A centrifugal governor is a specific type of governor with a feedback system that controls the speed of an engine by regulating the flow of fuel or working fluid, so as to maintain a near-constant speed. It uses the principle of proportional control.
Drawing of a centrifugal "fly-ball" governor. The balls swing out as speed increases, which closes the valve, until a balance is achieved between demand and the proportional gain of the linkage and valve.
Centrifugal governors were invented by Christiaan Huygens and used to regulate the distance and pressure between millstones in windmills in the 17th century.[1][2] In 1788, James Watt adapted one to control his steam engine where it regulates the admission of steam into the cylinder(s),[3] a development that proved so important he is sometimes called the inventor. Centrifugal governors' widest use was on steam engines during the Steam Age in the 19th century. They are also found on stationary internal combustion engines and variously fueled turbines, and in some modern striking clocks.
A simple governor does not maintain an exact speed but a speed range, since under increasing load the governor opens the throttle as the speed (RPM) decreases.
