Research On Precise Tracking Control Of Omnidirectional Mobile Robot

Aiming at the problem of Mecanum wheel omnidirectional mobile robot,it is difficult to track accurately due to uncertain factors such as vibration and slip.These uncertainties not only affect the mechanical properties of the robot,reduce the performance,but also bring noise to the sensors installed on the robot,and put forward higher requirements for the motion controller.In order to solve this problem,the main reasons for the vibration and skidding are the discontinuous contact of the ground and the interaction force between the wheels during the movement of the Mecanum wheel.The vibration of the shock absorber is reduced to a certain extent on the chassis of the robot,but the skid phenomenon is still obvious,so it is hoped that the precise path tracking can be achieved through control and elimination.Path tracking is a robot following a planned path.To achieve accurate path tracking in an omni-directional robot,accurate positioning and precise control are needed.Precise positioning is the prerequisite for precise control.The precise positioning of the robot includes two aspects of position and attitude,and the attitude is mainly the information of the course angle.In order to obtain accurate positioning information,this paper explores and studies the track estimation,inertial navigation system,photoelectric mouse positioning and visual odometer.Finally,it is made up of the gyroscope,accelerometer and magnetometer.Inertial navigation system provides information of heading angle,and location information is calculated by global location corrected by visual odometer.It is necessary to point out that in order to realize the intellectualization and modularization of sensing sensing system,an inertial navigation system is designed based on the embedded system,which can output the direction angle information through the digital interface and receive the control instruction.After obtaining accurate positioning information,this paper analyzes the existing path tracking control methods.Considering the difficulty in establishing an accurate kinematic and dynamic model of the omni-directional mobile robot,a model free control method is selected based on accurate position information.In particular,it is designed to control the heading channel from the disturbance rejection controller and two independent PI controller.The D controller controls the position of the X axis and the Y axis respectively.In order to verify the theoretical analysis,a set of control system is designed,which is divided into servo control layer,motion control layer and perception and decision layer.The PI controller is designed for the servo control layer to control the motor to follow the target speed accurately.The motion control layer controls the precise path tracking of the robot,and the perception and decision layer provide the planning.The path information is collected and processed by sensor information.The whole control system is completed in two platforms.The bottom servo control and motion control are designed in the FreeRTOS embedded real-time operating system,while the perception and decision are completed in the ROS robot operating system.Finally,the experiment of tracking the path of the control robot is designed.Through the experimental data,the position tracking error of the X axis is less than 10 cm,and the tracking error is less than 2 degree of the heading angle.