> Hello all,
> I need some guidance in programming a laplace transfer function into
> computer language -- pseudocode for now.
> The transfer function is a second order function:
> To^2*s^2 + zeta1*To*s + 1
> To^2*s^2 + zeta2*To*s + 1
> From what i've read the above transfer function is a bandstop filter, Zeta1
> and Zeta2 are adjustable paramaters. A demand signal is conditioned by the
> What are the steps I need to take to convert to software? Should I convert
> to z? Or???
> Any web site or recomended book??
> by the way, i've never programmed from transfer functions so I am new at
This is a perfect question for the comp.dsp group; I am taking the
liberty of cross-posting it there.
Yes, if you want this to actually execute in the digital domain you'll
need to convert to the z domain one way or another, then write software
to the resulting transfer function. If you must start from the s domain
and go to the z domain then your best bet is to use Tustin's
approximation ("bilinear transform") after prewarping the poles. When I
can I prefer to start with the requirements for the filter and just
design the whole darn thing in the z domain -- this is particularly
important (albeit frustrating) for a notch filter where you want to make
sure the gain above the notch is the same as the gain below.
"Understanding Digital Signal Processing" by Rick Lyons will get you a
long way down the road. It includes approximating Laplace-domain
filters in the z domain, but skimming through the table of contents and
flipping through the book I don't see anything that looks like a promise
of code (Rick?).
My book, "Applied Control Theory for Embedded Systems" gives you the
tools you need to go from a z-domain transfer function to code, but
it'll be pretty light in getting from the s-domain to the z-domain -- I
take refuge in claims of finite page counts and finite time.
I hope this helps.
Wescott Design Services
Posting from Google? See http://cfaj.freeshell.org/google/
"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html