% function [ka] = hinf_c(p,nmeas,ncon,xinf,yinf,f,h,gfin,r12,r21)
%
% Form the controller given the gamma value and xinf, yinf
%

%   Copyright 1991-2004 MUSYN Inc. and The MathWorks, Inc.
% $Revision: 1.1.8.1 $

function [ka] = hinf_c(p,nmeas,ncon,xinf,yinf,f,h,gfin,r12,r21)
[a,bp,cp,dp,b1,b2,c1,c2,d11,d12,d21,d22,ndata] = hinf_sp(p,nmeas,ncon);
np1 = ndata(1);
np2 = ndata(2);
nm1 = ndata(3);
nm2 = ndata(4);
np = max(size(a));
%
% form the submatrices f11,f12,f2 and h11,h12,h2
%
f11=f(1:(nm1-np2),:);
f12=f((nm1-np2+1):nm1,:);
f2=f((nm1+1):(nm1+nm2),:);
h11=h(:,1:(np1-nm2));
h12=h(:,(np1-nm2+1):np1);
h2=h(:,(np1+1):(np1+np2));
%
%  partition d11
%
d1111=d11(1:(np1-nm2),1:(nm1-np2));
d1112=d11(1:(np1-nm2),(nm1-np2+1):nm1);
d1121=d11((np1-nm2+1):np1,1:(nm1-np2));
d1122=d11((np1-nm2+1):np1,(nm1-np2+1):nm1);
%
%  form controller k
%
%  have to check for null ([]) values  of d1111,d1112,d1121,d1122
%
  [rd1111,cd1111]=size(d1111);
   % sd1112=max(size(d1112)); % V4 version
   % sd1121=max(size(d1121)); % V4 version
   % sd1122=max(size(d1122)); % V4 version
   sd1112=length(d1112);  % changed for matlab v5
   sd1121=length(d1121);  % changed for matlab v5
   sd1122=length(d1122);  % changed for matlab v5
%
if rd1111==0 | sd1112==0
  d11hat=-d1122;
else
  gdum=inv(gfin*gfin*eye(np1-nm2)-d1111*d1111');
  d11hat=-d1121*d1111'*gdum*d1112-d1122;
end
%
if sd1112==0
  d21hat=eye(np2);
elseif  rd1111==0
  d21hat=chol(eye(np2)-d1112'*d1112/gfin/gfin);
else
  gdum=inv(gfin*gfin*eye(np1-nm2)-d1111*d1111');
  dum=eye(np2)-d1112'*gdum*d1112;
  d21hat=chol(dum);
end
if  sd1121==0
  d12hat=eye(nm2);
elseif cd1111==0
  d12hat = chol(eye(nm2)-d1121*d1121'/gfin/gfin)';
else
  gdum=inv(gfin*gfin*eye(nm1-np2)-d1111'*d1111);
  dum=eye(nm2)-d1121*gdum*d1121';
  d12hat=chol(dum)';
end
%
z = inv(eye(np)-yinf*xinf/(gfin*gfin));
clear gdum dum
b2hat=(b2+h12)*d12hat;
c2hat=-d21hat*(c2+f12)*z;
b1hat=-h2+(b2hat/d12hat)*d11hat;
c1hat=f2*z+(d11hat/d21hat)*c2hat;
ahat=a+h*cp+(b2hat/d12hat)*c1hat;
%
% form the controller for the case where d22 is zero
%
%  back-substitute scaling factors r12 and r21
%
b1hat=b1hat*r21;
c1hat=r12*c1hat;
bhat=[b1hat,b2hat];
chat=[c1hat;c2hat];
dhat=[r12*d11hat*r21,r12*d12hat;d21hat*r21,(0.*d11hat')];
%
%  this part of the program allows for a d22 non-zero in the plant matrix
%  it assumes that phi=0
%
%  check that the det(i+d11hat*d22) is non-zero
%
% if (1-det(d11hat*d22)) < eps
% if abs(det(eye(nm2)+d11hat*d22)) < eps
if cond(eye(nm2)+r12*d11hat*r21*d22) > 1/eps
   error('  det(I+d11hat*d22) is zero ')
 end
d22new=[d22,(0.*eye(np2));(0.*eye(nm2)),(0.*d22')];
m=inv(eye(nm2+np2)+d22new*dhat);
mhat=inv(eye(nm2+np2)+dhat*d22new);
ahat=ahat-bhat*((eye(nm2+np2)-m)/dhat)*chat;
bhat=bhat*m;
chat=mhat*chat;
dhat=dhat*m;
ka = pck(ahat,bhat,chat,dhat);
%
%