Sliding Mode Control Design Of Systems Subject To Actuator Saturation

Actuator saturation is a common phenomenon in real control systems.When actuator force reaching its physical limitation,it is said to be saturated.It inevitably brings difficulties to the control design and stability analysis of the control systems.As a flexible control strategy with strong robustness to the matched uncertainties and parameter variations,sliding mode control(SMC)is widely used in most practical systems with uncertainty-inevitable factor.Since the sliding mode controller is designed to force the state trajectories of the closed-loop system to reach a predesigned sliding surface in a finite time,the reaching law of the sliding surface is usually required to promise the rapidness.Thus,some large control forces always lead to actuator saturation.The study of sliding mode control under actuator saturation possesses important theoretical and practical value,which has attracted considerable attention.To begin with,we will introduce the research background and some basic theory including the invariant set,convex optimization as well as attraction domain.The literature review regarding the sliding mode controller design for system subject to actuator saturation and event-triggered sliding mode control will be presented.The research presented in this thesis can be divided into three main part,they are saturated first-order sliding mode controller design and attraction domain estimation for uncertain linear system,saturated second-order sliding mode design for uncertain nonlinear system and corresponding sliding mode motion analysis,as well as event-triggered second-order sliding mode control design for uncertain nonlinear system subject to actuator saturation,respectively.In the first part,for a class of uncertain linear systems subjected to actuator magnitude and rate saturation,the structures of sliding mode controllers are designed.The attraction domains subject to some designed conditions of the closed-loop SMC system are estimated under the actuator saturation limitation,and a set of solvable conditions with less conservativeness are derived for the controller and the sliding surface design.The second part,a systematic analysis of a class of multi-input and multi-output nonlinear control systems with hard constraints is studied,based on high-order sliding mode observer and second-order sliding mode control strategy.The finite-time stability of the second-order sliding mode control system is analyzed under the designed second-order sliding mode control law subject to the unconstrained and constrained actuator/states,respectively.Accordingly,the geometric analysis of the resulting sliding motions is performed in terms of their maximal attraction domain.The third part presents an event-triggered second-order sliding mode controller design and system synthesis structure for nonlinear system,the stability of closed-loop system has been proofed.Besides,we calculate the minimum inter event time,and employed homogeneous invariant to analysis the attraction domain of the closed-loop system subject to actuator saturation.Illustrative examples are provided to validate the effectiveness of the presented control and estimation methods.And Finally,conclusion gives the concluding remarks.