X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?a=blobdiff_plain;ds=sidebyside;f=octave_packages%2Fcontrol-2.3.52%2F%40lti%2Fd2c.m;fp=octave_packages%2Fcontrol-2.3.52%2F%40lti%2Fd2c.m;h=63a165c3a4fc53703518085d8b01d2388b231669;hb=f5f7a74bd8a4900f0b797da6783be80e11a68d86;hp=0000000000000000000000000000000000000000;hpb=1705066eceaaea976f010f669ce8e972f3734b05;p=CreaPhase.git
diff --git a/octave_packages/control-2.3.52/@lti/d2c.m b/octave_packages/control-2.3.52/@lti/d2c.m
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+## Copyright (C) 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 .
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{sys} =} d2c (@var{sys})
+## @deftypefnx {Function File} {@var{sys} =} d2c (@var{sys}, @var{method})
+## @deftypefnx {Function File} {@var{sys} =} d2c (@var{sys}, @var{"prewarp"}, @var{w0})
+## Convert the discrete lti model into its continuous-time equivalent.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## Discrete-time LTI model.
+## @item method
+## Optional conversion method. If not specified, default method @var{"zoh"}
+## is taken.
+## @table @var
+## @item "zoh"
+## Zero-order hold or matrix logarithm.
+## @item "tustin", "bilin"
+## Bilinear transformation or Tustin approximation.
+## @item "prewarp"
+## Bilinear transformation with pre-warping at frequency @var{w0}.
+## @end table
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item sys
+## Continuous-time LTI model.
+## @end table
+## @end deftypefn
+
+## Author: Lukas Reichlin
+## Created: September 2011
+## Version: 0.2
+
+function sys = d2c (sys, method = "std", w0 = 0)
+
+ if (nargin == 0 || nargin > 3)
+ print_usage ();
+ endif
+
+ if (! isa (sys, "lti"))
+ error ("d2c: first argument is not an lti model");
+ endif
+
+ if (isct (sys))
+ error ("d2c: system is already continuous-time");
+ endif
+
+ if (! ischar (method))
+ error ("d2c: second argument is not a string");
+ endif
+
+ if (! issample (w0, 0))
+ error ("d2c: third argument is not a valid pre-warping frequency");
+ endif
+
+ sys = __d2c__ (sys, sys.tsam, lower (method), w0);
+ sys.tsam = 0;
+
+endfunction
+
+
+## bilinear transformation
+## both directions
+%!shared Mo, Me
+%! A = [ 1.0 0.5
+%! 0.5 1.0 ];
+%!
+%! B = [ 0.0 -1.0
+%! 1.0 0.0 ];
+%!
+%! C = [ -1.0 0.0
+%! 0.0 1.0 ];
+%!
+%! D = [ 1.0 0.0
+%! 0.0 -1.0 ];
+%!
+%! [Ao, Bo, Co, Do] = ssdata (d2c (c2d (ss (A, B, C, D), 2, "tustin"), "tustin"));
+%!
+%! Mo = [Ao, Bo; Co, Do];
+%! Me = [A, B; C, D];
+%!
+%!assert (Mo, Me, 1e-4);
+
+
+## zero-order hold
+## both directions
+%!shared Mo, Me
+%! A = [ 1.0 0.5
+%! 0.5 1.0 ];
+%!
+%! B = [ 0.0 -1.0
+%! 1.0 0.0 ];
+%!
+%! C = [ -1.0 0.0
+%! 0.0 1.0 ];
+%!
+%! D = [ 1.0 0.0
+%! 0.0 -1.0 ];
+%!
+%! [Ao, Bo, Co, Do] = ssdata (d2c (c2d (ss (A, B, C, D), 2, "zoh"), "zoh"));
+%!
+%! Mo = [Ao, Bo; Co, Do];
+%! Me = [A, B; C, D];
+%!
+%!assert (Mo, Me, 1e-4);
+
+
+## bilinear transformation with pre-warping
+## both directions
+%!shared Mo, Me
+%! A = [ 1.0 0.5
+%! 0.5 1.0 ];
+%!
+%! B = [ 0.0 -1.0
+%! 1.0 0.0 ];
+%!
+%! C = [ -1.0 0.0
+%! 0.0 1.0 ];
+%!
+%! D = [ 1.0 0.0
+%! 0.0 -1.0 ];
+%!
+%! [Ao, Bo, Co, Do] = ssdata (d2c (c2d (ss (A, B, C, D), 2, "prewarp", 1000), "prewarp", 1000));
+%!
+%! Mo = [Ao, Bo; Co, Do];
+%! Me = [A, B; C, D];
+%!
+%!assert (Mo, Me, 1e-4);