Preliminary Study of the Effect of Bearings on Twisted String Actuation Over a Curved Surface

Abstract

Twisted String Actuator (TSA) is gradually gaining popularity in robotic applications due to its high power-to-weight ratio, transmission efficiency and flexibility. When a small torque is applied at the ends of a string, it creates twists in the string which result in length contraction. This contraction, in turn, generates translation forces and can be used for actuation, and this is the working principle of a TSA. However, TSA exhibits a highly non-linear behavior due to friction between the strings, the surrounding conduit, and especially over high-curvature surfaces where the twists cannot propagate effectively. This leads to undesired effects like pull-back and chattering that affects TSA’s performance. In this short paper, we briefly present the initial experimental results of the effects of passing TSA through low-friction rotational bearing over a curved route. We analyze the twist propagation behavior compared to conventional PTFE conduit.