Abstract: Aiming at the problem that the theoretical analysis of spherical 3-RRP parallel mechanism is insufficient, resulting in unclear kinematics and dynamic characteristics, the specific structure of the mechanism is designed, and the kinematic characteristics of transfer and constraint and driving torque characteristics are analysed. According to the Panda-Kahan theory about inversed position solution, the distribution of flexible and reachable orientation space are clarified. Based on the reciprocal product of screw vector, the transfer and constraint energy efficiency coefficients of joints are established. On this basis, the multi-parameter plane model technology is applied to further reveal the coupling relationship among parameter scale, orientation space and performance index. Thereby，the parameter value is determined, and the range of high-quality orientation space and the distribution trend of performance index are illustrated. Based on the principle of virtual work, the dynamic model is derived, and the driving torque characteristic is qualitatively analysed. The results show that the wrist mechanism takes into account the characteristics of compact structure, large posture space, complete constraint performance, excellent transfer performance, and high load-weight ratio, which is in line with the functional characteristics of human wrist.

Key words: humanoid wrist joint, spherical 3-RRP parallel mechanism, scale optimization, performance analysis