Design and analysis of a tendon-driven snake-arm robot based on a spherical magnets

A tendon-driven snake-arm robot can achieve a bending motion with multiple degrees of freedom (DOF) with a compact structure, which enables the robot to be widely used in confined environments. However, if a conventional tendon-driven snake-arm robot is subject to a lateral force on the distal end, it will experience passive compliance. In this paper, a 2-DOF rolling joint is proposed, based on the opposite-pole attraction of spherical magnets, which has a relatively simple structure compared with traditional joints. By serially connecting the 2-DOF rolling joints, a novel snake-arm robot is designed utilizing a tendon-driven approach. The kinematic model and workspace of the snake-arm robot are obtained, and the bending motion is validated. Based on the kinematic model, it is theoretically proven that the proposed robot can avoid passive compliance. In addition, this feature is verified through load experiments on the developed prototype.