Trajectory Tracking Research Of Mobile Robots Based On Non-ningular Terminal Sliding Mode Control

The application of wheeled mobile robots is very extensive,and the problem of trajectory tracking control is a hot topic in the field of control in recent years.Therefore,this paper selects the research object as a two-drive non-holonomic mobile robot,and studies the trajectory tracking problem from the aspects of kinematics and dynamics,and then designs the corresponding non-singular terminal sliding mode controller.The main research works of this paper are as follows:(1)Firstly,based on the kinematics model of non-complete wheeled mobile robot,the non-singular terminal sliding surface is selected and the non-singular terminal sliding mode speed controller is designed.Then according to the defect of the original speed control rate,after the specific analysis,the local terminal sliding mode control law is used to realize the trajectory tracking control of the variable curvature.Considering that the kinematic model parameters are uncertain under certain conditions,an adaptive approximation law is proposed to estimate the unknown parameters.Finally,three simulation analyses are carried out,which are the comparative simulation of traditional PID control and non-singular terminal sliding mode control,the influence of changing the sliding element surface parameters on the tracking performance of the system and the feasibility simulation of the adaptive law approaching unknown parameters.(2)The general dynamic equation is added to the disturbance and constraint to complete the establishment of the dynamic model of the mobile robot,and the dynamic equations of the mobile robot are decoupled to obtain the left and right wheel torque and acceleration equations respectively.Then,the backstepping torque controller and the non-singular terminal sliding mode torque controller are designed separately,and the stability of the two is proved.Considering the chattering problem caused by sliding mode control,it is weakened by direct method and indirect method respectively.The direct method is to approximate the sliding mode switching term by the fuzzy adaptive algorithm,and the sliding mode switching term is continuous,thereby weakening the chattering.The indirect rule is to estimate the unknown disturbance by a nonlinear disturbance observer to reduce the value of the switching term,thereby indirectly weakening the chatter.Finally,three simulation analyses were carried out,including the influence of different masses on the tracking performance of the system,the dynamics simulation analysis of non-singular terminal sliding mode controller and the simulation analysis of the above two weakening chattering methods.(3)In order to complete the trajectory tracking experiment,pre-experiment preparation is required,including the construction of the experimental platform,the closed-loop communication between the computer and the single-chip microcomputer,and the positioning of the lidar sensor and the filtering of the data.Then,the influence of the tread and radius of the wheeled mobile robot on the accuracy of the actual moving distance is analyzed and calibrated.Finally,two experiments were completed separately.In order to analyze the difference of non-singular terminal sliding mode control and PID control tracking performance under different reference trajectories,a comparative experiment of the two is designed.Then,in order to analyze the influence of non-singular terminal sliding surface parameters and mass on the tracking performance of the system,a comparison experiment of different sliding mode parameters and mass was designed.According to the drawn speed graph and the line graph,the influence of sliding mode parameters and mass on the tracking performance of the speed curve is analyzed.