Analysis of the singularity of spatial parallel manipulator with terminal constraints

In this paper, we make an analysis on the singularity of spatial parallel manipulator. Although many scholars have discussed this topic, their works mainly focused on finding the methods to divide the cases of singularity or searching the solutions with Jacobian matrices. This paper, on the other hand, addresses the singularity problems of the manipulator with its terminal constraints, which are the reciprocal screws of the manipulator's sub-kinematic chains. Through investigating the kinematic screws and the terminal constraints of the sub-chains, this method not only avoids solving the Jacobian matrices, but also points out the physical meaning of singularity. Application analyses are presented to demonstrate the effectiveness of the method.