Drift-Free Foot Orientation Estimation in Running Using Wearable IMU.

Mathieu Falbriard,Frédéric Meyer,Grégoire P Millet,Kamiar Aminian,Benoît Mariani

doi:10.3389/fbioe.2020.00065

Abstract

This study aimed to introduce and validate a new method to estimate and correct the orientation drift measured from foot-worn inertial sensors. A modified strap-down integration (MSDI) was proposed to decrease the orientation drift, which, in turn, was further compensated by estimation of the joint center acceleration (JCA) of a two-segment model of the foot. This method was designed to fit the different foot strike patterns observed in running and was validated against an optical motion-tracking system during level treadmill running at 8, 12, and 16 km/h. The sagittal and frontal plane angles obtained from the inertial sensors and the motion tracking system were compared at different moments of the ground contact phase. The results obtained from 26 runners showed that the foot orientation at mean stance was estimated with an accuracy (inter-trial median ± IQR) of 0.4 ± 3.8° and a precision (inter-trial precision median ± IQR) of 3.0 ± 1.8°. The orientation of the foot shortly before initial contact (IC) was estimated with an accuracy of 2.0 ± 5.9° and a precision of 1.6 ± 1.1°; which is more accurate than commonly used zero-velocity update methods derived from gait analysis and not explicitly designed for running. Finally, the study presented the effect initial and terminal contact (TC) detection errors have on the orientation parameters reported.

Highlights

The orientation of the foot recorded slightly before, during, or after the ground contact phase is an essential parameter for running analysis
We emphasized on the initial contact (IC) and terminal contact (TC) detection differences between the force plate (FP) and the IMUbased method using vertical dashed lines
While inertial measurement units (IMUs)-based estimation generates drift due to strapdown integration operation, we proposed a modified strap-down integration (MSDI) supplemented with a drift compensation method (JCA)

Summary

Introduction

The orientation of the foot recorded slightly before, during, or after the ground contact phase is an essential parameter for running analysis. The continuous measurement of the 3D orientation of the foot is generally obtained using optical motion capture systems (Arndt et al, 2007; Riley et al, 2008; Altman and Davis, 2012). While these systems measure the foot pose (i.e., orientation and position) accurately, they are often restricted to well-equipped laboratories and treadmill running. As an alternative to this lack of portability, a growing number of studies have shown that wearable inertial sensors, if combined with state-of-the-art algorithms, can be used to provide reliable spatiotemporal information (Camomilla et al, 2018)

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Discussion

Conclusion