Tactile feedback enhances multi-legged locomotion on rugged landscapes

Organisms leverage various sensory modes when locomoting through complex environments, from long-range visual cues to short-range tactile feedback. In cluttered and crowded environments, long-range visual sensing becomes challenging. Instead, rapid localized response (short-range feedback) is presumed more effective. In recent robotic applications, short-range tactile sensing on feet improved locomotion in complex terrain via decentralized intra-leg coordination. However, it remains unclear if foot-level tactile information could contribute to overall locomotion via high-level centralized, intra-leg processing. To address this, we developed a centipede-like multi-legged robophysical model (L= 60 to 160 cm, 3 to 8 segments each with four degrees of freedom for limb and body movement) with point-like feet and tested it on rugose terrains. We found that adjusting the amplitude of a vertical body wave assisted in countering local heterogeneities and improved open-loop locomotion on the different terrains. We then developed a “binary” tactile sensor to detect ground contact at each foot and integrated this onto the model to estimate local terrain complexity to inform a centralized controller that determines suitable vertical waves. This improved speed by 50% over rough terrains as well as reduced variance by 60%, indicating that the robot was less impacted by the environmental “noise”. This approach to tactile information for multi-legged locomotion can improve our understanding for how such sensory cues affect biological systems when long range sensing is unavailable.