Emerson Exchange 365

Delta V DCS MPC implementation

Hello everyone, 

I am Shivanshu Patil from AISSMS IOIT, Pune. I am pursuing my Bachelor's Degree in Instrumentation and controls and for my final project, I am working on the Delta-V system. Basically, we are planning to interface the CSTR pilot plant with the Delta-v system but due to lack of expertise, I am not able to implement the MPC. I followed all the instructions mentioned in the Online-Books of DeltaV.

But after clicking the test process in DeltaV Predict I faced the following errors repeatedly:

1. BLKCAL_1 must be a constant.
2. MNPLT_1 is limited.

I am not able to get solutions for these errors and If possible can anyone share steps for implementing an MPC using Delta-V Predict to overcome these errors.

Thank you in advance!!!

• DeltaV #DCS
• MPC

Shivanshu Patil

• 16 Mar 2022 9:31 AM
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4 Replies

• Lou Heavner

  

  • 16 Mar 2022 1:11 PM

  There are some differences between Predict vs PredictPro. I will answer for Predict and you can reply if your problem is with PredicPro. To do the Auto Step-Test, you have to define the step sizes for each MV to be step tested in % and the TSS in seconds. To begin the step test, you have to switch the Predict from Local to MPC. This will force all of the downstream MVs to the desired mode.... CAS, RCAS, or ROUT. If you are using CAS, make sure in Control Studio that the BackCal is not being wired somewhere else. Since we may be working with loops such as flow as an MV that might also be cascaded to another PID such as temperature using the CAS mode, we try to use the convention of always using RCAS, but that does not matter. If the MV is the master of a cascade loop, the downstream loop also needs to be in cascade. You may have defined MV constraint limits too tight and they may be at the constraint limit or the selected step size may push them to the constraint limit. Check your MV constraint limits and I usually set them to 0 and 100% of scale in Predict for step testing, but they need to be set wide enough to allow step testing. Make sure the downstream loop is not SP limited. Then switch the Predict to MPC from Local. Check each variable to make sure it is within limits (Process outputs as well as MVs... DVs don't have limits) Make sure the MPC mode can go to manual and all of the MVs transition properly. They should have a blue box around them. Set up the test plan... MVs to be tested, step size, and TSS. Then the step-testing should begin when you click the start button.

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• James Beall

  

  • 16 Mar 2022 1:47 PM

  In reply to Lou Heavner:

  Great comments from Lou!   Note also for the MPC block, the input and outputs must be directly wired to the source as shown in the first diagram  OR use the MPC Reference Function Block to connect to source or destination in module different from the one the MPC block is within.  Make sure the mode used for the MPC mode in the MV block (e.g. AO or PID) is enabled. 

  

  

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• Shivanshu Patil

  

  • 28 Mar 2022 5:35 AM

  In reply to Lou Heavner:

  Thank you for your assistance !!!

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• Shivanshu Patil

  

  • 28 Mar 2022 5:35 AM

  In reply to James Beall:

  Thank you for your assistance !!!

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