Obtaining wheelchair kinematics with one sensor only? The trade-off between number of inertial sensors and accuracy for measuring wheelchair mobility performance in sports

Marit P Van Dijk,Rienk M.A Van Der Slikke,Rob Rupf,Marco J.M Hoozemans,Monique A.M Berger,Dirkjan H.E.J Veeger

doi:10.1016/j.jbiomech.2021.110879

Abstract

In wheelchair sports, the use of Inertial Measurement Units (IMUs) has proven to be one of the most accessible ways for ambulatory measurement of wheelchair kinematics. A three-IMU configuration, with one IMU attached to the wheelchair frame and two IMUs on each wheel axle, has previously shown accurate results and is considered optimal for accuracy. Configurations with fewer sensors reduce costs and could enhance usability, but may be less accurate. The aim of this study was to quantify the decline in accuracy for measuring wheelchair kinematics with a stepwise sensor reduction. Ten differently skilled participants performed a series of wheelchair sport specific tests while their performance was simultaneously measured with IMUs and an optical motion capture system which served as reference. Subsequently, both a one-IMU and a two-IMU configuration were validated and the accuracy of the two approaches was compared for linear and angular wheelchair velocity. Results revealed that the one-IMU approach show a mean absolute error (MAE) of 0.10 m/s for absolute linear velocity and a MAE of 8.1°/s for wheelchair angular velocity when compared with the reference system. The two-IMU approach showed similar differences for absolute linear wheelchair velocity (MAE 0.10 m/s), and smaller differences for angular velocity (MAE 3.0°/s). Overall, a lower number of IMUs used in the configuration resulted in a lower accuracy of wheelchair kinematics. Based on the results of this study, choices regarding the number of IMUs can be made depending on the aim, required accuracy and resources available.

Highlights

Kinematic variables like forward accel eration and angular velocity are important for the quantification of the athlete’s wheelchair mobility performance, which is an important aspect of overall game performance
The aim of this study was to quantify the decline in accuracy for measuring wheelchair kinematics using a stepwise sensor reduction
This study provides a clear overview on the trade-off be tween number of sensors and accuracy regarding wheelchair kinematics, a few limitations should be noted

Summary

Introduction

Kinematic variables like forward accel eration and angular velocity are important for the quantification of the athlete’s wheelchair mobility performance (van der Slikke et al, 2018), which is an important aspect of overall game performance. Van der Slikke et al (2015) used inertial measurement units (IMUs) attached to the rear wheels and frame to measure wheelchair kinematics on the court. To further increase accuracy in vigorous sports conditions, van der Slikke et al (2015) developed a skid detection algorithm to correct for mis interpretations due to wheel skidding. This three-IMU configuration was validated using an optical motion capture system and provides accurate linear- and angular wheelchair displacement and speed (van der Slikke et al, 2015)

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