PID tuning: It`s the method, not the rules
- Straight-Line Control Co., Newark, DE (United States)
- Applied Control Engineering, Inc., Wilmington, DE (United States)
Many authors have written rules for tuning controllers, providing formulas for PID settings based on the results of perturbing the process. This article is not one of those. Instead, the authors approach the subject from the other direction - focusing on the mechanics of just how you go about perturbing the process to get the numbers to use in the formulas. The basic principle of tuning is to set the time and amount parameters of the controller to fit the time and amount parameters (called dynamics) of the process. Tuning procedures show certain dynamic characteristics of the process. When tuning, it`s generally necessary to upset the process. While sophisticated, computer-based ways to learn process dynamics exist, there are two simple time-honored ways: automatic (closed-loop) and manual (open-loop). The key is to upset the process just enough to get the information you need, without getting into trouble. Before tuning a controller, you should have an idea of how fast and how far the process is going to respond to the controller output. You should know and agree on how much change you will allow in the process and in the controller output. You also should know and agree on who is going to do the actual adjusting of the controller settings, and be assured the person know how to do it. You should know, and agree on who is going to switch between manual, and automatic, and who is going to make set point or output changes. You will also need to understand the safety interlocks and any other safety concerns for the process. Record the existing settings and the controller output, in the event you want to return to them. Make sure changes are communicated to all operating people. If a log book is kept for this purpose, use it. 5 figs.
- OSTI ID:
- 459035
- Journal Information:
- InTech, Vol. 41, Issue 12; Other Information: PBD: Dec 1994
- Country of Publication:
- United States
- Language:
- English
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