Crash when running specific case in RRA

[Eric Stetz]

Hello,

I have been having a repeated issue with running RRA. I am attempting to simulate the effects of an exoskeleton attached to a human body. I am using the Simbody 2392 gait model as the human body and a custom made model for the exoskeleton. To model the attachment points I am experimenting with using a BushingForce at each attachment point, which are included in the model file's force set. When I first executed RRA on this model it successfully completed, although in the results it was evident that the BushingForces were not affecting the model at all. I guessed this was because they had been removed when the RRA replaced the model's force set with the RRA actuators in the RRA Actuators xml.

To rectify this I included the BushingForces in the RRA Actuators xml file, but now whenever I run this case Opensim immediately crashes soon after RRA begins running, and the only output file written is an error file with a name like "hs_err_pid8424.log" . This file says,

A fatal error has been detected by the Java Runtime Environment:
EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x0000000071efc1b0, pid=8424, tid=7376

And then continues on with lots more information and numbers. I can attach the rest of the error file if necessary.

I think this problem must be linked to including the BushingForce objects in the RRA Actuators file which is used to replace the model actuators. Are BushingForces not supported in this file? If so is there any other way for me to get these forces in the model when I run RRA? I'm pretty sure the problem is not with my model, as I went on the run the model in CMC successfully, where I could append the CMC Actuators and not delete the model's force set. The main reason I want to run this in RRA is that I need to repeatably run the model in order to tune the attachment locations and bushing stiffness in order to lower the residuals to get an accurate model. This is very time consuming running CMC, since each CMC run takes a couple hours, whereas RRA runs would probably take only 20-30 minutes.

Thanks for any help.

-Eric S.

[jimmy d]

Hi Eric -

The overarching problem is that RRA is used to resolve mass, kinematics and the real (collected) forces. The bushings have to be part of the model, not the actuators set (this is causing the crash), but they will get replaced when you are running the analysis. To see the effect of the bushings you will have to use CMC.

Cheers,
-James