Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / control-2.3.52 / @tf / __sys_inverse__.m

diff --git a/octave_packages/control-2.3.52/@tf/__sys_inverse__.m b/octave_packages/control-2.3.52/@tf/__sys_inverse__.m
new file mode 100644 (file)
index 0000000..8268c7c
--- /dev/null
+++ b/octave_packages/control-2.3.52/@tf/__sys_inverse__.m
@@ -0,0 +1,52 @@
+## Copyright (C) 2009, 2011   Lukas F. Reichlin
+##
+## This file is part of LTI Syncope.
+##
+## LTI Syncope is free software: you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## LTI Syncope is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with LTI Syncope.  If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## Inversion of TF models.
+
+## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
+## Created: October 2009
+## Version: 0.2
+
+function sys = __sys_inverse__ (sys)
+
+  nvec = size (sys);
+  num = sys.num;
+  den = sys.den;
+
+  if (all (nvec == 1))      # SISO
+    if (num{1,1} == 0)      # catch case num = 0
+      sys.num(1,1) = tfpoly (0);
+      sys.den(1,1) = tfpoly (1);
+    else
+      sys.num = den;
+      sys.den = num;
+    endif
+  elseif (all (nvec == 2))  # 2x2 MIMO
+    sys.num(1,1) = -den{1,1}*den{1,2}*den{2,1}*num{2,2};
+    sys.num(1,2) = den{1,1}*den{2,1}*den{2,2}*num{1,2};
+    sys.num(2,1) = den{1,1}*den{1,2}*den{2,2}*num{2,1};
+    sys.num(2,2) = -den{1,2}*den{2,1}*den{2,2}*num{1,1};  
+    sys.den(:) = den{1,1}*den{2,2}*num{1,2}*num{2,1} - den{1,2}*den{2,1}*num{1,1}*num{2,2};
+  else
+    ## I've calculated 3x3 systems with sage but the formula is quite long
+    [num, den] = tfdata (inv (ss (sys)), "tfpoly");
+    sys.num = num;
+    sys.den = den;
+  endif
+
+endfunction