Point-contact type foot with springs and posture control for biped walking on rough terrain

This paper proposes a new foot system to achieve stable biped walking on rough terrain. The new foot system, which is named point-contact type foot with springs (PCFS), has four passive joints each of which equips a spring and a sensor. The proposed foot system has the following advantages: 1) The geometrical adaptability to rough terrain. 2) The measurability of the posture of the robot. 3) The absorption of the influence of disturbances. The index of stability like ZMP and the posture of the robot can be estimated from the displacement of each spring. The foot system can also absorb not only the impact at the foot landing but also the influence of irregularities on the ground and unexpected disturbances. However, because the biped walking by use of the foot with springs corresponds to walking on a soft ground, posture control is indispensable. Therefore we consider an appropriate walking pattern generation and present feedback control for the proposed foot system. The effectiveness of the proposed foot system is demonstrated by simulation results.