{"id":12825,"date":"2025-09-12T09:43:41","date_gmt":"2025-09-12T14:43:41","guid":{"rendered":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin-new\/?post_type=campus_story&p=12825"},"modified":"2025-09-12T09:43:41","modified_gmt":"2025-09-12T14:43:41","slug":"robotic-space-rovers-keep-getting-stuck-uw-madison-engineers-have-figured-out-why","status":"publish","type":"campus_story","link":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/story\/robotic-space-rovers-keep-getting-stuck-uw-madison-engineers-have-figured-out-why\/","title":{"rendered":"Robotic space rovers keep getting stuck. UW-Madison engineers have figured out why."},"content":{"rendered":"
\"Photo<\/a>
Mechanical engineering professor Dan Negrut poses with a space rover used for testing. Photo by Joel Hallberg<\/figcaption><\/figure>\n

When a multimillion-dollar extraterrestrial vehicle gets stuck in soft sand or gravel \u2014 as did the\u00a0Mars rover\u00a0Spirit<\/em><\/a>\u00a0in 2009 \u2014 Earth-based engineers take over like a virtual tow truck, issuing a series of commands that move its wheels or reverse its course in a delicate, time-consuming effort to free it and continue its exploratory mission.<\/p>\n

While\u00a0Spirit<\/em>\u00a0remained permanently stuck, in the future, better terrain testing right here on terra firma could help avert these celestial crises.<\/p>\n

Using computer simulations, University of Wisconsin\u2013Madison mechanical engineers have uncovered a flaw in how rovers are tested on Earth. That error leads to overly optimistic conclusions about how rovers will behave once they\u2019re deployed on extraterrestrial missions.<\/p>\n

An important element in preparing for these missions is an accurate understanding of how a rover will traverse extraterrestrial surfaces in low gravity to prevent it from getting stuck in soft terrain or rocky areas.<\/p>\n

\n
\"A
A rover\u2019s operation is simulated in Project Chrono, an open-source physics simulation engine developed at UW\u2013Madison.\u00a0<\/em>Image courtesy of Dan Negrut<\/em><\/span><\/span>\u00a0<\/figcaption><\/figure>\n<\/div>\n

On the moon, the gravitational pull is six times weaker than on Earth. For decades, researchers testing rovers have accounted for that difference in gravity by creating a prototype that is a sixth of the mass of the actual rover. They test these lightweight rovers in deserts, observing how it moves across sand to gain insights into how it would perform on the moon.<\/p>\n

It turns out, however, that this standard testing approach overlooked a seemingly inconsequential detail: the pull of Earth\u2019s gravity on the desert sand.<\/p>\n

Through simulation, Dan Negrut, a professor of mechanical engineering at UW\u2013Madison, and his collaborators determined that Earth\u2019s gravity pulls down on sand much more strongly than the gravity on Mars or the moon does. On Earth, sand is more rigid and supportive \u2014 reducing the likelihood it will shift under a vehicle\u2019s wheels. But the moon\u2019s surface is \u201cfluffier\u201d and therefore shifts more easily \u2014 meaning rovers have less traction, which can hinder their mobility.<\/p>\n

\u201cIn retrospect, the idea is simple: We need to consider not only the gravitational pull on the rover but also the effect of gravity on the sand to get a better picture of how the rover will perform on the moon,\u201d Negrut says. \u201cOur findings underscore the value of using physics-based simulation to analyze rover mobility on granular soil.\u201d<\/p>\n

The team\u00a0recently detailed its findings in the Journal of Field Robotics<\/a>.<\/p>\n

The researchers\u2019 discovery resulted from their work on a NASA-funded project to simulate the\u00a0VIPER rover<\/a>, which had been planned for a lunar mission. The team leveraged Project Chrono, an open-source physics simulation engine developed at UW\u2013Madison in collaboration with scientists from Italy. This software allows researchers to quickly and accurately model complex mechanical systems \u2014 like full-size rovers operating on \u201csquishy\u201d sand or soil surfaces.<\/p>\n

