Design and Stiffness Analysis of a Novel 7-DOF Cable-Driven Manipulator

The lightweight design of robots is an important factor in the field of human-robot interaction. Thus, a lightweight 7-DOF cable-driven manipulator is proposed and manufactured, including a shoulder joint with 3-DOF, an elbow joint with 1-DOF, and a wrist joint with 3-DOF. The offset design of the shoulder joint increases the workspace and facilitates the electrical wiring of the manipulator. To solve the cable relaxation problem of the long-term operation of the manipulator, novel cable tensioning mechanisms are proposed based on the characteristics of shoulder, elbow, and wrist joints, which enable rapid tensioning during the motion process. Moreover, forward/inverse kinematic model are established based on virtual coupling joints to analysis the performance of the manipulator. Both the tensile tests of the cables and the stiffness experiments of the wrist and elbow joints are carried out The experimental results show that the maximum stiffness values of the elbow joint and the wrist joint are 1066.3 N $\cdot$ m/rad and 319.8 N $\cdot$ m/rad respectively, which can be comparable to the human arm.