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Redheffer star product (linear fractional transformation) of two LTI models
Syntax
sys = lft(sys1,sys2) sys = lft(sys1,sys2,nu,ny)
Description
lft
sys = lft(sys1,sys2,nu,ny)
sys of the two LTI models (or LTI arrays) sys1 and sys2. The star product amounts to the following feedback connection for single LTI models (or for each model in an LTI array).
nu outputs of sys2 to the last nu inputs of sys1 (signals 
), and the last ny outputs of sys1 to the first ny inputs of sys2 (signals 
). The resulting system sys maps the input vector 
to the output vector 
.
The abbreviated syntax
sys = lft(sys1,sys2)produces:
sys1 and sys2 if sys2 has fewer inputs and outputs than sys1. This amounts to deleting 
and 
in the above diagram.
sys1 and sys2 if sys1 has fewer inputs and outputs than sys2. This amounts to deleting 
and 
in the above diagram.
Algorithm
The closed-loop model is derived by elementary state-space manipulations.Limitations
There should be no algebraic loop in the feedback connection.See Also
connect feedback