Path: news.mathworks.com!not-for-mail
From: "Steven Lord" <slord@mathworks.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Simple ODE: Linearly Damped Spring Mass System
Date: Wed, 28 Jan 2009 09:40:27 -0500
Organization: The MathWorks, Inc.
Lines: 29
Message-ID: <glpqor$57b$1@fred.mathworks.com>
References: <gkjq5e$ph5$1@fred.mathworks.com> <gkjueb$1ts$1@fred.mathworks.com> <gkk08e$3dv$1@fred.mathworks.com> <glnejh$m7u$1@fred.mathworks.com> <glnf92$95p$1@fred.mathworks.com> <glpnvt$pa8$1@fred.mathworks.com>
Reply-To: "Steven Lord" <slord@mathworks.com>
NNTP-Posting-Host: lords.dhcp.mathworks.com
X-Trace: fred.mathworks.com 1233153627 5355 144.212.105.187 (28 Jan 2009 14:40:27 GMT)
X-Complaints-To: news@mathworks.com
NNTP-Posting-Date: Wed, 28 Jan 2009 14:40:27 +0000 (UTC)
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5512
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579
X-RFC2646: Format=Flowed; Original
Xref: news.mathworks.com comp.soft-sys.matlab:514485



"Hydroman S" <amirgsalem@gmail.com> wrote in message 
news:glpnvt$pa8$1@fred.mathworks.com...
> Sorry to bring this up again, but I was hoping that maybe anyone who is 
> familiar with solving ODE&#8217;s numerically in Matlab could help me 
> finalize the problem of finding the homogenous solution using ODE45 based 
> on the equation below in the matrix form:
>
> M*X"+C*X'+K*X=0
>

Convert the 2nd order ODE into a system of 1st order ODEs [massMatrix*y' = 
f(t, y)] and use ODE45 to solve this system.  If you're not sure how to 
generate the system of ODEs from the single 2nd order ODE, go to the support 
website:

http://www.mathworks.com/support

and search for "higher order ODE".  The first two hits each include examples 
of how to do that.

Alternately, you could use ODE15I, which can handle ODEs of the form f(t, y, 
y') = 0.

-- 
Steve Lord
slord@mathworks.com