The Passive Dynamics of Walking and Brachiating Robots: Results on the Topology and Stability of Passive Gaits

Simple walking models, like the compass-gait model, have yielded useful insight into the basic mechanics of walking. A similar model serves as a template for brachiation. With the ability of a two-link robot to walk and swing, we explore the multi-locomotion capability of a generalized two-link model with potential footholds at any location. We focus on the connected components of passive gaits in a five-dimensional state-time space. Our main results are: (1) a walking gait and a brachiating gait cannot be in the same connected component and (2) the stability of a gait depends on whether impacts are state-based (e.g., footfall in a biped walker) or time-based (e.g., time between clamping brachiator hands to a wall). For the same connected component of gaits, the different impact types result in different bifurcations.