Modeling and parametric optimization of 3D tendon-sheath actuator system for upper limb soft exosuit

TL;DR

This paper develops a mathematical model and parametric analysis for a tendon-sheath actuator in upper limb exosuits, addressing slack issues and proposing a spring-based design for improved performance and adaptability.

Contribution

It introduces a robust model and parametric study for tendon slack management, advocating a spring-integrated design for universal applicability in tendon-sheath actuators.

Findings

Spring incorporation eliminates need for customization.

Tendon slack controlled by pretension, spring constant, and spool geometry.

Model improves actuator performance and movement smoothness.

Abstract

This paper presents an analysis of parametric characterization of a motor driven tendon-sheath actuator system for use in upper limb augmentation for applications such as rehabilitation, therapy, and industrial automation. The double tendon sheath system, which uses two sets of cables (agonist and antagonist side) guided through a sheath, is considered to produce smooth and natural-looking movements of the arm. The exoskeleton is equipped with a single motor capable of controlling both the flexion and extension motions. One of the key challenges in the implementation of a double tendon sheath system is the possibility of slack in the tendon, which can impact the overall performance of the system. To address this issue, a robust mathematical model is developed and a comprehensive parametric study is carried out to determine the most effective strategies for overcoming the problem of slack and improving the transmission. The study suggests that incorporating a series spring into the system's tendon leads to a universally applicable design, eliminating the need for individual customization. The results also show that the slack in the tendon can be effectively controlled by changing the pretension, spring constant, and size and geometry of spool mounted on the axle of motor.