# Twisting Tube Artificial Muscle (TTAM) and Its Application in Agonist and Antagonist Drive

## TL;DR

A new artificial muscle called TTAM is developed, which can twist and contract to generate force, potentially improving robotic systems.

## Contribution

The TTAM design introduces a novel method of generating contraction force through twisting and fluid displacement.

## Key findings

- A prototype TTAM achieved an internal pressure increase to 219 kPa after a 6π twisting angle.
- The TTAM produced a maximum contraction force of 200 N at 100 kPa initial pressure.
- An antagonistic robotic joint using two TTAMs was successfully developed.

## Abstract

Pneumatic artificial muscles (PAMs) are inherently compliant and relatively safe. They are widely used in applications where human beings and robots interact closely, such as service robots or medical robots. However, PAMs are constrained by bulky pumps and valve control systems, limiting their mobility, portability, and practical applications. In this research, a novel type of artificial muscle, namely Twisting Tube Artificial Muscle (TTAM), is presented. In a TTAM design, fluid (pressurized air in this research) is contained inside an elastic tube (constrained by a braiding). By twisting the tube from one end, the fluid inside the twisted part will be extruded to the untwisted part, resulting in a pressure increase inside the untwisted part. Both the twisted and untwisted parts will thus contract. Modeling and experimental characterization of the TTAM are conducted. In an experimental test at 100 kPa initial air pressure, after a 6π twisting angle, the internal pressure of a prototype TTAM is increased to 219 kPa, and the largest contraction force of the TTAM was up to 200 N. A novel antagonistic robotic joint actuated by two TTAMs is developed as a sample application.