Different commands are used to drive the auto-tuning function:
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Starting auto-tuning (ORDER_CMD (%MWr.m.c.11) = 16#000E)
This command starts the auto-tuning process. It can be directly activated from the auto-tuning function grid.
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Stopping auto-tuning (ORDER_CMD (%MWr.m.c.11) = 16#000F)
This command stops the auto-tuning process. In this case, PID parameters are left unchanged and a diagnostic is performed.
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Restore previous adjustment (ORDER_CMD (%MWr.m.c.11) = 16#0010)
This command swaps the current loop controller parameters with the previous ones (KP_PREV, TI_PREV, TD_PREV). This command is not allowed if auto-tuning event is in progress.
Auto-Tuning Operating Modes
At the start of auto-tuning, the loop controller may be in automatic or manual mode. When auto-tuning begins, it switches to adjustment mode, and the output retains the last imposed or calculated value. At the end of auto-tuning:
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If auto-tuning is successful, the loop reverts to its previous mode (automatic or manual).
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If auto-tuning fails, the output is initialized at the pre-auto-tuning value, adjustments are not made and the loop reverts to its previous mode (automatic or manual).
The direction of loop controller action is checked and compared with the model gain sign. The system displays an error in case of incompatibility.
