[From Rick Marken (2007.01.14.0950)]

Bjorn Simonsen (2007.01.13,23:45 EUST)--

If there is no reference value, I think it is zero (very near). Then the error becomes negative and that doesnï¿½t work. Therefore the error is zero (very near).

Yes. This is a way to take out a one way control system.

I think that if the error is very near (not exact) zero there need not be any action and feedback effect. But I canï¿½t explain how there is an action and feedback effect if the error is zero (exact zero).

I was thinking of a situation where the output was a continuous change (like a slow increase) when the error is zero.

You didnï¿½t answer if we can use the negative feedback loop model if we donï¿½t control a perception. I think we can and we should, but I may be wrong.

Yes, the PCT model can certainly include uncontrolled perceptions.

Best

Rick