How to call the solver:
[t,Y] = ode45(@(t,x)sisdif(t,x,Fcm,m,Cx,r,R,Iy),[t0 t1],initialConditions);
where [t0 t1] is the integration interval initialConditions is a 4by1 array with the initial condition
Function (check the signs to be sure I did it right):
function dy = sisdif(t,y,Fcm,m,Cx,r,R,Iy)
x = y(1);
v = y(2);
theta = y(3);
omega = y(4);
dy = zeros(4,1);
dy(1) = v + (Fcm/m)
dy(2) = - (Cx/m)*x + (Cx*r/m)*theta
dy(3) = + omega
dy(4) = + (Cx*R/Iy)*x - (Cx*R^2/Iy)*theta