function ydot=TacomaODE(t,y)
ydot=zeros(size(y));
len=6; a=0.1; A=10;  %length len is also in the Animation program- don't change.
a1=exp(a*(y(1)-len*sin(y(3))));
a2=exp(a*(y(1)+len*sin(y(3))));
ydot(1) = y(2);
ydot(2) = -0.01*y(2)-0.4*(a1+a2-2)/a+A*sin(3*t);
ydot(3) = y(4);
ydot(4) = -0.01*y(4)+1.2*cos(y(3))*(a1-a2)/(len*a);