Design and Analysis of a Novel Sensory System for a Humanoid Robot Foot

This paper describes a novel design of force sensors arrangement for measuring ground reaction force on a humanoid foot to find the zero momentum point (ZMP) which is usually used as a stability criterion for a walking biped robot. Precise locating of ZMP highly depends on accurate measurement of reaction force distribution on the foot. Design and fabrication of a sole for a full scale humanoid robot, “Surena” is of interest. A rubber layer is placed on robot sole parallel to force sensors to reduce the effect of impact while robot is walking. Consequently, the force measured by sensors is not total force exerted by the ground. Several foot interaction condition with ground have been modeled using finite element method and force distribution in sole rubber and sensors have been obtained. The resultant is a model which predicts the total force distribution based on four point force measurement. Several experimental situations have been tested and forces have been measured. Experimental results have shown that numerical model could predict force distribution in a good way and location of ZMP has been found successfully.