Center weight mass

Simulation of a center weight for double trawl systems.

Collaboration diagram for Center weight mass:

Author

Karl-Johan Reite

Date

01.01.2006 KJR: Initial version.

26.05.2011 KJR: Rewritten to new version of FhSim.

This is basically just a mass object with gravitational forces and three external forces.

\begin{eqnarray*} \dot{\vec{x_1}} &=& \vec{x_2} \\ \dot{\vec{x_2}} &=& \frac{\sum \vec{F}}{m} \end{eqnarray*}

, where

• \(\vec{x_1}\) is the position of the center weight object
• \(\vec{x_2}\) is the velocity of the center weight object
• \(\sum \vec{F}\) is the sum of the forces acting on the center weight object
• \(m\) is the mass of the center weight object

Example configuration excerpt

<Lib
   LibName                   = "fishery"
   SimObject                 = "Trawl/CenterWeight"
   Name                      = "C"
   Mass                      = "1000"
   Material                  = "Simple/Green"
   Density                   = "7500"
/>

Todo:

Add config details (What is Force1, Force2 and Force3?)

Input Ports

Name	Width	Description
Force1	3	A force acting on the center weight.
Force2	3	A force acting on the center weight.
Force3	3	A force acting on the center weight.

Output Ports

Name	Width	Description
Pos	3	Position.
Vel	3	Velocity.

Configuration parameters

Name	Width	Description
Mass	1	The mass of the center weight object.
Density	1	The density of the center weight object.
Material	1	The visualization material of the center weight, specified by its name.
Mesh	1	The visualization mesh (geometry) of the center weight, specified by its filename (Default: fhSphere.mesh).
Scale	1	The scale of the center weight, related to the mesh. (Default: 1)

Initial conditions

Name	Width	Description
Pos	3	Initial Position.
Vel	3	Initial Velocity.

Full example file

<Contents>
   <OBJECTS>
      <Lib
         LibName                   = "base"
         SimObject                 = "Environment/Basic"
         Name                      = "Env"
         MeanDepth                 = "55"
         BottomRoughness           = "5"
         SurfaceTextureScale       = "1000"
         BottomTextureScale        = "15"
         BottomStructureScale      = "50"
         TerrainRadius             = "1000"
         SurfaceDepth              = "0"
         NumTerrainRings           = "170"
      />
      <Lib 
         LibName                   = "fishery"
         SimObject                 = "Trawl/CenterWeight"
         Name                      = "C"
         Mass                      = "1000"
         Material                  = "Simple/Green"
         Density                   = "7500"
      />
   </OBJECTS>
   
   <INTERCONNECTIONS>
      <Connection
         Env.CurrentVel = "2.5,0,0"
         C.Force1       = "10,10,10"
         C.Force2       = "10,10,10"
         C.Force3       = "10,10,10"
      />
   </INTERCONNECTIONS>
   
   <INITIALIZATION>
      <InitialCondition
         C.Pos = "0,0,-5"
         C.Vel = "0,0,0"
      />
   </INITIALIZATION>
   
   <INTEGRATION>
      <Engine
         IntegratorMethod           ="2"
         NumCores                   ="1"
         TOutput                    ="0, 1, 30"
         LogStates                  ="1"  
         stepsize                   ="0"
         HMax                       ="0.002"
         HMin                       ="0.00000001"
         AbsTol                     ="1e-3" 
         RelTol                     ="1e-3"
         UseRSSNormInsteadOfInfNorm ="0"
         FileOutput                 ="objects:all"
      />
   </INTEGRATION>
</Contents>

This SimObject is referred to as Trawl/CenterWeight