Differential Spiral Joint Mechanism for Coupled Variable Stiffness Actuation

TL;DR

This paper introduces the Differential Spiral Joint (DSJ) mechanism, a novel variable stiffness actuation system for tendon-driven robots that enables independent control of position and stiffness, with validated experimental performance.

Contribution

The paper presents the DSJ mechanism, which semi-decouples position and stiffness modulation, offering a compact design suitable for size-sensitive applications and validated through experiments.

Findings

Enables independent trajectory and stiffness control

Offers a compact and lightweight design

Demonstrates effective performance in experiments

Abstract

In this study, we present the Differential Spiral Joint (DSJ) mechanism for variable stiffness actuation in tendon-driven robots. The DSJ mechanism semi-decouples the modulation of position and mechanical stiffness, allowing independent trajectory tracking in different parameter space. Past studies show that increasing the mechanical stiffness achieves the wider range of renderable stiffness, whereas decreasing the mechanical stiffness improves the quality of actuator decoupling and shock absorbance. Therefore, it is often useful to modulate the mechanical stiffness to balance the required level of stiffness and safety. In addition, the DSJ mechanism offers a compact form factor, which is suitable for applications where the size and weight are important. The performance of the DSJ mechanism in various areas is validated through a set of experiments.