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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, 59 Temple Place, Suite 330, Boston, MA 02111 USA. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File } {@var{gm} =} dcgain(@var{sys}@{, 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 @var{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 function gm = dcgain(sys, tol) |
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28 ## Written by Kai P Mueller (mueller@ifr.ing.tu-bs.de) October 1, 1997 |
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29 |
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30 if((nargin < 1) || (nargin > 2) || (nargout > 1)) |
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31 usage("[gm, ok] = dcgain(sys[, tol])"); |
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32 endif |
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33 if(!is_struct(sys)) |
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34 error("dcgain: first argument is not a system data structure.") |
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35 endif |
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36 sys = sysupdate(sys, "ss"); |
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37 [aa,bb,cc,dd] = sys2ss(sys); |
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38 if (is_digital(sys)) aa = aa - eye(size(aa)); endif |
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39 if (nargin == 1) tol = 1.0e-10; endif |
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40 r = rank(aa, tol); |
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41 if (r < rows(aa)) |
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42 gm = []; |
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43 else |
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44 gm = -cc / aa * bb + dd; |
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45 endif |
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46 if(!is_stable(sys)) |
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47 [nn,nz,mm,pp] = sysdimensions(sys); |
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48 warning("dcgain: unstable system; dimensions [nc=%d,nz=%d,mm=%d,pp=%d]", ... |
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49 nn,nz,mm,pp); |
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50 endif |
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51 endfunction |