Observer-Based Output Feedback Control Methods For T-S Fuzzy Systems

With the rapid development of science and technology,nonlinear systems can be commonly found in modern control systems.The system complexity has also gradually increased.And the requirements for control performance have become higher.However,the traditional control theories are difficult to apply on the nonlinear systems due to their complexities.As an alternative,a so-called T-S fuzzy system can provide a linear system representation method.Therefore,using the T-S fuzzy system,mature linear control theories can be applied to complicated nonlinear systems.In this thesis,we will study a low-conservativeness robust observer-controller design method and a stability analysis method for T-S fuzzy systems with unmeasurable external disturbance.The main contents are as follows:When the premise variables and disturbance of a T-S fuzzy system are unknown,a H_? reduced-order observer based controller synthesis method is investigated.First,a reduced-order-observer-controller structure is given for the system,and an augmented error system composed of the estimation and control errors is obtained.The fuzzy modelling residual terms are seen as part of the external disturbance,and an extra design matrix is added to facilitate the design and analysis process.The robustness and stability conditions are given based on Lyapunov function approach,then the conditions are transformed into a solvable Linear Matrix Inequality(LMI)conditions.Finally,compared with the traditional observer-controller methods for the parking control problem of the suspended floater control system,the control performance and conservativeness reduction effects of the proposed methods are verified.Further,functional observer-controller synthesis problem of T-S fuzzy systems with unknown premise variables and unmeasured disturbance is investigated.First,assuming that the premise variables are known,a state feedback controller is designed based on the fuzzy Lyapunov function,and the system stability and robustness conditions are given.With a membership functions transformation technique,a functional observer is introduced to estimate the unknown premise variables and system control input.By using a robust separation principle,the observer-controller error augmented system is proved to be stable and robust to external disturbance.Finally,the effectiveness of the proposed method is verified by the suspended floater control system.