Removing the singularities of serial manipulators by transforming the workspace

Abstract

A new method of handling the kinematic singularities of serial robotic manipulators is proposed. The idea is to transform the manipulator's workspace W into a desingularized workspace W*. Robotic motions can then be planned anywhere in W*, subject to limits on spatial velocity and acceleration, and the resulting joint velocities and accelerations will be well-behaved and bounded. W* differs from W only near a singularity surface, where a deformation is applied in the direction normal to the surface. While the technique does not handle self-motion singularities and may not be practical in some cases, it is very easy to implement for certain manipulators, such as the PUMA, which is studied in the paper. When applicable, the method offers various advantages when compared with other methods of singularity control.