Portable Gait Lab: Estimating Over-Ground 3D Ground Reaction Forces Using Only a Pelvis IMU

Mohamed Irfan Mohamed Refai,Bert-Jan F Van Beijnum,Jaap H Buurke,Peter H Veltink

doi:10.3390/s20216363

Mohamed Irfan Mohamed Refai, Bert-Jan F Van Beijnum + Show 2 more

Open Access

https://doi.org/10.3390/s20216363

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Abstract

As an alternative to force plates, an inertial measurement unit (IMU) at the pelvis can offer an ambulatory method for measuring total center of mass (CoM) accelerations and, thereby, the ground reaction forces (GRF) during gait. The challenge here is to estimate the 3D components of the GRF. We employ a calibration procedure and an error state extended Kalman filter based on an earlier work to estimate the instantaneous 3D GRF for different over-ground walking patterns. The GRF were then expressed in a body-centric reference frame, to enable an ambulatory setup not related to a fixed global frame. The results were validated with ForceShoesTM, and the average error in estimating instantaneous shear GRF was 5.2 ± 0.5% of body weight across different variable over-ground walking tasks. The study shows that a single pelvis IMU can measure 3D GRF in a minimal and ambulatory manner during over-ground gait.

Highlights

Measuring kinetics of gait such as 3D ground reaction forces includes estimating the vertical and shear forces acting on the body during gait
We identified sharp peaks around the initial contact (IC) instances, possibly due to During preliminary analysis, we identified sharp peaks around the IC instances, possibly due to impact in the estimated 3D ground reaction forces (GRF)
The average NRMSE of 16.3 ± 1.7% for all walking tasks is slightly larger than our previous study [12], where we found an average NRMSE of 12.1 ± 3.3%, and that of Leporace et al [26] who found an average of 9.3 ± 6.4% in the horizontal plane

Summary

Introduction

Measuring kinetics of gait such as 3D ground reaction forces includes estimating the vertical and shear forces acting on the body during gait. The total ground reaction forces (GRF) acting on the body, and its derived parameters related to the center of mass (CoM) such as dynamic balance and stability measures [1], can be helpful in understanding gait quality [2]. The reliable estimation of GRF requires expensive measurement setups such as force plates. These may be installed under the floor or incorporated into treadmills. It is useful to explore wearable setups that allow freedom of movement, while providing reliable estimates of the GRF during gait or variable walking. ForceShoesTM are bulky [8], and pressure insoles require additional analytical or machine-learning-based models to extract the 3D GRF [7,9]

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