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[project @ 1998-12-09 18:42:12 by jwe]
author jwe
date Wed, 09 Dec 1998 18:42:13 +0000
parents ba1c7cdc6090
children 28aba52a2368
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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, 675 Mass Ave, Cambridge, MA 02139, USA.
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18
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19 function gm = dcgain(sys, tol)
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20 # Usage: gm = dcgain(sys[, tol])
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21 # Returns dc-gain matrix. If dc-gain is infinity
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22 # an empty matrix is returned.
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23 # The argument tol is an optional tolerance for the condition
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24 # number of A-Matrix in sys (default tol = 1.0e-10)
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25 # Prints a warning message of the system is unstable.
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26 #
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27
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28 # Written by Kai P Mueller (mueller@ifr.ing.tu-bs.de) October 1, 1997
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29 # $Revision: 2.0.0.0 $
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30
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31 if((nargin < 1) || (nargin > 2) || (nargout > 1))
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32 usage("[gm, ok] = dcgain(sys[, tol])");
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33 endif
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34 if(!is_struct(sys))
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35 error("dcgain: first argument is not a system data structure.")
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36 endif
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37 sys = sysupdate(sys, "ss");
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38 [aa,bb,cc,dd] = sys2ss(sys);
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39 if (is_digital(sys)) aa = aa - eye(size(aa)); endif
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40 if (nargin == 1) tol = 1.0e-10; endif
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41 r = rank(aa, tol);
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42 if (r < rows(aa))
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43 gm = [];
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44 else
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45 gm = -cc / aa * bb + dd;
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46 endif
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47 if(!is_stable(sys))
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48 [nn,nz,mm,pp] = sysdimensions(sys);
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49 warning("dcgain: unstable system; dimensions [nc=%d,nz=%d,mm=%d,pp=%d]", ...
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50 nn,nz,mm,pp);
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51 endif
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52 endfunction