Tendon-Driven Compliant Wheel-Less Snake Robot for Undulatory Locomotion Using Conformable Ground Contacts

Abstract

Replicating the flexible and efficient locomotion of biological snakes remains a significant challenge in robotics. Conventional snake robots, often built from serially linked rigid joints, require complex control strategies to simultaneously manage body undulation and propulsive ground forces. Based on the previous theoretical study, this article presents the first physical realization of a new principle that simplifies locomotion control by decoupling these two tasks. The core idea is that by using a flexible continuum body, different gaits can be generated by superimposing simple globally-applied tensions (for vertical bending and axial twisting) onto a basic planar undulation. These global tensions, combined with the robot's compliance and weight, passively shape the required ground contact patterns, eliminating the need for active force control at individual points. The design and implementation of a tendon-driven continuum snake robot that embodies this principle is presented. The robot uses globally routed tendons, actuated by centrally-located motors, to create uniform bending and twisting. Through experiments, it is demonstrated that the robot can produce three distinct gaits—forward, backward, and sidewinding—on flat ground simply by changing the global actuation mode, and demonstrate its capability for intuitive steering.