Design analysis of a 3-DOF cable-driven variable-stiffness joint module

Variable-stiffness manipulators can produce intrinsically-safe motions, which are essential for next generation service robots. In this paper, the design analysis of a 3-DOF cable-driven joint module with variable stiffness is proposed. To achieve significant change of the stiffness, a flexure-based variable-stiffness device is serially connected to each of the cables. Due to the existence of redundant actuation, the stiffness of the joint module is controlled by regulating the cable tensions. To this end, the relationship between the stiffness matrix of the joint module and the cable tensions has been formulated and analyzed. Simulation examples are provided to illustrate the effectiveness of the proposed stiffness evaluation algorithm.