An approach for ensuring manipulator tip accuracy near singularities

The approach is based upon the online planning of suitable alternative instantaneous motions (velocities). Planned alternative velocities are used to replace impracticable desired velocity specifications. Joint rate truncation and optimization subject to motion feasibility constraints are used to plan the alternative motion. The motion feasibility constraints are determined by screw quantities reciprocal to the nontruncated joint axes. A method is presented for resolving the reciprocal screw quantities required to enforce alternative motion feasibility. The method is suitable for manipulators having a least one pair of intersecting revolute axes