Technical Briefs

Accuracy of Inertial Motion Sensors in Static, Quasistatic, and Complex Dynamic Motion

[+] Author and Article Information
Alison Godwin

School of Human Kinetics, Laurentian University, Sudbury, ON P3E 2C6, Canada

Michael Agnew

Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA 24061

Joan Stevenson

School of Kinesiology and Health Studies, Queen’s University, Kingston, ON, K7L 3N6, Canada

J Biomech Eng 131(11), 114501 (Oct 16, 2009) (5 pages) doi:10.1115/1.4000109 History: Received September 13, 2008; Revised June 24, 2009; Posted September 01, 2009; Published October 16, 2009

Inertial motion sensors (IMSs) combine three sensors to produce a reportedly stable and accurate orientation estimate in three dimensions. Although accuracy has been reported within the range of 2 deg of error by manufacturers, the sensors are rarely tested in the challenging motion present in human motion. Their accuracy was tested in static, quasistatic, and dynamic situations against gold-standard Vicon camera data. It was found that static and quasistatic rms error was even less than manufacturers’ technical specifications. Quasistatic rms error was minimal at 0.3 deg (±0.15deg SD) on the roll axis, 0.29 deg (±0.20deg SD) on the pitch axis, and 0.73 deg (±0.81deg SD) on the yaw axis. The dynamic rms error was between 1.9 deg and 3.5 deg on the main axes of motion but it increased considerably on off-axis during planar pendulum motion. Complex arm motion in the forward reaching plane proved to be a greater challenge for the sensors to track but results are arguably better than previously reported studies considering the large range of motion used.

Copyright © 2009 by American Society of Mechanical Engineers
Topics: Sensors , Motion , Errors , Pendulums , Yaw
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Grahic Jump Location
Figure 1

IMS setup for static testing. Sensor is attached to rotating white block and rotated while the metal pointer indicated the orientation estimate on the protractor.

Grahic Jump Location
Figure 2

Angular orientation time series from gold-standard Vicon estimate versus IMS during pendulum motion occurring about dominant axis of (a) roll axis, (b) pitch axis, and (c) yaw axis

Grahic Jump Location
Figure 3

Angular orientation in three dimensions of the forearm performing a back and forth, up and down sweeping motions in the forward reach space envelope of the subject



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