Electromagnetic Feet With Soft Toes for Adaptive, Versatile, and Stable Locomotion of an Inchworm-Inspired Pipe Crawling Robot.

Muhammad Bilal Khan,Jettanan Homchanthanakul,Poramate Manoonpong,Thirawat Chuthong

doi:10.3389/fbioe.2022.842816

Abstract

Feet play an important role in the adaptive, versatile, and stable locomotion of legged creatures. Accordingly, several robotic research studies have used biological feet as the inspiration for the design of robot feet in traversing complex terrains. However, so far, no robot feet can allow legged robots to adaptively, versatilely, and robustly crawl on various curved metal pipes, including flat surfaces for pipe inspection. To address this issue, we propose here a novel hybrid rigid-soft robot-foot design inspired by the leg morphology of an inchworm. The foot consists of a rigid section with an electromagnet and a soft toe covering for enhanced adhesion to a metal pipe. Finite element analysis , performed under different loading conditions, reveals that due to its compliance, the soft toe can undergo recoverable deformation with adaptability to various curved metal pipes and plain metal surfaces. We have successfully implemented electromagnetic feet with soft toes (EROFT) on an inchworm-inspired pipe crawling robot for adaptive, versatile, and stable locomotion. Foot-to-surface adaptability is provided by the inherent elasticity of the soft toe, making the robot a versatile and stable metal pipe crawler. Experiments show that the robot crawling success rate reaches 100% on large diameter metal pipes. The proposed hybrid rigid-soft feet (i.e., electromagnetic feet with soft toes) can solve the problem of continuous surface adaptation for the robot in a stable and efficient manner, irrespective of the surface curvature, without the need to manually change the robot feet for specific surfaces. To this end, the foot development enables the robot to meet a set of deployment requirements on large oil and gas pipelines for potential use in inspecting various faults and leakages.

Highlights

Inchworms are biological creatures with an excellent ability to crawl on complex surfaces using a looping movement (Wang et al, 2014; Moreira et al, 2018) (Figure 1A), accompanied by the strong grip of its legs [9]
A great interest has been shown by the research and industrial organizations to tackle the remote inspection of complex sites such as oil pipelines, ships and ports, airports, renewable energy infrastructure etc. (Lim et al, 2008; Ogai and Bhattacharya 2018; Popek et al, 2018; Ruggiero et al, 2018; Yamamoto et al, 2018). This resulted in huge institutional investments in the research and development of inspection robots
Previous works for pipe inspection developed robots with various levels of locomotion capability mainly targeting in-pipe crawling (Neubauer 1993; Lim et al, 2008; Ogai and Bhattacharya 2018)

Summary

Introduction

Inchworms are biological creatures with an excellent ability to crawl on complex surfaces using a looping movement (Wang et al, 2014; Moreira et al, 2018) (Figure 1A), accompanied by the strong grip of its legs [9]. Little attention has been given to developing robots that can perform locomotion outside the pipe (despite the advantages such as effective gas/oil leakage detection outside the pipe (Khan et al, 2020)) This is due to the nature of the outer pipe surface which involves complex structures including curvatures of various diameters from small to infinite (plate), making it a challenging problem in robot locomotion. Due to the limited scope of existing solutions for pipe gripping and adhesion (typically targeting a specific pipe diameter to grip/adhere, unlike the real-world scenarios), a significant contribution is needed to develop a functional outer pipe crawling robot for adaptively crawling on pipes of various diameters From this perspective, learning from an inchworm’s morphology and crawling behaviors in detail can advance robot structure and locomotion control design for pipe inspection

Methods

Results

Conclusion