Trajectory Tracking And Formation Control Of Robot Based On Sliding Mode

Wheeled mobile robot has been widely used in many areas,such as life service industry,security defense and automated production workshops due to its advantages of easy operation and flexible maneuverability.The trajectory tracking control of wheeled mobile robots is one of the primary problems that need to be solved in the practical application of wheeled mobile robots,and has attracted the attention of scholars.However,wheeled mobile robot is a nonholonomic constraint system with nonlinearity,strong coupling,multiple input and multiple output and uncertain parameters.The system cannot be stabilized by smooth state feedback,and its control problems are extremely challenging.On the other hand,the sliding mode control technology allows the system to enter and maintain operation on a sliding surface with certain performance by switching of control laws,which has the characteristics of good robustness and fast response.Therefore,it is widely used in the control of wheeled mobile robots.In this paper,the trajectory tracking control problem of wheeled mobile robot is studied by using sliding mode control technology,based on which,the leader-follower formation control algorithm of multi-robots is studied.The contents are as follows:(1)Considering the case that the center of mass of the wheeled mobile robot does not coincide with the geometric center,based on the kinematics model,an trajectory tracking controller based on the sliding mode double power approach law is presented.Firstly,considering the case where the center of mass of the wheeled mobile robot does not coincide with the geometric center,combining the constraint equations of the wheeled mobile robot,the kinematics model of the wheeled mobile robot is established,and the trajectory tracking error model of the wheeled mobile robot is obtained.Then,a new sliding surface is designed based on the trajectory tracking error model.The linear velocity and angular velocity controllers are designed by using the double power approach law to ensure that the system trajectory tracking error can quickly converge to zero.The global asymptotic stability of the closed-loop system is proved by Lyapunov stability theory,and the convergence of the system is analyzed.The upper bound of the time of the system reaching the sliding surface is given.Finally,the effectiveness of the proposed method is verified by simulation.(2)Based on the kinematics and dynamics model of wheeled mobile robot,an algorithm of trajectory tracking controller based on backstepping method and sliding mode exponential double power approach law is presented.Firstly,based on the kinematics model,the linear velocity and angular velocity controllers designed by the backstepping method are used to track the reference trajectory.Secondly,a new sliding mode surface is designed based on the dynamicmodel,and the torque controller designed by exponential double power approach law is used to track the linear velocity and angular velocity output by the kinematic controller.The stability of the entire double closed-loop system is proved by Lyapunov stability theory.Finally,the MATLAB simulation is used to verify that the trajectory tracking error can converge to zero in a short time,which verifies the stability of the system.(3)Based on the position error model between followers and expected followers,a leader-follower formation control algorithm based on sliding mode control is presented.Firstly,in the process of the followers chasing the leader,the expected following position of the followers relative to the leader is calculated according to the formation constraints based on which a position error model between the followers and the expected followers is established,the followers' linear velocity and angular velocity controllers are designed by combining the sliding mode control technology.Based on the action of these controllers,the formation is formed by the followers tracking the position of the expected followers.Finally,the effectiveness of the proposed method is verified by simulation.