Research On Trajectory Tracking Control Of Wheeled Mobile Robot Chassis

With the development of robotics,mobile robots have been used in medical services,catering industry,logistics and transportation.How to achieve accurate and stable trajectory tracking of mobile robots has always been a key problem that the industry needs to solve.In this study,a small wheeled mobile robot chassis is used as the object,and the chassis hardware and software architecture and the trajectory tracking controller are studied to achieve accurate and stable planning and tracking for the problem of low trajectory tracking accuracy.The lateral posture and longitudinal velocity are decoupled,the lateral posture controller is designed based on the optimal feedforward LQR theory with understeer compensation,and the longitudinal hierarchical velocity controller is designed based on PID theory,and the feasibility of the controller is verified by designing various working conditions.The main work carried out in this paper is as follows.Firstly,the wheeled mobile robot chassis system and mathematical modeling are introduced.The wheeled structure,navigation method and drive method of the robot chassis are compared,the chassis type is selected according to the demand of the operation scenario,and the robot chassis composition and subsystem functions are analyzed.To simplify the controller design,a mathematical model including robot dynamics model and tire model is established.Secondly,lateral attitude controller design.In this study,the optimal feedforward LQR controller is used,including the posture compensation module,the optimal LQR feedback calculation module and the feedforward calculation module.Considering that the optimal feedforward LQR controller produces large lateral deviation,the understeer compensation module is added to the optimal feedforward LQR controller to form a lateral controller designed based on the optimal feedforward LQR with understeer compensation.Simulation analysis is conducted at three speeds to evaluate the effectiveness of the controller.The results show that the optimal feed-forward LQR controller with understeer compensation has higher tracking accuracy.Thirdly,the longitudinal velocity controller is designed.Based on the longitudinal hierarchical control method,the PID control theory is used to establish the upper layer controller to solve for the ideal acceleration of the robot chassis.The lower controller is formed by designing a table look-up module and mode arbitration,and the lower controller outputs torque duty cycle or braking pressure signals and makes decisions based on the acceleration signals input from the upper controller and the actual speed signals fed back from the robot chassis.The longitudinal speed controller is simulated and evaluated by considering two operating conditions of tracking ideal step change and sinusoidal change speed profile.The results show that the robot chassis achieves stable tracking of the planned speed.At last,Trajectory tracking controller simulation verification and real vehicle test.The lateral position controller and longitudinal speed controller are coupled together to form the trajectory tracking controller.The performance of the controller was simulated and analyzed by using Car Sim and MATLAB/Simulink to design a double-shifted line of work at three speeds.The simulation results show that the trajectory tracking controller has good trajectory tracking effect under the designed conditions.The stability and effectiveness of the trajectory tracking controller designed in this paper are further verified by building a real vehicle verification platform and testing it on closed park conditions and structured roads based on the platform hardware and software architecture.