Disturbance rejection for space-based manipulators

Most industrial manipulators operate from a fixed base. Hence, there are no disturbances from the environment to alter the position of the end-effecto r. On the other hand, manipulators that are mounted on mobile platforms are subject to disturbances emerging from unwanted motion at the base. Similar ly, manipulators that perform delicate operations in space while on board i n-orbit spacecraft experience disturbances. This article describes the desi gn and implementation of a disturbance rejection controller for a 6 degree- of-freedom (DOF) programable universal manipulator for assembly (PUMA) mani pulator mounted on a 3-DOF platform. A control algorithm is designed to tra ck the desired position and attitude of the end-effector in inertial space, subject to unknown disturbances in the platform axes. Experimental results are presented for step, sinusoidal, and random disturbances in the platfor m rotational axis and in the neighborhood of kinematic singularities, (C) 1 999 John Wiley & Sons, Inc.