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

Abstract

Ground contact modeling for multilegged 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 degree-of-freedom (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 root-mean-square-error (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.