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accounting_for_inertia [2018/06/13 13:53]
marijn.nijenhuis
accounting_for_inertia [2018/06/14 09:44] (current)
mark.naves [Adding mass and inertia properties to Spacar]
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 ===== Adding mass and inertia properties to Spacar ===== ===== Adding mass and inertia properties to Spacar =====
-For this example a single leafsprings is simulated between node 1 ([0,0,0]) and node 2 ([0 0.1 0]), with one end of the wrench attached to node 2 (which coincides with the position of the coordinate system in SolidWorks). Furthermore,​ a third node at the center of mass of the wrench ([0.055 0.1 0.003]) is rigidly ​connected to node 2. At this node in the center of mass of the wrench, both the mass and moment of mass properties are added with the ''​nprops(i).mass''​ and ''​nprops(i).mominertia''​ fields.+For this example a single leafsprings is simulated between node 1 ([0,0,0]) and node 2 ([0 0.1 0]), with one end of the wrench attached to node 2 (which coincides with the position of the coordinate system in SolidWorks). Furthermore,​ a third node at the center of mass of the wrench ([0.055 0.1 0.003]) is connected to node 2 with a rigid massless element. At the node in the center of mass of the wrench, both the mass and moment of mass properties are added with the ''​nprops(i).mass''​ and ''​nprops(i).mominertia''​ fields.
  
-** Check the full syntax list for the correct use of ''​nprops(i).mominertia''​ because the definition differs from the numbers that SolidWorks returns **. SolidWorks returns +** Check the full syntax list for the correct use of ''​nprops(i).mominertia''​ because the definition differs from the numbers that SolidWorks returns**. ​The Mass Properties window in SolidWorks returns ​the components 
-$$ \begin{bmatrix} ​I_xx & -I_xy & -I_xz \\ -I_xy I_yy & -I_yz \\ -I_yz & -I_xz I_zz \end{bmatrix} $$ +$$ \begin{bmatrix} ​I_{xx} ​& -I_{xy} ​& -I_{xz} ​\\ -I_{xy} ​I_{yy} ​& -I_{yz} ​\\ -I_{xz} ​& -I_{yz} ​I_{zz} ​\end{bmatrix} $$ 
- +while ''​nprops(i).mominertia'' ​in SPACAR Light requires the vector ​that contains the actual tensor componentsso ''​[Ixx Ixy Ixz Iyy Iyz Izz]'' ​in kgm<​sup>​2</​sup>​. ​In other words, ​the diagonal ​components ​(''​Ixx''​''​Iyy'' ​and ''​Izz''​) can be used directly, but the sign of the off-diagonal terms (''​Ixy'',​ ''​Ixz''​ and ''​Iyz''​needs to be flipped.
-''​nprops(i).mominertia'' ​consists of a vector ​with length six, [Ixx Ixy Ixz Iyy Iyz Izz] in kgm<​sup>​2</​sup>​. ​Note the tensor ​components ​are neededso Ixy, Ixz and Iyz represent ​the negative ​of the products of inertia ​(which are provided by SolidWorks).   ​+
  
 A visualization of the first two vibration modes of this system is provided below. In order to provide a clearer image of this system, the CAD file of the wrench is included in the visualization. The visualization of CAD files in Spacar is outside of the scope of this example and therefore not detailed. This example only treats the dynamic behavior of the wrench. The MATLAB code of this example is provided at the end of this page. A visualization of the first two vibration modes of this system is provided below. In order to provide a clearer image of this system, the CAD file of the wrench is included in the visualization. The visualization of CAD files in Spacar is outside of the scope of this example and therefore not detailed. This example only treats the dynamic behavior of the wrench. The MATLAB code of this example is provided at the end of this page.
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 %node 1 %node 1
 nprops(1).fix ​               = true;         %Fix node 1 nprops(1).fix ​               = true;         %Fix node 1
-nprops(3).mass ​              = 0.074; ​       %0.74Kg at the center of mass +nprops(3).mass ​              = 0.074; ​       %0.074 kg at the center of mass 
-nprops(3).mominertia ​        = [ 0.00000398 0.00000252 0.0000000 0.00013376 0.00000000 0.00013739];​ %Inertia at the center of mass+nprops(3).mominertia ​        = [0.00000398 0.00000252 0.0000000 0.00013376 0.00000000 0.00013739];​ %Inertia at the center of mass
  
 %% ELEMENT PROPERTIES %% ELEMENT PROPERTIES
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 %% SIMULATION %% SIMULATION
-out1 = spacarlight(nodes,​ elements, nprops, eprops);+out = spacarlight(nodes,​ elements, nprops, eprops);
 </​code>​ </​code>​
  
    
accounting_for_inertia.1528890785.txt.gz · Last modified: 2018/06/13 13:53 by marijn.nijenhuis