# WORKSHOP 6 NESTED COORDINATE SYSTEMS

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WORKSHOP 6 NESTED COORDINATE SYSTEMS

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Problem Description Investigate the nested coordinate system capabilities in MSC.Patran using a satellite model. Rotate the position of the satellite payload relative to a spacecraft platform using nested coordinate systems.

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Suggested Exercise Steps Start MSC.Patran and create a new database. Import the Nastran input file antenna.bdf. Note the existing coordinate systems. Export a .bdf file from Patran. Review the .bdf to see that the coordinate systems are not nested. Change the translation parameters in Patran and export another .bdf file. Review the second .bdf file to ensure that the coordinate systems are nested. Modify the .bdf to rotate the antenna assembly 90 degrees so that the X axis of coord 390000 is aligned with the basic Y axis. Save the .bdf file. Open a new database in Patran. Import the modified .bdf. View the rotated model. Explore additional transformations using coord 390003

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Step 1. Create a Database Create a new database. File / New. Enter coordinates as the file name. Click OK. Choose Default Tolerance. Select MSC.Nastran as the Analysis Code. Select Structural as the Analysis Type. Click OK. a b e f d c g

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Step 2. Import a .bdf File File: Import Set the source to MSC.Nastran Input. Select the file antenna.bdf. Apply. b c a d

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Step 3. Review Existing Coordinate Systems Review the existing coordinate systems. Coord 390000 defines the position of the base and is defined relative to Coord 0. Coord 390003 defines the position of the dish and is defined relative to Coord 390000. b a

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Step 4. Export a .bdf File Analysis: Analyze / Entire Model / Analysis Deck. Enter default_translation as the Job Name. Click Apply. a b c

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Step 5. Review the .bdf File Review the CORD2R entries at the end of the file. Note that field three is blank, which defaults to the basic coordinate system. . . .

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Step 6. Change the Translation Parameters Change the translation parameters to allow nested coordinate systems. Analysis: Analyze / Entire Model / Analysis Deck Change the job name. Click Translation Parameters. For Coord Frame Coordinates, set the value to reference frame. Click OK. Click Apply. a b d e f c

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Step 7. Review the Second .bdf File Note the nested coordinate system. Coord 390003 now references Coord 390000. . . . a

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Step 8. Modify the .bdf File Modify the .bdf file to rotate the antenna assembly 90 degrees. Since Coord 390003 is nested, we will only need to modify Coord 390000. The X Axis of Coord 390000 should be rotated to align with the basic Y Axis. One possible modified coordinate system is shown below. Modified .bdf: Original .bdf:

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Step 9. Save the .bdf File Save the changes that you made to rotate the coordinate systems.

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Step 10. Create a Database Create a new database. File / New. Enter rotated_antenna as the file name. Click OK. Choose Default Tolerance. Select MSC.Nastran as the Analysis Code. Select Structural as the Analysis Type. Click OK. a b e f d c g

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Step 11. Import a .bdf File File: Import Set the source to MSC.Nastran Input. Select the file rotated_antenna.bdf. Apply. b c a d

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Step 12. View the Rotated Model Note how the antenna dish and base have been rotated.

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Step 13. Optional: Explore Transformations As an optional exercise, try making rotational and translational changes to the coordiaate systems and view the resulting displacements in Patran.

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