Energy-Based Design Optimization of a Miniature Wave-Like Robot Inside Curved Compliant Tubes

This paper analyzes the crawling locomotion of a wave-like robot in curved tubes. We use an energy-based approach to determine the optimal crawling orientation of the robot that minimizes the surface energy while advancing. The results showed that the robot rotated its body along the roll direction so that the wave motion would be in the same plane as the curvature plane of the tube. The incorporation of a passive bending joint along the plane of the wave motion decreased the surface energy and enhanced the robot's ability to advance in even tighter curves. Given these findings we designed and manufactured two new robots with either one or two passive bending joints. We molded custom flexible surfaces and tubes and experimentally tested our robots in them. These validating experiments indicated that the bending joints substantially improved the robots' ability to traverse curved tubes (see video).