MATLAB CONTROL SYSTEM TOOLBOX 9 Guide de l'utilisateur télécharger pdf (Page 77)

100

101

LTI Properties

2-33

Direct Property Referencing

An alternative way t o q uery /mo d ify pro p ert y values is by s tructure- lik e

referencing. Recall t h at LTI ob jec ts are ba si c MAT L A B s tructure s ex cep t for

the additional f lag that marks them as TF, ZPK , S S, or F RD obj ects ( se e page

2-3). The field names for LTI objects are the property names, so you can

retrieve or modify property values with the structure-like syntax.

PropertyValue = sys.PropertyName% gets property value

sys.PropertyName = PropertyValue% sets property value

These commands are respectively equivalent to

PropertyValue = get(sys,'PropertyName')

set(sys,'PropertyName',PropertyValue)

For example, type

sys = ss(1,2,3,4,'InputName','u');

sys.a

and you get the value of the property “a” for the state- space mod el sys.

ans =

Similarly,

sys.a = –1;

resets the state transition matrix for sys to –1. S ee “LTI Arrays of SS Models

with Differing Numbers o f States” on page 4-23 for information on setting the

properties of LTI arrays of state-space models w ith differentnumbers of states

in each model.

Unlike standard MATLAB structures, you do not need to type the entire field

name or use upper-case characters. You only need to type the minimum

number of characters sufficient to identify the property name uniquely. Thus

either of the commands

sys.InputName

sys.inputn

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