User`s guide

Identifying State-Space Models
1 In the System Identification Tool GUI, select Estimate > Linear
parametric models to open the Linear Parametric Models dialog box.
2 In the Structure list, select State Space: n [n k].
This action updates the options in the Linear Parametric Models dialog box
to correspond with this model structure. For information about each model
structure, s ee “Wh at Are State-Space Models?” on page 3-73.
3 In the Orders field, specify the model order and delay, as follows:
• For single-input models. Enter the model order integer and the input
delay in terms of the number of samples. Omitting
nk us es the default
value
nk=1.
For example, enter
4 [2] for a fourth-order model a n d nk=2 .
• For multiple-input models. Enter the model order integer and the
input delay vector— w hich is a 1-by-nu vector whose ith entry is the
delay for the ith input.
For example, for a two-input system, enter
4[11]for a fourth-order
model and a delay of 1 for each input.
• For multiple-output models. Enter the model order integer the same
way as for single-input models.
Tip To enter mo de l order and any delays u sing the O rder Editor dialog
box, click Order Editor.
4 Select th e estimatio n Method as N4SID or PEM. For more information
about thes e methods, “A lgorithms for E stimating State-Space Models” on
page 3-101.
5 In the Name field,editthenameofthemodelorkeepthedefault. The
name of the model should be unique in the Model Board.
6 In the Focus list, select how to weigh the relative importance of the fitat
different frequencies. For more information about each option, see “Options
for Frequency-Weighing F ocus” on page 3 -100.
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