Auto-charging Robot Insertion And Removal Process Trajectory Planning And Compliant Control Technology

With the rapid growth of the electric vehicle market,the demand of auto-charging technology is increasing.Nowadays,the main control strategy of auto-charging robots is single position tracking control,which causes undesirable force during charging plug-in operations.The undesirable force will shorten the lifetime of the robot and charging device.To address this concern,a compliant control strategy is developed to enhance the compliance of the auto-charging process,which reduces the force on the charging plug during the charging plugging process and ensures the compliance of the robot's working track.The kinematics of the UR5-based robotic arm for auto-charging robot was analyzed.The D-H parametric method was applied to establish the joint coordinate system of the auto-charging robot.Afterwards,the robot forward kinematics formula was derived from the system.Based on the derived robotic forward kinematics,the conventional inverse kinematics solving process was investigated.The IKFast algorithm was applied for inverse solving algorithm.Besides,the established robot kinematics was validated and the workspace of the auto-charging robot was explored.In Cartesian space,a linear function with parabola at both ends was used to achieve the compliance of trajectory planning.A continuous linear planning method modified with arc transition was proposed in terms of the auto-charging characteristics.The RRT algorithm was used to plan the working path of the auto-charging robot.The principles of direct force feedback control and admittance control were discussed based on physical model.Then the control laws of the two control methods were determined,and the admittance control was discretized.The simulation analysis of the two control methods was carried out on the Simulink platform,in which the influence of different parameters on the control effect was investigated.The plug contact process was divided into three stages,and the strategy for each stages was adjusted according to their mechanical characteristics.The hardware and software of the auto-charging robot control system was designed.An embedded platform with RK3399 as the core was used as the control platform.Based on the ROS framework,the sensor driver software and compliant controller software were designed.The controllers can calculate the robot's compensation correction and interacts with the UR5 robot's controller,which can realize auto-charging operations.Based on the Qt framework,two types of operator interfaces are designed for different operator identities.The shared memory plus signal quantity was applied to achieve communication and interaction between different levels and processes of the auto-charging robot.A simulated operating platform for the auto-charging robot was built,and the results show that the design meets the intended objectives.The operation effect of the compliant control algorithm is verified.The direct force feedback control can reduce 15% power and 62% force during operation.The Admittance control reduces the 13% power and 51% force.The influence of control parameters on the control effect was verified.The robustness of the two control algorithms was verified,which can reduce need for positioning accuracy.The direct force feedback control can reduce 60% and the admittance control can reduce 40%.