Abstract
A new planning method of collision-free paths for a manipulator with 6 revolute joints is described.
Although a good description of free space is crucial for the path planning, it is practically impossible to construct it in 6 dimensional space which integrates position and orientation. The manipulator can be decomposed into a hand and an arm so that each of them has 3 degrees of freedom of motion. The collisionfree space for the arm is uniquely described in the 3 dimensional angular space. The collision-free space for the hand is characterized by the different constraint on its orientation. Given a range of orientation, the swept volume of the hand is made by sweeping it within the range. The free space for the hand is defined as collision-free space for this swept volume.
Combined with a local search technique for a collision-free hand motion in the real 3-D workspace, the collision-free path can be efficiently searched for using this characterized description of the free space.
The path planning system has beeen implemented for the ETA-2 (ETL's Torque Controlled Arm v. 2). The system has successfully solved the problems of 6 degrees-of-freedom pick-and-place operation.
