PID

[Clint1000]

If someone could make a recommendation on the use of a PID.  I have a fin that moves up and down "x" number of degrees.  The number of degrees is related to the voltage I send to a servo.  In the fins are a device that measures the angle the fins move.  This "feedback voltage" is also proportional to the angle the fins are moving.  So I basically have a setpoint to a System with a feedback similar to the explanation given here:

http://www.ni.com/white-paper/3782/en/

My questions is couldn't I just generate a voltage with a DAQ card  AO ( providing drive voltage and current are sufficient) and monitor it on another DAQ channel  AI and turn the drive voltage off when the voltage to the servo is equal to the feedback voltage??  Its seems awful complex to use a PID..(trial and error with K, P etc ) for a simple concept like what I have.  The thing that bothers me is that the PID definition sounds exactly what I'm looking for..its the details that seem more than I need. 

Thxs..

[GerdW]

Hi Clint,

couldn't I just generate a voltage with a DAQ card  AO ( providing drive voltage and current are sufficient) and monitor it on another DAQ channel  AI and turn the drive voltage off when the voltage to the servo is equal to the feedback voltage?

Sure you can. When the result is ok for you…

awful complex to use a PID..(trial and error with K, P etc )

Why "trial and error"? There are common rules to determine the PID gains…

a simple concept like what I have.

You have a moving mass with inertia. You have an electric drive with intertia. You have multiple connections between them.  I wouldn't call it "simple"…

[Clint1000]

Some of the topics on the web describe setting Kc until your process oscillates then adjusting Pc thats why I said trial and error.

Simple in concept..not so simple in implementation I guess..

So would you recommend the PID.vi or just the Analog Out /Analog In approach ??  Or haven't I provided enough info??

Thxs.

[GerdW]

Hi Clint,

So would you recommend the PID.vi or just the Analog Out /Analog In approach ??

That depends on your complete system and your requirements!

(I would go with the PID. When using the NI supplied functions you can easily switch from automatic to manual mode…)

Or haven't I provided enough info??

Surely not!

Some of the topics

Yes, and some other only use the step response timings…

[Clint1000]

thanks..