Design and Modeling of a Simple-Structured Continuously Variable Transmission Utilizing Shape Memory Alloy Superelasticity for Twisted String Actuator

TL;DR

This paper introduces a lightweight, simple CVT mechanism for Twisted String Actuators using superelastic Shape Memory Alloy rods, enabling continuous transmission ratio variation to improve efficiency under load.

Contribution

It presents a novel CVT design utilizing SMA superelasticity, with a comprehensive model addressing nonlinearities for improved TSA performance.

Findings

The proposed CVT achieves continuous TR variation.

Theoretical model accurately predicts SMA deformation behavior.

Experimental results validate the effectiveness of the CVT mechanism.

Abstract

Twisted String Actuators (TSAs) are widely used in robotics but suffer from a limited range of Transmission Ratio (TR) variation, restricting their efficiency under varying loads.To overcome this, we propose a novel lightweight, simple-structured Continuously Variable Transmission (CVT) mechanism for TSA utilizing Shape Memory Alloy (SMA) superelasticity. The CVT mechanism consists solely of a pair of highly lightweight superelastic SMA rods connecting the ends of twisted strings. These rods deform under external loads, adjusting the inter-string distance to enable continuous TR variation.We develop a comprehensive theoretical model that integrates three critical nonlinearities