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FB41 / PID problem

Created by: Spet59 at: 1/15/2015 9:38 AM (4 Replies)

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1/15/2015 9:38 AM	Rate (0)
Spet59 Posts: 27 Rating: (0)	Hi everybody, I've got a problem with the PID control FB41. Sometime my output value goes to 0 for one cycle... All my input value are OK: SP / PV / Gain / Ti, etc... No COM_RST / MAN_ON value. My controler: 315-2DP FB41 is calling every 1 sec (OB32). Just see attached file. Thanks all!! Attachment PID F7.jpg (215 Downloads)
Spet59 Posts: 27 Rating: (0)	Last edited by: Min_Moderator at: 1/15/2015 11:12 AM Edit attachment name Last edited by: Spet59 at: 1/15/2015 9:40 AM
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1/15/2015 10:46 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	Spet59 Hi everybody, I've got a problem with the PID control FB41. Sometime my output value goes to 0 for one cycle... All my input value are OK: SP / PV / Gain / Ti, etc... No COM_RST / MAN_ON value. My controler: 315-2DP FB41 is calling every 1 sec (OB32). Just see attached file. Thanks all!! Please upload your project here, specifically the part regarded PID controller, I guess you have a parameterization problem.
	Demo Channel on Youtube
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1/15/2015 11:25 AM	Rate (0)
Spet59 Posts: 27 Rating: (0)	Hello, thanks for reply! You can find the OB32's code. The problem is with the first PID controller (with DB59) Thanks! Attachment F:\ob32.zip (264 Downloads)
Spet59 Posts: 27 Rating: (0)
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1/15/2015 11:52 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	Spet59 Hello, thanks for reply! You can find the OB32's code. The problem is with the first PID controller (with DB59) Thanks! Your provided information doesn't help at all for a solid suggestion .Please , do the following checks if you can: If you have one of those logic analyzers , check DB59.DBX0.0 and DB59.DBX0.1 for any positive edge.Also check if internal registers DB59.DBD72 reahes 0.0.In your case, Set value, control value and process are handled with temp variables or other global data and I want to sure that this an internal behavior of FB41 or sth from outside linking logics. If you don't have a software to test, in OB1 use 3 spare counters and monitor 2 first binary values for positive edge .For the real value , use a comparator before counter. Next time , please share a S7-program of OB32,PID instant DB and the global DB that used for links.
	Demo Channel on Youtube
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1/16/2015 9:12 AM	Rate (0)
Spet59 Posts: 27 Rating: (0)	Hello, I just find the problem : for one cycle, my input goes to -27648. my equation to read the température is: (6es7331-7kf02) L PEW x T DBx.DBWy (For flexible application) IDT DTR L 10.0 /R T DBx.DBDy (This DBD is used for my PID controller) And so i receive 2764.8 to my PID PV_in. Thanks for your help hdhosseini.
Spet59 Posts: 27 Rating: (0)
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This contribution was helpful to 2 thankful Users hdhosseini Min_Moderator

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