Nowadays we are familiar with feedback as the principle which enables a
designer to endow an automatic control system of some kind with a capacity for
self-correction. As the entry on Feedback in the Automation section of Funk & Wagnalls
Multimedia Encyclopedia puts it:
| "The feedback principle has been used for centuries.
An outstanding early example is the flyball governor, invented in 1788 by the British
engineer James Watt to control the speed of the steam engine. In this device a pair of
weighted balls is suspended from arms attached to a spindle, which is connected by gears
to the output shaft of the engine. At the top of the spindle the arms are linked by a
lever with a valve that regulates the steam input. As the engine speeds up beyond the
desired rate, causing the spindle to rotate faster, the flyballs are driven upward by
centrifugal force. The action of the flyballs partly closes the input valve, reducing the
amount of steam delivered to the engine." |
The following links lead to discussions of feedback,
including James Watt's flyball governor, in a historical context.
Funk
& Wagnalls Multimedia Encyclopedia |
John H. Lienhard "Engines of Our
Ingenuity" |
From Conventional to Intelligent Control
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