function dxdt=tanker(t,x)
%Differential equation for tanker
tankerpar;
v=x(3);r=x(4);fi=x(5);
dxdt=[cos(fi)+v*sin(fi);-sin(fi)+v*cos(fi);a1*v+a2*r+al*v*abs(v);a3*v+a4*r;r];