PIDE freeze output?

[dginbuffalo]

i like the modified version you posted, although i also wonder about doing something like the attached file. i just dont know if i really have to drive the output on high or low current, or just stop freeze the output. do i want three loops to tune, or is it just overkill? what do you think?

OOPS- ACTUAL LOGIC IS ON PAGE 2 OF PDF!!!

 

[TConnolly]

That might work. I think you have your SEL blocks backwards though. One potential shortcoming I see is when you write Blower_CV to CVHLimit you are already in an an overload condition without anything to decrease you back to the desired current level. The PIDE output will just stay at the high limit. If your load is variable it also doesn't self adapt. Still, it might be adequate for what you are doing. You'll have to make that judgement call. Don't make the controls more complex than they need to be if it gets the job done.

Also in the single PID case you don't need to tie the output back to CVPrevious, thats only for keeping multiple PIDE blocks that have to work together in sync.

 

[dginbuffalo]

Your right-the SEL blocks are backwards!! the motor current on this 400hp is very slow to move and my setpoints would still have a little wiggle room built in.

on high current, i would eventually meet pressure setpoint and the CV would start to drop, in turn, taking the motor load down.

on low current, there is a recycle valve in the system that would bleed off if my pressure began to climb.

if it sits against those two limits all day long, it's just how the load is running. hopefully most of the time it will run in the middle. i may make both sets of logic and test both to make a decision. Thanks for all the feedback.

 

[Craig Spinharney]

Be aware that the median Select mode of the ESEL instruction does NOT properly output the true median value when the sample set (inputs used) is an even number.