An Improved RRT Algorithm for The Motion Planning of Robot Manipulator Picking up Scattered Piston

Taking the piston blank feeding line as the research background, motion planning for grabbing the random stacking of piston blanks is studied. Aiming at the obstacle avoidance of the manipulator caused by the obstacle piston with unknown posture around the target piston, an improved RRT algorithm is proposed. The algorithm divides the planning process into two phases by introducing a pre-pose point. In the first stage, the main purpose is to avoid the collision between the grippers of the robotic arm and the obstructing piston. The 3D mapping of area around the target piston, and the gripping direction of the robotic arm is obtained based on the principle of the highest safety factor. Afterward, the path between the target point and the pre-posture point is calculated by the space coordinate transformation formula. The main purpose of the second phase is to improve the path quality of the plan under the premise of fully exploiting the computational efficiency of the RRT algorithm. The path point is searched using the mechanical function as a cost function. Based on the shortest path principle, the path from the pre-gesture point to the home point is obtained after 20 iterations. Finally, the RRT algorithm of this paper is configured in the ROS environment with the piston blank feeding platform. The experimental results show that the mechanical arm can replace the person to complete the feeding of the piston blank.