Plantationpark
Member
Hi folks, so... firstly I have setup a hydraulic pressure test system. The system is used to pump up a volume to a set pressure - i.e. if we need to test at 10000psi, the operator will put in 10000psi to the SCADA and the system will pump up to this with an air driven pump - the air supply for the pump is electronically regulated (0-100psi) which "linearly" controls the output of the pump (0-30000psi).
I have programmed a ramp up to approx 80%* in line with our required ramp up requirements, then a PID function kicks in to take us up to set value - this works nicely.
*Reason its 80% is because the pumps are not very linear and can very quickly (<1sec) kick to over pressure - over pressure is considered as 5% above the set value.
I say it works nicely… it does the very first time the system is used... i.e. right after I have uploaded the programme to the PLC. After the pressure test is complete and vented down, we will inevitably perform another one with the system, however I notice that despite enabling the PID.SWM bit and "MOV"ing 0 to the PID.CV and PID.SP as soon as the PID is not in use, the PID function flickers between 0 and an old value (from the first time the PID was used) when monitoring on Studio 5000. Subsequently, the next time the PID is used (when the PID.SWM is disabled and the output is used) the system does not react properly (the pressure spikes before the PID can catch it (it looks as if the output flickers between 0 (from the MOV function) and the max output...
The PID is on its own live rung. It is clocked with a counter set at 50ms which matches the PID settings. While the ramp up is taking place (non PID, the .SWM bit is =1 and I do not use the PID Output. Once the ramp is finished, I then clear the .SWM bit to 0 and use the output of the PID. As I say, this works great the first time.
I'm happy to say I’m a beginner with Studio 5000 and PLC PIDs, it’s almost like I need to reset or clear the PID, which I thought I was doing by moving the 0's into the .CV and .SP.
Unfortunately, I left my work laptop in work so don't have the logic to show - I've had my head buried in this for a few days so let me know if that doesn't make sense...
I have programmed a ramp up to approx 80%* in line with our required ramp up requirements, then a PID function kicks in to take us up to set value - this works nicely.
*Reason its 80% is because the pumps are not very linear and can very quickly (<1sec) kick to over pressure - over pressure is considered as 5% above the set value.
I say it works nicely… it does the very first time the system is used... i.e. right after I have uploaded the programme to the PLC. After the pressure test is complete and vented down, we will inevitably perform another one with the system, however I notice that despite enabling the PID.SWM bit and "MOV"ing 0 to the PID.CV and PID.SP as soon as the PID is not in use, the PID function flickers between 0 and an old value (from the first time the PID was used) when monitoring on Studio 5000. Subsequently, the next time the PID is used (when the PID.SWM is disabled and the output is used) the system does not react properly (the pressure spikes before the PID can catch it (it looks as if the output flickers between 0 (from the MOV function) and the max output...
The PID is on its own live rung. It is clocked with a counter set at 50ms which matches the PID settings. While the ramp up is taking place (non PID, the .SWM bit is =1 and I do not use the PID Output. Once the ramp is finished, I then clear the .SWM bit to 0 and use the output of the PID. As I say, this works great the first time.
I'm happy to say I’m a beginner with Studio 5000 and PLC PIDs, it’s almost like I need to reset or clear the PID, which I thought I was doing by moving the 0's into the .CV and .SP.
Unfortunately, I left my work laptop in work so don't have the logic to show - I've had my head buried in this for a few days so let me know if that doesn't make sense...