Output Feedback Control Design For Switched Nonlinear System Based On Backstepping

Since the 1970s,the research of nonlinear control has achieved a series of important research results.The most significant challenge that control theory faces today is essential nonlinearity of the controlled object,such as satellite positioning and attitude control.Global feedback stability control design of nonlinear systems is now an important issue of control theory research.Due to the limitation of measurement techniques,measurement tools and cost control,measuring all states of system is almost unrealistic in some practical systems,so if it is feasible to achieve reliable performance of the system via output feedback,we usually use output feedback.Switched systems have been attracting a great deal of attention in the past decades due to the high performance requirements of control systems for handling nonlinear-ities and uncertainties.As an important class of hybrid systems,switched system is a front direction of current theory and research for hybrid dynamical systems.This thesis mainly investigates the problem of global output feedback stabilization and tracking for a class of switched nonlinear systems with uncertain control coefficients.The main contributions are as follows.On one hand,this thesis is mainly concerned with the problem of global output feedback stabilization for a class of switched nonlinear systems with uncertain control coefficients.First of all,it is shown that the unknown control coefficients are lumped together via a com-mon coordinate transformation,thus the original switched nonlinear system is transformed into a new switched system for which control design is feasible.Second,by constructing a common Lyapunov function relying on the designed state observer,the common output feed-back controller independent of switching signals is designed based on the backstepping meth-od so as to guarantee the global asymptotic stability of the resulting closed-loop switched system under arbitrary switchings.Two examples are included for verifying the effectiveness of the method proposed.On the other hand,in order to realize the tracking control objective,a common coordin-ate transformation for the original switched system is taken,which effectively removes the effect from the unknown control gain in the switching system model.Then,a simpler high-gain switched observer is designed.At the same time,the detailed design procedure of output feedback tracking controller is provided on the basis of backstepping.Also,some proper virtual control signals are constructed.The conclusions and perspectives are presented in the end of the thesis.