Model-Based Step Length Estimation Using a Pendant-Integrated Mobility Sensor

IEEE Transactions on Neural Systems and Rehabilitation Engineering, vol. 29, pp. 2655–2665

Abstract

The step length is an important parameter in gait analysis. Long-term monitoring applications for gait analysis are often based on inertial measurement units (IMUs) due to their low-cost and unobtrusive nature. Spatial gait parameters, such as step or stride length, are therefore not directly accessible. In this contribution, we focus on model-based algorithms for step length estimation based on a pendant-integrated IMU during slow walking speeds. We present a model-based approach to estimate the step length, which is divided into two successive steps. As the first part of our approach, we present an algorithm for estimation of the vertical displacement of the center of mass (CoM) during gait. Based on this estimate, we present a novel approach to estimate the step length, which we have deduced from a previously published, simplified gait model. The algorithm is compared to a commonly known approach for accelometry-based step length prediction and validated against reference data obtained from a force plate-integrated treadmill for gait analysis during a clinical study with ten healthy subjects. Due to the applicability to gait stability assessment in elderly or gait impaired patients, we focus on slow walking speeds (1 - 4 km h-1). The presented algorithms outperform the existing approach and the proposed model calculations provide a more accurate prediction. For the vertical displacement, we achieved a precision of 9.3% (CoV) with an RMSE of 1.5 mm in terms of the trajectory amplitude during normal gait patterns. The step length estimation yields satisfying results with a relative prediction error of lower than 10% for walking speeds of 2 - 4 km h-1.

Authors 6

1. Markus Lueken corresponding Aachen Medical Information Technology (MedIT) Department of Geriatrics with the Medical Information Technology (MedIT)

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Medical Information Technology (Med IT), RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany, corresponding. (e-mail: lueken@hia.rwth-aachen.de)

   Department of Geriatrics, RWTH Aachen University Hospital, Aachen, Germany

   with the Medical Information Technology (MedIT), RWTH Aachen Uni-versity, Pauwelsstr. 20, 52074 Aachen, Germany,

2. Johannes Loeser Aachen Medical Information Technology (MedIT) Department of Geriatrics with the Medical Information Technology (MedIT)

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Medical Information Technology (Med IT), RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany, corresponding

   Department of Geriatrics, RWTH Aachen University Hospital, Aachen, Germany

   with the Medical Information Technology (MedIT), RWTH Aachen Uni-versity, Pauwelsstr. 20, 52074 Aachen, Germany,

3. Nikolai Weber Aachen Medical Information Technology (MedIT) Department of Geriatrics with the Medical Information Technology (MedIT)

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Medical Information Technology (Med IT), RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany, corresponding

   Department of Geriatrics, RWTH Aachen University Hospital, Aachen, Germany

   with the Medical Information Technology (MedIT), RWTH Aachen Uni-versity, Pauwelsstr. 20, 52074 Aachen, Germany,

4. Cornelius Bollheimer Aachen Department of Geriatrics

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Department of Geriatrics, RWTH Aachen University Hospital, Aachen, Germany

5. Steffen K. Leonhardt Aachen Medical Information Technology (MedIT) Department of Geriatrics with the Medical Information Technology (MedIT)

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Medical Information Technology (Med IT), RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany, corresponding

   Department of Geriatrics, RWTH Aachen University Hospital, Aachen, Germany

   with the Medical Information Technology (MedIT), RWTH Aachen Uni-versity, Pauwelsstr. 20, 52074 Aachen, Germany,

6. Chuong Ngo Aachen Medical Information Technology (MedIT) Department of Geriatrics with the Medical Information Technology (MedIT)

   Universitätsklinikum Aachen · RWTH Aachen University

   Affiliation as printed

   Medical Information Technology (Med IT), RWTH Aachen University, Pauwelsstr. 20, 52074 Aachen, Germany, corresponding

   Department of Geriatrics, RWTH Aachen University Hospital, Aachen, Germany

   with the Medical Information Technology (MedIT), RWTH Aachen Uni-versity, Pauwelsstr. 20, 52074 Aachen, Germany,