Mercurial > hg > octave-nkf
annotate scripts/control/system/is_stable.m @ 7795:df9519e9990c
Handle single precision eps values
| author | David Bateman <dbateman@free.fr> |
|---|---|
| date | Mon, 12 May 2008 22:57:11 +0200 |
| parents | 59dcf01bb3e3 |
| children |
| rev | line source |
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| 7017 | 1 ## Copyright (C) 1993, 1994, 1995, 2000, 2002, 2004, 2005, 2006, 2007 |
| 2 ## Auburn University. All rights reserved. | |
| 3441 | 3 ## |
| 4 ## This file is part of Octave. | |
| 5 ## | |
| 6 ## Octave is free software; you can redistribute it and/or modify it | |
| 7016 | 7 ## under the terms of the GNU General Public License as published by |
| 8 ## the Free Software Foundation; either version 3 of the License, or (at | |
| 9 ## your option) any later version. | |
| 3441 | 10 ## |
| 7016 | 11 ## Octave is distributed in the hope that it will be useful, but |
| 12 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 14 ## General Public License for more details. | |
| 3441 | 15 ## |
| 16 ## You should have received a copy of the GNU General Public License | |
| 7016 | 17 ## along with Octave; see the file COPYING. If not, see |
| 18 ## <http://www.gnu.org/licenses/>. | |
| 3441 | 19 |
| 20 ## -*- texinfo -*- | |
| 3500 | 21 ## @deftypefn {Function File} {} is_stable (@var{a}, @var{tol}, @var{dflg}) |
| 22 ## @deftypefnx {Function File} {} is_stable (@var{sys}, @var{tol}) | |
| 23 ## Returns 1 if the matrix @var{a} or the system @var{sys} | |
| 3441 | 24 ## is stable, or 0 if not. |
| 25 ## | |
| 26 ## @strong{Inputs} | |
| 27 ## @table @var | |
| 28 ## @item tol | |
| 5016 | 29 ## is a roundoff parameter, set to 200*@code{eps} if omitted. |
| 3441 | 30 ## @item dflg |
| 31 ## Digital system flag (not required for system data structure): | |
| 32 ## @table @code | |
| 33 ## @item @var{dflg} != 0 | |
| 5016 | 34 ## stable if eig(a) is in the unit circle |
| 3441 | 35 ## |
| 36 ## @item @var{dflg} == 0 | |
| 5016 | 37 ## stable if eig(a) is in the open LHP (default) |
| 3441 | 38 ## @end table |
| 39 ## @end table | |
| 5642 | 40 ## @seealso{size, rows, columns, length, ismatrix, isscalar, isvector |
| 41 ## is_observable, is_stabilizable, is_detectable, krylov, krylovb} | |
| 3441 | 42 ## @end deftypefn |
| 43 | |
| 44 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> | |
| 45 ## Created: August 1993 | |
| 46 ## Updated by John Ingram (ingraje@eng.auburn.edu) July, 1996 for systems | |
| 47 ## Updated to simpler form by a.s.hodel 1998 | |
| 48 | |
| 49 function retval = is_stable (a, tol, disc) | |
| 50 | |
| 7136 | 51 if (nargin < 1 || nargin > 3) |
| 52 print_usage (); | |
| 53 elseif (isstruct (a)) | |
| 3441 | 54 ## system was passed |
| 7136 | 55 if (nargin < 3) |
| 56 disc = is_digital(a); | |
| 57 elseif (disc != is_digital (a)) | |
| 58 warning ("is_stable: disc =%d does not match system", disc) | |
| 3441 | 59 endif |
| 7136 | 60 sys = sysupdate (a, "ss"); |
| 61 a = sys2ss (sys); | |
| 3441 | 62 else |
| 7136 | 63 if (nargin < 3) |
| 64 disc = 0; | |
| 65 endif | |
| 66 if (issquare (a) == 0) | |
| 67 error ("A(%dx%d) must be square", rows (A), columns (A)); | |
| 3441 | 68 endif |
| 69 endif | |
| 70 | |
| 7136 | 71 if (nargin < 2) |
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72 if (isa (a, "single")) |
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73 tol = 200 * eps("single"); |
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74 else |
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75 tol = 200 * eps; |
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76 endif |
| 7136 | 77 elseif (! isscalar (tol)) |
| 78 error ("is_stable: tol(%dx%d) must be a scalar", rows (tol), | |
| 79 columns (tol)); | |
| 3441 | 80 endif |
| 81 | |
| 7136 | 82 l = eig (a); |
| 83 if (disc) | |
| 84 nbad = sum (abs(l)*(1+tol) > 1); | |
| 85 else | |
| 86 nbad = sum (real(l)+tol > 0); | |
| 87 endif | |
| 3441 | 88 retval = (nbad == 0); |
| 89 | |
| 90 endfunction |