# Center of Pressure Measurement Sensing System for Dynamic Biomechanical Signal Acquisition and Its Self-Calibration

## TL;DR

This paper introduces a foot-mounted sensing system and self-calibration method for real-time Center of Pressure measurement in dynamic bipedal robots.

## Contribution

A novel online self-calibration method for dynamic Center of Pressure sensing using foot-mounted sensors and robot proprioception.

## Key findings

- The self-calibration pipeline improves within-trial consistency of CoP measurements during dynamic walking.
- The system reconstructs vertical ground reaction force from load-cell readings, though with digitized stepwise behavior.
- The proposed solution enables reliable CoP acquisition using low-cost hardware on a NAO-V5 robot platform.

## Abstract

The development of highly dynamic bipedal robots demands sensing capable of capturing key contact-related signals in real time, particularly the Center of Pressure (CoP). CoP is fundamental for locomotion control and state estimation and is also of interest in biomedical applications such as gait analysis and lower-limb assistive devices. To enable reliable CoP acquisition under dynamic walking, this paper presents a foot-mounted measurement system and an online self-calibration method that adapts sensor scale and bias parameters during locomotion using both external foot sensors and the robot’s proprioceptive measurements. We demonstrate an online self-calibration pipeline that updates foot-sensor scale and bias parameters during a walking experiment on a NAO-V5 platform using a sliding window optimization. The reported results indicate improved within-trial consistency relative to an offline-calibrated reference baseline under the tested walking conditions. In addition, the framework reconstructs a digitized estimate of the vertical ground reaction force (vGRF) from load-cell readings; due to ADC quantization and the discrete offline calibration dataset, the vGRF signal may exhibit stepwise behavior and should be interpreted as a reconstructed (digitized) quantity rather than laboratory-grade continuous force metrology. Overall, the proposed sensing-and-calibration pipeline offers a practical solution for dynamic CoP acquisition with low-cost hardware.