Whole-body Posture Generation by Adjusting Tool Force with CoG Movement: Application to Soil Digging

Abstract

Exerting large force is one of the difficult problems for a humanoid robot. In particular, the task which needs large force with a tool or the task whose reference force is unknown such as digging are more difficult. The task of digging was realized in the previous research, but with that method the robot cannot exert large force even though force is not enough for digging because the decision method of reference shovel force is only changing the direction of the current shovel force, and modification of the robot's CoG (center of gravity) is only used for balancing. In this paper, we proposed methods to determine the reference shovel force which is necessary enough to realize the task of digging, and generate feasible posture which exerts the reference shovel force within joint torque limits. To verify the methods, we conducted experiments of the task of digging using a life-size humanoid robot JAXON. JAXON succeeded digging with some soil from soft to hard.