Simulink® Control Design™

Selecting an Operating Point

This section continues the magball example from Selecting Closed-Loop Responses to Design. At this stage in the example, a compensator design task has been created, tunable blocks have been selected, and closed-loop signals have been selected.

In this step of the compensator design task, you will select the operating point that you want to use in the compensator design. The Simulink Control Design software uses the operating point when it linearizes the model before creating a SISO Design Task.

Note   A compensator designed for the linearized model is likely to control the behavior of the nonlinear model only in a small region around the operating point that the model was linearized at. Therefore it is important that the linearization of the model is accurate and the selection of the operating point about which the system is linearized is an important step in the compensator design process.

In Specifying Operating Points, you created operating points for this model, exported one to the MATLAB workspace, and saved it in a MAT-file. This example imports the operating point that you saved. If you did not already compute and save an operating point for the magball model, you can import an operating point that was installed along with the Simulink Control Design demos.

To import an operating point for compensator design, perform the following steps:

1. Select the Operating Points node in the Control and Estimation Tools Manager.

2. Click the Import button, in the bottom-right corner of the Control and Estimation Tools Manager.

3. In the Operating Point Import dialog box, select MAT-file as the location to import from.

4. Click Browse and locate the file magball_operating_point.mat that you previously saved. If you did not previously save an operating point, browse to matlabroot/toolbox/slcontrol/slctrldemos/magball_operating_point.mat.

5. Click Open to return to the Operating Point Import dialog box.

   The Operating Point Import dialog box now shows all the operating points available within the selected MAT-file. In this case just a single operating point is contained in the MAT-file.

   

6. Select this operating point and click Import to import it into the Control and Estimation Tools Manager.

Click the Operating Points tab in the Simulink Compensator Design Task node to select an operating point for the compensator design. For this example, you should use the operating point that you just imported, called Operating_Point. To specify this operating point, first select the Linearize at one of the following operating points option button. Then select Operating_Point in the list, as shown in the following figure.

For information on performing compensator design at specified simulation times and events, see Linearizing at an Operating Point in the Simulink Control Design User's Guide.

Selecting Closed-Loop Responses to Design

Creating a SISO Design Task