This paper discusses an algorithm to make a quadruped machine walk dynamically and omnidirectionally following a real-time command from an operator. To produce a smooth body motion at high speed locomotion, we introduced a new gait, named the "intermittent trot gait", in which a four-leg-supporting phase and a two-diagonal-leg-supporting phase appear in orders. In this gait, the pitching and rolling motion of the body is suppressed to a lower level than that of the other gaits because the dynamic effects of the swinging legs almost cancel each other. To realize the intermittent trot gait, new algorithms to plan a landing point and body motion are discussed. A landing point is decided by considering an operator command and conversion to the standard leg formation. A body motion is planned to produce dynamic stability and to follow speed and direction commands. By using these algorithms, a mechanical vehicle TITAN VI can walk omnidirectionally, smoothly following a real-time operator command. The top speed is 1 m/sec on flat terrain and 125 mm/sec on 105 mm up and down over rough terrain.

This paper discusses foot force control of a quadruped walking vehicle on rough terrain. The proposed control algorithm has two parts. One is a feedforward 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 feedforward 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.>