Abstract:

Aiming at the Space Station Remote Manipulator System （SSRMS） type 7DOF redundant manipulator, with link offsets at the shoulder, elbow, and wrist parts, two parameterized methods, joint angle parameterized and arm angle parameterized, are proposed to solve the inverse kinematic problem analytically. For the former, any joint variable of  θ 1,  θ 2,  θ 6 and  θ 7 can be taken as parameters to be defined; then analytical expressions of other joint angles are derived according to the configuration characteristics, and 8 possible solutions can be obtained. For the latter, a zero-offset Spherical-Revolution-Spherical (SRS) manipulator corresponding to the SSRMS-type manipulator is first constructed. A parameter called arm angle is used to describe the redundancy of the SRS manipulator, then its inverse kinematics equation is solved for a given arm angle. According to the relationship between the SRS and SSRMS manipulators, eight solutions of the SSRMS-type manipulator’s inverse kinematics are determined. The proposed methods are verified by a case study.

Key words: Redundant Manipulator, Space Robot, Inverse Kinematics, Parameterization, Arm angle