A four-legged robot that is able to complete a marathon on a single battery charge is reported in Nature this week. The robot, which completed the event in 4 hours and 19 minutes alongside human runners, exhibited three times the travel range per charge of existing robots and could pave the way for improved battery life in legged robots.
Legged robots have the potential to assist in rescue operations in mountainous or disaster-stricken areas. However, recent advances in quadruped robots have been limited by their ability to operate beyond a range of approximately 20 km owing to a limited battery life. In contrast to robots on wheels, legged robots must continuously expend energy to support their body weight and mitigate energy loss from intermittent ‘steps’, reducing battery life between charges.
Jemin Hwangbo and colleagues present RAIBO2, a four-legged robot designed to address aspects of energy loss through both software and hardware. These features include lightweight legs, more-optimized motor driving circuits, and movement rules reinforced by machine learning. RAIBO2 was able to complete the 22nd edition of the Sangju Marathon in South Korea, finishing in 4 hours, 19 minutes and 52 seconds. The robot maintained an average speed of 2.64 metres per second, navigating a notoriously difficult course which features 286 metres of elevation change and slippery sections of terrain. Upon completion, RAIBO2 had used 1,280 Watt-hours (Wh) of energy and achieved an average total cost of transport of 0.25 (a measure of the energy expended during motion, factoring in the weight of the robot). The authors propose that this is the first quadruped robot to have a lower cost of transport than the human value of 0.37. Based on the fact that the robot’s total battery capacity is 2,016 Wh, the authors estimate that RAIBO2 could have travelled a further 25 km. The robot exhibits approximately three times the travel range per battery charge of existing quadruped robots.
The results derived from this study provide insights to improve the efficiency of legged robots, with the aim of contributing to extended operational ranges and boosted utility.
Article details
A quadruped robot designed to complete a marathon on a single battery charge
DOI: 10.1038/s41586-026-11102-5
Corresponding Author:
Jemin Hwangbo
KAIST, Daejeon, Korea
Email: [email protected]
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Ayako Miyazaki, Springer Nature, Tokyo
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Xi Chen, Springer Nature, Shanghai
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Lisa Boucher, Springer Nature, London
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Kevin Hurler, Springer Nature, New York
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