Model-Free Self-calibration of Force-Sensing Shoes for Humanoids

This paper presents a novel model-free method for humanoid robots to self-calibrate their foot force sensors using quasi-static movement control. The robot generates whole-body trajectories using our model-free framework with three steps: 1. Designing target trajectories containing discrete pairs of the center of pressure (CoP) and foot position. 2. Formulating a cost function that minimizes the error between the measured and desired objectives. 3. Updating the robot motion with an optimization algorithm by slightly moving the robot’s leg joints back and forth. The foot sensor parameters are then determined by minimizing the error between the measured and reference CoP and ground reaction force (GRF) during the robot’s movement. We demonstrate our approach on a NAO humanoid robot platform. Experimental results show that the model-free self-calibrated shoes can successfully estimate CoP and GRF.