RAIBO2: Highly efficient quadruped robot completing full marathon with a single battery charge

Recent advances in legged robot control have expanded the potential for quadrupedal robots in real-world applications, such as rescue operations in disaster zones and mountainous regions. However, practical deployment is hindered by the limited travel range per battery charge—a challenge compounded by the robots’ inherent structural characteristics. Unlike wheeled robots, quadrupeds continuously expend energy at their joints to support body weight and incur kinetic energy losses during intermittent foot–ground contact. Moreover, optimizing energy consumption is complicated by trade-offs among various physical effects, necessitating a holistic approach that optimizes both hardware and software components. Prior research has predominantly addressed isolated aspects of energy loss. In this work, we present RAIBO2, an energy-efficient quadruped designed through a comprehensive analysis of its energy loss model. Efficiency is enhanced via a force-transparent, lightweight mechanical hardware, a low-loss motor driving circuit, and an energy-optimized locomotion policy. RAIBO2 completed a full marathon in 4 hours, 19 minutes, and 52 seconds on a single battery charge, achieving a Total Cost of Transport (TCOT) of 0.25—the first quadrupedal robot to surpass the human benchmark of 0.37. Compared to existing quadrupeds, RAIBO2 offers more than three times the travel range per battery charge. This breakthrough in energy efficiency paves the way for extended outdoor applications where prolonged battery life is critical.