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1 ## Copyright (C) 1993, 1994, 1995, 2000, 2002, 2004, 2005, 2006, 2007 |
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2 ## John W. Eaton |
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3 ## |
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4 ## This file is part of Octave. |
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5 ## |
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6 ## Octave is free software; you can redistribute it and/or modify it |
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7 ## under the terms of the GNU General Public License as published by |
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8 ## the Free Software Foundation; either version 3 of the License, or (at |
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9 ## your option) any later version. |
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10 ## |
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11 ## Octave is distributed in the hope that it will be useful, but |
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 ## General Public License for more details. |
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15 ## |
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16 ## You should have received a copy of the GNU General Public License |
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17 ## along with Octave; see the file COPYING. If not, see |
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18 ## <http://www.gnu.org/licenses/>. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {} dcgain (@var{sys}, @var{tol}) |
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22 ## Returns dc-gain matrix. If dc-gain is infinite |
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23 ## an empty matrix is returned. |
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24 ## The argument @var{tol} is an optional tolerance for the condition |
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25 ## number of the @math{A} Matrix in @var{sys} (default @var{tol} = 1.0e-10) |
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26 ## @end deftypefn |
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27 |
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28 ## Author: Kai P. Mueller <mueller@ifr.ing.tu-bs.de> |
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29 ## Created: October 1, 1997 |
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30 |
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31 function gm = dcgain (sys, tol) |
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32 |
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33 if (nargin < 1 || nargin > 2) |
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34 print_usage (); |
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35 endif |
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36 if (! isstruct (sys)) |
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37 error ("dcgain: first argument is not a system data structure.") |
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38 endif |
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39 sys = sysupdate (sys, "ss"); |
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40 [aa, bb, cc, dd] = sys2ss (sys); |
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41 if (is_digital (sys)) |
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42 aa = aa - eye (size (aa)); |
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43 endif |
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44 if (nargin == 1) |
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45 tol = 1.0e-10; |
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46 endif |
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47 r = rank (aa, tol); |
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48 if (r < rows (aa)) |
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49 gm = []; |
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50 else |
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51 gm = -cc / aa * bb + dd; |
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52 endif |
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53 if (! is_stable (sys)) |
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54 [nn, nz, mm, pp] = sysdimensions (sys); |
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55 warning ("dcgain: unstable system; dimensions: nc=%d, nz=%d, mm=%d, pp=%d", |
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56 nn, nz, mm, pp); |
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57 endif |
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58 |
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59 endfunction |
