Research On Tracking Control For Nonlinear System With State Constraints Of Lower Triangular Structure

In the past few years,with the prosperous development in the fields of electric power system,mobile robots,aerospace craft,etc,the modern engineering control systems involves as many as complexities and challenges.As the scale becomes larger and larger,higher requirements are placed on the performance of the system.The controller design on large-scale nonlinear systems has attracted a great interest of scholars,in which a representative system model is lower triangular nonlinear systems.In addition to system complexity,the controller design procedure has to take safety,environmental protection and quality improving into consideration,and it will provide actual systems certainly hard or soft constraints.Once the constraints were broken,the system would account instability and even accidents.In this thesis,the lower triangular structure nonlinear system with full state constraints is studied,as well as with some other problems,such as the output delay,uncertain nonlinear function,quantization input and unknown parameters.The main research contents are presented as follows:(1)Research on the tracking problem aiming at with full state constraints and output delay is first studied for a class of triangular interconnected nonlinear systems.First of all,the initial period of error is converted into a new errors through the error-shifting function.Secondly,the constructed barrier Lyapunov function assure that all the states are confined in a given time-varying upper and lower constraints.Then,by means of the RBF neural network and backstepping method,a neural network adaptive controller is designed for the system states to track the given signals,furthermore,the system achieves semi-global uniformly final bounded.For the time-delay,Lyapunov-Krasovskii functional is adopted to eliminate its influence.Finally,a numerical example verifies the feasibility and effectiveness of the designed controller.(2)Research on the tracking control of triangular nonlinear systems with quantization input and full state constraints.First,considering the system with unknown state coefficients and quantization input.Second,an improved error-shifting transformation function is adopted to deal with the initial error.Then,the constructed barrier Lyapunov function assure that all the states are confined in a given time-varying upper and lower constraints.Next,based on the dynamic surface control method and the backstepping method,an adaptive tracking control strategy is designed,with which the system states can track the given signals in a finite time,furthermore,the semi-global uniform final bounded also is achieved.Finally,a numerical example verifies the feasibility and effectiveness of the designed control strategy.