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FB58 Auto Tuning Problem

10/28/2014 3:48 AM	Rate (0)
Edric Experienced Member Joined: 7/17/2011 Last visit: 12/3/2024 Posts: 20 Rating: (0)	Dear All, Now I'm in the commissioning with a heater exchanger using saturated steam as a hot source. It will heat up the water in a tank. I use the FB58 as the PID temperature control, during the auto tuning process, the tuning always stay at the phase 1(according to the manual, this phase 1 only lasts nearly 1 minute, but now it always stays more than 20 minutes even after the PV which at the begining is 50^oC reaches the SP 65 ^oC), guys who have the experience for the auto tuning of this block, it will be a greatly appreciated any hint providing to me. Please see the attached pictures for the parameter setting and the status of the tuning process. Attachment FB58.jpg (468 Downloads)

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10/28/2014 11:20 AM	Rate (0)
eisenpferdreiter Posts: 1058 Rating: (93)	Edric Dear All, Now I'm in the commissioning with a heater exchanger using saturated steam as a hot source. It will heat up the water in a tank. I use the FB58 as the PID temperature control, during the auto tuning process, the tuning always stay at the phase 1(according to the manual, this phase 1 only lasts nearly 1 minute, but now it always stays more than 20 minutes even after the PV which at the begining is 50^oC reaches the SP 65 ^oC), guys who have the experience for the auto tuning of this block, it will be a greatly appreciated any hint providing to me. Please see the attached pictures for the parameter setting and the status of the tuning process. Hello Edric, auto tuning problems have already been discussed here many times. Maybe you find some information here: i am having some problems in tuning the PID for AGC in s7-300 PID auto tune with FB58 TCONT_CP FB58 not auto tuned properly ! FB58 PID auto-tune Auto tune PID of Step 7 I hope it will help you, but there is a lot more. regards
eisenpferdreiter Posts: 1058 Rating: (93)
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10/28/2014 5:05 PM	Rate (0)
Edric Experienced Member Joined: 7/17/2011 Last visit: 12/3/2024 Posts: 20 Rating: (0)	Thank you very much! I check many posted topic, but I find no excectly same questoin about this. Today I try it again, and I set the TUN_ST to 1, but is shows another problem, how it should be the right time to start the trigger of the TUN_ST or I still have some points not noticed. Attachment PID_Phase 2.jpg (290 Downloads)

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10/29/2014 2:46 PM	Rate (0)
Edric Experienced Member Joined: 7/17/2011 Last visit: 12/3/2024 Posts: 20 Rating: (0)	I read the manual of the FB58 again, and find that : Set the parameter TUN_ON = TRUE. This makes FB 58 "TCONT_CP" ready for tuning (Phase 1). The TUN_ON bit must only be set in the steady state or during aperiodic settling to the steady state. If the quasi steady state changes after setting the TUN_ON bit, this must be reset and the new quasi steady state must be signaled to FB 58 "TCONT_CP" by setting the TUN_ON bit again. It means at the phase 1, the SP should equal PV, after that then can make a setpoint step change. Then the TUN_ST=1. My understanding is right? Some one who has such experience can prove this for me. This is my first time use this FB for auto tuning. It annoys me.

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