TABLE OF CONTENTS As a result of studying this chapter, and after having completed the relevant exercises, the student should be able to:
Identify and describe the mathematical form of the most important building blocks used in industrial control
Describe the principles applied in computer-based digital controllers
Indicate what a real time program is.
In order to best understand the control algorithms used in industrial control, it is appropriate to look at the building blocks first.
When selecting the type of control system required one must examine the alternatives that exist between digital and analog systems. Digital systems are compatible with computers, distributed control systems, programmable controllers and digital controllers.
Quantities or representations that are variable over a continuous range. These variables can take an infinite number of values, while the digital representation of these same variables are limited to defined states or values. Analog systems are more accurate in their representations of a value but at a cost, induced or additive noise and difficulty in accurate transmission being two of the major problems associated with this type of system.
This is a term used to define a quantity with discrete levels rather than over a continuous range.
Digital control loops differ from continuous control loops, their analog cousins, in that a continuous controller is replaced by a sampler. This is some form of a computer performing discrete control...
