# PID loop tuning



## Skeet (Nov 6, 2009)

Yes. A lot. All the time. Pretty much daily in the controls/automation biz.

Go here and search for PID. 

http://www.plctalk.net/qanda/forumdisplay.php?f=2&order=desc


----------



## Wirenuting (Sep 12, 2010)

Here is the quick and easy answer.

http://people.ece.cornell.edu/land/...ects/s2012/fas57_nyp7/Site/pidcontroller.html


----------



## NC Plc (Mar 24, 2014)

Yea I like that site. I picked up "The PID Control Algorithm. How it works, how to tune it, and how to use it" to get me started in this stuff.

I made the mistake of getting the "PI and PID Controller Tuning Rules" blindly, that thing is way over my head so it's gonna sit on the shelf for a long, long time.

The only thing I know about PID is... not much. The only thing I know about 4-20ma stuff is as it pertains to flowmeters and RTDs, so not very much haha. Is PID tuning calculus intensive?


----------



## Wirenuting (Sep 12, 2010)

Wirenuting said:


> Here is the quick and easy answer. http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/s2012/fas57_nyp7/Site/pidcontroller.html


I spent several years programming Siemens apogee controllers for building HVAC. It's not hard once you understand the lingo and do it awhile. No magic like some coworkers tell people..


----------



## Wirenuting (Sep 12, 2010)

NC Plc said:


> Is PID tuning calculus intensive?


No, bending a rolling offset is harder.. 

4-20ma is only an input or output of a controller.


----------



## NC Plc (Mar 24, 2014)

Yea lately I've been doing stuff that involves automating fans, motors, etc based off of field device 4-20ma stuff. I have no PID loop experience but the next thing I am installing with my boss involves a PID loop to control some fans.

Once I get more knowledgeable about PLCs and instrumentation I might start traveling for it. That's a goal for after I have my license at least.


----------



## Wirenuting (Sep 12, 2010)

NC Plc said:


> Yea lately I've been doing stuff that involves automating fans, motors, etc based off of field device 4-20ma stuff. I have no PID loop experience but the next thing I am installing with my boss involves a PID loop to control some fans. Once I get more knowledgeable about PLCs and instrumentation I might start traveling for it. That's a goal for after I have my license at least.


Getting your license first is the smart thing. You can always get your AC universal license later.


----------



## emtnut (Mar 1, 2015)

This is a good diagram to get a feel for what the PID does.
ex: Setpoint might be 5meters level in a tank
Process variable would be 4-20mA to a control valve
If Measured Value is 5meters, the PID does nothing
Based on what your PID values are, you can tune the valve to react quickly to changes in level, or very slowly to get your desired setpoint.
You don't "have" to do any control systems math, just play with the PID paramters (on a test system !!! ):thumbup:


----------



## triden (Jun 13, 2012)

Today. Had a loop to control a water pressure system in a plant and two VFD driven pumps. There are various methods that you can use to coarsely tune a loop, and every process is different. Your cruise control on your vehicle is some sort of control loop...most likely PID, or at least PI.


----------



## Skeet (Nov 6, 2009)

NC Plc said:


> Yea I like that site. I picked up "The PID Control Algorithm. How it works, how to tune it, and how to use it" to get me started in this stuff.
> 
> I made the mistake of getting the "PI and PID Controller Tuning Rules" blindly, that thing is way over my head so it's gonna sit on the shelf for a long, long time.
> 
> The only thing I know about PID is... not much. The only thing I know about 4-20ma stuff is as it pertains to flowmeters and RTDs, so not very much haha. Is PID tuning calculus intensive?


Calculus intensive...well...it CAN be pretty doggone math intensive...but I don't go there much.... Knowing the concept goes a long way.

One simple example is that YOU yourself are a PID loop.... 
Driving down the highway, trying to keep at a steady 60 mph...you take IN speed information and react accordingly by adjusting your OUTPUT on the throttle. All the other fancy shmancy math has to do with how HARD you throttle UP or DOWN, or even if you are riding that dang brake at the same time.... THAT is tuning a PID loop 

I do a ton of 4-20ma and other instrumentation stuff as well. Most, like you, as it concerns flowmeters, etc. When you think of these loops, think of maintaining a certain level of water in a tank, for example. Or mixing two solids together at a certain ration.... Not so dangerously difficult. Hell... I learned, anyone can


----------



## Skeet (Nov 6, 2009)

Google this:
ron beaufort PID plcs.net

Ron is a GREAT guy, a great PLC instructor.... Great videos on the U-Tubes and runs a great PLC Boot Camp in Charleston, SC.

This is not a paid endorsement... LOL


----------



## Widestance_Politics (Jun 2, 2010)

Most recently I had to tune the PID controller for my Kegerator.....


----------



## Skeet (Nov 6, 2009)

:thumbup:


----------



## Jhellwig (Jun 18, 2014)

It depends on what you are tuning on how time intensive it is to set up. A lot of stand all e controllers have auto tune but sometimes you can get it better by tweaking it or giving it a coarse setting to begin with.

I have done a lot of instrumentation and only had to tune a look once and it was an pi only. Pneumatic controller. Didn't even have to do the math.


----------



## NC Plc (Mar 24, 2014)

Are there any simulators to learn PID tuning? My boss could explain it to me 10 times but if I don't get any hands on practice I'll never remember it.


----------



## Jhellwig (Jun 18, 2014)

NC Plc said:


> Are there any simulators to learn PID tuning? My boss could explain it to me 10 times but if I don't get any hands on practice I'll never remember it.


I don't know about now but 7 or 8 years ago the one that I used at a Fisher class was very expensive to buy. It was almost more complicated that tuning a real one due to all the specs you had to come up with for the simulator to resemble something in real life.


----------



## emtnut (Mar 1, 2015)

NC Plc said:


> Are there any simulators to learn PID tuning? My boss could explain it to me 10 times but if I don't get any hands on practice I'll never remember it.


Here's an html one you can play with http://dexautomation.com/ps/


----------



## ScooterMcGavin (Jan 24, 2011)

NC Plc said:


> Are there any simulators to learn PID tuning? My boss could explain it to me 10 times but if I don't get any hands on practice I'll never remember it.



If you have access to a controllogix system I have a level simulation AOI and a self regulating system (flow, pressure, temp) AOI that I could send you that you can feed a PID into and play with it using various settings


----------



## MoscaWD (Apr 22, 2015)

lol like everyone else said, yes a lot of automation uses it. I've tuned a couple thousand loops now, mostly hvac


----------



## NC Plc (Mar 24, 2014)

scameron81 said:


> If you have access to a controllogix system I have a level simulation AOI and a self regulating system (flow, pressure, temp) AOI that I could send you that you can feed a PID into and play with it using various settings


Man I wish I did but all of our AB stuff is in very expensive assets that I am not allowed to touch. :laughing:

They provided me with a few DL06 Plcs with analog modules in them.


----------

