PID motor control

[Gaussy]

I am trying to implement closed loop PID control of DC motor using NI cDAQ 9178 module.

referring to : https://decibel.ni.com/content/docs/DOC-16983

The VI works fine in software.PID controller output is also within acceptable limits i.e <10V.

However,at interfacing stage following errors are seen :

PID controller gives a very large or a very small output  to DAQ 9264 and hence output signal cannot be generated.

Also,output DAQ assistant indicates an error involving buffer size.

I am posting the VI below.

Please help me out.

[GerdW]

Hi Gaussy,

your VI looks very different to the one shown in your linked example.

Why don't you use the PID toolkit? Why do you need the Simulation toolkit and a MathScript node?

How should your PID work, when it is bound to some static signal due to DATAFLOW? A PID loop should never run until the user stops the loop…

[Gaussy]

Thank you, I am now using the PID toolkit. I am able to run the motor, but I feel that there is some problem in the speed sensing part.I have two questions

1. Using cDAQ 9178 and Digital card 9401 how do I make connections for frequency measurement. I have read that counters can be accesed through PFI on the chassis.How to do that?

2. When using analog input card 9201, I am not able to get a stable reading of speed (motor runs and stops alternately) and the PID controller output oscialltes between +8 and -8 only. 

I am uploading both the VI's.

Pls help me out.

Thanks

[GerdW]

Hi Gaussy,

2) Are your PID parameters for real? What happens when you decrease Kp (a lot)?

1) Can't say, never used a cDAQ…