Simulink Control Design™ - MathWorks

• Stabilize closed loop system

By default, the tuning goal imposes a stability requirement on the closed-loop transfer

function from the specified inputs to outputs, in addition to the gain constraint. If

stability is not required or cannot be achieved, select No to remove the stability

requirement. For example, if the gain constraint applies to an unstable open-loop

transfer function, select No.

• Equalize loop interactions

For multi-loop or MIMO loop gain constraints, the feedback channels are automatically

rescaled to equalize the off-diagonal (loop interaction) terms in the open-loop transfer

function. Select Off to disable such scaling and shape the unscaled open-loop

response.

• Apply goal to

Use this option when tuning multiple models at once, such as an array of models

obtained by linearizing a Simulink model at different operating points or block-

parameter values. By default, active tuning goals are enforced for all models. To

enforce a tuning requirement for a subset of models in an array, select Only Models.

Then, enter the array indices of the models for which the goal is enforced. For

example, suppose you want to apply the tuning goal to the second, third, and fourth

models in a model array. To restrict enforcement of the requirement, enter 2:4 in the

Only Models text box.

For more information about tuning for multiple models, see “Robust Tuning

Approaches” (Robust Control Toolbox).

Algorithms

Evaluating Tuning Goals

When you tune a control system, the software converts each tuning goal into a normalized

scalar value f(x). Here, x is the vector of free (tunable) parameters in the control system.

The software then adjusts the parameter values to minimize f(x) or to drive f(x) below 1 if

the tuning goal is a hard constraint.

For Minimum Loop Gain Goal, f(x) is given by:

fx = WSD−^1 SD

∞

.

10 Control System Tuning