A four-legged robot called RAIBO2 ran a full marathon course, 42.195 kilometers, on one battery charge. It finished in 4 hours, 19 minutes and 52 seconds. Researchers at the Korea Advanced Institute of Science and Technology (KAIST) built it and published the work in Nature this month.
The robot ran the race back in November 2024, at the official Sangju Dried Persimmon Marathon in South Korea. The course included 286 meters of elevation change, with slopes up to 18.4 degrees.
Energy on the course
The battery holds 2,016 watt-hours, and the robot used 1,280 of them. Its cost of transport, a measure that relates energy use to weight and distance covered, came to 0.25. For a human runner, the same figure is 0.37, and RAIBO2 is the first quadruped to beat it.
The authors say RAIBO2 travels more than three times as far on a charge as existing four-legged robots. Recent comparable machines typically manage about 20 kilometers.
How they did it
Associate Professor Jemin Hwangbo's team combined three things: a lightweight body, low-loss motor-driving circuits and a gait the robot learned through reinforcement learning, a method in which a model finds the least energy-hungry movements by trial and error.
The run was not autonomous. The researchers note that the work assumes a human operator, and that navigating on its own would require further development.
Average speed was 2.64 meters per second, about 9.5 kilometers per hour.
