Sky-Hook Suspension Control of a Quadruped Walking Vehicle

This paper discusses foot force control of a quadruped walking vehicle on rough terrain. The proposed control algorithm has two parts. One is a feed-forward control to produce a smooth touch-down and lift-up motion of the leg. The other part is a feedback control to maintain the body's posture under the conditions of some disturbances.A command force of the feed forward control is calculated beforehand from the data of the body's position, its acceleration and leg positions. The force increases smoothly from zero after touch-down on the ground, and it decreases smoothly to zero before lift-up.On the other hand, a command force of the feedback control is calculated from the data of the body's posture measured by gyroscopes. The effect of the feedback control is as if the body is suspended to an absolute frame by springs and dampers. Therefore, it is called“Sky-Hook Suspension”.By this control algorithm, the experimental vehicle TITAN VI is able to walk smoothly on a rough terrain.