Research And Application Of Adaptive Control For Nonlinear Pure Feedback Systems

In practical engineering applications and various industrial control systems,the design difficulty of the controller is greatly increased due to the uncertainties of parameters and random disturbances in the system itself.With the development of nonlinear adaptive control for many years,this situation has been greatly improved.However,in most literatures,the selection of the controlled object system and the further improvement of the system performance of the nonlinear adaptive control still have some limitations.Based on these two contents,this paper does the following research:1.In the existing research,most of them consider nonlinear strict feedback system or input affine nonlinear pure feedback system,which requires the system to have certain particularity.For the adaptive control problem of non-affine structure in control input and state,the traditional method not only greatly improves the difficulty of solving the problem,but also leads to the simultaneous existence of multiple controllers.Therefore,in order to solve the problem of adaptive control for input non-affine nonlinear pure feedback systems,a new coordinate transformation and auxiliary integration system are introduced based on backstepping method.The original n-order nonlinear systems are transformed into an n(10)1-order affine input systems.The redundancy caused by the general design method is effectively reduced by the controller designed by the augmented system.The adaptive law can also estimate unknown parameters quickly and accurately.In addition,the controller based on the above theory is applied to the single link manipulator system.The results show that the designed controller not only has better tracking performance,but also has simple structure,which is conducive to engineering practice.2.In the research of adaptive control for nonlinear pure feedback systems,the asymptotic stability and error stability are usually taken as the control objectives,the tracking error converges to the origin,lacking further consideration of the dynamic performance of the system such as overshoot.In some methods,the dynamic or steady-state performance of the system can be optimized by adjusting the parameters of the controller,but this method can not make the dynamic or steady-state performanceconverge to the designed performance.Therefore,in order to solve the adaptive control problem of predetermined performance of the nonlinear pure feedback system,a new coordinate transformation is introduced to solve the non-affine structure in the state,and a relatively simple Lyapunov function is designed to satisfy the predetermined performance of the system.Using backstepping method,a new adaptive control algorithm is presented to solve the problem of unknown parameters.The control algorithm based on this theory is applied to Buck circuit to realize the tracking control of output voltage.The simulation results show that the designed controller not only guarantees the predetermined performance of the system,but also stabilizes the tracking error asymptotically,and makes the system possess robustness in the case of disturbance.