Design of a flexure-based variable stiffness device for cable-driven joint modules

Robots with variable stiffness can achieve intrinsically safe motions, which are essential for human-robot interactions. This paper aims to design a variable stiffness device (VSD) for cable-driven robots. In order to achieve a large stiffness variation with a compact design, a novel VSD based on flexure mechanisms is proposed. Through design optimization, the resultant flexure-based VSD exhibits a liner relationship between its stiffness and deformation, which is ideal for stiffness control of a cable-driven joint module. To illustrate the effectiveness of the proposed VSD, cable-driven revolute joint modules with different arrangement of VSDs are studied, in which the joint module stiffness is regulated through tension control of the driving cables.