How do I implement my own transfer function?

[Dan Stephenson]

LabVIEW has lots of built-in controls and filters, but I want my own.

I want to send data I collect through a transfer function of my own
specification, such as a second order where I can specify frequency and
damping. Or even something much higher-order.

But I cannot figure it out. I played with the H(z) discrete transfer
function, but there is no output from it, even when I specify just a
1/z lag. And the H(s) doesn't even drag out of the palette.

Please help, I'm new to LabVIEW. I ultimately want to implement a
feedback control systems on a motor with a rate loop and outer position
loop. I should be able to easily implement such a super-simple thing,
but heck if I can figure it out.

Please post or email,
--
Dan Stephenson
Photos, movies, panos from the Europe, USA, plus N.Z.:
http://homepage.mac.com/stepheda

(remove nospam from email address to reply via email)

[Pnt]

You have to be more specific.

What software, except Labview, and what hardware do you have?

Describe a little better the application

[hrh1818]

On Nov 10, 11:15 pm, Dan Stephenson <stephedanos...@mac.com> wrote:
> LabVIEW has lots of built-in controls and filters, but I want my own.
>
> I want to send data I collect through a transfer function of my own
> specification, such as a second order where I can specify frequency and
> damping.  Or even something much higher-order.
>
> But I cannot figure it out.  I played with the H(z) discrete transfer
> function, but there is no output from it, even when I specify just a
> 1/z lag.  And the H(s) doesn't even drag out of the palette.
>
> Please help, I'm new to LabVIEW.  I ultimately want to implement a
> feedback control systems on a motor with a rate loop and outer position
> loop.  I should be able to easily implement such a super-simple thing,
> but heck if I can figure it out.
>
> Please post or email,
> --
> Dan Stephenson
> Photos, movies, panos from the Europe, USA, plus N.Z.:http://homepage.mac..com/stepheda
>
> (remove nospam from email address to reply via email)

If you have a recent version of a full Labview Development System you
can use a Mathscript node to implement transfer functions. A
mathscript node can execute most Matlab functions. Labview's built in
help provides a lot more information on Mathscript nodes and you can
also search the examples that come with Labview for examples that use
mathscript nodes.

Howard

[CMal]

Dan,

If you're getting started with LabVIEW, and you want to create transfer functions and use them in control systems, then you should use the LabVIEW Control Design and Simulation module.  The "discrete transfer function" VI you mentioned is part of this module.  It must be used inside a Simulation loop, which is why you were unable to drag it from the palette.  I strongly recommend reading through the 3 Hour Control Design and Simulation course.  It explains the basic process of creating a transfer function and using it in a control loop, so it should be exactly what you need to get started.  Let me know if this helps.

Chris M.

[Dan Stephenson]

On 2008-11-11 10:41:24 -0600, hrh1818 <hrhan@att.net> said:

> If you have a recent version of a full Labview Development System you
> can use a Mathscript node to implement transfer functions. A
> mathscript node can execute most Matlab functions. Labview's built in
> help provides a lot more information on Mathscript nodes and you can
> also search the examples that come with Labview for examples that use
> mathscript nodes.
>
> Howard

Thanks Howard I've thought of that and for low order it would be easy.
You mean it'll just handle all the states for you?

But I still find it hard to believe LabVIEW cannot implement such as
super basic capability like sending the data acquisition signal through
a transfer function of my own specification.

--
Dan Stephenson
Photos, movies, panos from the Europe, USA, plus N.Z.:
http://homepage.mac.com/stepheda

(remove nospam from email address to reply via email)