PID control using USB-6009, need simple video or example vi

[labviewjoe]

I have a new usb-6009 and have tried all the videos on the NI

website for practice. However with version 8.6.1 I can not use

the simple pid vi that is used on the video. (its too old v 5x)

I just need a simple pid vi for 8.6.1..so far, I have seen to many complicated vi's

for pid demo..I have the control design tools..too many to choose... 

any help finding a simple vi or video? - like the demo shown

on the USB-6009 NI website...

Regards

JJ

[labviewjoe]

PS- I have tried a host of the pid vis in the control and sim tool box and

the ones in the example vi folder...for version 8.6.1....

Most of them do not work with the USB 6009...probably because

its not well suited for fast control applications....I just want the

simple pid vi...that works like the one on the video demo for the 6009..

Regards

J

ps- I give up today

[labviewjoe]

I hooked up a vi called PID (derivative with one pole and antiwindup)

this doesnt quite work well..but it at least is close..this is too unstable..

I need something like this that is easy to use with the USB-6009

using loop back from ai to ao..

J

[BruceAmmons]

You can't use a USB-6009 with realtime, and without realtime you won't be able to have very fast loops.  I would guess about the fastest you can loop would be around 5 msec.  Maybe a little faster with a dual core if you aren't running anything else.

Make sure you put a fixed delay in your PID loop.  Don't let it just run as fast as it can - that would be messy.

If your process needs faster control than 5-10 msec, you will never achieve it with the USB-6009.

Bruce

[labviewjoe]

Thanks for the info..I will try to put a delay in the vi....

The usb-6009 can do real-time control..please see the PID

demo video for the USB-6009 ...the old vi seems to track well with

user changes..I would like to get close to this..

Ill let you know..

J

[labviewjoe · Accepted solution]

Well, I made a simple proportional control for the usb-6009

with a delay inside the while loop..not sure if thats the

best place..my PID sub vi is very simple..

But, it does show how to use labview and the usb-6009 for

a very simple loop back PID...

Regards

J

[BruceAmmons]

Glad it works.  The while loop is a good place to put the delay.  The delay stabilizes the timing of your PID loop.

FYI, I was referring to the LV RT operating system, which does not use USB DAQ devices.  The RT operating system lets you get much higher rates in a PID loop.  Windows has latencies that prevent PID loops going much faster than 10 msec loops.  Multi-processor systems might be able to go faster, though.

Bruce

[hecmar.arreola]

labviewjoe - Not sure if you are familiar with the terminology on this board or not, but typically when someone says "real-time" they are referring to "LabVIEW RT" as oppose to LabVIEW Desktop.  I'm not super familiar with all the difference (I'm a desktop user myself).  The primary difference is that LabVIEW is running on a "real-time" operating system that gives absolute priority to LabVIEW.  Contrast that with a desktop enviornment (say Windows), where some background process may delay some operational thread within your LabVIEW program undesirably.  For example, an Antivirus program could update its virus definitions causing a delay in PID signal output to your hardware.

For almost all of my applications, this isn't a big deal.  My operations work in 100ms intervals and it isn't mission critical for everything to be timed just right.  Other environments are different and require the use of LabVIEW RT and a RT system.  These systems also come with a whole range of specific hardware that is compatible with RT systems.

[hecmar.arreola]

To you or I, we can't perceive a few msecs here and there loss so it looks all "realtime" for us.

[yugiha]

Hi Joe,

I faced the same problem. I am very frustating because I cannot open the simple PID.vi version provided by NI coz the version is too old (i'm using LV 2010). May I have the .vi you have designed? I am very new to LabVIEW and basically a life science student instead of engineering student. Thank you so much.

Yugiha