Simulink Control Design™ - MathWorks

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.

Desired Response

Use this section of the dialog box to specify the shape of the desired step response.

• First-order characteristics

Specify the desired step response (the reference model Href) as a first-order response

with time constant τ:

Href=

1/τ

s+1/τ

.

Enter the desired value for τ in the Time Constant text box. Specify τ in the time

units of your model.

• Second-order characteristics

Specify the desired step response as a second-order response with time constant τ,

and natural frequency 1/τ.

Enter the desired value for τ in the Time Constant text box. Specify τ in the time

units of your model.

Enter the target overshoot percentage in the Overshoot text box.

The second-order reference system has the form:

Href=

1/τ^2

s^2 +2ζ/τs+1/τ^2

.

The damping constant ζ is related to the overshoot percentage by ζ =

cos(atan2(pi,-log(overshoot/100))).

• Custom reference model

10 Control System Tuning