loop system are continuous and bounded.The simulation results verify the effectiveness of the designed control scheme.Secondly,the fault-tolerant tracking problems of a class of input saturation saturated feedback nonlinear systems with guaranteed the pre-specified performance bounded is studied.By introducing a soft saturation function and a bounded function to approximate the input saturation characteristic curve,the input saturation nonlinearity problem in the actuator is subtly solved.Also,the pre-performance constraint condition is handled through the performance function.And the robust adaptive control theory is used to deal with unpredictable and time-varying actuator faults,the designed controller is faulttolerant.Nussbaum type functions are introduced to solve the problem of system control gains unknown.Combine traditional backstepping controller design method and dynamic surface control idea to avoid the problem of “differential explosion”.The final designed control scheme can ensure that the system implement fault-tolerant tracking control that guarantees pre-specified performance requirements under the constraints of actuator input saturation,unpredictable and time-varying actuator faults,parameter uncertainties and external disturbances.The stability of the control scheme is proved by Lyapunov stability theory.The simulation results verify the effectiveness of the control scheme.