Fit an uncertain model to set of LTI responses

`usys = ucover(Parray,Pnom,ord)`

usys = ucover(Parray,Pnom,ord1,ord2,utype)

[usys,info] = ucover(Parray,...)

[usys_new,info_new] = ucover(Pnom,info,ord1_new,ord2_new)

`usys = ucover(Parray,Pnom,ord)`

returns
an uncertain model `usys`

with nominal value `Pnom`

and
whose range of behaviors includes all responses in the LTI array `Parray`

.
The uncertain model structure is of the form $$usys=Pnom\left(1+W(s)\Delta (s)\right)$$, where

Δ is an

`ultidyn`

object that represents uncertain dynamics with unit peak gain.*W*is a stable, minimum-phase shaping filter that adjusts the amount of uncertainty at each frequency.

`ord`

is the number of states (order) of *W*```
.
Pnom
```

and `Parray`

can be `ss`

, `tf`

, `zpk`

,
or `zpk`

models. `usys`

is of class `ufrd`

when `Pnom`

is
an `frd`

model and is an `uss`

model
otherwise.

`usys = ucover(Parray,Pnom,ord1,ord2,utype)`

specifies the order `ord1`

and `ord2`

of
each diagonal entry of *W*1 and *W*2,
where *W*1 and *W*2 are diagonal,
stable, minimum-phase shaping filters. `utype`

specifies
the uncertain model structure, as described in Uncertain Model Structures,
and can be '`InputMult`

' (default), '`OutputMult`

'
or '`Additive`

'. `ord1`

and `ord2`

can
be:

`[]`

, which implies that the corresponding filter is 1.Scalar, which implies that the corresponding filter is scalar-valued.

Vectors with as many entries as diagonal entries in

*W*1 and*W*2.

`[usys,info] = ucover(Parray,...)`

returns
a structure `info`

that contains optimization information. `info.W1opt`

and` Info.W2opt`

contain
the values of *W*1 and *W*2 computed
on a frequency grid and `info.W1`

and` info.W2`

contain
the fitted shaping filters W1 and W2.

`[usys_new,info_new] = ucover(Pnom,info,ord1_new,ord2_new)`

improves
the fit using initial filter values in `info and`

new
orders `ord1_new`

and `ord2_new`

of *W*1
and *W*2. This syntax speeds up command execution
by reusing previously computed information. Use this syntax when you
are changing filter orders in an iterative workflow.

The `ucover`

command designs the minimum-phase
shaping filters *W*_{1} and *W*_{2} in
two steps:

Computes the optimal values of

*W*_{1}and*W*_{2}on a frequency grid.Fits

*W*_{1}and*W*_{2}values with the dynamic filters of the specified orders using the`fitmagfrd`

command.