Reliable computation of minimum-time motions for manipulators moving in obstacle fields using a successive search for minimum-overload trajectories

In this paper we present a practical method for finding obstacle-free minimum-time motions for manipulators subject to the limits of velocity-dependent actuator forces. An optimal motion-planning problem is converted into a finite-dimensional nonlinear programming problem by means of parameter optimization with quintic B-splines. We introduce the concept of the minimum-overload trajectory in which the motion time is specified to be faster than the actuators can handle, and the actuator overloads are minimized with the motion time fixed. By successive searches for minimum-overload trajectories, minimum-time motions are determined for three example manipulators without simplifying any of the kinematic, dynamic or geometric properties of the manipulators or the obstacles. In the resultant minimum-time motions, almost all of the joint actuators are close to saturation during the motions. (C) 2005 Wiley Periodicals, Inc.