Underactuated bipedal walking with knees that generates measurable period of double-limb support

Through modeling and analysis of a rimless wheel with active knees and semicircular feet, we showed that measurable period of double-limb support (DLS) emerges immediately after landing of the fore leg as in the case of a telescopic-legged one. In this paper, we extend the analysis to an underactuated biped model only with revolving joints and investigate the potentiality of the emergence of DLS motion in level dynamic walking. We numerically show that non-instantaneous DLS motion emerges after the instant of landing of the swing leg if the knee-joints are free and semicircular feet have a sufficient radius. Furthermore, we numerically analyze the tendency of the emergence of DLS motion according to the robot´s physical parameters and shapes.