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accounting_for_inertia [2018/06/13 13:54] marijn.nijenhuis |
accounting_for_inertia [2023/06/08 16:35] (current) marijn.nijenhuis |
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- the total mass of the object | - the total mass of the object | ||
- the moments of inertia taken at the center of mass and aligned with the output coordinate system. | - the moments of inertia taken at the center of mass and aligned with the output coordinate system. | ||
- | - the position of the center of mass (note: | + | - the position of the center of mass (note: |
+ | |||
+ | ** Important: ** Depending on the version of SolidWorks, different conventions are used for the crossproducts (the off-diagonal components of the inertia tensor). With version 2021 and later, you can set the convention: we want the positive tensor notation. You can set this in the Options panel within the Mass Properties window. For older versions of SolidWorks where you don't have this option, be very wary of what SolidWorks returns. In that case, it's mostly likely that SolidWorks shows the inertia tensor with minus signs in front of the off-diagonal components: | ||
+ | $$ \begin{bmatrix} I_{xx} & -I_{xy} & -I_{xz} \\ -I_{xy} & I_{yy} & -I_{yz} \\ -I_{xz} & -I_{yz} & I_{zz} \end{bmatrix} $$ | ||
+ | If it's unclear, check the manual for your version to see which sign convention is being used for the off-diagonal terms. | ||
{{ : | {{ : | ||
===== 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, | + | 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, |
- | + | ||
- | ** Check the full syntax list for the correct use of '' | + | |
- | $$ \begin{bmatrix} I_{xx} & -I_{xy} & -I_{xz} \\ -I_{xy} & I_{yy} & -I_{yz} \\ -I_{xz} & -I_{yz} & I_{zz} \end{bmatrix} $$ | + | |
- | '' | + | ** Check the full syntax list for the correct use of '' |
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 | nprops(1).fix | ||
- | nprops(3).mass | + | nprops(3).mass |
- | nprops(3).mominertia | + | nprops(3).mominertia |
%% ELEMENT PROPERTIES | %% ELEMENT PROPERTIES | ||
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eprops(1).orien | eprops(1).orien | ||
eprops(1).nbeams | eprops(1).nbeams | ||
- | eprops(1).flex | + | eprops(1).flex |
eprops(1).color | eprops(1).color | ||
eprops(1).opacity | eprops(1).opacity | ||
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%% SIMULATION | %% SIMULATION | ||
- | out1 = spacarlight(nodes, | + | out = spacarlight(nodes, |
</ | </ | ||