The 50+ articles in the controlguru.com table of posts
represent perhaps 40% of a complete textbook.
It is all on-line. There are no pop-ups or in-your-face advertising. And it is all free. I post a new article twice a month and expect the project to continue for a few more years.
I currently have over 4000 unique visitors every month at
I know of faculty from more than a dozen institutions who are migrating bit-by-bit from my textbook (currently used in 125 schools) to this online resource because of its practical orientation. I conclude from this that there is benefit from my efforts.
With that said, I acknowledge that electrical engineers, mechanical engineers and chemical engineers all approach control from a different perspective for valid reasons.
site has a chemical/process orientation. The primary focus is on PID control and related architectures. Applications of interest include processes with streams comprised of gases, liquids, powders, slurries and melts. Final control elements for these applications tend to be valves, variable speed pumps and compressors, and cooling and heating elements. Industries that operate such processes include chemical, bio-pharma, oil and gas, paints and coatings, food and beverages, cement and coal, polymers and plastics, metals and materials, pulp and paper, and consumer and personal care products.
The control system at one of these plants may have from 20 to over 250 PID loops and from 50 to over 1000 measurements. Often, the controls people have a different supervision structure from the production staff trying to meet schedule. A control person seeking to tune a loop 'might' receive permission to make a couple of bump tests. On the other hand, they may be told to take a hike and be forced to dig out what they can from the data historian.
They are almost never given permission to conduct extensive testing. It is simply too expensive and sometimes even dangerous. A couple of bump tests can take much of a shift in many plants, and they are using expensive feedstock and consuming utilities the whole time. For one loop.
The PID controllers in these production facilities tend to be a horrifying mix from several of the roughly 20 major manufacturers. Each manufacturer uses different terminology and formulates the PID algorithm in its own fashion. Tuning these controllers is a challenge too often addressed with trial-and-error fiddling by the operators, technicians and engineers at these facilities.
works to address the needs of these individuals.
Most all processes comprised of gases, liquids and such are overdamped and self regulating. The time constants have units expressed not in milliseconds or rarely even seconds, but most often in minutes (and sometimes hours). Dead time, measurement noise, and nonlinear behavior are always complicating issues. If underdamped behavior shows up in a trend plot, it likely means that an upstream controller is cycling and needs to be checked out. It is almost never the characteristic behavior of the process itself.
No loop in these plants is truly first order plus dead time (FOPDT). Not a single one. In fact, if modeled from first-principles including the thermo, transport and kinetic equations, we would likely find such processes to be accurately described with tenth or even twentieth order differential equations.
But in my experience, 85%+ of PID loops when the application is a process with streams comprised of gases, liquids and such can be well-tuned using the FOPDT approximation. If we introduce non self regulating overdamped processes (also discussed on
we are up to maybe 90%
If readers start at the top of the table of posts
they will find, presented in a logical order and free of any charge, the details, methods and practices I believe provide the best general methods for the application domain I am focused upon.
I hope readers will visit and judge its value as a resource for themselves.
And I know my posts on this newsgroup announcing the publication of the next installment of the e-book are valued by some of the readership. So it is a practice I intend to continue.