Robust Stability Analysis And Fault-Tolerant Sliding Mode Control For Several Classes Of Stochastic Time-Delay Systems

In practical engineering systems,the effects of time-delay and external disturbance noise frequently occur,which result in performance degradation and even instability of the system.Stochastic time-delay systems have attracted extensive attention since stochastic systems have strong modeling ability to the actual physical model.On another research front,sliding mode control is considered to be an important branch in the domain of the control theory.The advantages of the sliding model control is simple algorithm,well robust performance and highly reliability.However,most of the existing results about sliding mode control are based on ordinary differential systems.There are still few results on analysis and synthesis for stochastic systems with Brownian motions modelled by It? stochastic differential equations.Combining with the stochastic differential equation theory,the sliding mode control theory and methods of observer design,this thesis analyzes and investigates the problem of stability analysis and the design of sliding mode controller for neutral-type stochastic time-delay systems and stochastic Markovian jump systems.The main contents are as follows:Firstly,the problem of stochastic stability analysis is investigated for neutral-type stochastic time-delay systems.By Lyapunov-Krasovskii functional approach,together with the free weight matrix method,a time-delay dependent sufficient condition is proposed.Combining with a time-delay segmentation method and S-process,our results are much less conservative than some existing ones in literature since more time-delay information is used.A non-fragile state feedback controller is developed to stabilize the closed-loop system.Secondly,investigates the robust stability problem in the presence of uncertain parameters for a class of stochastic neutral-type systems with mixed time-varying delays,where external disturbance and nonlinearity are considered together.The nonlinear function is assumed to satisfy the one-sided Lipschitz condition and the quadratic inner-boundedness condition.By constructing a modified Lyapunov–Krasovskii functional and using the free-weighting matrix technique,some new delay-dependent criteria for the stability of the problem are presented.In particular,the derivatives of the time-varying delays are no longer limited to being less than one.Finally,numerical examples are given to illustratethe effectiveness of the derived results.Thirdly,the robust sliding mode control problem is considered for stochastic Markovian jump systems.Unknown actuator degradation factors and matched nonlinearity are considered simultaneously.In order to estimate the system state,an adaptive robust observer is proposed for the system.Based on the estimation,a sliding mode variable structure controller scheme against fault and disturbance is developed to stabilize the resulting closed-loop control system.Finally,the problem of finite-time adaptive sliding mode control for It? stochastic systems with Markovian switching is investigated?The transition rate matrix of the jump systems is partially available.To reconstruct the system state,an adaptive sliding mode observer is proposed firstly.The effect of actuator degradation is compensated by the adaptive estimation mechanism.Based on the state estimation,an observer-based adaptive sliding mode control law is developed to stabilize the overall closed-loop system,which can also ensure the state trajectories to be driven onto the sliding surface in finite-time with a pre-specified interval.