Hello guys,
First of all I am sorry if my question is something very basic and I'm just wasting your time, but I tried to solve the issue and until now I got no positive results. I am trying to use the DeltaV model predictive control (MPC block) to control some parameters of a evaporator plant for my undergraduate thesis and the initial goal is to control the voltage value applied to a motor based on a level value; however, I always get an yellow circle with a question mark in it at the output. The control is working flawlessly when I use a PID control though.
Thank you very much for your help!
Pedro.
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EDIT 1: Thank you very much for all the support, I'm sorry for the long time I took to answer but this week has been very busy. Anyway, I am attaching two images, the first one shows how I was connecting the MPC block, the interrogation mark was showing up over the MNPLT1 output. I read about it and it could mean that that output was OOS. As I couldn't figure out how to solve the problem, I decided to connect the MPC block directly to the main panel in which I have all the inputs and outputs as shown in the second picture below to see if it would work properly. Apparently, the problem was solved, but I still would like to use a separate module like the one shown in the first picture. Too clarify, the LT001 represents a level sensor and the SC001 represents the signal that goes to the frequency inverter responsible for the pump.
EDIT 2: Hello guys, as I said in the last edit, the MPC block seemed to work fine when inserted in the same module as the inputs and outputs (Attempt #2). However, when I tried to use it as the input to a PID controller, I got a problem similar to the initial one described on the main post, a yellow question mark at the BKCAL_OUT of the PID block. Both the MPC and the PID seemed to work just fine when working alone, but I can't get them to work together. Another problem is that the PID keeps changing the actual mode to MANUAL although it is configured to CASCADE.
Again, thank you very much.
EDIT 3: Yellow question mark problem was solved; however, MNLPT and BKCAL_IN values of the MPC block equal to zero.
Attempt #1: DIDN'T WORK - Yellow question mark over the MNPLT
Attempt #2: IT WORKED
Attempt #3: DIDN'T WORK - Yellow question mark over the BKCAL_OUT in the PID block.
Attempt #4: DIDN'T WORK - MNPLT and BKCAL_IN of the MPC block equal to zero
MPC Operate:
In reply to James Beall:
In reply to Pedro Torreao:
If I am using the MPC block as the master to the PID, I would have to use the CAS_IN of the PID, right?! The control works fine when I use only the MPC or only the PID, the problem happens when I try to use the PID in cascade mode with the MPC as its master.
James, First of all, thank you for the support. Based on your previous orientation I was able to put the PID block in the cascade mode; however, the values of the MNPLT1, BKCAL_IN of the MPC block and the value of the BKCAL_OUT of the PID block are equal to zero and when I try to use the Predict to identify the model I get an error that says that the it was not possible to perform the test because the value is constant. Also, I included a picture of the new settings. Pedro.
Update from Emerson Exchange 365 <4U4NFM53MD4I-jpg_2D00_70x70x2-jpg> Pedro Torreao I actually need the PID as the slave loop because the process is not stable so I need the PID to stabilize it. View online You received this notification because you subscribed to the forum. To unsubscribe from only this thread, go here. Flag this post as spam/abuse.
I actually need the PID as the slave loop because the process is not stable so I need the PID to stabilize it.
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In reply to JoseCarias:
Update from Emerson Exchange 365 James Beall Jose, MPC, MPCPro and MPCPlus can run as fast as 1/second (Tss/120) and so there are many application where it is appropriate to them to go to the AO. However, they can, and most often do, go to a slave PID controller. It depends on the application but you make a good point. James View online You received this notification because you subscribed to the forum. To unsubscribe from only this thread, go here. Flag this post as spam/abuse.
Jose, MPC, MPCPro and MPCPlus can run as fast as 1/second (Tss/120) and so there are many application where it is appropriate to them to go to the AO. However, they can, and most often do, go to a slave PID controller. It depends on the application but you make a good point. James