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

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.

Answer 1

[Jonathan LeSage]

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:

• http://www.mathworks.com/help/symbolic/ilaplace.html
• http://www.mathworks.com/help/control/ref/tfdata.html

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);

[lithika]

Thank u.This helped me a lot.