Linear control analysis and design has been an active subject for some time, perhaps since WW II. Among all techniques and approaches invented, many have become standards in control engineering courses, say, Bode and Nyquist plots, while others may have only aesthetic values. Now humankinds reach an era where digital systems dominate our world. Few people, if any, would want to use an analog PID controller constructed from operational amplifiers. An analog control circuit is inflexible, consumes more space, and its operating point depends on factors like temperature and component aging. A digital controller could overcome such disadvantages, assuming that it is designed and implemented properly.
Crafting a decent digital controller involves many steps with a lot of details. This document is by no means complete. We hope it could serve as a guideline for you, to delve more into this fascinating field by yourself.
Typical steps can be summarized as follows:
- Initial Study: get basic knowledge of the system under control (normally called a “plant”)
- Strategy Select: choose the control scheme. For PID control, you can go to step 6
- Modeling: find a suitable math model for the plant, either from physics or system identification (preferred) , and verify that the model is good enough.
- Analysis & Design: use CAD software tools to get a controller, evaluate stability and performance.
- Simulation: see if the controller satisfies your needs. If not, go back to 4
- Implementation: discretize the controller and program the target system
In this document we discuss only linear control and emphasize on implementation procedure.