Toe joint mechanism using parallel four-bar linkage enabling humanlike multiple support at toe pad and toe tip

In this paper, the authors propose a novel toe joint mechanism using a parallel four-bar linkage. This mechanism enables a humanoid robot to contact with the floor at points of a multilink, namely the toe pad and toe tips, similar to human motion. Using this toe mechanism, a major part of the reaction force acts on the non-movable portion of a link rather than on the toe tip. Because of this, it is possible to decrease the constraint force acting on the joint. At the same time, the following multiple roles of the toe are expected: one is to generate a large kicking force at the toe pad, and another is to maintain multipoint contact with the floor by the toe joint control. The authors have also designed and developed the proposed toe mechanism for an actual miniature humanoid robot.