Jul 9, 2010


 Reference : Applied Optimal Control and Estimation, Prentice-Hall, 1992 

Feedback (Automatic) control

is an engineering discipline. As such, its progress is closely tied to the practical problems that needed to be solved during any phase of human history. The key developments in the history of mankind that affected the progress of feedback control were:
1-The Water Clocks of the Greeks and Arabs.
2-The Industrial Revolution. 
3-Age of Computer and programmable devices

1-The Water Clocks of the Greeks and Arabs.
Motivated by the need for the accurate determination of time, the Greek invented the float regulator around 270 BC for a water clock. This regulator would maintain the water level in a tank at a constant depth, which yielded a constant flow of water through a tube that would fill a second tank at a constant rate. Therefore the level of water in the second tank depended on the time elapsed. This was possible since as the water level dropped, a float would gradually open a valve, which would in turn replenish the reservoir--the simple mechanism that controls our flush toilets today!
Interestingly, not only did the ancient Greeks use the float regulator for accurate timekeeping, but they also used it for the automatic dispensing of wine .Between 800 and 1200 AD, various Arab engineers also designed many systems that relied on the principle of feedback control and introduced the concept of on/off control--a very simple but elegant method of regulation. Unfortunately, their fruitful research largely came to an end when Baghdad fell to the Mongols in 1258.
Eventually, the mechanical clock rendered the water clock and feedback control obsolete in the 14th century. Feedback control would not appear again until the Industrial Revolution.greek-water-clock
Greek water clock

2-The Industrial Revolution.

An industrial revolution occurs when people move from living and working on farms to working in factories and living in cities. This occurred in North American in the late 1800s and early 1900s. During this time, "self-driven" machines such as advanced grain mills, boilers, furnaces, and steam engines were introduced which could not be adequately regulated by hand. This, of course, lead to the introduction of a wide variety of control devices including float regulators, temperature regulators, pressure regulators, and speed control devices .
Industrial Revolution
3-Age of Computer and programmable devices.
with the rise of modern computing, digital control would also be introduced via the theory of sampled data systems. Discrete time systems--those modeled and controlled by computers. Although  the additional complications introduced by digital control, its advantages would be large, especially when the design of modern control systems became possible for any engineer with the introduction of the PC in 1983
Reference : Applied Optimal Control and Estimation, Prentice-Hall, 1992