Research On Performance Robust Control Of Uncertain Time Delay System And Its Application

Time-delay systems quite widely exist in practical engineering problems, such as aeronautics and astronautics systems, communication systems, industrial production, and ocean engineering. The existence of delay makes the system analysis and synthesis more complicated and difficult. Meanwhile, time delay is frequently a source of instability and performance degradation in many dynamic systems. In addition, the uncertainty of system describes the difference between the mathematic model and controlled plant, which reflects the existing of the variation of the system parameters and disturbance. Thus, it's of great importance in theoretical and practical application to study the robust control for uncertain time-delay systems. The dissertation focus on the robust controller design for uncertain time-delay systems and its application on flight control system.Firstly, based on Lyapunov stability theory and by introducing new Lyapunov-Krasovskii functions, the problems of state feedback non-fragile guaranteed cost controller are studied for a classe of norm bounded uncertain time-delay systems. According to a specified linear quadratic cost function and the uncertainty and control disturbance, a sufficient condition which makes the system robust stable is presented and the smallest upper bound of the function is found. By solving linear matrix inequalities (LMIs), the non-fragile guaranteed cost controller can be easily obtained.Then, based on Lyapunov stability theory and linear matrix inequality (LMI), delay-dependent state feedback non-fragile H∞controller is designed for a class of interval time-delay neutral system. If the interval uncertainty and controller execution are gain bounded, the designed controller can guarantee the system gradually stable and satisfy the H∞performance. By solving linear matrix inequalities (LMIs), the robust H∞controller can be easily obtained.Following, a kind of H∞control method is presented for a class of uncertain system with perturbation and time delay. The control scheme combines the robust control with the neural network control. For one thing, the reference model--the linear part of the system of the robust controller is designed by linear matrix inequality(LMI). And then, the modeling uncertain nonlinear part is compensated by the neural network. The stability analysis synthesizes the parameter perturbation, the time delay and the neural network weight. The stability of the closed loop system is proved by choosing an appropriate Lyapunov function.Finally, a novel adaptive robust control scheme based on RBF neural networks is studied for uncertain time delay nonlinear systems and its application in flight control system. The controller consists of an equivalent controller and a H∞controller .The RBF neural networks are used to approximate the unknown nonlinear functions and the approximation errors of the neural networks is used in the adaptive law to improve performance of the systems. H∞controller is proposed for attenuating influence of external disturbance and neural network approximation errors. The controller can not only guarantee stability of the nonlinear systems, but also attenuate the effect of the external disturbances and neural networks approximation errors to reach performance indexes.