Look at my new blue force-sensing shoes!

TL;DR

This paper introduces lightweight, cost-effective force-sensing shoes for small humanoid robots, along with a calibration method that significantly enhances force measurement accuracy, especially for center of pressure and ground reaction force.

Contribution

The paper presents open-source force-sensing shoes and a calibration technique that improve force measurement precision in small humanoid robots.

Findings

Shoes outperform factory-installed sensors in measurement accuracy.

Calibration method enhances performance of both shoes and existing sensors.

Experimental validation on NAO robot confirms effectiveness.

Abstract

To function autonomously in the physical world, humanoid robots need high-fidelity sensing systems, especially for forces that cannot be easily modeled. Modeling forces in robot feet is particularly challenging due to static indeterminacy, thereby requiring direct sensing. Unfortunately, resolving forces in the feet of some smaller-sized humanoids is limited both by the quality of sensors and the current algorithms used to interpret the data. This paper presents light-weight, low-cost and open-source force-sensing shoes to improve force measurement for popular smaller-sized humanoid robots, and a method for calibrating the shoes. The shoes measure center of pressure (CoP) and normal ground reaction force (GRF). The calibration method enables each individual shoe to reach high measurement precision by applying known forces at different locations of the shoe and using a regularized least squares optimization to interpret sensor outputs. A NAO robot is used as our experimental platform. Experiments are conducted to compare the measurement performance between the shoes and the robot's factory-installed force-sensing resistors (FSRs), and to evaluate the calibration method over these two sensing modules. Experimental results show that the shoes significantly improve CoP and GRF measurement precision compared to the robot's built-in FSRs. Moreover, the developed calibration method improves the measurement performance for both our shoes and the built-in FSRs.