Research On Robust Finite-time Control Algorithms For Nonholonomic Mobile Robots

As an important research direction in the field of system control, the control design of nonholonomic system is difficult because of the existence of nonholonomic constraints.Wheeled mobile robots is a typical nonholonomic system, and it has been widely applied to many fields, such as industrial production, national defense, services and so on. In the practical control system, the system is always affected by the internal, external disturbances and unmodeled dynamics on the one hand, and on the other hand, the actual system often has high requirements on convergence speed and control precision. Therefore,to study the robust finite-time control of nonholonomic wheeled mobile robots becomes meaningful in both theory and application.In this thesis, for the wheeled mobile robots control system with disturbances, two classes of control problems are studied, and the robust finite-time controllers are proposed, respectively. The effectiveness of the theoretical results are demonstrated by simulation. The main contributions include:1、For the single individual system of mobile robots, when the velocities are unmeasured, dynamic model based robust finite-time tracking control algorithm is studied.(i).In the case that the angular velocity of the mobile robot is unmeasurable, the finite-time observer is designed to estimate the angular velocity and disturbances, and a composite controller including the observer-based partial state feedback control and the disturbance feed-forward compensation is designed, which guarantees that the tracking errors converge to zero in finite time.(ii). If the linear velocity as well as the angular velocity of mobile robot is unmeasurable, the finite-time linear velocity observer is designed based on a stronger constraint, and the finite-time output-feedback tracking controller is proposed.2、For the multi-agent mobile robot systems, considering the existence of disturbances, kinematic model based robust finite-time consensus algorithm is studied.(i).To design the controller, a coordinate transformation is adopted to transform the mobile robot systems into a third-order chained systems, which are composed of a first-order and second-order subsystems. Then, the robust finite-time consensus protocols are designed for the two subsystems, respectively.(ii). Based on the consensus protocols designed for the two subsystems, a time-dependant switching strategy is adopted to design the final consensus algorithm, which guarantees that the states consensus of the multiple nonholonomic mobile robots can be achieved in a finite time.