Trajectory Tracking Control Of Wheeled Mobile Robot Subject To Slipping And Skidding

With the development of science and technology,robots have been widely used in various fields.As an important branch of robotics,wheeled mobile robots have received extensive attentions in recent years.However,due to the non-holonomic constraints,under-actuation,and nonlinear characteristics of wheeled mobile robots,the motion control of wheeled mobile robots is extremely challenging.Most of the current researchs are carried out under ideal condition,that is,the wheels are pure rolling and there is no skidding between the wheels and the ground.This is difficult to be satisfied in the actual working environment.For example,when the robot is on a soft or wet ground,moving upwards or turning sharply at a high speed,slipping and skidding always occur between the wheels and the ground,which degrade the tracking performance and even lead to the failure of the tracking task.In this paper,taking the displacement between the center of mass of the robot and the midpoint of the driving wheel axis into consideration,the trajectory tracking control problem for wheeled mobile robot subject to longitudinal sliding and lateral slipping between the wheels and the ground is studied.The main contents are as follows:(1)Considering the longitudinal slip between the wheels and the ground,an adaptive controller is designed to achieve fast and accurate tracking of the reference trajectory.First,the kinematic model of the wheeled mobile robot in the presence of longitudinal slip is established and the trajectory tracking error model is obtained.Then,an adaptive controller is designed to achieve fast and accurate tracking of the reference trajectory,and an online tuning method of controller parameters based on gradient descent algorithm is proposed to improve transient performance of the control system.Finally,the effectiveness of the proposed algorithm is verified by simulations.(2)Considering the sideslip of the wheels and the ground,a sliding mode observer and integral sliding mode controller are designed to realize the trajectory tracking control of the wheeled mobile robot.First,a sliding mode observer is designed to observe the unknown sideslip speed.Then,the integral sliding mode method is used to design the kinematic controller,and the Lyapunov stability theory is used to prove the stability of the tracking error system.Finally,the effectiveness of the sliding mode observer and the sliding mode controller is verified by simulations.(3)Considering the simultaneous existence of longitudinal slip and sideslip,the kinematic and dynamic controllers are designed respectively to realize the trajectory tracking control of the wheeled mobile robot.First,the kinematic controller is designed using the Lyapunov direct method,which realizes the tracking of the reference trajectory in the ideal condition.Second,considering the influence of longitudinal slip and sideslip,a dynamic model is established by the Lagrangian method.Then a torque controller is designed to track the output of the kinematic controller and a RBF neural network is designed to compensate the unknown disturbance to improve the control accuracy.Then,the Lyapunov theory is used to prove the stability of the entire closed-loop system.Finally,simulations verify the effectiveness of the kinematic and dynamic controller.