simtk.org

Posted: **Thu Apr 20, 2017 9:07 am**

Hello,

I am working on the model of the arm 26 and I was in need to get the x and y points of the curves: passive and active force-length as well as force-velocity curve(fv)

on the github I found under opensim-core the force-length curves (x and y points) however for the fv curve i found only the implementation in ThelenMuscle of the contaction velocity (modified fv relationship)

should i do some calculation on my own for fv based on active and passive force length values then extract corresponding V and so gather some x and y points for the force-velocity curve.. or there exist somewhere on the github for uncalibrated arm26 model ?

thanks in advance for your time

Sariah

Posted: **Thu Apr 20, 2017 4:06 pm**

The arm26 model contains Thelen muscles. You can use the Thelen2003Muscle::printCurveToCSVFile() method (https://simtk.org/api_docs/opensim/api_ ... 212911e4c3) to sample and export the curves. Here's a basic GUI script that will export all curves for a specified muscle:

Code: Select all

myModel = getCurrentModel()
if not myModel:
	print "ERROR: Must load a model first\n"

muscleName  = "TRIlong"
destination = "C:/OpenSim3.3/myMuscleCurves/"

mcl = modeling.Thelen2003Muscle.safeDownCast( myModel.getMuscles().get(muscleName) )
mcl.printCurveToCSVFile(modeling.Thelen2003Muscle.CurveType.FiberActiveForceLength, destination)
mcl.printCurveToCSVFile(modeling.Thelen2003Muscle.CurveType.FiberPassiveForceLength, destination)
mcl.printCurveToCSVFile(modeling.Thelen2003Muscle.CurveType.FiberForceVelocity, destination)
mcl.printCurveToCSVFile(modeling.Thelen2003Muscle.CurveType.TendonForceLength, destination)

You can modify this script to ensure the specified muscle exists or to iterate over all muscles, for example. Scripting in the GUI is described in the Confluence documentation here: http://simtk-confluence.stanford.edu:80 ... in+the+GUI. Also see the "Common Scripting Commands" page (http://simtk-confluence.stanford.edu:80 ... g+Commands) for more information.

Posted: **Wed Apr 03, 2019 3:06 am**

Hello all,

is there any way to use this command in the Matlab API (OpenSim 4.0)?
I don't really know how to access to the "Thelen2003Muscle$CurveType" variable in order to select the curve I need from the enum

https://simtk.org/api_docs/opensim/api_ ... c05a87a546

Thank you in advance

Posted: **Wed Apr 03, 2019 10:11 am**

I don't really know how to access to the "Thelen2003Muscle$CurveType" variable in order to select the curve I need from the enum

Not sure this will work, but I would try "0" for FiberActiveForceLength, "1" for FiberPassiveForceLength, etc. (https://simtk.org/api_docs/opensim/api_ ... bf21ebf940).

Posted: **Fri Apr 05, 2019 1:55 am**

Thank you for the reply,

but I still can't make it work, as I do not know how to create a CurveType variable to modify the enum. I think once I get to access this OpenSim variable I will be able to choose the enum value. Any thoughts?
printCurveToCSVFile (const CurveType ctype, const std::string & path )

Thank you!

Posted: **Fri Apr 05, 2019 3:58 am**

Did you try using "0" as the first argument?

Posted: **Fri Apr 05, 2019 4:41 am**

Yes I did, as you can see here:

Code: Select all

>> mcl.printCurveToCSVFile(0, destination)
No method 'printCurveToCSVFile' with matching signature found for class
'org.opensim.modeling.Thelen2003Muscle'.
 
>> mcl.printCurveToCSVFile("0", destination)
No method 'printCurveToCSVFile' with matching signature found for class
'org.opensim.modeling.Thelen2003Muscle'.

being "destination" an string for the path.

Is it there any other way to plot this kind of curves from Matlab?

Posted: **Fri Apr 05, 2019 1:56 pm**

Unfortunately, I don't have a Matlab license so I can't investigate, but the CurveType enum (the first argument to printCurveToCSVFile()) may not be available in Matlab. You can check by typing "methodsview mcl" and seeing whether the first argument to printCurveToCSVFile() is recognized.

Posted: **Mon Apr 08, 2019 8:53 am**

Thank you! I think you're right, it's not available in Matlab. There is no other way to plot this kind of curves from Matlab?

Posted: **Wed Apr 10, 2019 9:14 am**

Just for the record and future use, I managed to plot this kind of curves by creating a Millard muscle with the same characteristics as the muscle I was working on. Once you have the Millard muscle there's a function that gives you access to all the muscle curves classes.

Code: Select all

import org.opensim.modeling.*
myModel = Model('Model.osim');
model_muscles = myModel.getMuscles();

% Get parameters that define the muscle
DELT1 = model_muscles.get('DELT1');
    MIF = DELT1.getMaxIsometricForce()
    OFL=DELT1.getOptimalFiberLength()
    TSL=DELT1.get_tendon_slack_length()
    PA=DELT1.getPennationAngleAtOptimalFiberLength()

% Create a Millard Muscle that replicates the previous muscle
MillardMuscle = org.opensim.modeling.Millard2012EquilibriumMuscle('DELT1Millard',MIF,OFL,TSL,PA);
% Get the curves
ffl=MillardMuscle.getFiberForceLengthCurve();
afl=MillardMuscle.getActiveForceLengthCurve();
fv=MillardMuscle.getForceVelocityCurve();
tfl=MillardMuscle.getTendonForceLengthCurve();

% Print curves
ffl.printMuscleCurveToCSVFile('D:\User\...\Curves');

% Import curves into Matlab environment 
ffl_data=importdata("D:\User\...Curves\ActiveForceLengthCurve.csv");

% Plot x and y
plot(ffl_data.data(:,1),ffl_data.data(:,2))

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forve-velocity curve(model arm26)

forve-velocity curve(model arm26)

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Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)

Re: forve-velocity curve(model arm26)