Re: A problem with ilaplace()

[Leo Baumann]

Am 14.11.2017 um 18:22 schrieb Doug Stewart:

On Tue, Nov 14, 2017 at 9:47 AM, Leo Baumann <address@hidden> wrote:

Hello folks,

I have reduced the problem. -

It is explained in Octave script:

#--------------------------------------------------------------------------

clc;
clear all;
pkg load symbolic;
syms p t;

#a few simple calculations
Rgen=50;C1=100e-9;Rlast=50;
fg=10e3;
R1=1/(2*pi*10e3*C1)-Rgen;
wg=2*pi*fg;

#this works fine, Tp1 is a simple imagined example ...
Tp1=1/(5*p+6);
laplace1=1/p*Tp1;
ux=function_handle(ilaplace(laplace1, p, t));

#this doesn't work, I don't understand that because Tp2 is the same
#as the example with other numbers
Tp2=1/(1+(Rgen+R1)/Rlast+p*C1*(Rgen+R1));
laplace2=1/p*Tp2;
ux=function_handle(ilaplace(laplace2, p, t));

#----------------------------------------------------------------------------------------

I don't understand that the second example doesn't work, all variables are defined.

Any hint?

Thanks - Leo


_

What results are you looking for. What is your overall goal?

Doug, I found a solution for Octave. Watch the script, please :)

#-------------------------------------------------------------------------------------
clc;
clear all;
pkg load symbolic;
syms p t;

#a few simple calculations
Rgen=50;C1=100e-9;Rlast=50;
fg=10e3;
R1=1/(2*pi*10e3 *C1)-Rgen;
wg=2*pi*fg;
a=5.3;b=7.1;

#this works fine, Tp1 is a simple imagined example ...
Tp1=1/(p*a+b);
laplace1=1/p*Tp1;
ux1=function_handle(ilaplace(laplace1, p, t));

#this works now, too - I have made the coefficient of p in the denominator of Tp2 to 1
c=C1*(Rgen+R1);d=1+(Rgen+R1)/Rlast;
Tp2=1/c/(p+d/c);
laplace2=1/p*Tp2;
ux2=function_handle(ilaplace(laplace2, p, t));
#--------------------------------------------------------------------------------------------------------------

It works if the coefficient of p in the denominator of Tp2 is 1.

Regards - Leo