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Explanation of PID process variable and set point timing and optimization

Hello I've been a longtime viewer and fan of the NI discussions forums and finally have a question worthy of the expertise.

 

Recently I've been trying to tackle to PID loop control system. I've been able to tune a system and create a  crude but functional simulation. Unfortunately I feel I'm missing some of the crucial rules of the PID loop. For example I've heard people say that the process variable need to run faster than the setpoint, and if this is so then how do you have the PID in a loop that is running slower than the process variable actually utilize the faster updating of the feedback. I've research the dt function and the timming of loops but have yet to been able to grasp how this actually works. I understand that the process variable needs to run faster than the setpoint, so would this require just slowing down the set point and keeping the PID loop, feedback, and motor control in a faster loop. That's the way I seem to be understanding it, but people mention the dt function all the time in order to tune timings. I'm interesting learning how exactly and all the ways the control system on the PID loop is actually optimized. Any help would be greatly appreciated.

 

Thanks

Taylor S. Amarel 

Learning is living.
Co-Founder and CEO of http://3dprintingmodel.com/

"If we did all the things we are capable of, we would literally astound ourselves."
-Thomas Edison
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Hi Taylor,

 

Can you link me to where you were reading this previously about setpoint speed and all this?

 

Generally, you simply stick the PID.vi into a loop and wire things up as you would expect. You can use timed loops as you discussed and can sync them up to other clocks (perhaps even a DAQ clock) if you so desire, but it's not critical.

 

Is there some strange behavior you're seeing that you're trying to alleviate?

Jeff | LabVIEW Software Engineer
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