Inverse kinematics of SSRMS-type manipulators with single joint locked failure

Redundant space manipulators, including Space Station Remote Manipulator System (SSRMS), Special Purpose Dexterous Manipulator (SPDM) and European Robotic Arm (ERA), have been playing important roles in the construction and maintenance of International Space Station (ISS). They have similar joint layout and are referred to SSRMS-type manipulators. This paper presents an effective inverse kinematics resolution method for this type of manipulators for single joint locked failure. Firstly, the configuration characteristics of the SSRMS-type redundant manipulators are analyzed. Secondly, the D-H frames and corresponding D-H parameters of the new 6-DOF manipulator formed by locking a joint in an arbitrary position are re-constructed. Thirdly, the inverse kinematics problems are classified into two cases: completely analytical inverse kinematics for locking joint 1, 2, 6 or 7, and hybrid inverse kinematics for locking joint 3, 4 or 5. The corresponding approaches are presented to solve them. Finally, some practical examples for typical single joint locking are analyzed. The results verify the proposed methods.