How can I call the highest order solution (e.g. x'') of an ode in another ode?

1 vue (au cours des 30 derniers jours)
I want to solve the following differential equations, a-f are known variables which are manually set before solving the equations:
u'' = -a/d*u' - b/d*u - x''
x''= (c+d)^(-1)*( - e*x' - f*x - d*u'')
I do not know how to call x'' in the first and u'' in the second ode. My approach (given below) does run, but the results are wrong (u and u' are always 0). How do I implement my equations correctly?
The code I tried to use:
tspan = [0 200];
z0 = [0; 0; 5; 0];
[t,z] = ode45(@(t,z)f(t,z),tspan, z0);
function dzdt = f(t,z)
u = z(1:2);
x = z(3:4);
% Definition of a-f here
dzdt = zeros(4,1);
dzdt(1) = u(2);
dzdt(2) = -a/d *u(2)-b/d *u(1)-dzdt(4);
dzdt(3) = x(2);
dzdt(4) = (c+d)^(-1)*(-e*x(2)-f*x(1)-d*dzdt(2));
end

Réponse acceptée

Alan Stevens
Alan Stevens le 24 Fév 2021
Modifié(e) : Alan Stevens le 24 Fév 2021
You can rearrange the equations as follows to get a consistent set:
(you will need to use explicit multiplication where my equations have implicit multiplication. For example,
where I have fx(1) you will need f*x(1) etc.)

Plus de réponses (0)

Tags

Produits

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by