Development of Leg-Wheel Hybrid Quadruped “AirHopper”: Lightweight Leg-Wheel Design

The “AirHopper” leg-wheel hybrid jumping robot we propose is expected to navigate uneven terrain difficult to traverse for ordinary vehicles carrying supplies for disaster-hit areas or isolated districts. To give it high mobility and enable jumping, the AirHopper consists of (1) 4 widespred spiderlike legs for stability, (2) active wheels on its feet driven by built-in motors and transmissions, (3) 2 decoupled pneumatic cylinders, and (4) a built-in piston that drives a 4-bar linkage leg. We propose a powerful leg with a wide movable range and a compact, lightweight wheel drive that minimizes adverse effects. Experiments verified the feasibility of these mechanisms. We also developed an “AirHopper-II” leg-wheel hybrid jumping robot using these 2 mechanisms. AirHopper-II jumped 850 mm vertically and landed softly by controlling in-cylinder pressure. In preliminary experiments, we tested wheel drive jumping to acquire basic data for the next model.