ZERO REACTION WORKSPACE IN THE OPERATIONS OF MULTI DEGREES OF FREEDOM SPACE MANIPULATORS FOR ORBITAL MAINTENANCE

The control of the reactions transferred to the spacecraft during a manipulator manoeuvre is an important issue in order to reduce the energy consumption and extend the operating life of the Attitude Control System. In this paper the performance of a novel least-squares-based reaction control method recently introduced by some of the authors is analyzed in the case of multi-degrees-of-freedom 3D space manipulators. The proposed method locally minimizes the base reactions transferred by the manipulator to the base spacecraft by exploiting its redundancy, and has some important advantages with respect to the previous ones presented in the literature: a simple mathematical formulation, the possibility to use simple least-squares real-time routines for the solution, and the possibility to take into account the joint limits and the joint velocity and acceleration limits of the manipulator. The methods can be profitably used for the minimization of the base reaction torques, forces, and weighted combinations of them. The main objectives of the study presented in this paper are the implementation in a software simulator and the validation of the aforementioned reaction control solution in the case of 3D space robots, the study of the Zero Reaction Workspace of a modular 3D space robot, and the analysis of its dependence on the robot initial configuration and on the number of degrees of freedom of the robot. The minimization of the base reaction torques, forces, and both of them is considered.