Some control loops cannot be improved by tuning. In fact, you might even make matters worse by tuning them. This white paper discusses four types of PID control loops that you absolutely should NOT tune. Download the white paper to discover how you can save time and get better results by NOT tuning.
We can tune PID controllers, but what about tuning the operator?
The purpose of tuning loops is to reduce errors and thus provide more efficient operation that returns quickly to steady-state efficiency after upsets, errors or changes in load. State-of-the-art manufacturers in process and discrete industries have invested in advanced control software, manufacturing execution software and modeling software to "tune" everything from control loops to supply chains, thus driving higher quality and productivity.
The "forgotten loop" has been the operator, who is typically trained to "average" parameters to run adequately under most steady-state conditions. "Advanced tuning" of the operator could yield even better outputs, with higher quality, fewer errors and a wider response to fluctuating operating conditions. This paper explores the issue of improving operator actions, and a method for doing so.
Over the past decade we've spent, as an industry, billions of dollars and millions of man-hours automating our factories and plants. The solutions have included adding sensors, networks and software that can measure, analyze and either act or recommend action to help production get to "Six Sigma" efficiency. However, few, if any, plants are totally automated. Despite a continuing effort to remove personnel costs and drive repeatability through automation, all plants and factories have human operators. These important human assets are responsible for monitoring the control systems, either to act on system recommendations, or override automated actions if circumstances warrant.
Most of the time, operators let the system do what it was designed and programmed to do. Sometimes, operators make errors of commission, with causes ranging from misinterpretation of data to poor training or errors of omission attributed to lack of attention or speedy response. An operator's job has often been described as hours of boredom interrupted by moments of sheer panic. What the operator does during panic situations often depends on how well he or she has been trained, or "tuned."
Controller tuning can be accomplished quickly and accurately using proven techniques. While many engineers and technicians resort to "tune by feel," most will admit that this approach yields inconsistent results. While some might claim that controller tuning is "part art, part science," use of these best practices can ensure that it is 98% science.
Proportional integral derivative (PID) control is the most commonly used control algorithm in the industry today. PID controller popularity can be attributed to the controllers effectiveness in a wide range of operating conditions, its functional simplicity and the ease with which engineers can implement it using current computer technology. This paper covers some of the PID drawbacks and how to resolve them while improving performance in current implementations through changes in the algorithm.
PID Loop Tuning Tips Pocket Guide has been expanded. Now it includes both open and closed loop tuning procedures, in addition to the original reference material of the first version. This eight-page publication was created to give engineers a short easy-to-use guide to tuning PID loops, and it includes a reference section that summarizes many of the more common controllers available.
PID Control (proportional-integral-derivative) is by far the widest type of automatic control used in industry. Even though it has a relatively simple algorithm/structure, there are many subtle variations in how it is applied in industry. This has probably resulted in confusion for plant engineers and operators, who are happy to leave control loops in a sub-optimal configuration.
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