New Variable Stiffness Joint (VSJ): Study and Simulation

Abstract

Variable stiffness joints are devices that allow changing the joint stiffness of a mechanism. The development of this joint has increased, and various applications have emerged, most to improve human-robot interaction. This paper presents a proposal design of a new variable stiffness joint (VSJ). The working principle consists of antagonist extension springs with a rack and pinion mechanism. The springs are attached to a set of racks that allow varying the spring length, the main factor in varying the stiffness. The racks engage with a set of gears; one has a motor attached, which is responsible for varying the joint stiffness. Its mathematical model describes the joint behavior to maintain a constant force at the end of a link. Its simulation is performed with a constant force placed at the end of the link to evaluate the joint’s performance in a rotational situation.