Article

Orientation sensors containing magnetometers use the earth's magnetic field as a
reference. Ferromagnetic objects may distort this magnetic field, leading to
inaccurate orientation output. We explored the viability of these orientation
sensors for motion analysis in an assistive mobility device rehabilitative
setting. We attached two MTx orientation sensors (XSens; Enschade, the
Netherlands), connected to the XBus Master data collection unit (XSens), to a
plastic frame such that the relative angle between sensors was constant. We then
moved a series of mobility devices in proximity to the plastic frame: two
knee-ankle-foot orthoses (aluminum, stainless steel), one ankle-foot orthosis,
two transtibial prostheses (exoskeletal, endoskeletal), two walkers (standard,
Challenger Low Wide [Evolution Technologies; Port Coquitlam, Canada]), and two
wheelchairs (Tango [OrthoFab; Quebec City, Canada], GTi [Quickie; Phoenix,
Arizona]). For each mobility device, we calculated the average difference in
relative angle between the baseline and peak angles for each of five trials.
Errors ranged from less than 0.10 to 35.29 degrees, depending on the mobility
device and frame positioning near the device. This demonstrated the large errors
that can occur when magnetometer-based orientation sensors with mobility devices
are used. While strategic orientation sensor placement on some mobility devices
can minimize these errors to an acceptable level, testing protocols should be
implemented to verify orientation sensor accuracy for these applications.

Langue : ANGLAIS