Foot Vision: A Vision-Based Multi-Functional Sensorized Foot for Quadruped Robots

Quadruped robots equipped with sensorless feet can only provide limited information regarding the foot interaction with the surroundings, limiting their off-road exploration capability in unstructured environments. To tackle this problem, we present Foot Vision, an innovative vision-based sensorized foot for quadruped robots. It consists of a compliant ankle, a transparent foot sole with visual markers, and an internal camera. This foot is designed to be low-cost, lightweight, and adaptable to both deformable and rigid terrains. The camera can efficiently track marker displacements to estimate the foot pose. We extract the foot deformation features from the foot pose and develop a learning-based method to reconstruct 6D contact forces leveraging these features. Representative loading tests validate the foot's ability to accurately (R-2 >0.95) and dynamically predict contact forces and torques in real-time (100 Hz). Installed on the quadruped robot, the sensorized foot demonstrates its capabilities to perceive 6D contact forces on terrains with varying stiffness and estimate the local inclination of the contact surface. Furthermore, thanks to the transparent foot sole, the in-foot camera can directly identify the terrain types and measure the soil flow distribution. Experimental results confirm that the proposed vision-based sensorized foot can enhance the contact perception capability of legged robots in diverse environments.