Hello,
I have a issue with tuning a slow acting PID loop using AB PIDE instruction. The system is designed to cool a tank after it heats up using a proportional valve that allows glycol to circulate through the tank.
My main issue is that the CV does not begin open to allow cooling until after the PV has passed the SP and does not start to close until after the PV has fallen below the SP. This creates an oscillation that wont correct its self over time.
If attached a picture to show what is happening in the tank right now. The time span is 24 hours For clarity this is the legend.
Blue = Tank Temp (used in the PID loop)
Purple = Secondary Tank Temp (not used in the PID loop)
Red = Setpoint (12C)
Orange = position of glycol valve (its stepped in 1% intervals)
I have a basic tuning parameter already set, information below.
P = 5
I = 8
D = 1.5
Execution Time for PID algorithm = 45 seconds
deadband = 0.01
Control Action = Direct acting (PV-SP)
Gains Equation = Dependent
I'm looking to make the system more predictive to throttle back the valve before the PV goes below the SP line. Any help would be greatly appreciated.
All the best,
I have a issue with tuning a slow acting PID loop using AB PIDE instruction. The system is designed to cool a tank after it heats up using a proportional valve that allows glycol to circulate through the tank.
My main issue is that the CV does not begin open to allow cooling until after the PV has passed the SP and does not start to close until after the PV has fallen below the SP. This creates an oscillation that wont correct its self over time.
If attached a picture to show what is happening in the tank right now. The time span is 24 hours For clarity this is the legend.
Blue = Tank Temp (used in the PID loop)
Purple = Secondary Tank Temp (not used in the PID loop)
Red = Setpoint (12C)
Orange = position of glycol valve (its stepped in 1% intervals)
I have a basic tuning parameter already set, information below.
P = 5
I = 8
D = 1.5
Execution Time for PID algorithm = 45 seconds
deadband = 0.01
Control Action = Direct acting (PV-SP)
Gains Equation = Dependent
I'm looking to make the system more predictive to throttle back the valve before the PV goes below the SP line. Any help would be greatly appreciated.
All the best,