A Twisted String Actuator-Driven Soft Robotic Manipulator

To make robots more ubiquitous, robotic structures that are compliant, lightweight, and low-cost are desired. Soft robots, which are fabricated using compliant materials and soft actuators, are ideal for such applications. However, producing high-performance soft robots is challenging due to the lack of systematic procedures and availability of standard components. In this paper, a soft robotic manipulator powered by twisted string actuators (TSAs) is presented. Although TSAs have been widely adopted in multiple robotic applications, their inclusion in soft robots has been limited. Due to their tendon-based (muscle-like) linear actuation, high force generation, and high operational bandwidth, TSAs are highly suitable to actuate soft robotic devices with advantages over other soft actuators. The design of the proposed soft robotic manipulator was presented. The performance of the manipulator was analyzed by experimentally characterizing and modeling the correlations between (1) the bending angle and motor rotations and (2) the tip force and motor rotations. Furthermore, closed-loop control was successfully employed to control the bending angle of the manipulator. Through experiments, the proposed robotic manipulator was found to exhibit a maximum bending angle of 97.4°and exerted a force of nearly 500 mN.