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[project @ 2007-10-12 06:40:56 by jwe]
author jwe
date Fri, 12 Oct 2007 06:41:26 +0000
parents 34f96dd5441b
children a1dbe9d80eee
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1 ## Copyright (C) 1993, 1994, 1995 John W. Eaton
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2 ##
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3 ## This file is part of Octave.
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4 ##
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5 ## Octave is free software; you can redistribute it and/or modify it
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6 ## under the terms of the GNU General Public License as published by
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7 ## the Free Software Foundation; either version 3 of the License, or (at
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8 ## your option) any later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 ## General Public License for more details.
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14 ##
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15 ## You should have received a copy of the GNU General Public License
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16 ## along with Octave; see the file COPYING. If not, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Function File} {} dcgain (@var{sys}, @var{tol})
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21 ## Returns dc-gain matrix. If dc-gain is infinite
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22 ## an empty matrix is returned.
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23 ## The argument @var{tol} is an optional tolerance for the condition
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24 ## number of the @math{A} Matrix in @var{sys} (default @var{tol} = 1.0e-10)
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25 ## @end deftypefn
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26
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27 ## Author: Kai P. Mueller <mueller@ifr.ing.tu-bs.de>
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28 ## Created: October 1, 1997
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29
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30 function gm = dcgain (sys, tol)
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31
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32 if((nargin < 1) || (nargin > 2) || (nargout > 1))
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33 print_usage ();
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34 endif
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35 if(!isstruct(sys))
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36 error("dcgain: first argument is not a system data structure.")
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37 endif
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38 sys = sysupdate(sys, "ss");
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39 [aa,bb,cc,dd] = sys2ss(sys);
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40 if (is_digital(sys)) aa = aa - eye(size(aa)); endif
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41 if (nargin == 1) tol = 1.0e-10; endif
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42 r = rank(aa, tol);
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43 if (r < rows(aa))
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44 gm = [];
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45 else
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46 gm = -cc / aa * bb + dd;
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47 endif
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48 if(!is_stable(sys))
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49 [nn,nz,mm,pp] = sysdimensions(sys);
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50 warning("dcgain: unstable system; dimensions [nc=%d,nz=%d,mm=%d,pp=%d]", ...
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51 nn,nz,mm,pp);
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52 endif
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53
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54 endfunction