Introduction

Abstract

A lunar lander approaches the moon and settles gently onto that dusty surface. A giant commercial aircraft crossing the Atlantic in a storm is blown off course and is smoothly brought back by the plane’s automatic pilot. The temperature in a Chicago town house drops on a cold winter night but is quickly and quietly restored as the furnace clicks on. All of these are examples of feedback control systems. The radar on the lunar lander feeds back the distance to the moon’s surface and the blast of the rockets is adjusted. The navigational equipment feeds back latitude and longitude to the automatic pilot on the plane and the course is corrected. The thermostat records a drop in temperature and the furnace is turned on.