%% Author: epokh
%% Website: www.epokh.org/drupy
%% This software is under GPL

function yrate=d2ydt2(vr,vl,theta0,t,b)
%% This function calculate the drift rate from center line (x axis)
    yrate=(vr+vl)*(vr-vl)*cos((vr-vl)*t/b+theta0);
end