Study and resolution of singularities for a 7-DOF redundant manipulator

The singularity problem of a 7-degrees-of-freedom (DOF) redundant manipulator is analyzed, and a new resolution method is proposed. In this paper, the singularities are decoupled into the position singularities and the orientation singularity by the technique of workspace decomposition, then all sigularity conditions for both cases are derived, and the new singularity avoidance (NSA) method is proposed. The NSA method resolves the escapable singularities which can be reconfigured into a nonsingular posture via self motion. Unlike some existing methods, the NSA method considers the position singularities and the orientation singularity separately. This method only needs to optimize two order-3 minors, one for the 3x4 Jacobian translational submatrix and the other for the 3x7 Jacobian rotational submatrix. Therefore, the computation for the optimization is greatly reduced. Three examples are presented to demonstrate the generality and efficiency of this new method.