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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) 2010 - INRIA - Serge Steer
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function [sl]=tf2ss(h,tol)
// Transfer function to state-space.
//Syntax : sl=tf2ss(h [,tol])
// h = transfer matrix
// sl = linear system in state-space representation (syslin list)
//!
[lhs,rhs]=argn(0)
if type(h)<=2 then
sl=syslin([],[],[],[],h);
return;
end
[num,den]=h(["num","den"]);
//
[nd,md]=size(den)
a=[];b=[];c=[];d=[];n1=0; // s=[]
for k=1:md
for l=1:nd
[r,q]=pdiv(num(l,k),den(l,k));
dk(l)=q;
num(l,k)=r;
end
if nd<>1 then
[nk,pp]=cmndred(num(:,k),den(:,k));
else
pp=den(k);nk=num(k);
end;
slk=cont_frm(nk,pp);
[ak,bk,ck,dk1]=slk(2:5);
// [s sk]
[n2,m2]=size(bk);
if n2<>0 then
a(n1+1:n1+n2,n1+1:n1+n2)=ak;
b(n1+1:n1+n2,k)=bk;
c=[c ck];
n1=n1+n2;
else
if n1<>0 then b(n1,k)=0;end
end;
d=[d dk];
end;
if degree(d)==0 then d=coeff(d),end
if n1<>0 then
nrmb=norm(b,1);
nrmc=norm(c,1);
fact=sqrt(nrmc*nrmb);
b=b*fact/nrmb;
c=c*fact/nrmc;
atmp=a;
[a,u]=balanc(a);
//next lines commented out to fix bug 3796
// if rcond(u)< %eps*n1*n1*100
// nn=size(a,1);u=eye(nn,nn);a=atmp;
// end
//apply transformation u without matrix inversion
[k,l]=find(u<>0) //get the permutation
u=u(k,l);c=c(:,k)*u; b=diag(1 ./diag(u))*b(k,:);
if rhs<2 then
[no,u]=contr(a',c',%eps);
else
[no,u]=contr(a',c',tol);
end
u=u(:,1:no);
a=u'*a*u;b=u'*b;c=c*u;
sl=syslin(h("dt"),a,b,c,d);
else
sl=syslin(h("dt"),[],[],[],d)
end
endfunction
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