Specifications

3 Operations on LTI Models
3-6
The following rules apply when modifying LTI models:
•
sys, the LTI model that has had a portion reassigned, retains its original
modeltype (TF, ZPK,SS,orFRD) regardless ofthemodeltype of
NewSubSys.
•Subsystem assignment does not reassign any I/O names or I/O group names
of
NewSubSys that are already assigned to NewSubSys.
•Reassigning parts of a MIMO state-space model generally increases its
order.
•If
NewSubSys is an FRD model, then sys must also be an FRD model.
Furthermore, their frequencies must match.
Other standard matrix subindexing extends to LTI objects as well. For
example,
sys(3,1:2)
extracts the subsystem mapping the first two inputs to the third output.
sys(:,1)
selects the first input and all outputs, and
sys([1 3],:)
extractsa subsystemwith the same inputs, but only the firstandthirdoutputs.
For example, consider the two-input/two-output transfer function
.
To extract the transfer function from the first input to the first output,
type
T(1,1)
Transfer function:
1
-------
s + 0.1
Ts
()
1
s 0.1+
-----------------
0
s 1–
s
2
2s 2++
----------------------------
1
s
---
=
T
11
s
()