/usr/share/octave/packages/control-2.6.2/@ss/__c2d__.m is in octave-control 2.6.2-1build1.
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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 | ## 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 -*-
## Convert the continuous SS model into its discrete-time equivalent.
## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: October 2009
## Version: 0.4
function sys = __c2d__ (sys, tsam, method = "zoh", w0 = 0)
switch (method(1))
case {"z", "s"} # {"zoh", "std"}
[sys.a, sys.b, sys.c, sys.d, sys.e] = __dss2ss__ (sys.a, sys.b, sys.c, sys.d, sys.e);
[n, m] = size (sys.b); # n: states, m: inputs
## TODO: use SLICOT MB05OD
tmp = expm ([sys.a*tsam, sys.b*tsam; zeros(m, n+m)]);
sys.a = tmp (1:n, 1:n); # F
sys.b = tmp (1:n, n+(1:m)); # G
case {"t", "b", "p"} # {"tustin", "bilin", "prewarp"}
if (method(1) == "p") # prewarping
beta = w0 / tan (w0*tsam/2);
else
beta = 2/tsam;
endif
if (isempty (sys.e))
[sys.a, sys.b, sys.c, sys.d] = __sl_ab04md__ (sys.a, sys.b, sys.c, sys.d, 1, beta, false);
else
[sys.a, sys.b, sys.c, sys.d, sys.e] = __dss_bilin__ (sys.a, sys.b, sys.c, sys.d, sys.e, beta, false);
endif
case "m" # "matched"
tmp = ss (c2d (zpk (sys), tsam, method));
sys.e = tmp.e;
sys.a = tmp.a;
sys.b = tmp.b;
sys.c = tmp.c;
sys.d = tmp.d;
otherwise
error ("ss: c2d: '%s' is an invalid or missing method", method);
endswitch
endfunction
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