PID Output Problem

[michaeltello]

Hi guys,

Im programming a software using LabVIEW PID Advanced and Gain Scheduling. But as my gain changes, the output doesnt change accordingly with my gain. For example:

Error =10

Gain=10

Output=100

Then

Gain=0,01

Output=100 suppose to be Output=1

Seems like bumpless transfer? I couldnt tell.

Do yo have any idea why? The VI of "PID Gain Schedule Example" change the output accordingly with error. But mine is not. Hope you guys could help 😞

[P@Anand · Accepted solution]

No the Gain Schedule vi doesn't change your output depending on the input it will select the set of gains that you want to use. In some type of profiles we may need to use different set of gains so in those cases you can have different set of gains and apply that accordingly. For your case simple PID should be suffucient.

[michaeltello]

Hi P Anand,

First thank you for the quick reply.

Yes I am aware of the PID Gain Schedule function. When the process variable (PV) value change into a certain "zone" of gain schedule, my gain changes and therefore also my output (given the same error value).

I connected the output of the Gain Schedule VI to the PID Advanced VI, the gain changes accordingly to my PV and Gain Schedule Matrix, but when the these gains go into the PID Advanced VI (I have also tried with normal PID VI by the way), from my observation the output changes BUT starting from the last output value. For Example.

Error 8

Gain 10

Output 80

Then PV change and my Gain Schdule value change

Error 8

Gain 0.01

Output 80.08 NOT 0.08

When somehow I click on reinitialize or change to manual mode and then back to auto mode, the output suddenly changes accordingly. In this case to 0.08. Im very confused. The VI Example Library for Gain Schedule changes the output instantly/automatically to a new value when the gain changes, but in my case, NOT. It somehow change the value IN ADDITION to the old value of the output. 

I do not know wether its the cRIO or the LabVIEW program itself. Anyone ?