Meeting Abstract
Natural substrates like sand, snow, leaf litter and soil vary widely in penetration resistance. To search for the principles of foot design in robots and animals that permit high performance on flowable ground, we developed a novel ground control technique by constructing an air-fluidized bed trackway in which penetration resistance of one millimeter granular substrates can be continuously reduced to zero by increasing the upward flow rate of air,Q, to the fluidization transition. Using a bio-inspired hexapedal robot as a physical model, we systematically studied how locomotor performance (average forward speed, v) varies with ground penetration resistance and robot leg frequency. Average robot speed decreased with increasing Q, and leg frequency. A universal scaling model revealed that the leg penetration ratio (foot pressure relative to penetration force per unit area per depth and leg length) determined v for all robot ground penetration resistances and leg frequencies. Despite variation in morphology and gait, the performance of running lizards, geckos and crabs on flowable ground could be predicted from leg penetration ratio. Foot designs resulting in decreased foot pressure can passively minimize leg penetration ratio as the ground becomes weaker, and therefore permits maintenance of effective high-speed running over a range of terradynamically challenging surfaces.
