Solving system of second order differential equations

Hi,

I tried to solve a system of coupled differential equations.

Can anyone help me with this error?

"Error using odearguments (line 93) ODE_FUNCTION must return a column vector.

Error in ode23tb (line 135) odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in ODE_Function_Solver (line 4) [t,y] = ode45(@ODE_Function,tspan,y0);"

Thank you.

    tspan = 0:0.001:2;
    y0 = [0 0;0 0;0 0;0 0;0 0;0 0];
    [t,y] = ode23tb(@ODE_Function,tspan,y0);

    function dydt = ODE_Function(t,y)
    m1 = 1;
    k1 = 100;
    m2 = 1;
    k2 = 100;
    w = 2*pi*50;
    F = sin(w*t);
    h = 0.1;
    w = 0.1;

%  First ODE
dydt(1) = y(2);
dydt(2) = F - k1/m1*(y(1)-y(5))-2*k2/m1*cos(atan((2*h-2*y(3))/w))*(y(1)-y(3));

%  SecondODE
dydt(3) = y(4);
dydt(4) = -2*k2/m2*cos(atan((2*h-2*y(3))/w))*(y(3)-y(1));

%  Third ODE
dydt(5) = y(6);
dydt(6) = -k1/m1*(2*y(5)-y(1)-y(9))-2*k2/m1*cos(atan((2*h-2*y(7))/w))*(y(1)-y(3));

%  Fourth ODE
dydt(7) = y(8);
dydt(8) = -2*k2/m2*cos(atan((2*h-2*y(7))/w))*(y(7)-y(5));

%  Fifth ODE
dydt(9) = y(10);
dydt(10) = -k1/m1*(y(9)-y(5))-2*k2/m1*cos(atan((2*h-2*y(11))/w))*(y(1)-y(3));

%  Sixth ODE
dydt(11) = y(12);
dydt(12) = -2*k2/m2*cos(atan((2*h-2*y(11))/w))*(y(11)-y(9));

Answer 1

[lokender Rawat]

The return type of the parameter from the function block must be a column vector. So, you can add the below statement at the end, inside the function block:

dydt=dydt';

I think you were missing this.

[Torsten]

... and you shouldn't supply y0 as a (6x2) matrix, but as a (12x1) vector.