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| R2012a Documentation → SimMechanics | |
Learn more about SimMechanics |
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| Contents | Index |
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In this example, you export an assembly with one part and no constraints. Look for the following two example CAD files in the SimMechanics Link demos folder:
The full assembly file, cup_assembly.ASSEMBLYFILETYPE
The part, a cup, in a file called cup.PARTFILETYPE
Although it has only one part, you must export the full assembly into XML, not just the cup part.
Open the cup assembly file in your CAD platform and check its geometry and mass properties.
Cup Assembly in a CAD Platform
| Property | Value |
|---|---|
| Volume | 0.0001 cubic meters (m3) |
| Surface area | 0.0381 square meters (m2) |
| Density | 3.0 grams/cm3 = 3000 kg/m3 |
| Mass | 0.2906 kilograms (kg) |
| Principal moments of inertia at the center of gravity | Ix = 0.00015, Iy =
0.00067, Iz = 0.00067 kg-m2 |
The inertia tensor is computed at the center of gravity, with the coordinate axes aligned with assembly base-origin axes, indicated in the preceding figure, Cup Assembly in a CAD Platform. The x-axis is the cup's axis of symmetry, and the y- and z-axes point across the cup.
Using the SimMechanics Link interface to your CAD platform, export the assembly into Physical Modeling XML format. The XML file cup_assembly.xml appears in your working CAD folder.
To import the Physical Modeling XML with the SimMechanics importer:
Move or copy the exported XML file into a MATLAB working folder to generate a SimMechanics model from the file.
Generate the model from cup_assembly.xml with the mech_import command.
Once you generate the SimMechanics model, it has six blocks, a combination representing the entire assembly:
Machine Environment – Root Ground – Weld – Root Part – Weld – Cup
The Ground origin is coincident with the World origin and maps the CAD assembly origin.
The Root Part is a nondynamical zero-mass/zero-inertia body inserted between ground and the cup.
The second joint is a Weld because the original CAD assembly has no degrees of freedom.
Deleting the Root Part and one of the Welds does not physically change the model, as long as you reconnect the remaining blocks.
 | About the CAD Translation Case Studies | Translating CAD Constraints into Joints |  |
Learn more about Simulink through this collection of videos, articles, technical literature and the Getting Started with Simulink Guide.
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