function [Kp,Ti,Td,key,lb]=pid_le_tune(G,key1,key2,vars)  
key=0; Kp=[]; Ti=[]; Td=[]; lb=[];
K=vars(1); L=vars(2); T=vars(3); id=vars(4);
[Gm,Pm,Wcg,Wcp]=margin(G);
switch key1
    case 1
        switch key2
            case 4
               wcn=(2.82-Pm-atan(T*(3.1416/2-Pm)/L))/L;
               Ti=tan(Pm-3.1416/2+L*wcn+atan(wcn*T))/wcn;
               Kp=wcn*T*((1+(wcn)^2*T^2)/(1+(wcn)^2*(Ti)^2))^0.5/K;
               key=1;
        end
end