Adaptive Planar Foot with Compliant Ankle Joint and Multi-modal Sensing for Quadruped Robots

An adaptive sensorized robot foot that can adapt to uneven and rough terrains and have contact state sensing capability is vital for legged locomotion in exploration missions. Inspired by quadruped animals, we present an adaptive planar foot with large contact area to reduce sinkage, two degrees of freedom (2-DOF) compliant ankle joint for better terrain adaptation, in-foot multi-modal sensing capability. We propose customized ankle design with encoders instead of IMU for ankle joint angle measurement, in order to mitigate the noise injected by large impact forces. The foot also provides an accurate estimated force according to foot-shank relative orientation and the 6-axis force/torque sensor data. We develop a control algorithm for a quadruped robot equipped with our proposed robot feet and test its performance through simulation. Real-world experiments including foot orientation estimation, swing sensitivity, and force perception verify that our robot foot is suitable for dynamic quadruped locomotion.