\n
\"A
A rover on sand in the Simulation-Based Engineering Lab.\u00a0<\/em>Photo by Joel Hallberg<\/em><\/span><\/span>\u00a0<\/figcaption><\/figure>\n<\/div>\n

While simulating the VIPER rover, they noticed discrepancies between the Earth-based test results and their simulations of the rover\u2019s mobility on the moon. Digging deeper with Chrono simulations revealed the testing flaw.<\/p>\n

The benefits of this research also extend well beyond NASA and space travel. For applications on Earth, Chrono has been used by hundreds of organizations to better understand complex mechanical systems \u2014 from precision mechanical watches to U.S. Army trucks and tanks operating in off-road conditions.<\/p>\n

\u201cIt\u2019s rewarding that our research is highly relevant in helping to solve many real-world engineering challenges,\u201d Negrut says. \u201cI\u2019m proud of what we\u2019ve accomplished. It\u2019s very difficult as a university lab to put out industrial-strength software that is used by NASA.\u201d<\/p>\n

Chrono is free and publicly available for unfettered use worldwide, but the UW\u2013Madison team puts in significant ongoing work to develop and maintain the software and provide user support.<\/p>\n

\u201cIt\u2019s very unusual in academia to produce a software product at this level,\u201d Negrut says. \u201cThere are certain types of applications relevant to NASA and planetary exploration where our simulator can solve problems that no other tool can solve, including simulators from huge tech companies, and that\u2019s exciting.\u201d<\/p>\n

Since Chrono is open source, Negrut and his team are focused on continually innovating and enhancing the software to stay relevant.<\/p>\n

\u201cAll our ideas are in the public domain and the competition can adopt them quickly, which is drives us to keep moving forward,\u201d he says. \u201cWe have been fortunate over the last decade to receive support from the National Science Foundation, U.S. Army Research Office and NASA. This funding has really made a difference, since we do not charge anyone for the use of our software.\u201d<\/p>\n

This work was supported by\u00a0<\/em>NASA STTR (80NSSC20C0252), the National Science Foundation (OAC2209791) and the U.S. Army Research Office, (W911NF1910431 and W911NF1810476).\u00a0<\/em>Read more about this research at the College of Engineering news site<\/em><\/a>.<\/em><\/p>\n

\n

Written by Adam Malecek<\/p>\n

Link to original story: https:\/\/news.wisc.edu\/robotic-space-rovers-keep-getting-stuck-uw-engineers-have-figured-out-why\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

When a multimillion-dollar extraterrestrial vehicle gets stuck in soft sand or gravel \u2014 as did the\u00a0Mars rover\u00a0Spirit\u00a0in 2009 \u2014 Earth-based engineers take over like a virtual tow truck, issuing a series of commands that move its wheels or reverse its course in a delicate, time-consuming effort to free it and continue its exploratory mission. While\u00a0Spirit\u00a0remained […]<\/p>\n","protected":false},"author":15,"featured_media":12828,"comment_status":"closed","ping_status":"closed","template":"","institution":[103],"story_category":[],"class_list":["post-12825","campus_story","type-campus_story","status-publish","has-post-thumbnail","hentry","institution-uw-madison"],"_links":{"self":[{"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/campus_story\/12825","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/campus_story"}],"about":[{"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/types\/campus_story"}],"author":[{"embeddable":true,"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/comments?post=12825"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/media\/12828"}],"wp:attachment":[{"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/media?parent=12825"}],"wp:term":[{"taxonomy":"institution","embeddable":true,"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/institution?post=12825"},{"taxonomy":"story_category","embeddable":true,"href":"https:\/\/wwwtest.wisconsin.edu\/all-in-wisconsin\/wp-json\/wp\/v2\/story_category?post=12825"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}