CAGE User's Guide    

Multimodel Tradeoffs

There are two types of tradeoff that you can add to your session, a tradeoff of independent models, as described earlier (see Performing a Tradeoff Calibration), or a tradeoff of interconnected models (a multimodel tradeoff).

A multimodel tradeoff is a specially built collection of models from the Model Browser.

You can build a series of models so that each operating point has a model associated with it. In the Model Browser, you can export models for a multimodel tradeoff from the test plan node. The models must be two-stage and must have exactly two global inputs.

The procedure for calibrating by using a multimodel tradeoff follows:

  1. Add the multimodel tradeoff. (See the following section, Adding a Multimodel Tradeoff.)
  2. Calibrate the tables. (See Calibrating Using a Multimodel Tradeoff.)
  3. Export your calibration. (See Exporting Calibrations.)

When you calibrate the tables in a multimodel tradeoff, you can only adjust a value in the tables if there is a model defined at this operating point. These cells are colored purple in the table. At each of these operating points, you have a model that you use to trade off, and by doing this you can adjust the value in the table. All other cells in the table do not have models associated with them and you cannot edit them (but they can be filled by extrapolation). You trade off values at each of the model operating points in exactly the same way as when using independent models, as described in Determining a Value at a Specific Operating Point. When you have determined table values at each of the model operating points, you can fill the whole table by extrapolation by clicking . See Filling the Table by Extrapolation.

Adding a Multimodel Tradeoff

To add a multimodel tradeoff to your session:

  1. Select File -> New -> Multimodel Tradeoff. The file must have been exported from the MBC Model Browser using the Tradeoff button (only enabled for two-stage models with exactly two global inputs).
  2. Select the correct file to import and click Open. This opens a dialog box.

  3. In the Operating points pane, you can clear the check boxes for any operating points that you do not want to import.
  1. Notice that the operating points are displayed graphically in the Current location set pane. If an operating point is deselected, it is displayed as gray here, rather than red.

    CAGE creates tables for all the models and input variables, with breakpoints at all the operating points.

  1. You can adjust any of the operating points to reduce the number of breakpoints.
  1. For example, in the session pictured, there are operating points at values of 2001, 2002, 2000.489, and 1997. This results in breakpoints in the table at each of these four values. However, all four operating values are very close to 2000 and might all have been intended to run at exactly 2000. You can choose to adjust all these to 2000 by typing in the edit boxes. The table then has a single breakpoint at 2000 instead of the four closely spaced breakpoints. You can click Reset Values to return to the original operating points.

  1. In the Available models pane, clear any model that you do not want to import.
  1. For example, you might want to perform a tradeoff of soot (SOOT) and torque (TQ) in the preceding example. Clear the check boxes for HCEMISS and NOEMISS.

  1. Click OK.

When you import the multimodel tradeoff, you import the tables and normalizers, so you do not have to calibrate the normalizers.

You can now calibrate your tables. See the next section, Calibrating Using a Multimodel Tradeoff.


  Using Regions Calibrating Using a Multimodel Tradeoff