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FB41 problems

2/15/2012 4:23 PM	Rate (0)
kaspergl Posts: 39 Rating: (1)	Hi I'm using a FB41 PID regulator, but nothing happens.. I have a setpoint of 25 (SP_INT), and a measured value of 0-60 bar (PV_IN), but my output (LMN) stays constant. See screenshot! The PID is in OB35 an is running every 2000ms Is my I value wrong or...?? Attachment PID regulator.JPG (486 Downloads)
kaspergl Posts: 39 Rating: (1)	Last edited by: O_Moderator at: 2/16/2012 11:09 AM subject edited
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2/15/2012 4:46 PM	Rate (0)
Marcjan Platinum Member Joined: 4/22/2010 Last visit: 3/31/2025 Posts: 5697 Rating: (716)	Hello, First thing i noticed, you forgot to enter the Cycle off your FB41, must be the same as your OB 35 cycletime. P-SEL and I_SEL too. Attached OB 35 with FB41, my ob35 cycle is 500ms, dont forget to initialise the PID in ob100 (startup) By putting manual on with value 0 Regards, Marcjan Attachment OB35.pdf (495 Downloads)
	Last edited by: Marcjan at: 2/15/2012 4:56 PM attached OB35 Last edited by: Marcjan at: 2/15/2012 4:48 PM Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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2/15/2012 5:31 PM	Rate (0)
Darius Platinum Member Joined: 9/28/2005 Last visit: 7/24/2025 Posts: 2957 Rating: (243)	Hi, In addition I can say that better is to organize program so that you don't need to initialize it in OB100. What I want to say is that if you don't need to use PID, make special flag and turn on manual mode or even reset PID controller with that flag. If you don't have such flag and initialize FB41 in OB100 then PID regulator will never stop even if its not needed by your algorithm. So better is to have some flag which resets or turns off your regulator.
	Best regards, Darius
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This contribution was helpful to 1 thankful Users Marcjan

2/16/2012 11:29 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 8/31/2025 Posts: 6874 Rating: (1368)	kaspergl Hi I'm using a FC41 PID regulator, but nothing happens.. I have a setpoint of 25 (SP_INT), and a measured value of 0-60 bar (PV_IN), but my output (LMN) stays constant. See screenshot! The PID is in OB35 an is running every 2000ms Is my I value wrong or...?? Dear kaspergl, It is crystal clear that you are running the whole PID Controller algorithm as a pure "P-Controller" LMN=LMNP_section+LMNI_section+LMND_section+DISV If I&D sections disabled and DISV=0 LMN = LMNP_section= GAIN (SP_INT - PV_IN) = 1.0 (25.0 -3.75)=21.25 and it will be constant till the nect error signal change(via setpoint or process value change).See the attachment for more details on FB41 and a STEP response of PID transfer finction. Also check the following clustered threads on "FB41 Sample projects": Standard PID Package - FB41 Samples and finally , check this thread for a special scenario while controllers restarts(Attachment:Nojmp.zip): Pitfalls of PID controllers Best regards, Hamid Hosseini Attachment PURE_P_REG.zip (368 Downloads)
	Demo Channel on Youtube
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This contribution was helpful to 1 thankful Users Marcjan