checkFeedback
Identify possible feedback data
Since R2023a
Syntax
[fbck,fbck0,nudir] = checkFeedback(Data) [___ = checkFeedback(Data,'InputName',inputname,'OutputName',outputname)
Description
Data contains uniformly sampled input/output data in one of the
following forms:
timetablein which the variables contain the input and output data.Comma-separated pair of input/output numeric matrices u,y with dimensions Ns-by-Nu for u and Ns-by-Ny for y. Here, Ns is the number of samples, Nu is the number of inputs, and Ny is the number of outputs.
iddataset with Ny outputs and Nu inputs.
InputName and OutputName — Input and output
channel names. Use these arguments especially when Data is a
timetable that has more variables than you want to use, or when there. Also use
OutputName to identify the output channels when the timetable
data contains more than one output variable. Otherwise, the
software interprets only the last variable as an output channel.
For example, specify the input and output signal variable names using fbck =
checkFeedback(Data,'InputName',["u1","u3"],'OutputName',"y1").
fbck is an Ny-by-Nu matrix
indicating the feedback. The ky,ku entry is a measure of feedback
from output ky to input ku. The value is a
probability P in percent. Its interpretation is that if the
hypothesis that there is no feedback from output ky to input
ku were tested at the level P, it would
have been rejected. An intuitive but technically incorrect way of thinking about this is
to see P as “the probability of feedback.” Often only
values above 90% are taken as indications of feedback. When fbck is
calculated, direct dependence at lag zero between
u(t) and
y(t) is not regarded as a feedback
effect.
fbck0: Same as fbck, but direct dependence at
lag 0 between u(t) and
y(t) is viewed as feedback effect.
nudir: A vector containing those input numbers that appear to have
a direct effect on some outputs, that is, no delay from input to output.
