Experimental Validation of a Variable Stiffness Joint Based on Antagonistic Principle

Abstract

AbstractIn human-robot interaction environments, flexible mechanisms have been implemented to relate force with movement to make interaction safer. Mechanism flexibility can be established through the use of variable stiffness joints which allow simultaneous change of the position and stiffness in joints. This paper presents a Variable Stiffness Joint (VSJ) based on the antagonistic principle with two springs. The proposed VSJ can provide constant or variable torque, depending on the task requirements. It includes a motor, associated with a set of gears and racks, to vary the lengths of the springs. The stiffness behavior is controlled with a position control law of the motor. This work details the joint mathematical model and its validation by simulation. For this purpose, a specific experimental setup is developed for torque measurement. The design of a new proposal VSJ is a compact version that maintains the same antagonistic configuration of springs consisting of two stages is presented.KeywordsVariable stiffness jointAntagonistic springsAntagonist principleHuman-robot interactionVariable torque