MorphuisOGrady
Member
Hi,
I've recently tuned a PID for a level control in a channel application. Everything was functional fine until a new feed pump was added to the system. The additional feed pump naturally has increased the flow to the chamber that my PID is level controlling.
The clients control philosophy calls for an assist pump in the chamber to start when the Duty pump has reached 95% of MaxSpeed. The assist pump will remain on until the Duty pump has dropped to 45%.
My thinking was I could use the PID output to modulate both pump speeds but as I'm sure you more experienced guys are about to point out this is not possible for this application.
The results observed where as follows:
When the Duty pump hit 95% the assist kicked in at 95% also. This in turn drove the level down drastically (small channel) cuasing both pumps to stop in a Low level setpoint.
The channel level then increased above the Duty start setpoint causing the duty pump to start flat out and again calling the Assist pump.
How do you guys control an application like this? My next thoughts were to perhaps only control the assist on the PID when its needed but how should I decide what speed to control the duty pump?
Does this make sense? Any comments greatly appreciated.
I've recently tuned a PID for a level control in a channel application. Everything was functional fine until a new feed pump was added to the system. The additional feed pump naturally has increased the flow to the chamber that my PID is level controlling.
The clients control philosophy calls for an assist pump in the chamber to start when the Duty pump has reached 95% of MaxSpeed. The assist pump will remain on until the Duty pump has dropped to 45%.
My thinking was I could use the PID output to modulate both pump speeds but as I'm sure you more experienced guys are about to point out this is not possible for this application.
The results observed where as follows:
When the Duty pump hit 95% the assist kicked in at 95% also. This in turn drove the level down drastically (small channel) cuasing both pumps to stop in a Low level setpoint.
The channel level then increased above the Duty start setpoint causing the duty pump to start flat out and again calling the Assist pump.
How do you guys control an application like this? My next thoughts were to perhaps only control the assist on the PID when its needed but how should I decide what speed to control the duty pump?
Does this make sense? Any comments greatly appreciated.