Applied Embedded Electronics

Chapter 10. Digital Feedback Control

Digital feedback control is used in a plethora of devices. The device under control (DUC) can be a motor, temperature, servo actuator, system pressure, flow rate, and many others. Many control textbooks will use the term process or plant instead of DUC due to the historical use of control systems by industrial processes and manufacturing plants.

Before diving into this chapter, readers should be familiar with Chapters 7, 8, and 9, as that material will be utilized here.

Control system textbooks usually take an approach that is heavily mathematical with well-defined system models. Many have found problems with this approach in application:

…the mathematics of control involves such a bewildering assortment of exponential and trigonometric functions that the average engineer cannot afford the time necessary to plow through them to a solution of his current problem. (Ziegler & Nichols, 1942)

A minimal math approach is desirable for expediency and ease of design. Also, a “mostly digital” control system is highly preferred over analog methods due to cost, consistency of performance, and ease of adjustment. However, a DUC has analog behavior that’s being controlled. Consequently, a control system design needs to deal with those analog behavior issues. Because of that, the approach used here can best be described as digital emulation of an analog system.

With this “analog functionality in a digital box” approach, some select topics from control theory ...