Closed-loop control is a term used in cybernetics and control engineering to describe a system that monitors the impact of its outpits and uses this to adjust its behaviour. A simple exmaple is the Centrifugal governor in steam engines. As the engine move faster it spins a mechanism with two heavy balls attached. As they spin they rise up opening.a vavlue that reduce the pressure and hence maintains the speed close to a desired level.
Used on pages 352, 354
Closed-loop control schematic
Centrifugal Governor