MATLAB Answers

How can I convert a transfer function into time dependent using ilaplace

52 views (last 30 days)
Tejas
Tejas on 17 Oct 2013
Commented: lithika on 28 Feb 2014
I have tried to use ilaplace
X2=(F*G3+C*G3)/(1+C*G3); % F,G3,C are transfer functions generated using tf
v=sym('X2');
x=ilaplace(v);
then i use it to plot a function using plot but when i try to run the code i get an error as shown below
??? The following error occurred converting from sym to double: Error using ==> mupadmex Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.

Answers (1)

Jonathan LeSage
Jonathan LeSage on 17 Oct 2013
The ilaplace function works on symbolic expressions and not transfer function models. You need to convert the transfer function, X2, into a symbolic expression prior to using the ilaplace function.
Here are some links to some relevant functions:
To get you started, here is some example code of one potential method of conversion:
% Your transfer function model
X2 = (F*G3+C*G3)/(1+C*G3);
% Extract the numerator/denominator
[num,den] = tfdata(X2);
% Build symbolic expression using the numerator/denominator
syms s
arrayNum = cell2mat(num);
arrayDen = cell2mat(den);
X2_symbolic = poly2sym(arrayNum,s)/poly2sym(arrayDen,s);
% Valid usage of ilaplace on a symbolic
x = ilaplace(X2_symbolic);

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!