Researches On Disturbance Decoupling And Attenuation Control For Nonlinear Systems

The nonlinear control systems have attracted more and more attention in the cur-rent research fields.Simultaneously, the problem to avoid or attenuate the influence of external disturbance is also considered by researchers for the control system. Therefore, the further research on disturbance decoupling and attenuation for nonlinear systems is of significance on academic and practical aspects. In this dissertation,based on differ-ential geometry theory and fuzzy hyperbolic model(FHM),the research on disturbance decoupling and attenuation of nonlinear systems is developed and explored, for general nonlinear system,time-delay nonlinear system, parameter uncertain time-delay nonlinear system,and structure uncertain time-delay nonlinear system, etc. The main research work is as follows:1.The disturbance decoupling control problem is considered for a class of MIMO continuous nonlinear systems. Based on differential geometry theory, the relative degree vector with respect to disturbance is proposed. A nonlinear state feedback control law is constructed,which can ensure that outputs of the closed-loop system are unaffected by disturbances. Sufficient and necessary condition is derived for the existence of such feedback control law.The resulting closed-loop system is also input-output decoupled and linearized.Moreover,the stable condition is discussed briefly. A simulation to a practical system of induction motor is provided to illustrate the effectiveness of the presented method.2.The disturbance decoupling control problem is considered for a class of time-delay continuous nonlinear systems. Under some assumptions and based on differential geometry theory, sufficient and necessary conditions are proposed for the existence of memorial and memoryless state feedback control law.The controllers can guarantee outputs the resulting closed-loop systems are unaffected by disturbances and independent of time-delays.Moreover, the overall decoupled systems are input-output decoupled and linearized.3.The robust H∞disturbance attenuation control scheme based on fuzzy hyperbolic model(FHM)is proposed for a class of continuous time nonlinear systems with parametric uncertainties and multiple delays.FHM modeling method for time-delay nonlinear sys-tems is presented.By using a novel Lyapunov-Krasovskii functional and LMI technology, delay-dependent sufficient condition for the existence of a kind of state feedback controller is proposed in terms of linear matrix inequalities(LMIs).The controller can guarantee that the resulting closed-loop system is robustly asymptotically stable with a prescribed H∞performance level for all admissible uncertainties and time-delays.Compared with the existing results of our earlier work, the proposed result has the following advantages: the condition of the existence of controller is delay-dependent and dependent on more system parameter information.It can guarantee the designed controller reaches better performance. So, the conservativeness of result is reduced largely.4.The robust H∞disturbance attenuation control scheme based on FHM is pro-posed for a class of continuous time nonlinear systems with parametric uncertainties and time-varying delay. By using Lyapunov-Krasovskii approach and LMI technology, delay-dependent sufficient condition for the existence of a kind of state feedback controller is proposed in terms of linear matrix inequalities.The controller can guarantee that the resulting closed-loop system is robustly asymptotically stable with a prescribed H∞performance level for all admissible uncertainties and time-delay. The condition is also dependent on more system parameter information,and the controller is also based on FHM.5.For a class of continuous time nonlinear systems with parametric and structural uncertainties and time-varying delay, the robust adaptive H∞disturbance attenuation control scheme based on fuzzy hyperbolic model is proposed.it is assumed that nonlinear perturbations in system structure are normObounded and the gains are unknown.Based on FHM and using Lyapunov-Krasovskii approach and LMI technology, delay-dependent sufficient condition for the existence of a kind of state feedback robust adaptive controller is given in terms of linear matrix inequalities.The novel adaptive law and estimation method for unknown parameters are used to eliminate the influence of the structural uncertainties.The presented controller can guarantee resulting closed-loop system robustly asymptotically stable with a prescribed H∞performance level. The result is more all-pervading and significant.