function[gc]=leadbode(g,K,PM,GM)
%This function using the Bode diagram make the phase lead compensation, 
%input is tf, Kp(or Kv, Ka) (if have no K, Kc=1),phase margin and gain 
%margin which expect.
%-------------------------------------------------------|%
%|(C)2005 Bui Trung Hieu				|%
%|Website: www.khvt.com					|%
%|Email: hieu@khvt.com				|%
%-------------------------------------------------------|%
if (nargin==3) 
    GM=PM;
    PM=K;    
    Kc=1;
elseif (nargin==4)
    Kc=Kc_error(g,K);
end

%Now, find margin
g1=Kc*g;
[gm1,Pm,wcg1,wcp1]=margin(g1);
clear gm1 wcp1 wcg1

%Step 4 in course, loop at here...
%Phase angle adder
%Step 5
theta=2;
max_ang=30;
while(theta<max_ang)
    phimax=(PM-Pm+theta)*pi/180;
    if (phimax>89*pi/180)
        Result=sprintf('Bai toan vo nghiem')
        gc=nan;
        break;
    end
    %Step 6
    anpha=(1+sin(phimax))/(1-sin(phimax));
    %Step 7
    [mag phase w]=bode(g1);
    clear phase
    mag=mag(:);
    w=w(:);
%Find freq value which satisfies relation: Abs(G1(jw'c))=1/sqrt(anpha)
    temp=1/sqrt(anpha);
    t=find((mag>temp-7)&(mag<temp+7));
    [vltemp,degree]=min(abs(mag(t)-temp));
    clear vltemp mag
    wc=w(min(t)+degree-1);
    clear w degree t
    wc=wc-0.5:0.001:0.5+wc;
    mag=abs(freqresp(g1,wc));
    mag=mag(:);
    [value,degree]=min(abs(mag-temp));
    clear value
    wc=wc(degree);
    T=1/wc*temp;
    gc=Kc*tf([anpha*T 1],[T 1]);
%Step 9
    gkq=g*gc;
    [gmc pmc wgc wpc]=margin(gkq);
    gmc=20*log10(gmc);
    if ((gmc>=GM)&(pmc>=PM))
        clf;
        hold on
        bode(gc,g);
        bode(gkq,'r')
        legend('Phase lead compensation','Org Tranfer Function','Compensated Tranfer Function');
        margin(g*gc);
        pause();
        clf;
        hold on;
        step(feedback(gkq,1),feedback(g,1));
        grid on
        legend('Compensated Tranfer Function','Org Tranfer Function');
        pause();
        close();
        break
    else
        clear gc gmc pmc wgc wpc gkq
        theta=theta+1;
        if (theta==max_ang)
            Result=sprintf('Bai toan vo nghiem')
            gc=nan;
        end
    end
end
%End