function y=torq_xian(u)
if(u(1)<1500)
   u(1)=5.25;
elseif(u(1)<=2450)
   u(1)=5.1-(u(1)-1600)*0.6/400;
else
   u(1)=3.825-(u(1)-2450)*1.83/350;
end
if(u(2)>=u(1))
   u(2)=u(1);
elseif (u(2)<=-u(1))
      u(2)=-u(1);
end
   y=u(2);