Disturbing Error

[from Gary Cziko 921294.2100 GMT]

Rick Marken (921204.1030) said:

if you add a disturbance to the error
signal it will not be resisted: it acts like an offset to the reference for
the controlled perception (I think I posted the algebra for this some
time ago)

I don't remember seeing the algebra, and this does not make sense to me.
If error = reference signal - perception, a good control system will keep
error near zero. If I add in a disturbance to the error so that, e.g.,
error = reference signal - perception + 5, then error will still be kept
near zero. The system will do what it has to do to get rid of the effect
of the +5. How is this not controlling error?--Gary

ยทยทยท

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[From Rick Marken (921204.1530)]

Am I a busy little netter today or what?

Gary Cziko (921294.2100 GMT) --

I don't remember seeing the algebra, and this does not make sense to me.
If error = reference signal - perception, a good control system will keep
error near zero. If I add in a disturbance to the error so that, e.g.,
error = reference signal - perception + 5, then error will still be kept
near zero. The system will do what it has to do to get rid of the effect
of the +5. How is this not controlling error?--Gary

Ah, the problem of time lags. You should have the algebraic solution
before you get this.

Actually, your intuition is based on VERY GOOD circular control
system reasoning. So this result (about the effect of directly disturbing
the error signal) is kind of counter-intuitive to your well - developed
counter-intuitive PCT intuition. Will the circle be unbroken??

Love ya

Rick