Research On The Trajectory Control Of A Wheeled Mobile Robot

Wheeled mobile robots motion control(WMRMC)is now a hot topic in mobile robot research.Wheeled mobile robots are widely use in various fields because of the stable structural characteristics and strong adaptability to the environment.According to the wheel number structure,there are two-wheeled,three-wheeled and four-wheeled mobile robots.In this paper,based on the movement characteristics of Seekur four-wheeled mobile robot,the problem of four-wheeled mobile robot trajectory tracking control based on the combination of Backstepping controller design,robot nonholonomic constraints,Lyapunov stability analysis,four wheel steering form analysis,sliding mode variable structure control design,nonlinear disturbance observer theory,etc.The main work of robot motion control and trajectory tracking can be summarized as follows:(1)According to the structural characteristics of wheeled mobile robot and the characteristics of motion constraints,the kinematic modeling of the four wheeled mobile robot is analyzed.According to the constraint conditions of nonholonomic mobile robots,the reasonable assumptions and constraints of robot motion are carried out.The motion of four wheeled mobile robot is simplified by using the motion model of differential wheeled mobile robot.(2)Based on the particle model of four-wheeled mobile robot designed a Backstepping feedback control law,using a more effective virtual feedback function,improved the classical Backstepping algorithm.Through simulation experiments,verified the effects on straight line tracking and circle trajectory tracking.The effectiveness of the control effect is proved.(3)This paper studies the four wheeled mobile robot based on the structural characteristics,combined with the design for Ackermann steering theorem,designed a steering method for four-wheeled omni-directional mobile robots,summarizes four kinds of robot steering forms,and focuses on the all wheel drive differential steering movement strategy.Through simulation experiments,the effectiveness of the robot in the trajectory of the constant radius of curvature and the radius changed curvature of the”8” trajectory is verified respectively,and the effectiveness of the special steering form to the trajectory tracking problem of the mobile robot is proved.(4)The dynamic model of four-wheeled mobile robot based on the classical theory and sliding mode variable structure controller design,designed a combined control strategy of the dynamic controller and the kinematic controller.the kinematic controller output virtual control variables,then the dynamic controller output torque to the wheel dynamics of specific vehicle.Based on the dynamic controller,an external disturbance is added,and a nonlinear disturbance observer is designed to compensate the disturbance of the robot.The results of simulation show that,joined the union control law disturbance observer can impact on the robot trajectory tracking motion compensation external disturbance,and greatly reduce the output torque of sliding mode variable structure controller dynamic jitter,reduce chattering,improve the robot trajectory tracking stability.