njit-etd2003-081 - New Jersey Institute of Technology

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Make sure the agreement is quite good. Else rerun the
13. Finally, plot the step response of the model. The model comes with an estimate of
its own uncertainty. Ten different step responses are computed and graphed. They
correspond to "possible" models, drawn from the distribution of the true system
(according to our model):
step=ones(30,1);
idsimsd(step,th);
Spectral Analysis
14. The function spa performs spectral analysis according to the procedure in (3.35)-
(3.37) of [42].
[G,PHIV] = spa(z);
15. Here z contains the output-input data as above. G and PHIV are matrices that
contain the estimated frequency function GN and the estimated disturbance spectrum
Фv
in (3.37). They are coded into a special format, the freqfunc format, which allows you
to plot them using the function bodeplot or ffplot:
[G,PHIV] = spa(z);
bodeplot(G);
bodeplot(PHIV);
bodeplot gives logarithmic amplitude and frequency scales (in rad/sec) and linear
phase scale, while ffplot gives linear frequency scales (in Hz). The details of the freqfunc
format are given in [42] and by typing:
help freqfunc;