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How did James Watt’s flying-ball governor control the speed of a steam engine?

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Jacquard loom engraving, 1874 — automation At the top of the machine is a stack of punched cards that would be fed into the loom to control the weaving pattern. This method of automatically issuing machine instructions was employed by computers well into the 20th century.

James Watt’s flying-ball governor controlled the speed of a steam engine by utilizing centrifugal force as a mechanism for negative feedback.

The device consisted of weighted balls attached to hinged arms, which were mechanically coupled to the engine's output shaft. As the engine's rotational speed increased, centrifugal force caused the balls to move outward. This outward motion was transmitted to a valve that reduced the supply of steam being fed to the engine, thereby slowing it down. Conversely, if the engine's speed decreased, the balls moved inward, allowing more steam to enter and increasing the engine's speed.

By automatically adjusting the steam flow based on the engine's output, the governor eliminated the need for constant human intervention to regulate speed and power, serving as an elegant early example of an automatic control system.12