Background:
PID (proportional-integral-derivative) control has been around for a long time.
It was in textbooks in the early 1900's. The Routh-Hurwitz stability criterion is from 1895. link Nyquist stability is from the 1930's. link
Question:
What is the oldest example of intentional PID control containing all the components (proportional, integral, and derivative)?
I would not be surprised to find something between 500 and 2500 years old.
More details:
PID control, also called PID, is defined (briefly) as the use of a weighted sum of the measured value (aka proportional), a sum (aka integral), and a difference (aka derivative) of some measured quantity, typically a distance from target, to control a system.
- (P) A tax of 10% of the period-over-period increase could be considered derivative control, because if the period-over-period value acquired is constant then the increase is 0%.
- (PD) If the tax were 1% of current value, and 10% of year-over-year increase, then it would be PD control, because it is taxing the measurement (proportional) and the change (derivative).
- (PID) A tax of 10% on increase, 1% of total, and 1% times the sum of the last 2 years less a target, would be PID, because it would have all three components.
These sorts of things have been used (with varying degrees of success) for automobile cruise-control, guidance of heat-seeking missiles, electric coffee-pots, and control of investment portfolios. Because it is control-systems-engineering it applies to any "system" that meets the applicability criteria, whether electrical, mechanical, thermal, or economic.
Ongoing:
Antikythera mechanism was an extremely elaborate astronomical clock. I'm looking for PID indication there, perhaps in anti-backlash gearing.
An Embry-Riddle paper on the Ancient Control Systems