Stable Path Tracking With JEMRMS Through Vibration Suppression Algorithmic Singularities Using Momentum Conservation

A new path tracking control method for the Japanese Experiment Module Remote Manipulator System (JEMRMS) / Small Fine Arm (SFA) “macro-mini” manipulator system on the International Space Station is proposed. The method ensures almost reactionless motion within wide areas of workspace. This feature is achieved via continuous inertial damping of the vibrations in the rst three joints of the macro part (JEMRMS), using vibration suppression control with the nine-DOF mini-arm (SFA plus the last three joints of JEMRMS). To deal with persisting algorithmic singularities due to the constraints imposed via the path tracking and vibration suppression subtasks, we propose to use reactionless motion instead of vibration suppression while crossing the algorithmic singularity. Such motion is ensured by conserving the inertia coupling momentum upon entering a suitably dened neighborhood of the singularity. In contrast to previous studies, where momentum has been conserved at zero, here the momentum is conserved at a nonzero value. This helps avoiding other types of algorithmic singularities which are due to the reactionless motion control subtask. The performance of the method is examined via simulations. Results from two other methods, known from previous studies, are obtained and compared with those from the proposed method. These results clearly demonstrate that stable control can be achieved while passing through algorithmic singularities.