Torque Transmission Mechanism that Realizes from Zero to Extremely High Passive Stiffness based on Mechanical Singularity and Its Application for Robot Joint

Abstract

To introduce a passive compliant mechanism for robot joints is an effective way for impact absorption. However, because robot joints also require high torque transmission characteristic, the simultaneous implementation of stiffness and softness is a significant issue. In this paper, we develop a torque transmission mechanism with nonlinear passive stiffness that realizes from zero to extremely high stiffness based on mechanical singularity. The analysis of nonlinearity of the stiffness is established and the experimental evaluations are shown. A four-legged robot with the proposed mechanism is designed and the effectiveness of high nonlinearity of the proposed mechanism is illustrated.