Abstract: Since singularity is the inherent character of parallel manipulator and has various effects on manipulator’s working performance, for certain mechanism, it has great significance to find out all of its singularities. From the view of kinematics, there exist three different types of singularities, each having a different physical interpretation. The singularity loci of a new 6-DOF parallel manipulator with 3 limbs 3-UrPS are studied, where Ur is compound universal joint, i.e. a 2-DOF spherical parallel mechanism, P is prismatic joint and S is spherical joint. It is very expedient to obtain the unique inverse solution in analytical form by the mechanism’s geometry character. Differentiating the inverse functions with respect to time can derive the regular speed Jacobian matrices. Singularities’ analytical form can be achieved easily through solving the determinant of the matrices. The singularities of type I and type II of the parallel manipulator are discussed and 3 cases special singularities are obtained. The analysis of the singular configurations provided here has great significance for manipulator trajectory planning and control.

Key words: Inverse solution, Jacobian matrix, Parallel manipulator, Singularity loci