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[project @ 2005-04-26 19:24:27 by jwe]
author jwe
date Tue, 26 Apr 2005 19:24:47 +0000
parents bdbee5282954
children 34f96dd5441b
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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 the
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7 ## Free Software Foundation; either version 2, or (at your option) any
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8 ## later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but WITHOUT
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11 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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12 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 ## 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, write to the Free
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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18 ## 02110-1301 USA.
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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) || (nargout > 1))
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34 usage("[gm, ok] = dcgain(sys[, tol])");
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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)) aa = aa - eye(size(aa)); endif
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42 if (nargin == 1) tol = 1.0e-10; endif
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43 r = rank(aa, tol);
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44 if (r < rows(aa))
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45 gm = [];
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46 else
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47 gm = -cc / aa * bb + dd;
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48 endif
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49 if(!is_stable(sys))
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50 [nn,nz,mm,pp] = sysdimensions(sys);
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51 warning("dcgain: unstable system; dimensions [nc=%d,nz=%d,mm=%d,pp=%d]", ...
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52 nn,nz,mm,pp);
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53 endif
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54
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55 endfunction