On the stability of passive dynamic walker with flat foot and series ankle spring

In this study, the effects of a flat foot and series ankle spring on walking stability and efficiency are investigated with three passive dynamic walking models. These models are tuned on the same gait parameters to compare local and global stability with three indicators, including the largest Floquet multiplier, size of basin of attraction, and incircle of basin of attraction. Investigations show that the flat foot helps achieve better global stability on most gait parameters and better local stability near the human-like gait parameters. However, the series ankle spring degrades local stability and global stability on most gait parameters. These findings may provide an insight into the design of efficient and robust bipedal robots