Development of a high-performance twisted string actuator based on dedicated direct drive motor for robotics applications

1. Funding Agency

Ministry of National Defense of the Republic of Korea

2. Motivation

Conventional gear-reduced actuators burden wearable and multi-joint robots with mass, backlash and limited efficiency. Direct-drive twisted string actuators (TSA) promise lightweight, high power-density motion, yet their nonlinear kinematics and reliability hurdles remain unsolved. KAIST aims to overcome these barriers to enable next-generation assistive suits demanded by aging, industrial and defense sectors.

3. Objectives

Leveraging nonlinear modeling, adaptive high-bandwidth control and modular engineering, KAIST will create direct-drive twisted string actuator modules that maximize efficiency, motion range and responsiveness. The technology will be validated in exosuits, laying the foundation for reliable, lightweight actuation solutions scalable to diverse industrial, medical and defense applications.

4. Ongoing Progress

Actuator efficiency has been experimentally elevated to the target range, and the maximum stroke enlarged to broaden motion capability. Consistent average tension confirms high-gear-ratio performance, while material-and-structure optimization has markedly extended service life. A wider control bandwidth now guarantees real-time responsiveness. The soft lower-limb exosuit has been further lightened, and human trials verify noticeable reductions in muscular effort.

5. Related Publications

• Baek, S., Jang, J., & Ryu, J. H. (2024). Enhancing Maximum Stroke of Twisted String Actuators by Adjusting Twisting Ratio. IEEE Robotics and Automation Letters, 9(6), 5887-5894.

6. Contact

• HyeonSeok Seong
• Seungjoon Baek
• Euibin Shin
• Juyeong Seo