{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T06:02:15Z","timestamp":1773295335687,"version":"3.50.1"},"reference-count":34,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2023,9,21]],"date-time":"2023-09-21T00:00:00Z","timestamp":1695254400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Robot. AI"],"abstract":"<jats:p>This paper presents an in-pipe robot with three underactuated parallelogram crawler modules, which can automatically shift its body shape when encountering obstacles. The shape-shifting movement is achieved by only a single actuator through a simple differential mechanism by only combining a pair of spur gears. It can lead to downsizing, cost reduction, and simplification of control for adaptation to obstacles. The parallelogram shape does not change the total belt circumference length, thus, a new mechanism to maintain the belt tension is not necessary. Moreover, the proposed crawler can form the anterior-posterior symmetric parallelogram relative to the moving direction, which generates high adaptability in both forward and backward directions. However, whether the locomotion or shape-shifting is driven depends on the gear ratio of the differential mechanism because their movements are only switched mechanically. Therefore, to clarify the requirements of the gear ratio for the passive adaptation, two outputs of each crawler mechanism (torques of the flippers and front pulley) are quasi-statically analyzed, and how the environmental and design parameters influence the robot performance are verified by real experiments. From the experiments, although the robot could not adapt to the stepped pipe in vertical section, it successfully shifted its crawler\u2019s shape to parallelogram in horizontal section only with our simulated output ratio.<\/jats:p>","DOI":"10.3389\/frobt.2023.1234835","type":"journal-article","created":{"date-parts":[[2023,9,21]],"date-time":"2023-09-21T18:39:27Z","timestamp":1695321567000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":3,"title":["Effect of underactuated parallelogram shape-shifting for environmental adaptation movement of a three modular in-pipe robot"],"prefix":"10.3389","volume":"10","author":[{"given":"Atsushi","family":"Kakogawa","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shugen","family":"Ma","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1965","published-online":{"date-parts":[[2023,9,21]]},"reference":[{"key":"B1","first-page":"2632","article-title":"Compliant motion of a multi-segmented inspection robot","author":"Birkenhofer","year":"2005"},{"key":"B2","first-page":"1","article-title":"Pipetron series-robots for pipe inspection","author":"Debenest","year":"2014"},{"key":"B3","first-page":"5121","article-title":"Design of a robot for in-pipe inspection using omnidirectional wheels and active stabilization","author":"Dertien","year":"2014"},{"key":"B4","first-page":"5044","article-title":"Development of an inspection robot for small diameter gas distribution mains","author":"Dertien","year":"2011"},{"key":"B5","first-page":"5665","article-title":"A snake-like robot for internal inspection of complex pipe structures (piko)","author":"Fjerdingen","year":"2009"},{"key":"B6","first-page":"2309","article-title":"Design of in-pipe inspection vehicles for\/spl phi\/25,\/spl phi\/50,\/spl phi\/150 pipes","author":"Hirose","year":"1999"},{"key":"B7","doi-asserted-by":"publisher","first-page":"629368","DOI":"10.3389\/frobt.2021.629368","article-title":"Unified approach to the motion design for a snake robot negotiating complicated pipe structures","volume":"8","author":"Inazawa","year":"2021","journal-title":"Front. 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