Development of Tendon-Driven Compliant Snake Robot with Global Bending and Twisting Actuation

TL;DR

This work addresses the challenge of achieving biologically inspired snake locomotion on flat ground by leveraging body compliance and lengthwise-globally applied bending and twisting tensions. It introduces the first hardware implementation of a tendon-driven, compliant snake robot with global actuation, combining planar undulation with vertical bending and axial twisting to realize forward, backward, and sidewinding motions, along with steerable navigation. The 13-module robot uses dual-axis motors and globally routed tendons, a torque coil for torsional stiffness, and a constant-curvature bending model to map motor commands to joint curvature, validated through indoor experiments that measured speeds and demonstrated 90° steering capability. While locomotion is demonstrated, the speeds are modest due to torsional backlash and joint stiffness, pointing to manufacturing improvements and control refinements as key future directions for robust, high-speed operation.

Abstract

Snake robots have been studied for decades with the aim of achieving biological snakes' fluent locomotion. Yet, as of today, their locomotion remains far from that of the biological snakes. Our recent study suggested that snake locomotion utilizing partial ground contacts can be achieved with robots by using body compliance and lengthwise-globally applied body tensions. In this paper, we present the first hardware implementation of this locomotion principle. Our snake robot comprises serial tendon-driven continuum sections and is bent and twisted globally using tendons. We demonstrate how the tendons are actuated to achieve the ground contacts for forward and backward locomotion and sidewinding. The robot's capability to generate snake locomotion in various directions and its steerability were validated in a series of indoor experiments.

Figures (12)

• Figure 1: Undulatory locomotion principles using lengthwise-globally applied body tensions: (a) forward locomotion, (b) backward locomotion, and (c) sidewinding. The red arrows represent the locomotion directions, and the body is bi-colored to visualize the body twist.
• Figure 2: Our snake robot mechanism consists of $13$ motors arranged in series, with the three central motors being dual-axis. These dual-axis motors utilize their second axes for vertical bending and axial twisting.
• Figure 3: Robot configuration with vertical upper bending: In this configuration, the ground contacts facilitate sinus-lifting forward locomotion.
• Figure 4: Robot configuration with vertical lower bending: In this configuration, the ground contacts facilitate center-lifting backward locomotion.
• Figure 5: Robot configuration with axial twisting: In this configuration, the ground contacts facilitate sidewinding.