Crank rotation in bicycle model

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1

Hi,

I’m trying to control the rotation of the cranks in the bicycle model at all times. As such I have replaced this section:

AnyKinEqSimpleDriver CrankRotation = {
AnyRevoluteJoint &Jnt = .CrankJoint;
DriverPos = {0};
DriverVel = {-(…BikeParameters.Cadence/60)pi2};
Reaction.Type = {Off}; //This has to be zero otherwise the driver will carry the applied moment
};

with this:

AnyKinEqInterPolDriver CrankRotation = {
AnyRevoluteJoint &Jnt = .CrankJoint;
Type = Bspline ;
BsplineOrder = 4;
FileName = “RotateW.txt”;
Reaction.Type = {Off};
};

Apart from this change the model is the same as found in the AnyBody Model Repository V1.0, with the cadence changed to 90. When I do this change, I get a long list of warnings when running the inverse dynamics stating there is an overloaded muscle configuration and the resulting max muscle activities hit almost 14. The rotation given by the file should be the same as it was previously so I’m unsure as to why the muscle activity is changed so dramatically. The rotation text file is attached.

Any assistance would be greatly received.
Best regards
Alex

2

Hi Alex,

This is because you very high acceleration. When looking at the interpolation driver you made, the position curve looks good, but the velocity and acceleration show large picks (3000 m/s2 for the acceleration). So of curse the model cannot take such accelerations. The solution is to filter the data before using it in the driver.

Best regards, Sylvain.

3

Thanks for clearing that up for me Sylvain,

Best regards
Alex

4