Date: Apr 30, 2013 10:06 AM
Author: Torsten
Subject: Re: How to get second derivatives using ode45
"stanley ontario" wrote in message <kloi4k$8u3$1@newscl01ah.mathworks.com>...

> Hello!

>

> I am stuck in solving a problem with ode45. I would like to get the second derivatives in order to plot the acceleration and to calculate some other values.

>

> However I only get the velocity and position.

>

> It looks like this:

>

> options= odeset('RelTol',1e-3,'AbsTol',1e-6);

> [t_vec,Y]=ode45(@(t,y) vib_equ(t,y,c_s_f,c_s_r,v_val,F_d_val,m_c,I_g_c,l,l_f,l_r,u_f,u_f_dot,v,L,i_d),[0 t_max], zeros(1,4), options);

>

>

> z_cf= Y(:,1);

> z_cf_dot= Y(:,2);

> z_cr= Y(:,3);

> z_cr_dot= Y(:,2);

>

> I would like to use the function vib_equ to get both z_cf_ddot and z_cr_ddot but I cannot figure it out, maybe there is another way, much easier but I really don't know.

vib_equ returns the first and second derivative of Y(:,1) in dy(1) and dy(2) as well as the first and second derivative of Y(:,3) in dy(3) and dy(4). So what's the problem ?

Best wishes

Torsten.