Applied Process Control

1Introduction

1.1 The Idea of Control

Plant and animal life relies on numerous control mechanisms. Here one thinks of an ‘open-loop’ causal system in which cause (input) generates effect (output). Then the ‘control’ part operates around this in order to modify the effect (Figure 1.1).

Figure 1.1 Feedback control mechanism.

All autonomous entities need ‘feedback’ paths like this. One might shut a door to reduce the noise level, eat to reduce hunger or turn the car steering wheel to keep in a lane. The control decision can be discrete, such as when the geyser thermostat switches on or the reserve bank adjusts the prime lending rate in order ...