RRA model falls through floor

[Michael Dube]

Hello,

When running RRA the model falls through the floor. I have been inputting GRF data for the left and the right but even when cropping the GRF data to the stance phase where there is a significant y vector force the model still falls through the floor. I was wondering if anyone could help with this.

Thank you.

[Mohammadreza Rezaie]

Hi,

You must have all external loads, otherwise the residual forces and moments exceed the "GOOD" and "OKAY" range and thus, the model falls. Not only the residual forces and moments, but also, joint angle errors. See "Best Practices and Troubleshooting":
https://simtk-confluence.stanford.edu/d ... d+with+RRA
During the stance phase of walking (which I assume your task is), there are first double-limb support, single limb support, and second double-limb support sub-phases. Indeed, three floor embedded force plates or an instrumented treadmill with embedded force plates are needed to contain all external loads.
To keep the kinematics errors below the recommended ranges, you can increase the weight of pelvis_ty and other coordinates in the RRA_Tasks.xml file.

Best,
Mohammadreza