Design, analysis, and simulation of a new variable stiffness joint based on antagonist principle

In robotics, the variable stiffness joints have been developed as an alternative to include flexibility to a rigid mechanism. Variable Stiffness Joint (VSJ) allows for varying the stiffness in a mechanism during the performance of a trajectory. The development of this joint has increased, and various applications have emerged, most to improve human-robot interaction. This paper presents a VSJ based on the principle of antagonistic springs with a set of gears and racks that allow the extension or compression of the springs. The joint provides constant torque or variable torque to obtain a constant or variable force at the output of the link, so a relationship is between the torque provided by the spring’s effort and the output force; however, it is possible to achieve a desired variable force with this joint design. Simulations are realized to obtain the behavior for both a constant and a variable force.