Frictional constraints on the sole of a biped robot when slipping

Abstract

The traction force of any moving object on a floor is the frictional force between the object and the floor. Therefore, investigation of the frictional constraint is very important for such moving object on a floor as well as a biped walking robot. Conventionally, the study of frictional constraint of a biped robot was only constrained in translational slip, without considering rotational slip, which is important in actual biped walking. This is one of the causes the walking speed of biped robots lower than the one of human beings. In this paper, an evaluation method of frictional constraints for biped robots is proposed. The translational friction force and the twist frictional torque acting on the biped robot's sole are both deduced and verified for single support phase. First, based on a biped robot model, an approach to calculate the frictional force and torque is deduced as the quantitative expression of frictional constraint. Then, the experimental verification method is designed and the proposed calculation approach is confirmed. Finally, the consideration of the result of experiments is discussed. This approach is expected to be used for helping the realization of fast biped walkings.