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Inverse Laplace Transform of a Transfer Function Using Matlab

In this topic, we will find out how to calculate inverse Laplace of a transfer function using Matlab.

Let’s find out Inverse Laplace of the following function


Let’s write a little code in Matlab now:

%% % Calculate Inverse Laplace of a function using Matlab
%Let's write numerator and denumerator from the given transfer function
num = [10 20 40]; % Numerator Coefficients
den = [1 12 47 60]; %Denumerator Coefficients
% "residue" command is used to do Partial Fraction Operation &;
% returns "residue", and "Poles" and direct term of the partial fraction
% expansion
% Write "help residue" in Maltab GUI to get better insight
[Residue,Poles,Direct_Term] = residue(num,den)


Here, we get the following results:

Residue =




Poles =




Direct_Term =


Using above mentioned results, let’s write the partial fraction expansion of the function X(s)


From partial fraction expression, we can easily write the inverse Laplace transform as:


In order to convert partial fraction expansion back to the original function, we can use the following Matlab command:

\[[b,a]\text{ }=\text{ }residue(r,p,k)\]

Here, we have b (coefficients for numerator) and a (coefficients for denumerator) to write the function like X(s).

About Ahmad Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.

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