Real World Instrumentation with Python

Chapter 9. Control System Concepts

If everything seems under control, you’re just not going fast enough.

—Mario Andretti

A book on real-world data acquisition and control systems would be incomplete without a discussion of the basics of control systems and the theory behind them. Although this chapter is not intended as a detailed or rigorous treatment of control systems, it will hopefully provide enough of a foundation, if you should need it, to enable you to start assembling usable control systems of your own.

Building on the material presented in Chapter 1, this chapter further explores common control system concepts and introduces additional essential details in the form of slightly more formal definitions. It also provides an introduction to basic control system analysis, and gives some guidelines for choosing an appropriate model.

Our primary focus in this chapter will be on simple control systems based on software and electromechanical components. These types of systems would ideally be constructed from readily available instrumentation and control devices such as DMMs, data acquisition units, motor controller modules, power supplies, and power control modules. You shouldn’t have to design and assemble any circuit boards (unless you really want to, of course), or deal with esoteric devices and interfaces—everything you need should be available in an off-the-shelf form. In fact, it might already be on a shelf somewhere gathering dust.

We’ll start off the chapter with an overview ...