Background: PLC AB 1756-L61 v13 redundant via SRMs
I have a thermal refractory furnace which allows excess air to enter the process to quench the refractory if a temperature exceeds a certain setpoint. The problem is that the PID controller winds up on positive error causing the air to enter and quench, but as the temperature begins to downturn toward the setpoint I still have + error which causes more air to enter so that by the time the setpoint is reached there is enough CV, it takes a long time before the PID CV reaches 0.0 that I am considerable under the setpoint.
Id like to be able to reset the PID to 0.0 CV when the PV is below the SP, but moving a 0.0 to the CV doesn't work as the PID accumulator becomes active the CV begins at whatever value it left off from when the PV is below the SP.
v13 doesn't allow PIDE, and due to this being an older processor with SRM I am limited to a low revision. I need the PID loop to act rather quickly to + error so I can't slow the loop down too much for fear of possibly having the temperature run-away.
Any ideas on how to reset the error and CV, so that the accumulator begins at 0?
This furnace has been in operation for several years. It combusts process fuel to heat a large boiler, but the current logic has caused the temperature to fluctuate enough out of control that operators tend just run everything manually. There are so many mathematical errors that had to be corrected.
I have a thermal refractory furnace which allows excess air to enter the process to quench the refractory if a temperature exceeds a certain setpoint. The problem is that the PID controller winds up on positive error causing the air to enter and quench, but as the temperature begins to downturn toward the setpoint I still have + error which causes more air to enter so that by the time the setpoint is reached there is enough CV, it takes a long time before the PID CV reaches 0.0 that I am considerable under the setpoint.
Id like to be able to reset the PID to 0.0 CV when the PV is below the SP, but moving a 0.0 to the CV doesn't work as the PID accumulator becomes active the CV begins at whatever value it left off from when the PV is below the SP.
v13 doesn't allow PIDE, and due to this being an older processor with SRM I am limited to a low revision. I need the PID loop to act rather quickly to + error so I can't slow the loop down too much for fear of possibly having the temperature run-away.
Any ideas on how to reset the error and CV, so that the accumulator begins at 0?
This furnace has been in operation for several years. It combusts process fuel to heat a large boiler, but the current logic has caused the temperature to fluctuate enough out of control that operators tend just run everything manually. There are so many mathematical errors that had to be corrected.