# Development of Variable Elastic Band with Adjustable Elasticities for Semi-Passive Exosuits

## TL;DR

A new adjustable elastic band is developed for exosuits to provide customizable assistive force profiles without the need for batteries.

## Contribution

The paper introduces a variable elastic band that allows semi-passive exosuits to adjust stiffness dynamically.

## Key findings

- The variable elastic band successfully generated different stiffness levels with high accuracy (R2 of 0.9985).
- Tests with participants showed the band effectively modulated assistive force profiles.
- This innovation addresses limitations of passive exosuits by enabling customizable force assistance.

## Abstract

Active exosuits provide various assistive force profiles but are limited by battery life, weight, and complex maintenance requirements. Passive exosuits, by contrast, are economical and lightweight while also offering unlimited usage times; however, due to their fixed stiffness levels, they can provide only a limited set of optimized assistive force profiles for different movements. To address these issues, this paper proposes a new variable elastic band for semi-passive exosuits. It comprises rubber bands and webbings connected in parallel, with the elongation of the rubber bands restricted according to the webbing length. By connecting these segments in series, a range of elasticities can be generated. Experimental results confirmed that the band could generate different stiffness levels, which were accurately predicted with an average coefficient of determination (R2) of 0.9985 and an average root mean square error of 0.8993. Additionally, based on tests involving participants wearing the device, the variable elastic band effectively modulated the assistive force profile. These findings overcome the previous limitations of passive components, opening the door to future research on enhancing the efficiency of passive systems and enabling further customization.