MATLAB: Solving system of second order differential equations

differential equationsode45

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));

Best Answer

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.
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