Wriflex: Design and Kinematic Analysis of a Self-aligning Parallel Wrist

This paper presents a new self-aligning parallel wrist called Wriflex. Wriflex is composed of four legs: one of RRR type and the remaining three of PRRS type that connect a moving platform to a fixed platform (base). Leg RRR is a passive-motion-constraint leg designed to generate the spherical movement of the end-effector. The three prismatic (P) pairs, one for each PRRS leg, are the only actuated joints and are located on the base. Here, the kinematic analysis of Wriflex is studied. In particular, the forward and the inverse position analyses are solved in closed form. Then, its instantaneous kinematics is addressed till to identify all its singularities. Eventually, its self-aligning capability is proved by employing the Conditioning Index as kinetostatic-performance measure.