  This paper presents a novel method for smaller-sized humanoid robots to
self-calibrate their foot force sensors. The method consists of two steps: 1.
The robot is commanded to move along planned whole-body trajectories in
different double support configurations. 2. The sensor parameters are
determined by minimizing the error between the measured and modeled center of
pressure (CoP) and ground reaction force (GRF) during the robot's movement
using optimization. This is the first proposed autonomous calibration method
for foot force-sensing devices in smaller humanoid robots. Furthermore, we
introduce a high-accuracy manual calibration method to establish CoP ground
truth, which is used to validate the measured CoP using self-calibration. The
results show that the self-calibration can accurately estimate CoP and GRF
without any manual intervention. Our method is demonstrated using a NAO
humanoid platform and our previously presented force-sensing shoes.
