Adaptive Control Design And Prescribed Performance Analysis Of Switched Nonlinear Systems

With the development of modern aviation industry,the performance requirements of the control system of near space vehicles are increasing.Obviously,the traditional linear control theory cannot satisfy the control performance requirements of near space vehicles in various practical working environments.Therefore,nonlinear control theory receives more attentions in the literature.On one hand,because of the large working range and the complicated working environment of near space vehicles,the near space vehicle has the characteristics including large flight envelope,many working modes and many working states.Besides,the near space vehicle also needs good maneuverability,load performance,and so on.Hence,the flight control system of the near space vehicle exhibits high nonlinearities.On the other hand,as a kind of hybrid system,switched systems have received more and more attention.This is because that many practical systems can be modeled as switched systems,such as power systems,mechanical systems,transportation systems.It is an effective way that the systems with high nonlinearities are studied by using switched system theory to obtain better control performance.In addition,for an actual control system,it is not enough that systems are just stability.Other performance requirements including transient performance and steady-state performance should be also considered.Thus,ensuring the prescribed performance of the system has gradually received attention.However,the current results in this field are still very limited.This paper mainly studies the problem of adaptive prescribed performance control of nonlinear switched systems.The details are as follows:First,the adaptive prescribed performance control of a class of nonlinear switched strict feedback systems is studied.An adaptive control method is used to deal with the unknown external disturbance.By designing the performance function and the error transformation function and combining the common Lyapunov function method and the backstepping method,switched state feedback controllers and a common Lyapunov function are constructed to ensure that all signals of the closed-loop system are bounded under the condition that the switching signal satisfies a dwell time and the tracking error satisfies the prescribed performance.At the same time,according to the Generalized Barbalat’s Lemma,it is proved that the state of the original system is asymptotically stable.Finally,the proposed design method is applied to near space vehicles to illustrate its effectiveness.Second,for a class of nonlinear switched systems with input nonlinearity,the problem of robust adaptive prescribed performance control under arbitrary switching is studied.The effect of input nonlinearity on the system is handled by designing auxiliary systems.A neural network control method is used to estimate unknown functions in the system.By designing performance function and error transformation function and combining the common Lyapunov function theory and the backstepping method,a switched state feedback controller of each subsystem is constructed to achieve the control target:all signals of the closed-loop system are bounded,and the tracking error of the switched system meets the prescribed performance.The effectiveness of the design method is verified by simulation applied to the flight control system of near space vehicles.Finally,conclusions and perspectives are presented in the end of this paper.