delay in a signal acquisition ( number of samples)

[hammer87]

hi felipe.

thx for your answer i'm gonna see about the error, i can't open the vi than you send me because i work on labview 2010, if you can save the vi in this version i'm gonna thank you.

i need make some controls, P, PI, PD, the P control, i did it very easy, but the PI control, i need the difference equation. in this moment i find a big problem, i need work my adquisition in a frequency higher than i work actually, my daq asistant is configurated in "one sample on demand" but by the effect of the "while loop" only i can work a max frequency of 1Khz (delay = 1ms), but i need configured the adquistion in a "continuos samples".

when i try to make this i have a problem because the generation in the asistant say me that "the buffer length is too small" is because to de asistant to generation arrives only a sample and this pased because i did do change of the format of samples for the difference equation, i´m thinking in create a vector that acts as a buffer but i don't have idea how to do it and i don't know if whit this i can resolve my problem.

grettings from colombia.

manuel girsales.

[FloresFe]

Sorry Manuel,

I attached it again for LV 2010! Sorry for that. Have you ever thought about using the NI LabVIEW Control Design and Simulation Module? It has ready to use specific control functions, including PID controllers.

Here's a link for that: http://sine.ni.com/nips/cds/view/p/lang/en/nid/206895. You are able to downlad that for 30 days evaluation.

But if you really need to use a difference equation, I'll look for an example and send to you as soon as possible!

Att. 

[FloresFe]

Sorry again. Now I really attached the VI

Att.

[hammer87]

thanks so much felipe.

really i need do this with difference equation, the idea of the exercise is do the control algoritm, i remeber you that my hardaware is a NI myDAQ and i want do this in "continuos samples" for that, i can get my samples in a better frequency.

i'm gonna try to make a array for de daq-assistant that generates my output signal (control signal), i await don't get this same error later.

by another site, i have this package and the "PID", too i'm gonna see how i can work with this package beacuse i think that it's interesting but really i need do the difference ecuation.

again, thx for your help.

manuel grisales.

[FloresFe]

Hi Manuel, Sorry for taking too long to answer you! I would like to know if you got succes in you issue? were you able to implement the difference equation for the PI control? Best Regards.

[hammer87]

Hi Felipe.

i can't do it with de "continuos samples", but i can do it in a "sample on demand"

the problem is that i can not take samples faster than 20 HZ or take sample faster than 50msg time sample.

the code it's the same but if you know how i can do it faster I'd appreciate if you can do it and help me.

thanks.

MANUEL GRISALES.

[hammer87]

Hi, finally, i could do my project with good results, the difference ecuations work very good with your code, i could not do in continiud samples but, i worked with a time sample of 50ms and the controls worked perfectly.

very thanks Felipe, i added the archives VI and my report IEEE (spanish)

[FloresFe]

What a good thing you have resolved it!!

You're very welcome. Any other doubt you have, please use the NI forum again.

Could you assign this topic as solved?

Have a nice day!