pid problems

siggibald · Feb 23, 2015

hi

i have an program to control motor valve with temperature and pid

and the problem is if the setpoint is 12 then it dosent start control until temp is 14°c and dosent stop until the temp id 8-9°c

here is the program maby you can se some faults in it ???

siggibald · Feb 23, 2015

here it is

Mickey · Feb 23, 2015

Check the control mode to see if that is what you want. You have it set for "Reverse Acting" now. See picture...

I would set the "Rate term to zero to start with. You can then try adjusting the Gain up to make it more responsive. The "Reset" term can also be increased to make it more responsive.

siggibald · Feb 24, 2015

no that is not the problem

Mickey · Feb 24, 2015

siggibald said:
no that is not the problem

That's a little vague.

It may help if you give the forum more info about the process.

What is this valve controlling?

shooter · Feb 25, 2015

check if integration is at limit.
this is called over/under sgoot, common problem with pid.

Peter Nachtwey · Feb 25, 2015

shooter said:
check if integration is at limit.
this is called over/under sgoot, common problem with pid.

Only for poor implementations of PID written by people that get the formulas out of a text book without REALLY understanding what is happening.. My PIDs NEVER have this problem.

In motion control an actuator can be stalled. The PID should not wind up so if the actuator is freed it will over shoot the set point.

pid problems

siggibald

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shooter

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