Modeling and analysis of passive viscoelastic-legged rimless wheel that generates measurable period of double-limb support

Limit cycle walking including passive-dynamic walkers is generally modeled as a nonlinear hybrid dynamical system with state jumps. The inelastic collision model is usually derived on the assumption that the rear leg leaves the ground immediately after landing of the fore leg. This model is, however, inappropriate in the case of compliant-legged walkers. This paper then reconsiders the traditional collision model and discusses the conditions for transition to double-limb support (DLS) motion, which is not instantaneous through investigations of passive dynamic walking of a viscoelastic-legged rimless wheel. First, we experimentally confirm that measurable period of DLS motion emerges after landing of the fore leg, and develop the corresponding mathematical model. Second, we numerically analyze the fundamental properties of the generated passive-dynamic gaits. Furthermore, we discuss the conditions for transition to DLS motion and specify the computational procedures.