A solution to the singularity problem for six-joint manipulators

A solution to the problem of singularities for six-joint manipulators is presented. By using this method, the unachievable components of the commanded motion are removed, while an exact inverse kinematic solution is used for the remaining motion components. At a singularity there are directions in Cartesian space where a differential translation or rotation cannot be specified. The underlying area is to identify these directions and then to eliminate the corresponding components of the commanded motion when the manipulator becomes singular using a pseudoinverse of the manipulator Jacobian. In order to avoid excessive joint velocities close to the singularities, the manipulator is treated as singular in the neighborhood of the singularity. A continuous solution is achieved by interpolation in the degenerate directions