Simulink Control Design™ - MathWorks

Disturbance Rejection Goal

Purpose

Attenuate disturbances at particular locations and in particular frequency bands, when

using Control System Tuner.

Description

Disturbance Rejection Goal specifies the minimum attenuation of a disturbance injected

at a specified location in a control system.

When you use this tuning goal, the software attempts to tune the system so that the

attenuation of a disturbance at the specified location exceeds the minimum attenuation

factor you specify. This attenuation factor is the ratio between the open- and closed-loop

sensitivities to the disturbance, and is a function of frequency.

The following diagram illustrates how the attenuation factor is calculated. Suppose you

specify a location in your control system, y, which is the output of a block A. In that case,

the software calculates the closed-loop sensitivity at out to a signal injected at in. The

software also calculates the sensitivity with the control loop opened at the location z.

y z

A

To specify a Disturbance Rejection Goal, you specify one or more locations at which to

attenuate disturbance. You also provide the frequency-dependent minimum attenuation

factor as a numeric LTI model. You can achieve disturbance attenuation only inside the

control bandwidth. The loop gain must be larger than one for the disturbance to be

attenuated (attenuation factor > 1).

10 Control System Tuning