zeroion
Lifetime Supporting Member
I am working on a project using AB PLCs and PanelView HMIs.
There is a desire to allow control loop setpoints to be provided through the HMI or remotely from the plant PLC (via produced/consumed tags).
The challenge is how to handle the situation where the HMI and plant PLC provide different setpoints.
I have come up with some ideas, but none of them sound all that great:
Has anybody come up with some good solutions for this problem?
There is a desire to allow control loop setpoints to be provided through the HMI or remotely from the plant PLC (via produced/consumed tags).
The challenge is how to handle the situation where the HMI and plant PLC provide different setpoints.
I have come up with some ideas, but none of them sound all that great:
- Have the HMI setpoint always win. I would probably have to retransmit the current setpoint as a produced tag for the plant PLC so they would know that they are being overridden by the HMI value.
- Track changes in both setpoints by time, using the latest value as the setpoint.
Has anybody come up with some good solutions for this problem?