STATUS default value

[wcottee]

I have an optimal control problem in GEKKO that is functioning ONLY if I include u.STATUS = 1 in the script ("u" is the control MV). Without it, the optimizer won't vary its value.

In the documentation https://gekko.readthedocs.io/en/latest/MV_options.html, it states that the default value of STATUS is 1...so why do I need to include u.STATUS = 1 in my script?

What am I missing? Thanks

[John Hedengren]

Thanks for finding that error in the documentation. It has been fixed and is now consistent with other parts of the documentation that had the default (STATUS=0) listed:

https://gekko.readthedocs.io/en/latest/MV_options.html

https://gekko.readthedocs.io/en/latest/tuning_params.html#status

https://apmonitor.com/wiki/index.php/Main/OptionStatus

The reason for the default STATUS=0 comes from the Model Predictive Control area where controllers are first run in a predictive mode where you are able to see the model performance or WARM mode where you can see the next controller action before turning on the controller. Another useful parameter (global) is REQCTRLMODE: https://apmonitor.com/wiki/index.php/Main/OptionApmReqctrlmode

 Type: Integer, Input
 Default Value: 3
 Description: Requested control mode
              0=off
              1=simulate
              2=predict
              3=control

REQCTRLMODE is the requested controller mode as an input for the application. The requested control mode (REQCTRLMODE) is set as an input to the desired level of control but sometimes the CTRLMODE is not able to match the request because of a failed solution, a critical MV is OFF, or other checks with the application. REQCTRLMODE level of 0 indicates that the program should not run and the program terminates without attempting a solution. REQCTRLMODE level of 1 (cold mode) indicates that the program should be run as a simulator with all STATUS values turned off on FVs, MVs, and CVs. REQCTRLMODE level of 2 (warm mode) indicates that the application should calculate control actions but only after the second cycle. This mode is commonly used to observe anticipated control actions before the controller is activated to level 3. REQCTRLMODE level of 3 means that the controller should be turned ON and implement changes to the process.

-John Hedengren

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Best regards,

John Hedengren

GEKKO Optimization Suite

https://machinelearning.byu.edu