function u = pendulum(x)

global epsSqr l m g

x1 = x(1);
x2 = x(2);
v1 = x(3);
v2 = x(4);

temp = 1/epsSqr*(1 - l./sqrt(x1.^2+x2.^2));

u = [v1
     v2
     -1/m*temp*x1
     -g-1/m*temp*x2];

end

Published with MATLAB® R2012b