/usr/share/octave/packages/control-2.6.2/@lti/d2c.m is in octave-control 2.6.2-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 | ## Copyright (C) 2009-2014 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 -*-
## @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 @acronym{LTI} model into its continuous-time equivalent.
##
## @strong{Inputs}
## @table @var
## @item sys
## Discrete-time @acronym{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}.
## @item 'matched'
## Matched pole/zero method.
## @end table
## @end table
##
## @strong{Outputs}
## @table @var
## @item sys
## Continuous-time @acronym{LTI} model.
## @end table
## @end deftypefn
## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## 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);
|