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You can model an extrusion using the SimMechanics™ shape General Extrusion. Examples of extrusions include the I-beam and box-beam shapes. In this example, you model a simple solid with I-beam shape using the General Extrusion shape. For an example that shows you how to model a box beam, see Model Box Beam.
To represent the I-beam geometry, first identify its cross-section. This is the 2-D area that SimMechanics extrudes to obtain the 3-D I-beam. You can then specify the cross-section coordinates in the Solid block dialog box. The figure shows the I-beam cross-section that you specify in this example.
The [0 0] coordinate identifies the solid reference frame origin. To place the reference frame at the center of the I-beam, specify the coordinates so that the [0 0] coordinate is at the cross-section center. Because the I-beam cross-section is symmetric about the horizontal and vertical axes, you need only define the coordinates for one cross-section half—e.g, the right half. You can then define the left half coordinates in terms of the right half coordinates.
By parameterizing the cross-section coordinates in terms of relevant I-beam dimensions, you can quickly change the I-beam dimensions without having to reenter the cross-section coordinates. The figure shows the cross-section dimensions and coordinates that you must specify to represent the I-beam.
Using the cross-section points that the figure shows, you define the coordinate matrix as:
HalfCS = [A; B; C; D; E; F]; CS = [HalfCS; -HalfCS];
Add and connect the blocks to represent the I-beam. Include a Solver Configuration block so that you can visualize the solid in Mechanics Explorer during the modeling process.
Drag these blocks into a new model.
|Simscape™ Utilities||Solver Configuration||1|
Connect the blocks as shown.
In the Solid block dialog box, specify these parameters.
|Geometry > Shape||Select General Extrusion|
|Geometry > Cross-Section||Enter CS. Select units of cm.|
|Geometry > Length||Enter L. Select units of cm|
|Graphic > Visual Properties > Color||Enter RGB|
Select the Solid block and generate a new subsystem, e.g., by pressing Ctrl+G.
In the subsystem mask, initialize the solid parameters. Then, in the subsystem dialog box, specify their values.
Select the Subsystem block and create a subsystem mask, e.g., by pressing Ctrl+M.
In the Parameters & Dialog tab of the Mask Editor, drag five edit boxes into the Parameters group and specify these parameters.
|Color [R G B]||RGB|
In the Initialization tab of the Mask Editor, enter the initialization code for the xsection variable and click OK:
D = H/2-T; HalfCS = [W/2, -H/2; W/2, -D; T/2, -D; T/2, D; W/2, D; W/2, H/2]; CS = [HalfCS; -HalfCS];
In the Subsystem block dialog box, specify these parameters.
|Color||[0.85 0.45 0]|
You can now visualize the I-beam that you modeled. To do this, on the Simulink® menu bar, select Simulation > Update Diagram. Mechanics Explorer opens with a 3-D display of your model. Rotate, pan, and zoom to explore.
Try modifying the I-beam geometry. To do this, in the subsystem dialog box, change the dimension parameter values. Then, update the model. The figure shows some examples.