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Wheel-legged hybrid locomotion is an increasingly popular solution, as robots combine the energy efficiency and speed of wheels with the versatility and adaptability of legs. Most of the literature focuses on the actuated or active-wheel variant because it is simpler to control. However, recent advances in control strategies and computing power have made the advantages of unactuated or passive wheel-legged robots, such as their mechanical simplicity, low weight, and high energy efficiency, accessible. In this survey, we provide a comprehensive analysis of the unactuated wheel-legged hybrid robot literature, together with similar systems, to review the alternative implementations and design techniques in the context of the inherent challenges of controlling a legged robot that has passive skates on its feet. We aim to outline the critical factors that determine the system\u2019s viability and propose some directions for future research.<\/jats:p>","DOI":"10.3389\/frobt.2026.1857985","type":"journal-article","created":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T04:46:57Z","timestamp":1781671617000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Passive wheels on legged robots: a survey"],"prefix":"10.3389","volume":"13","author":[{"given":"James Florin","family":"Petri","sequence":"first","affiliation":[{"name":"Department of Electronic Engineering, Maynooth University","place":["Maynooth, Ireland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gerard","family":"Lacey","sequence":"additional","affiliation":[{"name":"Department of Electronic Engineering, Maynooth University","place":["Maynooth, Ireland"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,6,17]]},"reference":[{"key":"B1","first-page":"7438","article-title":"LEVA: a high-mobility logistic vehicle with legged suspension","author":"Arnold","year":"2025"},{"key":"B2","first-page":"2693","article-title":"Training in task space to speed up and guide reinforcement learning","author":"Bellegarda","year":"2019"},{"key":"B3","first-page":"1703","article-title":"Design and evaluation of skating motions for a dexterous quadruped","author":"Bellegarda","year":"2018"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.48550\/arXiv.2107.07507","article-title":"Optimization-based quadrupedal hybrid wheeled-legged locomotion","author":"Belli","year":"2021"},{"key":"B5","doi-asserted-by":"crossref","DOI":"10.1109\/IROS60139.2025.11246770","volume-title":"Interactive Navigation for Legged Manipulators with Learned Arm-Pushing Controller","author":"Bi","year":"2025"},{"key":"B6","first-page":"7555","article-title":"Skating with a force controlled quadrupedal robot","author":"Bjelonic","year":"2018"},{"key":"B7","first-page":"8388","article-title":"Whole-body MPC and online gait sequence generation for wheeled-legged robots","author":"Bjelonic","year":"2021"},{"key":"B8","doi-asserted-by":"publisher","first-page":"397","DOI":"10.3390\/machines13050397","article-title":"Robotic applications in skiing: a systematic review of current research and challenges","volume":"13","author":"Boboc","year":"2025","journal-title":"Machines"},{"key":"B9","doi-asserted-by":"publisher","first-page":"037713","DOI":"10.1242\/bio.037713","article-title":"Motion characteristics of human roller skating","volume":"8","author":"Chen","year":"2019","journal-title":"Biol. 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