Offline motion planning on spherical surfaces for a manipulator

For many tasks such as welding and polishing on complex surfaces with manipulators, teaching-and-playback is difficult and inefficient. Motion planning with offline programming is an effective and efficient alternative control mode for these tasks. In this paper, we present a method to plan motion by offline programming for tasks on spherical workpieces and develop a corresponding planning module of the offline programming system, with practical factors including the reachable workspace and orientation constraint token into account. A calibration approach for workpiece coordinate system is first proposed, and an algorithm for orientation search is then presented. Minimal motion and energy consumption are considered as objectives in motion planning of a manipulator. A reachable workspace search method is presented, and several indexes are used to determine the optimal manipulability workspace to increase work efficiency and stability. Experiments are conducted to verify the feasibility and effectiveness of the proposed methods.