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PID library

Created by: Ton Verra at: 4/23/2008 3:22 PM (9 Replies)

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4/23/2008 3:22 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 11/7/2024 Posts: 728 Rating: (43)	Hi everybody, I was just wondering a bit. I'm using various PID regulators in my programs. Some programs also contain Cascade PID regulators. Now I sometimes see people talking about some PID libraries. I wonder if this could be a advantage for me. Like a self setting PID regulator. Any people have used these and what are your thoughts?! Thank in advance! Ton

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4/23/2008 9:13 PM	Rate (1)
Late Platinum Member Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating: (318)	Ton Verra I'm using various PID regulators in my programs. Some programs also contain Cascade PID regulators. Now I sometimes see people talking about some PID libraries. I wonder if this could be a advantage for me. Like a self setting PID regulator. Dear Ton, There are several controllers that have their own special options. So there are standard controllers, standrad controllers wioth some more functions, modulair controllers where you can built your own controllers (modulair) and fuzzy controllers that are adapting themself. Of course it is depending which controllers you choose to do the job. Also the PID Selftuner could be used to make it easier to make your controllers faster. So normally I am charmed from the modulair controllers, there you can built your own controller from scratch. But when you diidn't need that then you could also use the standard controllers that are delivered with STEP7 (FB41/FB42).
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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4/23/2008 9:40 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 11/7/2024 Posts: 728 Rating: (43)	Hi! Thanks for the swift answer, as always . For now I am using the two regulators you mentioned. Mainly to regulate pressure in steam boilers, or temperature in warm/hot water boilers. Depending on the boiler its a two step burner, or burner with continious regulation or step regulation. In adition we use regulators to control the level, conductivty, etc. of the boiler. Setting the parameters of the regulator is always a difficult thing to do, because basicly every single boiler we deliver is different. I was just wondering if any other then the standard regulators would be wise for me to use. I wonder if there are any users here that have some experience with for example the self setting regulator. Or by any chance in the same field of work as i am. Thanks!

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4/24/2008 7:39 AM	Rate (1)
Aret Posts: 2348 Rating: (264)	I've used PID SeflTuner for standart PID control, but i wasn't satisfied with results. Since that moment i choose PID parameters so - i let PID SelfTuner to get parameters, but i use only Gain. Usually it can be increased to getsteadierreaction,ordecreasedtomakeI,Dparamterschoiceeasier (on temperature regulators usually). After that deadband can be tuned properly. Choosing I component is usually dependsondemandedregulationcurve(with/withoutoverregulation,with/withoutfadingoscillationandsoon). Used D-component only 1 time to get rid of oscillations - so i guess in 90%systemsit'sobsessive. Good luck in tunung^)
Aret Posts: 2348 Rating: (264)
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4/24/2008 9:43 AM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 11/7/2024 Posts: 728 Rating: (43)	Hi Aret, Thanks for your answer. I am open to more experiences!

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4/26/2008 1:01 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 11/7/2024 Posts: 728 Rating: (43)	No more people got some experience they want to share?

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4/27/2008 12:19 AM	Rate (1)
Krish Silver Member Joined: 5/24/2007 Last visit: 4/24/2024 Posts: 284 Rating: (27)	Fundamentally the PID function is the same if the basic principles are maintained. The perfromance difference comes more from the impementation and the understanding.For implementation the user has to know how the function should be implmented if it is fast reacting system put inn a fast loop and some temperature control sort of stuff in slower cycle. Forproperunderstanding it is important to knowthe algorithm and what the parameters which are given for tuning. Though everybody talks about gain..you can see there subtle differencesaboutwhat the parameters refer to in each implementation. So unless you get the feel of this it is difficult to tune. Considering this I see no reason why somebody has to go for another PID solution other than the standard blocks. Sometimes some application do needsome special implementationand some modification are made to it. But essentially thismeans that they are no longer PID controllers. So my opinion would be use the standard controller, understand how it works and impelment accordingly.

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4/27/2008 1:47 PM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 11/7/2024 Posts: 728 Rating: (43)	Thanks Krish, But wouldn't using seperate blocks make me understand the process better?

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4/27/2008 4:59 PM	Rate (1)
Aret Posts: 2348 Rating: (264)	Ton, it's like inventing a bicycle:^) Standart block are good. If i need to add some fuctionality (for example include work time in auto/manual mode, make some messages depending on regulator outputs etc.) i make so - i create my own FB, with standart regulator FB inside (as multiinstance). On the one hand this structure is transparent from functionality side of view, on the other hand it adds any flexibility you want. Does some has PRACTICAL experience with fuzzy regulation? Theory seems attractive, but i've never done it....
Aret Posts: 2348 Rating: (264)
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4/28/2008 8:48 AM	Rate (0)
Ton Verra Gold Member Joined: 4/20/2007 Last visit: 11/7/2024 Posts: 728 Rating: (43)	Hi, Thanks again. I know, the theory is very interesting. But I know it's very though to get through. I'm one year out of school and Control Technology was the subject I had most trouble with. And no, I don't have any experience or knowledge on Fuzzy Control. Based on everything people say up here, I stick with the Standard PID blocks for now. As long as the seem to suit my need . Thanks everybody for answering.

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