Kinematics analysis and simulation of the 7 DOF redundant
cable-driven manipulator

XV Wei¹, CHEN Bai¹, LI Bin-bin¹, HUA Da-ren¹, WANG Yao-yao^1,2

                                     (1. College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics & Astronautics, 
                                Nanjing 210016, China; 2. The State Key Laboratory of Fluid Power and Mechatronic Systems,
                                 Zhejiang University, Hangzhou 310027, China)

Abstract: Aiming at the problems of low load-to-weight ratio, high inertia, and weak physical human-robot interaction for the traditional manipulator, cable-driven manipulator was researched on structure, joints coupling and redundant kinematics. A novel 7 DOF redundant cable-driven manipulator was designed. The first 4 DOF were driven indirectly by cables for the position control. The distal 3 DOF of the wrist joint were directly driven by motors for the pose control. Motion and force were transmitted by cables from actuators on the base to joints, which achieved the postposition of driving system. A mapping between motor angle and joint angle was established after analyzing the effect of cable coupling in the kinematics. A method, combining the position-pose separation and the weighted least-norm solution, was used to solve the redundant inverse kinematics. The simulation results indicate that the coupling mapping is correctness and the kinematics solution is accurate and efficient, which lays the foundation of structural optimization and dynamics modeling of the cable manipulator.
Key words: redundant cable-driven manipulator; cable coupling; position-pose separation; weighted least-norm solution