Help with Field Function describing Force

VinayKS · March 12, 2013, 04:25

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?

VinayKS · March 12, 2013, 04:27

Apologies - the expression I used was

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

lava12005 · March 12, 2013, 23:59

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.

March 12, 2013, 04:25	Help with Field Function describing Force	#1
VinayKS New Member VKS Join Date: Jan 2013 Posts: 6 Rep Power: 13	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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March 12, 2013, 04:27		#2
VinayKS New Member VKS Join Date: Jan 2013 Posts: 6 Rep Power: 13	Apologies - the expression I used was [50.0, ($$Centroid [1] > -2.5) ? -25.0 : 25.0 , 0.0]

March 12, 2013, 23:59		#3
lava12005 Senior Member KHB Join Date: Aug 2010 Location: Singapore Posts: 118 Rep Power: 16	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.