Motek's D-Flow 3.32: Accurate force measurement on moving platforms

[Johannes Gijsbers]

Dear reader,

Many biomechanics labs use instrumented treadmills for gait analysis and biomechanics research. Both goals require highly accurate force measurements, which instrumented treadmills can provide without further compensation when measuring steady state walking. However, there is increasing interest in perturbing subjects by swaying, pitching, or otherwise moving the platform on which the instrumented treadmill is mounted. This is a new challenge for accurate force measurement, as the platform movement induces inertial and gravitational forces.

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To obtain accurate forces during platform movement, these inertial and gravitational forces should be compensated for. D-Flow 3.32 introduces a compensation method based on estimation using custom accelerometers. During a calibration trial on an empty platform, an inertia compensation model is fitted by measuring the forces from the force plate, and the accelerations using the custom accelerometers.

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During trials with subjects, inertia and gravitational forces are then estimated by D-Flow in real-time, and subtracted from the forces measured by the force plate. The corrected forces are then only the forces exerted by the subject.

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In order to use inertia compensation, custom accelerometers need to be installed in and connected to a Motek CAREN, GRAIL or M-Gait. If you'd like to know more, please contact us at info@motekforcelink.com.

With kind regards,
Johannes Gijsbers,
Product Manager