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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA -
//
// 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 [Sl1,right,left]=ss2ss(Sl,T,F,G,flag)
// State-space to state-space conversion
// Returns the linear system Sl1=[A1,B1,C1,D1]
// where A1=inv(T)*A*T,B1=inv(T)*B,C1=C*T,D1=D.
// Optional parameters F and G are state feedback
// and output injection respectively. For example,
// Sl1=ss2ss(Sl,T,F) returns Sl1=[A1,B1,C1,D1] with
// A1=inv(T)*(A+B*F)*T;B1=inv(T)*B;C1=(C+D*F)*T;D1=D;
// If F is given as input then right is a non singular
// linear system such that Sl1=Sl*right.
// Sl1*invsyslin(right) is a factorization of Sl.
// Idem for left: if F and G are given, Sl1=left*Sl*right.
// Example: Sl=ssrand(2,2,5); trzeros(Sl);
// Sl1=ss2ss(Sl,rand(5,5),rand(2,5),rand(5,2));
// trzeros(Sl1), trzeros(rand(2,2)*Sl1*rand(2,2))
// See also : projsl
[A,B,C,D]=abcd(Sl);
[LHS,RHS]=argn(0);
select RHS
case 2 then
Sl1=syslin(Sl(7),inv(T)*A*T,inv(T)*B,C*T,D);
right=eye(A);left=right;
case 3 then
A1=A+B*F;C1=C+D*F;
A1=inv(T)*A1*T;B1=inv(T)*B;C1=C1*T;D1=D
Sl1=syslin(Sl(7),A1,B1,C1,D1);
right=syslin(Sl(7),A+B*F,B,F,eye(F*B));
left=eye(size(C,1),size(C,1));
case 4 then
A1=A+B*F+G*C+G*D*F;C1=C+D*F;B1=B+G*D
A1=inv(T)*A1*T;B1=inv(T)*B1;C1=C1*T;D1=D
Sl1=syslin(Sl(7),A1,B1,C1,D1);
right=syslin(Sl(7),A+B*F,B,F,eye(F*B));
// Warning left is computed as [ At + G*Ct,G;Ct,I]
// where [At Bt; Ct Dt] is Sl1*right
At=A+B*F; Ct=C+D*F
left=syslin(Sl(7),At+G*Ct,G,Ct,eye(Ct*G));
case 5 then
if flag==1 then
// x in R^n , y in R^p, u in R^m
// output injection [ A + GC, (B+GD,-G)]
// [ C , (D , 0)]
// then feeback ( since output injection increase the
// size of the feedback the F matrix must be of size
// (m+p,n) --> F=[F1;F2] with F1 (m,n) and F2 (p,n)
//
// Sl1= [ A+GC +BF1+G*D*F1 -GF2, (B+GD,-G)]
// [ C+D*F1 , (D , 0)]
//
// We have then the following property
// Sl1 equiv left*sysdiag(sys,eye(p,p))*right
//
//
n=size(A,"r");p=size(C,"r");
A1=A+G*C+[B+G*D,-G]*F;B1=[B+G*D,-G];C1=C+[D,zeros(p,p)]*F;
D1=[D,zeros(p,p)];
A1=inv(T)*A1*T;B1=inv(T)*B1;C1=C1*T;D1=D1
Sl1=syslin(Sl(7),A1,B1,C1,D1);
left=syslin(Sl(7),A+G*C,[G,-G],C,[eye(p,p),zeros(p,p)]);
// Now we compute the right associated to left*Sl1
A1=A+G*C;B1=[B+G*D,-G];C1=C;D1=[D,zeros(p,p)];
right=syslin(Sl(7),A1+B1*F,B1,F,eye(F*B1));
return
end
if flag==2 then
// x in R^n , y in R^p, u in R^m
// feedback first F of size(m,n)
// [ A+BF,B]
// [ C+DF,D]
// then output injection
// Sl1= [ A+GC +BF+G*D*F, (B+GD,-G)]
// [ C+D*F , (D , 0)]
// this is a generalization of the case 4
// We have then the following property
// Sl1 equiv left*sysdiag(sys*right,eye(p,p)))
//
A1=A+B*F+G*C+G*D*F;
C1=C+ D*F;
D1=[D,zeros(p,p)];
B1=[B+G*D,-G];
A1=inv(T)*A1*T;B1=inv(T)*B1;C1=C1*T;D1=D1
Sl1=syslin(Sl(7),A1,B1,C1,D1);
right=syslin(Sl(7),A+B*F,B,F,eye(F*B));
// Warning left is computed as [ At + G*Ct,(G,-G);
// [ Ct ,(I, 0)]
// where [At Bt; Ct Dt] is Sl1*right
At=A+B*F; Ct=C+D*F
left=syslin(Sl(7),At+G*Ct,[G,-G],Ct,[eye(Ct*G),zeros(Ct*G)]);
end
end
endfunction
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