[From Rick Marken (2006.04.29.1110)]

Sorry. Made an error due to posting in haste:

Rick Marken (2006.04.29.0840)

If control is measured in terms of stability of the controlled variable (stability measured as the ratio of observed to expected variation in the controlled variable; S = v(O)/v(E)) then the stability of the pendulum is probably something like S = 0.0000000001 whereas the stability of the thermostat is probably something like S = 1000.

Given the above definition of S, there is no control when S = 1.0 (expected and observed variance of the controlled variable are the same) and perfect control when S = 0 (observed variance is much less than expected. So the stability (S) of the pendulum is probably about .9999999999 while the stability of the the thermostat is probably about .00001.

Best

Rick

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