On-line collision-free path planning for service and assembly tasks by a two-arm robot

This paper presents a new approach for on-line collision-free path planning of a two-arm manipulator system, integrated in an on-line task-level planning system. For service and assembly tasks, pick and place operations are requested asynchronously by the action sequence planning. Collision-free paths for independent tasks are planning using a 2D geometric model in consideration of the swept regions by the robot arms and the pay loads during their motions. A dynamic, deadlock-free scheduling concept coordinates the robot motions in the case that a collision-free path for one arm can not be found at moment. The on-line path planning for two-arm cooperations for exchanging and regrasping parts incorporates an off-line connectivity analysis, avoiding both collisions and kinematic restrictions. The implemented on-line planning system can generate collision-free path for one manipulator while the other is moving. The time needed for motion planning is in the average case shorter and in the worst case comparable with that needed for motion execution. Experiments have been successfully conducted with the mobile two-arm robot KAMRO at the author's institute.