Simulink Control Design™ - MathWorks

• Compute input/output gain with the following loops open

Select one or more signal locations in your model at which to open a feedback loop for

the purpose of evaluating this tuning goal. The tuning goal is evaluated against the

open-loop configuration created by opening feedback loops at the locations you

identify. For example, to evaluate the tuning goal with an opening at a location named

'x', click Add signal to list and select 'x'.

TipTo highlight any selected signal in the Simulink model, click. To remove a signal

from the input or output list, click. When you have selected multiple signals, you can

reorder them using and. For more information on how to specify signal locations
for a tuning goal, see “Specify Goals for Interactive Tuning” on page 10-39.

Options

Use this section of the dialog box to specify additional characteristics of the gain goal.

• Limit gain to

Enter the maximum gain in the text box. You can specify a scalar value or a frequency-

dependent gain profile. To specify a frequency-dependent gain profile, enter a SISO

numeric LTI model. For example, you can specify a smooth transfer function (tf, zpk,

or ss model). Alternatively, you can sketch a piecewise maximum gain using an frd

model. When you do so, the software automatically maps the profile to a smooth

transfer function that approximates the desired minimum disturbance rejection. For

example, to specify a gain profile that rolls off at –40dB/decade in the frequency band

from 8 to 800 rad/s, enter frd([0.8 8 800],[10 1 1e-4]).

You must specify a SISO transfer function. If you specify multiple input signals or

output signals, the gain profile applies to all I/O pairs between these signals.

If you are tuning in discrete time, you can specify the maximum gain profile as a

discrete-time model with the same sampling time as you use for tuning. If you specify

the gain profile in continuous time, the tuning software discretizes it. Specifying the

gain profile in discrete time gives you more control over the gain profile near the

Nyquist frequency.

Gain Goal