Locomotive analysis of a single-input three-link snake robot

Abstract

When commanding gaits for snake robots and other articulated systems, direct control of all possible joint inputs may not always be necessary or optimal to achieve a locomotive goal. Here we consider a three-link nonholonomic snake robot-an already underactuated system with locomotive capabilities in SE(2)-and reduce its input space to a single actuated joint, replacing the other joint's motor with a passive mass-spring-damper system. We show that the modified system can operate dynamically in addition to kinematically, and that it is possible to find gaits that produces locomotion similar to a fully actuated system. In particular, we describe the emergence of a new type of gait that incorporates the system's singular configurations to produce high locomotive efficiency without incurring unbounded constraint forces.