Simulink Control Design™ - MathWorks

Estimate Frequency Response Using Linear Analysis Tool

This example shows how to estimate the frequency response of a portion of a Simulink

model using the Linear Analysis Tool. To estimate the frequency response, you specify the

portion of the model you want to estimate, the operating point for estimation, and the

input signal to use for estimation.

Open Simulink Model and Linear Analysis Tool

Open the Simulink model.

sys = 'scdDCMotor';

open_system(sys)

In the Simulink Editor, select Analysis > Control Design > Linear Analysis. The Linear

Analysis Tool opens.

Specify Portion of Model to Estimate

By default, Linear Analysis Tool uses the linearization analysis points defined in the model

(the model I/Os) to determine where to inject the test signal and where to measure the

frequency response. The model scdDCMotor contains predefined linear analysis points:

an input point at the compensator output, and an open-loop output after the unit gain

block. For this example, use these predefined model I/Os to obtain the frequency response

of the inner loop of the model with the outer loop open.

If you want to obtain the frequency response of a different portion of the model, in the

Estimation tab of Linear Analysis Tool, use the Analysis I/Os drop-down list. (Analysis

points for estimation work the same way as analysis points for linearization. For more

information about linear analysis points, see “Specify Portion of Model to Linearize” on

page 2-13.)

Estimate Frequency Response Using Linear Analysis Tool