Emergence of measurable period of double-limb support in limit cycle walking with knees

The authors have studied the roles and effects of double-limb support (DLS) motion whose the time interval is measurable in limit cycle walking. It was clarified that DLS motion emerges in passive dynamic walking of a viscoelastic-legged rimless wheel through numerical simulations and experiments. This paper then investigates the potentiality of the emergence of DLS in a kneed limit cycle walking. We introduce the model of a planar, underactuated, eight-legged rimless wheel with active knees and semicircular feet, and discuss the conditions for generating DLS. We numerically show that DLS motion emerges during a measurable time interval after impact in the case that the knee joints are free and semicircular feet have an enough radius.