closed-loop control

Page numbers are for draft copy at present; they will be replaced with correct numbers when final book is formatted. Chapter numbers are correct and will not change now.

Closed-loop control is a term used in cybernetics and control engineering to describe a system that monitors the impact of its outputs and uses this feedback 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. In contrast open-loop control has no feedback, so has to predict the exact outcome.

Used on Chap. 15: pages 358, 360, 365