Hi All,
Condition: Level - Master Loop, Flow - Slave Loop
When Slave Loop fails, let say Transmitter failure, the whole loop goes to Man and the operator have to control the valve output. I had a requirement before that when this happen, Master Loop should have a direct control to the valve, meaning from Cascade Control to simple Level Control.
There are ways to do this:
1. Use of tracking, TRK_VAL = Level controller output. TRK_IN_D = True when Slave Loop fails
2. Use of two controllers, 1 for Cascade Control and 1 for Direct Control. AO_BKCAL is connected to both for bumpless transfer and an input selector to do the switching when Slave Loop fails
3. Use of Selector for the switching and CALC block for the switching of BKCAL output from AO for bumpless transfer
but is there any Standard way of doing this? i prepare to use #1 option?
Thanks,
Gelo
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