A four-legged robot has completed a full marathon on a single battery charge, covering 42.195 kilometers in 4 hours, 19 minutes and 52 seconds while using substantially less energy to move its weight than a human.

The robot, called RAIBO2, was developed by researchers at South Korea’s KAIST and completed the marathon during the 2024 Sangju Dried-Persimmon Marathon. The team published its findings in Nature on September 23, 2026.

The achievement addresses one of the biggest limitations facing legged robots: endurance. Unlike wheeled machines, quadruped robots must continuously spend energy supporting their bodies while also losing energy through impacts, joint movement, and foot-ground interactions.

RAIBO2 maintained an average speed of about 2.64 meters per second, or 5.9 mph, throughout the marathon. It completed the 42.195-km course without replacing or recharging its battery.

The result followed an earlier failed attempt by the research team. In September 2024, an earlier version ran out of battery at around the 37-km mark during a marathon event. KAIST said the robot consumed more energy than expected because it repeatedly changed speed while adjusting to other runners on the course. The team subsequently redesigned several aspects of the system and continued refining its locomotion.

Rather than simply installing a larger battery, the researchers focused on reducing how much energy the robot loses while moving.

The Nature study describes RAIBO2 as an energy-efficient quadruped developed through a comprehensive analysis of mechanical, electrical, and locomotion losses.

The researchers made its legs lightweight and designed the motor-driving electronics to reduce electrical losses.

Source link