Force plate install on second floor

[Rachel Hybart]

Good afternoon.
I am working with a group who may need to install a force plate in a second story lab.
I was curious if anyone has had issues with vibration in such an install, or if there are suggested ways to verify your data are not being affected by the vibrations?
Thanks!

[Wagner De Godoy]

Dear Dr. Rachel Hybart,

I am not an expert in vibrations, even though I am trained as a mechanical engineer.

I had a few weeks of experience with a motion capture system that was affected by intermittent vibrations caused by the renovation of an adjacent building. The structural vibrations generated by heavy machinery propagated only in part of the gait laboratory - located on the 3rd floor -, and especially affected one of the side walls, where 3 infrared cameras for 3D motion capture were installed. A temporary solution was to remove the cameras from the wall mounts and mount the cameras on tripods. This change showed that the calibration parameters were preserved, and it was not necessary to reschedule gait exams. Fortunately, two AMTI platforms showed no noise in the signals.

I think that in new laboratories it is important to carry out vibration studies in environments close to heavy machinery and elevators. It is possible to hear noises when the floor propagates shocks or vibrations - the signal from vertical forces, for example, presents these noises. Perhaps the platforms can be temporarily fixed to the floor by screws, without the adhesive provided by the manufacturer. After a period of testing and evaluation of the signals, the recommended fixing would be made.

I hope this little information helps you with your project. I apologize for the poor translation.

Best Regards,

Wagner de Godoy
Brazil

[Edmund Cramp]

Wagner, that's a good description, I worked in that environment for years but eventuality I discovered that the AMTI noise reduction was a result of AMTI filtering the data to remove noise and the filtering resulted in the entire data from the force plate being slightly delayed by a few milliseconds. This can be observed in a data collection by creating a test in the 3D world and the force plate world - I wrapped the retro-reflective tape on a golf ball and dropped it on the force plate while the 3D data and force data was collected, so you can see the instant that the golf ball hits the force plate and compare that instant to the force plate response.
The original "problem" I saw was that data from a foot-switch on the heel was saying the switch was indicating heel contact before the Force Plate data "confirmed" that the heel was on the floor.
Creating a single event and detecting it with multiple sensors is always very helpful so that you can verify your data.