Noise in GRF file

Provide easy-to-use, extensible software for modeling, simulating, controlling, and analyzing the neuromusculoskeletal system.
POST REPLY
User avatar
Gnapika Talluri
Posts: 3
Joined: Sat Sep 28, 2019 10:04 am

Noise in GRF file

Post by Gnapika Talluri » Mon Dec 23, 2019 10:53 am

Hi everyone,

I am new to OpenSim. I extracted .trc and .mot files from the .c3d file using MATLAB code. When I previewed the motion file, I observed there is a lot of noise in the ground reaction force (As shown in the below figure). How can I remove the noise?

noiseGRF.png
noiseGRF.png (286.32 KiB) Viewed 171 times
Thanks in advance!



Gnapika

User avatar
Ton van den Bogert
Posts: 165
Joined: Thu Apr 27, 2006 11:37 am

Re: Noise in GRF file

Post by Ton van den Bogert » Mon Dec 23, 2019 12:24 pm

This is noise in the center of pressure (COP). The center of pressure is calculated from the force plate's load cells, and is undefined (zero divided by zero) when the force is zero. See eq. [3] in http://www.kwon3d.com/theory/grf/cop.html

It won't affect any mechanical analysis, only the visualization.

Some visualization systems have an option to turn the force visualization off when the force is below a certain threshold. If Opensim does not have this option, that might be a useful feature to consider.

Ton van den Bogert

POST REPLY