#1.INF as Mass Change

[Suraj Panigrahi]

Even though I am able to get my residual forces and torques within the limit as stated by the Opensim developers, I am unable to get 0 mass change.I am using the '2015 Full Body Musculoskeletal Model by Rajgopala' and 'ipopt' algorithm. This what I am getting.
* Recommended mass adjustments:
* Total mass change: 1.#INF
* ground: orig mass = 0, new mass = -1.#IND
* pelvis: orig mass = 10.4268, new mass = 1.#INF
* femur_r: orig mass = 8.23504, new mass = 1.#INF
* tibia_r: orig mass = 3.28245, new mass = 1.#INF
* patella_r: orig mass = 0.0763176, new mass = 1.#INF
* talus_r: orig mass = 0.0885355, new mass = 1.#INF
* calcn_r: orig mass = 1.10669, new mass = 1.#INF
* toes_r: orig mass = 0.191768, new mass = 1.#INF
* femur_l: orig mass = 8.23504, new mass = 1.#INF
* tibia_l: orig mass = 3.28245, new mass = 1.#INF
* patella_l: orig mass = 0.0763176, new mass = 1.#INF
* talus_l: orig mass = 0.0885355, new mass = 1.#INF
* calcn_l: orig mass = 1.10669, new mass = 1.#INF

Please let me know where I am going wrong. I appreciate your time.

[Thomas Uchida]

The "total mass change" is computed as [the average residual forces] / [the Y-component of the gravity vector]. Is the second component in your gravity vector 0?

[Suraj Panigrahi]

Thank you for the response, Dr Uchida. I now realize that it's because of different coordinate frame of reference. The ground reaction force measurements are in z-direction instead of usual y-direction. I was using the Grand Challenge 4 data. So,during RRA, I change the gravity to z-axis and then run the simulation.

How can I change the settings file so that instead of y-component, the residuals are divided by the z-component of gravity?

[Thomas Uchida]

How can I change the settings file so that instead of y-component, the residuals are divided by the z-component of gravity?

The recommended mass change is hard-coded as

Code: Select all

double dmass = aFAve[1] / g[1];

(see https://github.com/opensim-org/opensim- ... .cpp#L1137). You could change this line of code and recompile OpenSim locally, but it would probably be easier to transform your data.

[Suraj Panigrahi]

Dear Dr Uchida,
I changed the lab coordinates to the model coordinates using the rotational transformations. The simulations worked fine. However, I am unable to resolve the residuals at the double limb support stages. Do you have any suggestions for this?
Thank you.

[Thomas Uchida]

I am unable to resolve the residuals at the double limb support stages. Do you have any suggestions for this?

Please see the documentation for RRA on Confluence; there are some troubleshooting tips at the bottom of this page: https://simtk-confluence.stanford.edu:8 ... d+with+RRA. You may also want to work through some of the examples that demonstrate using RRA (e.g., "The Strength of Simulation: Estimating Leg Muscle Forces in Stance and Swing", https://simtk-confluence.stanford.edu:8 ... +and+Swing).