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300 Chapter 6. Function Reference
Keywords: Hertz Boolean. This keyword is mandatory as the function must
know whether the domain is in Hertz or radians/second
(specified by !Hertz) to fit correctly. Note that the Xmath
function freq assumes that the frequency range is specified
in Hertz.
plotweight Boolean, default = 0. This will generate a second plot
showing the weighting function. This can be useful is as-
sessing the quality of a given transfer function fit. If the
variable M is also specified, the weighting function plot
takes priority over the upper bound comparison plot.
fit Integer specifying the routine to be used in fitting the
data. This sets the default routine which may be changed
interactively by the user. The choices are:
fit = 1 Xmath function: tfid
fit = 2 Xmu function: fitsys
The default is fit = 2.
Outputs: Dsys New left D scale system.
Dinvsys New D inverse system (to be multiplied to M on the right).
Description
Fits stable, minimum phase, transfer functions to each block of the D-scale matrix. A
complex cepstrum technique is used to generate the phase response from the provided
magnitude data.
The user may interactively select a fitting order and compare the result with the data. A
choice of fitting routines is provided. If the order is specified in the command line the
function is not interactive.
Example
# The nominal plant is a double integrator.
# A multiplicative perturbation weight reflects
# increased uncertainty at high frequencies