In-Situ Calibration of Six-Axis Force/Torque Transducers on A Six-Legged Robot

Ground contact modeling for multi-legged locomotion is challenging due to the possibility of multiple slipping legs. To understand the interplay of contact forces among multiple legs, we integrated a robot with six high-precision 6-DoF force-torque sensors, and measured the wrenches (forces and torques) produced in practice. Here we present an in-situ calibration procedure for simultaneously measuring all foot contact wrenches of a hexapod using 6-DoF load cells installed at the hips. We characterized transducer offset, leg gravity offset and the wrench transformation error in our calibration model. Our calibration reduced the RSME by 63% for forces and 90% for torques in the residuals of the robot standing in different poses, compared with naive constant offset removal.