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,

[hrh1818]

Post by 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)

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

[Dan Stephenson]

Post by hrh1818
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.

[hrh1818]

Post by hrh1818
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?

Your terminology has me confused. What do you mean by it will 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.

But that is exactly what you can do with a Mathscript Node. You can
put a transfer function that meets your specification in a Mathscript
Node, send your data acquisition signal to a Mathscript Node and get a
filtered signal at the output. Labview also has the capability to
implement FIR and IIR Filters. You really should think about using
either a FIR or a IIR filter as your data acquisition signal is a
sampled signal. It is not a continuous signal. The full version of
Labview comes with a lot of examples of FIR and IIR filters.
Note by transfer function I mean your filter is specified as a ratio
of the powers of S in the numerator and denominator. By FIR and IIR I
mean you filter is specified as the ratio of the powers of Z^-1 in the
numerator and denominator.

Howard

--
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)