Thread Subject:

converting mathematica code to matlab

Hi, I'm trying to make something similar to http://demonstrations.wolfram.com/PendulumOnAMovingSupport/ , I already have a function to do the animation given the position of the cart and angle of pendulum but I just don't know how to do the solving of those differential equations in matlab, can someone please help me? thank you in advance

On Nov 26, 6:23 pm, "Paulo " <paulojmdsi...@gmail.com> wrote:
> Hi, I'm trying to make something similar tohttp://demonstrations.wolfram.com/PendulumOnAMovingSupport/, I already have a function to do the animation given the position of the cart and angle of pendulum but I just don't know how to do the solving of those differential equations in matlab, can someone please help me? thank you in advance


did you try 'dsolve' ?

"EDU>> help dsolve
 DSOLVE Symbolic solution of ordinary differential equations.
    DSOLVE('eqn1','eqn2', ...) accepts symbolic equations representing
    ordinary differential equations and initial conditions."

--Nasser

"Nasser M. Abbasi" <nma@12000.org> wrote in message <d15de460-70e9-4d4a-99a5-99a6335248ec@i10g2000prd.googlegroups.com>...
> On Nov 26, 6:23 pm, "Paulo " <paulojmdsi...@gmail.com> wrote:
> > Hi, I'm trying to make something similar tohttp://demonstrations.wolfram.com/PendulumOnAMovingSupport/, I already have a function to do the animation given the position of the cart and angle of pendulum but I just don't know how to do the solving of those differential equations in matlab, can someone please help me? thank you in advance
>
>
> did you try 'dsolve' ?
>
> "EDU>> help dsolve
> DSOLVE Symbolic solution of ordinary differential equations.
> DSOLVE('eqn1','eqn2', ...) accepts symbolic equations representing
> ordinary differential equations and initial conditions."
>
> --Nasser

Hi thanks for the reply, I tried like this:

clc;syms a;syms x;l=1;t=0:0.1:1;
eq='D2a(t)+D2x(t)/l*cos(a(t))+9.8/l*sin(a(t))=0,2*D2x(t)+l*D2a(t)*cos(a(t))-l*(Da)^2*sin(a(t))=0)';
dsolve(eq,'x(0)=0','a(0)=0','Dx(0)=0','Da(0)=0')

but it doesn't work, error:

??? Attempted to access Eqn(1); index out of bounds because numel(Eqn)=0.

Error in ==> dsolve at 240
if isequal(Eqn(1),'[') & isequal(Eqn(end),']')

Error in ==> testeDSOLVE at 3
dsolve(eq,'x(0)=0','a(0)=0','Dx(0)=0','Da(0)=0')

I don't know what to do in order to make it work, any ideas?

I had a mistake on the previous code but after the correction the error remains

clc;syms a;syms x;l=1;t=0:0.1:1;
eq1='D2a(t)+D2x(t)/l*cos(a(t))+9.8/l*sin(a(t))=0';
eq2='2*D2x(t)+l*D2a(t)*cos(a(t))-l*(Da)^2*sin(a(t))=0';
dsolve(eq1,eq2,'x(0)=0','a(0)=0','Dx(0)=0','Da(0)=0')

I found some errors, this version works but I didn't check if the result is correct yet

clc;l=1;
eq1='D2a+D2x/l*cos(a)+9.8/l*sin(a)=0';
eq2='2*D2x+l*D2a*cos(a)-l*(Da)^2*sin(a)=0';
[angulo,posicao]=dsolve(eq1,eq2,'x(0)=0','a(0)=0','Dx(0)=0','Da(0)=0','t')

"Paulo Silva" wrote in message <icpq27$evn$1@fred.mathworks.com>...
> Hi, I'm trying to make something similar to http://demonstrations.wolfram.com/PendulumOnAMovingSupport/ , I already have a function to do the animation given the position of the cart and angle of pendulum but I just don't know how to do the solving of those differential equations in matlab, can someone please help me? thank you in advance

Hey there,

since you already have the equations of motion in Mathematica, why not do the solving there and neatly convert it to MATLAB M-code? There's a Mac-tool called "Converso" which does exactly that (and more - generating C-code for example). Its still in beta, but already fully functional for common equation cases.

You can get it from the Facebook page: http://www.facebook.com/ConversoEngine

There's also an example covering a single pendulum: http://optinetics.net/Converso/Versions/0.92b/Pendulum_Example.zip

I know, this answer might be a bit late, but maybe it helps someone else.

Cheers,
Jan