Skin Normal Force Calibration Using Vacuum Bags

Abstract

This paper presents a proof of concept to calibrate iCub’s skin using vacuum bags. The main idea of the method consists of inserting the skin, made of distributed capacitive sensors, in a vacuum bag and then decreasing the pressure in the bag to create a uniform pressure distribution on the skin surface. The capacitance changes of each sensor were then related to the applied differential pressure using a least square fitting with a fifth order polynomial model. After calibration, integration of the pressure distribution over the skin geometry provides us with the net normal force applied to the skin. Experiments were conducted using the forearm skin of the iCub humanoid robot and the calibration results were validated using standard weights. The validation results indicate acceptable average errors in force prediction.