Re: Using GNU Octave: Time Delay Representation

[A S Hodel]

A pure transport delay P(s) = e^{-s*T) is an infinite dimensional function, and so you either need to
implement it with a deadbeat FIR filter
P(z) = 1/(z^N) 
for some large N (and appropriately fast sampling time Ts = T/N) or, if you prefer, use a Pade approximation of P(s) (formulae in Moler and Van Loan's 1978 paper "nineteen dubious ways to compute the matrix exponential); I don't recall the expansion myself.  It's only an approximation, though (as is the discrete-time version).

Octave's expm function uses an 8th order Pade approximation (along with other preconditioning techniques).

On Monday, November 25, 2002, at 09:58 PM, Fuertes, Dale A. wrote:

> Good day!
>
> I am a senior BS Chemical Egineering student in the University of the Philippines. I wrote as regards to using the Development version of Octave. We cannot find a discussion on Time delay representation in a transfer function. Hope you could help in any way. I am looking forward to your reply.
>
> Thank you.
>
> Respectfully yours,
>
> Dale A. Fuertes
>
>  
>
>
>
> ____________________________________________________________________
> Dale Arceo Fuertes
> University of the Philippines
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