Identifying multi-DOF-loss velocity degeneracies in kinematically-redundant manipulators

A new methodology for identifying multi-DOF (degree-of-freedom) loss velocity-degenerate (singular) configurations of kinematically-redundant manipulators is presented. The methodology is based on extending an existing single-DOF-loss velocity degeneracy identification methodology [J. Robot. Syst. 17 (11) (2000) 633; Mech. Mach. Theory 36 (3) (2001) 397]. The new methodology uses the properties of reciprocal screws to determine the multi-DOF-loss velocity-degenerate configurations of kinematically-redundant manipulators. A by-product of the multi-DOF-loss methodology is that reciprocal screws for each velocity-degenerate configuration are determined. These reciprocal screws characterize the motion loss for each degenerate configuration. The 2-DOF-loss velocity degeneracies for a 7-jointed spherical-revolute-spherical manipulator are derived to demonstrate the effectiveness of the reciprocity-based methodology for determining multi-DOF-loss velocity degeneracies.