STEP 7 Additional Software
Adjust PI parameter in PLC S7-313C
Thread Starter: Boong Started: 2/16/2009 7:47 AM Replies: 6
2/16/2009, 7:47 AM
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Dear All
In PLC S7-313C I have uses funtion PID (FB41) to control for Spooler, I have problem to adjust parametter PI ( at now I put Gain = 0.08 ; TI= 510 ms)
- When spooler have reel empty to middle product (I use reel to roll the cable) Spooler is balancy but When spooler have reel full, spooler is stabilize.
What should I adjust.
TKS.
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2/16/2009, 8:09 AM
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Hello Try in this way: Set the desired setpoint and, in the manual mode, reduce the control error to zero.
Switch over to the automatic mode.
Slowly increase Gain to a value at which the control loops starts oscillating as a response to small
setpoints changes.
Slightly reduces Gain until the oscillations have disappeared.
Reduce Ti until the oscillating response sets in again.
Now slightly increase the value to Ti until finally the oscillations have disappeared. Also use this FAQ: What should you watch out for when calling and assigning parameters to the controller functions in function blocks (S)FB41, (S)FB42 and (S)FB43? Hope this will help you. regards
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2/17/2009, 8:18 AM
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Dear UMENCHO,
Tks your help, I will try to do follow your help.
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2/17/2009, 10:16 AM
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Dear All
In PLC S7-313C I have uses funtion PID (FB41) to control for Spooler, I have problem to adjust parametter PI ( at now I put Gain = 0.08 ; TI= 510 ms)
- When spooler have reel empty to middle product (I use reel to roll the cable) Spooler is balancy but When spooler have reel full, spooler is stabilize.
What should I adjust.
TKS.
Hello binh;
One word of caution: a winder/unwinder is a non-linear application.
By that I mean that the physics of the process are not linear within the range of the control you wish to establish. Mass varies with the roll diameter (which changes during the process, obviously), acceleration ans decelleration curves have to be taken into account at the beginning and end of ther applicsation and the model of the process you are trying to adapt to also changes as the application evolves. The control parameters will be different if you decide to control on different variables, such as line speed, inertia, tension, torque... Look at the information available on the web, such as here,
So the gain values you select for different points of your winder in your process evolution might not be adequate for other sets of points. Adjustment of the parameters for the middle of the roll only could lead to instability (oscillations) at another point.
You might have to select different gains tested for different points and load them into your PID loop as your process evolves. It is not a perfect solution, and requires a lot of testing and adjustments, and does need adjustment if any of the physical parameters of the process change, but we have done something like this on an old wire winder (tension control and web break were not a great issue).
If you need something more precise and robust for controls, you could use the onboard PID controls of your drive, as proposed by Siemens in the following application note:
http://support.automation.siemens.com/WW/view/en/22095333
Hope this helps,
Daniel Chartier
=== Edited by O_Moderator @ 9/16/2010 2:59 PM [GMT ] ===
link edited
=== Edited by dchartier @ 2/17/2009 10:50 AM [GMT ] ===
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2/19/2009, 4:55 AM
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Dear Daniel,
Tks your guide,
I follow UMENCHO's guides, but can not.
My system use Drive Simoreg 6RA70 (DC motor), i can use onboard PID funtion of the Drive,
If can, how can i do,
Best regard.
Binh
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2/19/2009, 5:29 AM
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Hello bihn;
I have found the following application note for a 6RA70 as a Center Winder, on Siemens' support pages (see the profduct Support link at the top of this page):
http://support.automation.siemens.com/WW/view/en/9716319
I am not very familiar with the Simoreg 6RA70, unfortunately, so I will not be able to help you with the details of the application. But the manual seems to discuss using the internal PID control of the drive to optimize the winder control, based on speed, tension and torque, which should give you a good balance in your design.
I hope your study of this document will give you more insight on this type of application. If you have specific details required on the parameters or communictaions of the Simoreg, come back to the forum, where other specialists may have your answers. Also please look at the support link at the top of the page to look for more manuals ansd application notes on the drive.
Hope this helps,
Daniel Chartier
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2/20/2009, 7:00 AM
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