The Kinetics and Workspace of a Satellite-Mounted Robot
Satellite-mounted robots are considered that manipulate loads whose masses are not negligible compared to the satellite mass. In this paper the satellite attitude control system is considered to be turned off, as is often done on the space shuttle during Remote Manipulator System operation. Thus the satellite is considered to be free to not only translate, but to rotate in reaction to robot motions. Three basic topics in robotics, the forward kinematics, the inverse kinematics, and the robot work space, are all generalized here for satellite-mounted robots. The generalized version of the forward kinematics problem has become a dynamics problem with the property that the robot load position at the end of a maneuver is not just a function of the final joint angles, but of the whole history of the joint angles instead. For this reason, the new terms forward kinetics and inverse kinetics have been coined here. An interesting property of the inverse kinetics problem is that one not only specifies the desired load position and orientation, but one can choose any desired final satellite attitude as well. One complete solution to the very complex inverse kinetics problem for six degree-of-freedom satellite-mounted robot manipulators is presented. The robot workspace is also generated, and found to be a perfect sphere whose radius is a function of the load mass. Comparison of the free-flying satellite robot workspace to that of a robot mounted on an attitude fixed satellite, and to an inertially mounted robot, shows that it is usually larger than either one.
KeywordsJoint Angle Inverse Kinematic Satellite Attitude Attitude Control System Inertial Space
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