Modeling and applications of space manipulators

Abstract

To control robot or teleoperated manipulators in space, the motion of the satellite (which is actually the base of the manipulator) which will move due to the force exerted by the moving manipulator, must be considered. Most of the algorithms developed to control a robot manipulator assume that the manipulator is connected to a fixed base. Since the satellite moves due to the motion of the robot manipulator, the control schemes developed for fixed-base manipulators cannot be used for space robots and telerobots. In this paper, using a modified resolved motion rate control and angular momentum conservation law, a generalized Jacobian matrix is derived to control the space manipulator. It is shown that a manipulator controlled in this manner follows a prescribed path independent of the motion of the satellite. For some operations the attitude of a space vehicle must be corrected to achieve the mission objectives. The orientation of a space vehicle can be changed by using reaction jets and/or wheels. This increases both the cost and complexity of the system. However, existing manipulator systems on the vehicle may be used to change spacecraft orientation. An algorithm is developed which uses manipulator motions to rotate the base of the manipulator to the desired orientation [1].