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Analog Tracking Function Block, Hold in Manual Behaviour

I have the Analog tracking block (AT) connected to PID track input. PID track is enabled. I have a tracking condition that puts the controller in manual.

Books Online States:

Hold in Manual for control loop modules

When any tracking condition's T_L_OUT_Dnand T_HOLD_MANn parameters are True, the mode of the target analog block wired to OUT_D is set to Manual.

 

But when I check the Hold in Manual Block. Upon activation of tracking condition, The PID Mode goes from Auto/Auto to Auto/Local Override instead of Manual. 

In control options, Tracking is enabled and Track in Manual is disabled. Even if I enable both the issue remains.

Any Suggestions?

Thanks

Anupam_C
  • Trista VanDerVeeken
    Hi Anupam,

    I created a test module with the parameters for control opts and T_HOLD_MAN1 set up the same way you have described and when I trigger the interlock expression, the PID does go into manual with an out of 0 (this is what I have set as T_VAL1 ) but I am able to manipulate the output if I would like. With the expression still triggered, I am also able to change the target mode from manual to auto. I then see the mode go to Auto/Local Override and I am unable to manipulate the output. If I change my target mode back to Manual then both target and actual are manual and I am able to manipulate the output again.

    Do you have something in your logic setting the target mode of that loop to auto? If you have more than one expression being used, can you ensure you have set the proper T_HOLD_MANn to True?
  • Anupam_C

    In reply to Trista VanDerVeeken:

    Something went wrong with the module I guess. I created a new module and copied the loop from the old one to the new one and it started working. I had used AT block with Bias/Gain and it worked but did not work with the PID.

    I only had one condition in the tracking block and that tooa simple boolean parameter i created for testing as the block was not working as expected.

    But I noticed that the block does not go directly to Manual. When track is true the Mode goes from Auto/Auto --> Auto/Local Override --> Manual/Manual. Maybe it was getting stuck at LO when the mode was shedding to manual.

    Well its working now. Thanks Trista.
  • Matt Stoner

    The first out trapping as well as the driving of the mode to manual when enabled will only be done if the output has changed.

    • This is defined by the output (PID Output wired to FDBK_IN parameter) being outside the range of +/- OUT_HYS from the configured track value (T_VALx) for the Condition (T_EXPx).

    Make sure your PID output is outside of this range before triggering the condition in your testing.

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