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Help with Field Function describing Force

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Old   March 12, 2013, 04:25
Default Help with Field Function describing Force
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VKS
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Hi,

I am attempting to model the motion of a vehicle that behaves as follows -- While above a certain Depth (say, 2.5m), there is a force acting downwards. And when it goes below 2.5m, the force begins to act upwards.

I have tried modeling this by using a field function for a Force acting on the CM of the object. However, I am getting the following error --

"Error: field function 'Simulation>BodyManager>Body("Body 1")>ExternalForceAndMomentManager>ExternalForceCM( "Force CM 1")>VectorPhysicalQuantity>InlineFieldFunction("In lineFieldFunction")' compilation error: syntax error
Cannot evaluate expression"

The expression I am using is

[50.0, ($$Centroid [1] > -2.5) ? -25.0, 0.0]

This is given in the DFBI --> 6-DOF Bodies --> External Forces and Moments --> <Name of Force> --> Force space.

Any idea why this is happening?
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Old   March 12, 2013, 04:27
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Apologies - the expression I used was

[50.0, ($$Centroid [1] > -2.5) ? -25.0 : 25.0 , 0.0]
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Old   March 12, 2013, 23:59
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The centroid field function is used for getting the centroid of the mesh.
You need to refer to the centroid of the vehicle I believe.
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field function, marine vehicle, variable force

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