Inchworm-Inspired Bipedal Crawling Soft Robot With Forward and Backward Locomotion for Confined Spaces

Abstract

Soft crawling robots have broad application prospects in rescue, exploration, and medical fields. Currently, many bionic soft crawling robots achieve multi-directional locomotion through steering mechanisms. However, their steering capabilities are limited when crawling in pipes or confined spaces, preventing autonomous retreat and restricting crawling performance. Therefore, robots capable of bidirectional movement with easy directional switching, without relying on steering functions, are key to overcoming the limitations of bionic soft crawling robots' performance in confined spaces. This paper proposes a bipedal crawling soft robot inspired by the inchworm, which achieves forward and backward movement through posture control. The structure of the bipedal robot was designed, and the robot's structure was modeled and simulated. Simulation results show that the robot can achieve forward and reverse locomotion by altering its posture. A fully soft robot was fabricated using a flexible magnetically driven membrane, and a magnetic actuation system consisting of a microcontroller and bar magnets was constructed. By simply changing the magnetic field strength, the robot's posture and thus its movement direction can be altered. The maximum crawling speeds in the forward and reverse directions are 1.8 body lengths per second (bl/s) and 0.51 bl/s, respectively, which are the best in its class of soft crawling robots. To the best of our knowledge, achieving bidirectional crawling at such speeds with a soft bionic crawling robot has never been accomplished. The robot achieved bidirectional crawling on different rough surfaces and in confined spaces such as pipes. By leveraging simple magnetic field modulation to adjust crawling posture, forward and reverse locomotion was realized without structural alterations, offering a scalable and practical solution for advancing bionic soft crawling robot applications.