Twist Snake: Plastic table-top cable-driven robotic arm with all motors located at the base link

Table-top robotic arms for education and research must be low-cost for availability and lightweight and soft for safety. Therefore, as such a robot, this study focuses on designing a plastic table-top cable-driven robotic arm with all motors located at the base link. However, locating all motors at the base link results in a significant distance between a driving motor and driven joint, increases the number of parts for the force transmission, and increases the risk of a cable loosening and coming off of a pulley. To overcome these issues, this study proposed a novel cable-driven robotic arm named Twist Snake. We designed a joint composition of Twist Snake to minimize the number of parts for the force transmission. In addition, it has a compact cable-pretension/termination-mechanism and covering parts to prevent the cable from loosening and coming off of the pulley. The arm comprised 475 mm long moving links with an 802 g. The feasibility of the arm was experimentally demonstrated by contact rich tasks, the insertion of a toy peg into a hole and swiping a whiteboard with a cleaner. The optimization of the proposed design and the development of a learning method for the arm that leverages contact will be investigated in future work.