Quadrupedal Locomotion on Uneven Terrain With Sensorized Feet

Sensing of the terrain shape is crucial for legged robots deployed in the real world since the knowledge of the local terrain inclination at the contact points allows for an optimized force distribution that minimizes the risk of slipping. In this letter, we present a reactive locomotion strategy for torque controllable quadruped robots based on sensorized feet. Since the present approach works without exteroceptive sensing, it is robust against degraded vision. Inertial and force/torque sensors implemented in specially designed feet with articulated passive ankle joints measure the local terrain inclination and interaction forces. The proposed controller exploits the contact null-space in order to minimize the tangential forces to prevent slippage even in case of extreme contact conditions. We experimentally tested the proposed method in laboratory experiments and validated the approach with the quadrupedal robot ANYmal.