Tuning Controllers

Sorry, I don't know them. Don't know who you're talking about.

About the available methods for tuning control loops, yeah, they're all used, depending on the controller and the process. Some are self tuned, some are not. I am currently in charge of tuning one with a "Ze-Ni" like procedure, but with different approach.

Do a google search for it, you'll notice that there's a world of choices. I may even risk myself to say that most of all are based on try and error - and work.

Hi there,

There is no simple answer to your question. Why do I say this? Firstly you need to know the type of controller you are working with. Is it a series, ideal, parrallel type of algorythm? You also need to look at whether you have all three terms, or only one? Then you need to look at the type of loop - integrating or self regulating? You would also need to know the process dynamic. And to top it all off - some control is just not possible to make work.

Now while all this sounds like a mouthfull - there are methods to get you into the ballpark. I have found a very good package that works 99% of the time - protuner. But I must stress that you need to know and understand the controller type that you are working with.

You also need to make sure that your measuring and regulatory equipment is 100% in working order - if you cannot measure it you cannot control it. If your control equipment has problems - no amount of PID in the world will fix it for you.

ZN type tuning is not possible under most cases as you cannot afford to put your process into a huge swing.

You will also need to understand whether your controller works with proportional or gain, etc etc etc.

As stated above, I recomend you look at the protuner package. You also need to understand that loop tuning should be a continous process. You need to retune your loops at least twice a year.

In my experience I have found that many people are not very experienced at loop tuning. They seem to find it some dark, arcane science and are very scared of it. I believe that this is because it is not taught with enough practical exposure and people battle to apply the theory.

There is no rule of thumb I can give you for tuning your controllers without knowing the controller algorythm and your process dynamics.

You will also need to know that you are scanning your controller at a regular fixed interval and not a free scan as you need this fixed scan time for the controller to do the integration. Another huge problem is filters - you might actually be filtering out the process and not noise.

This is just a brief response, but loop tuning is not a simple thing. I suggest you look at the following website for some additional reading to put you on the right path. www.controlloop.co.za

Good luck and I hope you come right

Regards

Craig