T-S Fuzzy-Affine-Model-Based Output Feedback Control Of Nonlinear Systems

Nonlinear systems extensively exist in many industrial processes,and these inherent nonlinearities with different forms always cause a substantial body of additional difficulties for stability analysis and controller synthesis.The T-S fuzzy-model-based approach has been suggested to be a powerful model-based nonlinear control method.The key procedure of this model is first to utilize a group of fuzzy IF-THEN rules to characterize a nonlinear plant in the form of a family of local affine or linear models,which can effectively characterize the local features of the nonlinear systems,and these local affine or linear models are connected via fuzzy membership functions smoothly.The T-S fuzzy model provides a universal technique framework to describe complicated nonlinear systems.On the other hand,the full system states are generally unmeasurable in many practical situations,thus,it is of great significance to study the output feedback control problem.Combined with the sliding mode control theory,adaptive control theory,and observer design technique,this paper will investigate the output feedback control problem for large-scale systems and continuous-time/discrete-time nonlinear systems based on T-S fuzzy affine models,and some new robust output feedback control methods will be proposed.The detail content of this thesis is given as follows:Chapter 2 investigates the decentralized robust H?fixed-order dynamic output feedback control problem for discrete-time nonlinear large-scale systems.Through utilizing a descriptor-system-based method and piecewise quadratic Lyapunov functions(PQLFs),sufficient conditions for the asymptotic stability of the closed-loop system are given.It is also noted that the couplings between the piecewise affine controller gains and system matrices are eliminated.The controller gains can be obtained via solving a set of linear matrix inequalities.Chapter 3 is concerned with the problem of decentralized robust H?output feedback control for a class of continuous-time nonlinear large-scale systems based on T-S fuzzy affine models.Since the premise variables cannot be measured,thus,the plant and the controller may not synchronize in transition from one region to another.Firstly,a piecewise fuzzy affine observer is designed,and then a piecewise affine output feedback controller is synthesized based on the estimated system states.Via a common quadratic Lyapunov function(CQLF)and piecewise quadratic Lyapunov functions(PQLFs),somenew results are proposed for the asynchronous observer-based controller synthesis for T-S fuzzy affine large-scale systems with unmeasurable premise variables.Chapter 4 attempts to investigate the output feedback sliding mode control(SMC)problem for a class of uncertain nonlinear systems via T-S fuzzy affine models.Through sufficiently exploring the dynamical properties of the original system and combining with the sliding surface function,a descriptor system is firstly constructed to characterize the holonomic dynamics of the sliding motion.Some new results on asymptotic stability analysis conditions for the sliding motion are proposed based on CQLF and PQLFs,respectively,and the sliding surface gain can be attained within a convex optimization setup.Then two output feedback SMC design approaches are proposed to force the resulting system states onto the sliding surface locally for a prescribed sliding region in finite time.Chapter 5 will propose a fuzzy output feedback dynamic SMC design method for uncertain T-S fuzzy affine systems with mismatched exogenous disturbances.Through adopting a state-input augmentation scheme,the dynamical properties of the sliding motion are characterized by a descriptor system.Some new results on asymptotic stability analysis of the sliding motion are proposed based on CQLF and PQLFs,respectively,and the sliding surface gain can be obtained via solving a set of linear matrix inequalities.Then a fuzzy output feedback dynamic SMC approach is proposed to force the resulting closed-loop system states onto the designed sliding surface locally for a prescribed sliding region in finite time.It is also worthy of pointing out that the designed controller can relax the assumption that each local affine model possesses one common control input channel,and the control input matrices are allowed to contain parameter uncertainties.Chapter 6 addresses the output feedback SMC problem for a class of discrete-time uncertain nonlinear systems through T-S fuzzy dynamic models.Combining with the sliding surface,a descriptor system is first constructed to characterize the sliding motion dynamics via a state-input augmentation technique.Based on PQLFs,sufficient conditions for asymptotic stability analysis of the sliding motion are attained under a uniform convex optimization framework.Two SMC design approaches are proposed to ensure the finite-time local convergence of the sliding surface.