init

FOTF Toolbox/@fotf/inv.m

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+function G1=inv(G)
+% inv - inverse of a multivariable FOTF system
+%
+%   G1=inv(G)
+% 
+%   G, G1 - an FOTF object and its inverse system
+%   not recommended for MIMO FOTFs, use fotf2sym and work the
+%   model G under symbolic framework
+
+% Copyright (c) Dingyu Xue, Northeastern University, China
+% Last modified 28 March, 2017 
+% Last modified 18 May, 2022 
+   [n,m]=size(G);
+   if n*m==1
+      if G.ioDelay>0, error('Delay terms are not allowed');
+      else, G1=fotf(G.num,G.den); end
+   elseif n~=m
+      error('Error: non-square matrix, not invertible')
+   else, G1=fotfinv(G); end
+end
+function G1=fotfinv(G)
+   [n,~]=size(G); A1=G; E0=fotf(eye(n)); A3=E0;
+   for i=1:n, ij=1:n; ij=ij(ij~=i);
+      E=fotf(eye(n)); a0=inv(A1(i,i));
+      for k=ij, E(k,i)=-A1(k,i)*a0; end
+      E0=E*E0; A1=E*A1; A3(i,i)=a0;
+   end, G1=A3*E0;
+end