Introduction to Modeling and Simulation

11Feedback Systems

11.1 Introduction

In this chapter we discuss feedback and control systems [9, 10]. A history of engineering by Frederick Kilgour [45] describes the development of automatic control in the twentieth century as “[one] of the great events of history which totally changed the ways of human life.” Indeed, our present age is the age of automatic control. Factory automation, robots, autonomous vehicles, drones, medical devices, and a host of other products, processes, and applications of sensor‐based feedback control are profoundly changing the ways we live, work, play, and interact.

Feedback is also one of the most fundamental properties in natural systems in addition to engineered systems. In biological systems, feedback is present in regulating many processes, from body temperature, to cell metabolism, gene expression, hormone production, as well as balance and locomotion. In weather and climate dynamics, feedback is an important mechanism affecting global temperatures, weather patterns, ocean currents, and so on.

We recall our definition of a (closed‐loop) feedback system from Chapter 1 as “a system where the input is influenced by the output” (Figure 11.1)

Identifying when feedback occurs in a particular system may not be easy at first glance. For example, a thermostat that measures room temperature and turns the heating, ventilation, and air conditioning system on and off to maintain a constant temperature is an obvious use of feedback. On the other hand, ...