User`s guide

Troubleshooting Models
Inputs need not be control s ignals. Any m easurable signal can be considered
an input, i n cluding measurable disturbances.
Complicated Nonlinearities
If the Model Output plot and Residual Analysis plot shows a poor t, consider
if nonlinear effects are present in the system.
You can model the nonlinearities by performing a simple transformation
onthesignalstomaketheproblemlinearinthenewvariables. For
example, if electrical power is the driving stimulus in a heating process and
temperature is the output, you can f orm a simple product of vo ltage and
current measurements.
If your problem is sufciently complex and you do not have physical insight
into the problem, you might try tting nonlinear black-box models. For more
information, see Chapter 4, “Nonlinear Black-Box Model Identication”.
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