Modeling Multilegged Locomotion: the Friction Dominated Case

Engineers and biologists often assume non-slip contact for modeling multi-legged locomotion. In our hexapedal robots and cockroaches (Blaberus discoidalis) experiments, a significant fraction of total foot motion is while slipping. Multi-legged contact with slipping poses a modeling challenge: uncertainty about inter-leg force distribution and consequent foot slipping outcomes. Low Reynolds numbers swimmers are governed by a “connection” model. We present a connection model for friction dominated multi-legged locomotion. It takes egocentric leg motions and predicts foot slippage and body center of mass motions. Applied to cockroach data, our model correctly predicts steering directions, but the predicted displacement and curvature of turns are too small. Applied to data from hexapedal robots, our model correctly predicts steering directions under a variety of steering gaits, and is more accurate than that for cockroaches by several metrics. We hope such a model may explain how multi-legged animals control and plan their motions. We also plan to use this reduced order physics models for robot control and design.