An efficient robot arm control under geometric path constraints

Conventionally, robot control algorithms are divided into two stages, namely, path planning and path tracking (or path control) This division has been adopted mainly as a means of alleviating difficulties in dealing with complex, coupled robot arm dynamics. Unfortunately, the simplicity obtained from the division comes at the expense of efficiency in utilizing robot´s capabilities. To remove at least partially this inefficiency, this paper considers a solution to the problem of moving a robot arm in minimum time along a specified geometric path subject to input torque/force constraints. We first describe the robot arm dynamics using parametric functions which represent geometric path constraints to be honored for collision avoidance as well as task requirements. Secondly, constraints on input torques/forces are converted to those on the parameters. Finally, the minimum-time solution is deduced in an algorithm form using phase-plane techniques.