Finite-Time Active Disturbance Rejection Control And Its Application To Multi-Agent Systems

Due to diverse disturbances in the control system,how to design disturbance rejection strategy becomes a challenging issue.Active disturbance rejection control has gained extensive applications for its superior disturbance rejection performance.Simultaneously,finite-time approach attracts extensive interests owing to its strong robustness and high precision.Finite-time method can greatly promote the performance of active disturbance rejection control.Cooperative control of multi-agent systems has been widely applied to practical engineering,and the control protocol should possess the ability of high precision and strong disturbance rejection.This thesis mainly focuses on the finite-time active disturbance rejection control and its application to multi-agent systems.The major contents are summarized as follows:First,the design of finite-time active disturbance rejection control for a class of high-order uncertain systems is researched.The proposed finite-time extended state observer consists of three parts: the linear term and the fractional power term guaranteeing the convergence rate of the system,and the signum function term ensuring that the observation error can strictly converge to zero.Then a finite-time controller is constructed in terms of the observer and applied to the tracking control of a wheeled mobile robot.Second,the design of fixed-time active disturbance rejection control is investigated for a class of high-order uncertain systems.A specific Lyapunov function is presented for the fixed-time extended state observer to prove the fixed-time convergence of the observation error.Besides,an integral sliding mode surface is constructed for the fixedtime controller,which is applied to the tracking control of a wheeled mobile robot.Third,the fixed-time formation control problem for a class of high-order uncertain multi-agent systems is studied.The proposed time-varying fixed-time extended state observer reduces the peaking value effectively.The desired trajectory for each follower is acquired by adopting a fixed-time distributed observer.In terms of the above observer,a prescribed performance control strategy is developed to keep the estimation of the formation error within the predetermined boundaries for all time.And the fixed-time convergence of the formation error is achieved eventually.The proposed strategy is applied to the formation of the wheeled mobile robots.Forth,a prescribed-time containment control protocol is put forward for a class of high-order uncertain multi-agent systems.The proposed prescribed-time extended state observer is utilized to estimate the unknown states and total disturbance of each follower.And the desired trajectory for each follower is obtained by a prescribed-time distributed observer.Based on the designed setup,the prescribed-time containment control protocol is suggested to steer each follower into a convex hull formed by the states of leaders within prescribed time.And an experiment is carried out with the help of wheeled mobile robots.Finally,the fixed-time formation-containment control problem is investigated for a class of high-order uncertain multi-agent systems under directed graph.The proposed extended state observer can regulate its gain with the observation error during the whole operation of the system to reduce the peaking,which is more flexible than that of time-varying gain.Two kinds of fixed-time distributed observers are designed for the formation leaders and the followers respectively to obtain their desired trajectories.With this formulation,a fixed-time formation-containment control protocol is constructed and applied to the wheeled mobile robots.