Simulink Control Design™ - MathWorks

Definitions

Sensitivity Function

The sensitivity function, also referred to simply as sensitivity, measures how sensitive a
signal is to an added disturbance. Sensitivity is a closed-loop measure. Feedback reduces
the sensitivity in the frequency band where the open-loop gain is greater than 1.

To compute the sensitivity at an analysis point, x, the software injects a disturbance
signal, dx, at the point. Then, the software computes the transfer function from dx to x,
which is equal to the sensitivity function at x.

Analysis Point in Simulink

Model

How getSensitivity

Interprets Analysis Point

Sensitivity Function

x dx

x

Transfer function from dx to

x

For example, consider the following model where you compute the sensitivity function at
u:

Here, the software injects a disturbance signal (du) at u. The sensitivity at u, Su, is the
transfer function from du to u. The software calculates Su as follows:

getSensitivity