A robophysics approach to bipedal walking in granular media
Kingsbury, Mark A.
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Humanoid robots will need capabilities to traverse environments ranging from factory floors to disaster areas. However, most of today's devices fail when faced with more complex ground conditions such as loose sand. To uncover the principles of bipedal walking in complex environments and improve techniques for robotic locomotion, we took a "robophysics" approach. Robophysics stands at the intersection of robotics and physics where robots are used to uncover the underlying physics of a system and insights gained from experiments lead to improvements in real robots. We designed and studied a planarized bipedal robot (1.6 kg, 42 cm) that walked in a fluidized bed of poppy seeds. We additionally modeled this robot using the Chrono::Engine with empirical granular Resistive Force Theory (RFT). During the two foot interaction, one foot slipped through the material while the other remained stationary. This originated from the solid-like and fluid-like properties of granular media where the foot with higher predicted drag forces by RFT experience solid-like constraint forces while the other foot yielded through the fluid-like material. We applied these findings to a human scale humanoid robot, HUBO. While traditional strategies for walking on hard ground failed in loose material, the HUBO robot walked successfully and without slip in granular media with a terrain-aware gait.