The Operation in FRD systems #611

Something like L = inv(S)-1 in matlab, which S is the FRD system. I try to use the inv function in np.linalg (np.linalg.inv(S) in python), but it doesn't work.

The inv function is not implemented. If you are trying to doing block diagram algebra, it is better to just use feedback. For example: S = ct.feedback(Id, P * C) where Id is a system implementing the identity I/O system in the appropriate dimensions. (You have to create the Id function manually since nobody has implemented broadcasting of constants yet.)

May I ask what p and c （in S = ct.feedback(Id, P * C)） stand for?

Process and controller transfer function. Here's is a working example using FRDs:

import control as ct
import numpy as np

omega = np.logspace(-1, 1, 10)
P = ct.frd(ct.rss(3, 2, 2), omega)
C = ct.frd(ct.rss(2, 2, 2), omega)
Id = ct.frd(ct.ss([], [], [], np.eye(2)), omega)
S = ct.feedback(Id, P * C)