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Communication error while updating values

AnshuljaswalAnshuljaswal
in PLCnext Technology & PLCnext Controls

Hi

I am using Model predictive control block from Simulink in PLCnext engineer, when I increase my prediction horizon beyond 500 for MPC block, i get the following error.


image.png


Comments

  • Martin PLCnext TeamMartin PLCnext Team

    What do the LEDs on the PLCnext Control device look like when this happens?

    Are there any other notifications in PLCnext Engineer that might give a clue about why these errors occurred?

    What steps did you take to restore normal operation?

    One possibility is that the execution time of the Simulink model exceeded the Watchdog time for the Task that is executing that model instance.

  • AnshuljaswalAnshuljaswal

    There is no change in the LEDs. The image attached previously is all the PLCnext engineer shows.

    I have to reconnect the controller, change the prediction horizon to a lower value.

    I am not sure of the last one, what should i do if execution time is greater than watchdog time.

    image.png


  • Martin PLCnext TeamMartin PLCnext Team

    For a cyclic task, the Task Watchdog time is normally set to a value less than or equal to the Task Interval. That means that the task execution time will never exceed the task interval time without triggering the watchdog. It is usually not a good idea for the execution time of a cyclic task to exceed the task interval time, especially consistently.

    In this case, because the task Watchdog value is so much higher than the task Interval value, it could be that the task execution time is exceeding the task Interval value consistently, which will probably affect other processes on the device (like communications to PLCnext Engineer).

    In this case I would:

    • Set the Watchdog to a value less than or equal to the task Interval. If the interval stays at 1ms, then the Watchdog should also be set to 1ms.
    • Monitor the task execution time using the elements of the ESM_DATA structure, in a Watch window, as you change the model parameters. If the execution time (in micro-seconds) consistently approaches the task interval, then you need a bigger task interval.


  • AnshuljaswalAnshuljaswal

    I just observed that on my axc f 2152 controller the red led (FAIL) is on.

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