An improved Maxima function for inverse Laplace transform

Maxima has a fairly serviceable Laplace transform utility built-in.  Here’s an example from the popular ordinary differential equations book by Blanchard, Devaney and Hall:

laplace1

Trouble arises when we look at discontinuous forcing functions, which is especially sad because it seems to me that’s what makes it worthwhile to spend time with Laplace transforms.  In particular, the inverse transform function ilt() fails on the Heaviside Function and Dirac Delta, even though the built-in laplace() treats them correctly:

laplace2

So, I’ve written an alternative inverse Laplace function laplaceInv() that fixes that problem:

laplace3

Here are a few differential equation solutions to show how the new function behaves:

A second-order linear equation with a constant forcing function that vanishes at t=7

laplace6

laplace7

A second-order equation with two impulsive forces:

laplace4

laplace5

The new Laplace transform Maxima function can be downloaded here.

Advertisement

5 thoughts on “An improved Maxima function for inverse Laplace transform”

  1. The fractional calculus, via the Laplace and Inverse Laplace Transform, is of
    some value in solving differential equations and possibly circuits with non
    linear components.
    Might you implement this for Maxima.

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: