Slip detection for robotic locomotion

A method comprising:

• determining, by a robot, a first estimate of a distance traveled by a body of the robot in a time period, wherein the first estimate is relative to a position of a first foot of the robot that is in contact with a surface;
• determining, by the robot, a second estimate of the distance traveled by the body of the robot in the time period, wherein the second estimate is based on inertial measurements of the body of the robot;
• determining that a difference between the first estimate and the second estimate exceeds a threshold difference and that a second foot is not in contact with the surface;
• causing, by the robot, the second foot to discontinue ground reaction force control;
• causing, by the robot, the second foot to engage in position control by extending the second foot toward the surface;
• and
• after the second foot is in contact with the surface, causing, by the robot, the second foot to resume ground reaction force control.

An article of manufacture including a non-transitory computer-readable medium, having stored thereon program instructions that, upon execution by a processor, cause a robot to perform operations comprising:

• obtaining a sequence of measurements of distances between a pair of feet of the robot, wherein the sequence includes a first measurement taken when the pair of feet are in contact with a surface and in a stance state, wherein the sequence includes a second measurement taken when the pair of feet remain in the stance state from a time of the first measurement, and wherein the first measurement is of a first distance and the second measurement is of a second distance;
• determining that a difference between the first distance and the second distance exceeds a threshold difference and that a particular foot of the pair of feet has lost contact with the surface;
• causing the particular foot to discontinue ground reaction force control;
• causing the particular foot to engage in position control by extending the particular foot toward the surface;
• and
• after the particular foot is in contact with the surface, causing the particular foot to resume ground reaction force control.