Design and experimental test of a new robot foot for a quadrupedal jointed-leg type walking robot

This paper presents the development of a new foot for a quadrupedal jointed-leg type walking robot. The foot has two toes, each at the front and the rear side, for stable landing on uneven ground by point contacts. The toes can move up and down independently, guided by double-wishbone shaped parallel links which enable the lower leg to rotate with respect to a remote center on the ground surface. The motion of each toe is damped by a hydropneumatic shock absorber integrated in the foot in order to absorb the dynamic landing shock. Furthermore, the new foot can reduces the maximum hip joint torque by shortening the moment arm length between the hip joint and the acting point of the reaction force vector on the ground. Intensive experiments were carried out in this study by using a one-leg walking model to investigate the soft landing performance of the foot, which could hardly be achieved by conventional robot foot such as a flat plate with a gimbal type ankle joint. It was verified that the hip joint torque could greatly be reduced by using this new foot.