Design and analytical kinematics of a robot wrist based on a parallel mechanism

This paper proposes a new humanoid robot wrist with forearm based on a 3SPS-1S parallel mechanism. This parallel mechanism has a central strut to increase the stiffness of the platform and constrain the platform to have wrist motion. Inverse and forward kinematics is solved analytically based on the geometrical constraint equations and Dixon's resultant is used in the forward displacement analysis which is a difficult problem in parallel mechanism research. A numerical example is given to validate those theoretical results. Workspace of the new wrist is also discussed and comparison is made with the human wrist. The new wrist shows potential to improve robot performance by integrating advantages of parallel mechanisms.