Singularity Analysis of a 3 Degrees-of-Freedom Parallel Manipulator

The paper deals with the kinematic study of a parallel manipulator with 3 degrees-of-freedom named HPR (heave, pith, roll). The inverse kinematics is solved and jacobian matrixes are evaluated. Then singularity loci are analyzed within a dimensionless geometrical description of the parallel structure. Singularity loci determination is revealed scaling factor independent for this kind of mechanism. Besides, workspace boundaries based on the concept of first and second type singularity are studied varying characteristic geometrical ratios of the manipulator. Finally a methodology to design HPR mechanism with desired workspace free of singularities is proposed.