PID with Programmable Ramp Rate

[Virtuwool]

I am attempting to build a temp controller with LabVIEW's PID toolkit. The controller needs to get to the correct temperature without overshoot and do it with a programmable ramp rate. However, PID does not (as far as I can tell) allow a programmable ramp rate with respect to the process variable. This must be a common requirement of a process controller. How's it done?

[Ben]

The set point is ramped.

The PID takes care of all of rest.

Ben

[A.S.]

Hello,
Thanks for contacting National Instruments. The PID toolkit used to have a ramp function for the setpoint. However, we have replaced it with a more versatile function called PID Setpoint Profile VI. This will let you ramp your setpoint if needed. Check out the following KnowledgeBase: http://digital.ni.com/public.nsf/websearch/125F27AC143B6AFD86256C2B0004A4DC?OpenDocument .

The response/output ramp of the PID VI itself is controlled by the PID parameters.

Hope this information helps. Please let us know if you have any further questions.

Regards,

A Saha
Applications Engineering
National Instruments

[nitad54448]

Hello

I may not talk about the same thing, but in my PID toolkit there no ramp rate related PID. The Vi dealing with the rate is actually taking a cluster of values (time, setpoint) and calculates a setpoint values by taking into account the actual time.

Is there a way to make a ramp rate ?

sorry for this question, I see that the message is several years old

regards

N

[RavensFan]

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nitad54448 wrote:

Hello

I may not talk about the same thing, but in my PID toolkit there no ramp rate related PID. The Vi dealing with the rate is actually taking a cluster of values (time, setpoint) and calculates a setpoint values by taking into account the actual time.

Is there a way to make a ramp rate ?

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It is just basic math.  ramp rate = (SP(n+1)-SP(n))/ (T(n+1)-T(n))

[nitad54448]

Hi

I am using a simple vi to make temperature profiles (sawtooth, gaussian and so on). I was questioning this comment : "The PID toolkit used to have a ramp function for the setpoint. However, we have replaced it with a more versatile function called PID Setpoint Profile VI."

N

[DavidMaidman]

I remember the old setpoint ramp VI in the PID toolkit (version 6) - i think it dissapeared when the Toolkit went to 7.1

Try this one. You can specify positive and negative ramp rates and can ramp to a final value.

Hope it helps.

[nitad54448]

hi

thanks; can you post it in 8.6 N

regards

[DavidMaidman]

Hi,

I have not used this in 8.6 so let me know if you have any problems

[SnowForest]

Do you mean that you want limit contreller output? E.g if control gap ABS(SP-PV ) > [limit] is too large and you want freeze controllers output? If you need that I have a very easy solution for you. By the way why you need this kind of ramp ?

BR, Jim