Abstract:

In this paper, the influences of friction coefficient and rolling resistance coefficient on the gait of a passive dynamic walker with round feet are studied. Firstly, the normal forces and frictional forces acting on the feet of the passive dynamic walker are described based on a modified Hertz contact model and LuGre friction model, and the rolling friction resistance of the supporting foot during walking was also considered. Secondly, the dynamic equations of the passive dynamic walker are obtained by using Lagrange's equations of the second kind, and the appropriate parameters of LuGre friction model are selected by comparing with the previous studies. Finally, the influence of friction coefficient and rolling resistance coefficient on the gait of passive dynamic walker are simulated and analyzed. It is found that although the change of friction coefficient has little effect on the average speed, stride and the maximum normal contact force at the contact point of the supporting foot, the reduction of friction coefficient will change the gait types, such as periodic doubling motion or chaotic motion. However, the change of the rolling resistance coefficient will lead to a great difference on the average speed, stride and the maximum normal contact force at the contact point of the supporting foot, but it has not been found that the change of rolling resistance coefficient will cause the change of the walker's gait types.

Key words: passive dynamic walker, LuGre friction model, rolling resistance, walking gait, period doubling bifurcation