A Hybrid Inverse Kinematics for 2n-DOF Redundant Manipulator Based on General Spherical Wrist

A hybrid approach of using both analytical and numerical methods is proposed for solving the inverse kinematics of 2n DOF (degree of freedom) redundant manipulators consisting of n identical UJs (universal joints). By analyzing the structure of the proposed manipulator, a novel concept, named as “general spherical wrist” (GSW), is introduced. Then, based on this concept, the relationship between the last five GSW angles and the rest of ones for any given pose within the workspace is given in closed-form. Because of the introduction of the above closed-form relationship, the computational efficiency of the proposed hybrid method is higher than the pure numerical method. Finally, simulations on a 5-UJ manipulator are shown and the accuracy and efficiency of the proposed method is verified.