TABLE OF CONTENTS Marc Thompson
| Note | Dr. Marc Thompson leads us to an appreciation of how the world has learned about FEEDBACK (negative) over the years, so we can understand how to do better feedback in our systems. /rap |
A feedback system is one that compares its output to a desired input and takes corrective action to force the output to follow the input. Arguably, the beginnings of automatic feedback control [1] can be traced back to the work of James Watt in the 1700s. Watt did lots of work on steam engines, and he adapted [2] a centrifugal governor to automatically control the speed of a steam engine. The governor comprised two rotating metal balls that would "fly-out" due to centrifugal force. The amount of "fly-out" was then used to regulate the speed of the steam engine by adjusting a throttle. This was an example of proportional control.
The steam engines of Watt's day worked well with the governor, but as steam engines became larger and better engineered, it was found that there could be stability problems in the engine speed. One of the problems was hunting, or an engine speed that would surge and decrease, apparently hunting for a stable operating point. This phenomenon was not well understood until the latter part of the 19th century, when James Maxwell [3] (yes, the same Maxwell famous for all those equations) developed the mathematics of the stability of the Watt...
