Twisted String Actuator mechanism with adjustable offset of strings for continuous variable transmission system

This paper presents a novel TSA mechanism with an adjustable offset between strings, which enables a variable transmission system. TSA is designed to be used in a variety of applications, including exoskeletons, and robotics. The fixed contraction range of TSAs limits their ability to provide comprehensive support. The proposed mechanism overcomes this limitation by adjusting the offset between strings. The mechanism consists of six parts with two motors. Each motor in the mechanism operates to adjust offset with only one motor and operates simultaneously to twist the strings. This enables the contraction range of TSA to be varied a wide range. Furthermore, an analytical model is also introduced for controlling the contraction range of TSA. In the experiment, the proposed mechanism shows the contraction range of TSA to be increased by up to 20%. Additionally, it showed that it is possible to vary the maximum force of TSA by up to 47%. Moreover, the analytical model has a low error. These findings suggest the promising potential for the developed TSA mechanism in a variety of applications.