The Anatomy of a Mecha Goat

At Expo 2025 Osaka, Kawasaki unveiled Corleo, a rideable four-legged robot designed for off-road terrain. It’s not a motorcycle, ATV, or mule—but a hydrogen-powered quadruped that blends advanced robotics with a distinctly mechanical engineering mindset. And it’s designed to go where wheels can’t.

Corleo walks using four independently powered robotic limbs. Each leg terminates in split rubber hooves designed to maintain grip on unstable terrain—rocks, scree, mud, and slopes. The leg design draws heavily from motorcycle suspension systems, especially in the rear, where swing-arm-style linkages absorb vertical impacts and maintain chassis levelness while climbing or stepping over obstacles.

Each leg likely employs multi-stage reduction gear systems—possibly strain wave or cycloidal drives—at the hip, knee, and ankle joints. These compact, high-torque mechanisms are favored in legged robotics for their low backlash and high positional repeatability. Such systems allow the robot to precisely control gait, balance, and reactive step placement. For terrain this varied, backlash minimization and joint stiffness are critical not just for control but for long-term durability.

Power is supplied by a compact 150cc hydrogen internal combustion engine, not mechanically linked to the drivetrain, but acting as an onboard generator. The electricity it produces is routed to in-leg electric motors, allowing for decoupled, distributed actuation. This hybrid approach eliminates the need for gearboxes between engine and limb but shifts precision load management to the electric actuators and their associated gear trains.

While Kawasaki has not disclosed details about the limb gearboxes, a quadruped operating under variable load and unpredictable terrain likely requires high-ratio planetary reductions combined with torque-dense actuators and robust encoders. These systems must be sealed against dust, moisture and impact loads while maintaining thermal stability and service life under repeated shock cycles.

Control is entirely body-driven. Instead of throttle or steering, Corleo uses a weight-shift interface, where pressure sensors in stirrups and handlebars detect the rider’s posture and translate it into movement commands—forward lean initiates motion, lateral shifts trigger turning. The system relies on real-time sensor fusion and feedback to manage gait transitions, requiring tightly integrated mechanical response from the gear and motor assemblies to prevent lag or oscillation.

An onboard control panel provides diagnostics for route planning, hydrogen level, and center-of-gravity tracking—especially useful on sloped or unstable terrain. At night, a ground-projection system highlights navigable paths with visible markers.

Hydrogen is stored in a rear-mounted tank, with the only exhaust being water vapor. This design avoids the energy density limitations and recharge time of lithium-ion battery systems while raising questions about hydrogen refueling logistics, particularly for field deployment.

Corleo is not a consumer product, but a prototype platform. Kawasaki presents it as a mobility research tool for legged locomotion, clean energy propulsion, and human-machine interface design. Potential applications include remote logistics, search and rescue, environmental monitoring, and defense—all settings where traditional wheeled systems encounter terrain limits.

From an engineering perspective, Corleo addresses a broad set of mechanical challenges: limb synchronization, joint torque control, gait stability, actuator thermal management, and long-term wear in field conditions. Material selection for moving parts—lightweight alloys, reinforced composites, or high-cycle fatigue-resistant steels—is key to maintaining performance under constant directional loads and unpredictable ground contact.

Corleo may never see mass production, but its engineering implications are clear: as robotics and mobility converge, the role of precise power transmission, especially in complex, multiaxis systems, will only grow. This isn’t just a new type of vehicle. It’s a new kind of drivetrain challenge, one that trades speed for adaptability and traction for autonomy.

To view an animation of Corleo in action, visit: youtube.com/watch?v=vQDhzbTz-9k