Development of Leg-Wheel Robot and Cooperational Motion of Legs and Wheels

Abstract

The wheel mechanism is effective for the flat terrain because of its speed and efficiency. The leg mechanism is effective for the irregular terrain because of its flexibility. Until now, several leg-wheel mobile robots which have both benefits have been constructed. But those have several disadvantages. We have constructed a leg-wheel mobile robot called Chariot which has mechanically separated wheels and legs. Chariot has two large wheels at the center of the body and has two legs attached to the body. Chariot can move at a speed of 20km/h on a flat plane. It can rotate around the vertical axis with small radius. It also can get over step and ditch by changing the phases (the leg-support phase and the wheel-support phase) one after the other. In this paper, as the motion utilizing one of advantages of separated leg-wheel mechanism, we describe the cooperational motion of legs and wheels when Chariot goes over step. Pushing the wheel to the step by legs makes the wheel torque be effective and reduces the load of legs. This causes the reduction of the energy consumption.