Output Tracking And Feedback Control Of Two Types Of Uncertain Nonlinear Systems

With the improvement of system control requirements and the development of control theory,more and more complex nonlinear system control designs are widely used in power system,aerospace system,industrial process control and other fields.In these practical control systems,on the one hand,even for a simple linear time-invariant system,the closed-loop system becomes a highly nonlinear equation after the feedback control is adopted,and the input and output signals given by the closed-loop system are often complex random processes.Therefore,nonlinearity and randomness are essential difficulties in the research of control theory.On the other hand,based on the fact that the change law of things usually depends on the current state and the state in the past period of time,it can be concluded that there are time delays in most practical systems.Due to the limitation of measurement tools and control methods,it is difficult for people to clearly understand the internal mechanism of complex systems,which leads to the inevitable uncertainty in the modeled nonlinear systems with time delays.The existence of these phenomena proposes new challenges to the existing nonlinear control design methods.In addition,the demand for control accuracy is getting higher and higher,and it is urgent to develop new and more effective control strategies.This thesis is carried out from the following two parts:The first part is concerned with the problem of output tracking control for a class of high-order stochastic nonlinear systems with dynamic uncertainties.The systems under investigation have dynamic uncertainties,unknown high-order terms and uncertain nonlinear functions simultaneously.The packaged unknown nonlinearities are manipulated successful by using radial basis function neural networks.Two dynamic signals are introduced to dominate the dynamic uncertainties and adjust the tracking accuracy,respectively.The proposed continuous controller guarantees that all states of the closedloop system are bounded in probability,and the tracking error converges to a preassigned range.Finally,a simulation example is provided to demonstrate the effectiveness of the control scheme.The second part investigates the problem of robust output feedback control for a class of time-delay nonlinear systems with input dead-zone and unknown continuous timevarying output function.A remarkable features of the system is considered not only the dead-zone input and continuous disturbances,but also the unknown measured output under the effect of continuous time-varying functions.Based on the double-domination methods and the technique coordinate transformation with the dead-zone characteristic,the robust output controller is constructed to guarantee that all closed-loop signals are ultimately uniform bounded.Finally,a simulation example is given to illustrate the effectiveness of the theoretical results.In conclusion,this thesis can provide new ideas for the problems that can not be solved under the existing framework,and enrich the output tracking and feedback control of uncertain nonlinear systems,therefore the control design of uncertain nonlinear systems has both theoretical significance and practical value.