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1 ## Copyright (C) 1993, 1994, 1995, 2000, 2002, 2004, 2005, 2006, 2007 |
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2 ## Auburn University. All rights reserved. |
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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} {[@var{retval}, @var{u}] =} is_controllable (@var{sys}, @var{tol}) |
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22 ## @deftypefnx {Function File} {[@var{retval}, @var{u}] =} is_controllable (@var{a}, @var{b}, @var{tol}) |
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23 ## Logical check for system controllability. |
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24 ## |
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25 ## @strong{Inputs} |
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26 ## @table @var |
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27 ## @item sys |
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28 ## system data structure |
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29 ## @item a |
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30 ## @itemx b |
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31 ## @var{n} by @var{n}, @var{n} by @var{m} matrices, respectively |
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32 ## @item tol |
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33 ## optional roundoff parameter. Default value: @code{10*eps} |
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34 ## @end table |
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35 ## |
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36 ## @strong{Outputs} |
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37 ## @table @var |
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38 ## @item retval |
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39 ## Logical flag; returns true (1) if the system @var{sys} or the |
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40 ## pair (@var{a}, @var{b}) is controllable, whichever was passed as input |
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41 ## arguments. |
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42 ## @item u |
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43 ## @var{u} is an orthogonal basis of the controllable subspace. |
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44 ## @end table |
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45 ## |
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46 ## @strong{Method} |
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47 ## Controllability is determined by applying Arnoldi iteration with |
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48 ## complete re-orthogonalization to obtain an orthogonal basis of the |
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49 ## Krylov subspace |
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50 ## @example |
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51 ## span ([b,a*b,...,a^@{n-1@}*b]). |
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52 ## @end example |
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53 ## The Arnoldi iteration is executed with @code{krylov} if the system |
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54 ## has a single input; otherwise a block Arnoldi iteration is performed |
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55 ## with @code{krylovb}. |
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56 ## @seealso{size, rows, columns, length, ismatrix, isscalar, isvector |
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57 ## is_observable, is_stabilizable, is_detectable, krylov, krylovb} |
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58 ## @end deftypefn |
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59 |
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60 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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61 ## Created: August 1993 |
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62 ## Updated by A. S. Hodel (scotte@eng.auburn.edu) Aubust, 1995 to use krylovb |
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63 ## Updated by John Ingram (ingraje@eng.auburn.edu) July, 1996 for packed systems |
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64 |
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65 function [retval, U] = is_controllable (a, b, tol) |
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66 |
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67 deftol = 1; # assume default tolerance |
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68 |
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69 if (nargin < 1 || nargin > 3) |
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70 print_usage (); |
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71 elseif (isstruct (a)) |
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72 ## system structure passed. |
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73 sys = sysupdate (a, "ss"); |
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74 [a, bs] = sys2ss (sys); |
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75 if (nargin > 2) |
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76 print_usage (); |
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77 elseif (nargin == 2) |
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78 tol = b; % get tolerance |
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79 deftol = 0; |
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80 endif |
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81 b = bs; |
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82 else |
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83 ## a,b arguments sent directly. |
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84 if (nargin < 2) |
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85 print_usage (); |
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86 else |
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87 deftol = 1; |
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88 endif |
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89 endif |
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90 |
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91 ## check for default tolerance |
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92 if (deftol) |
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93 tol = 1000*eps; |
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94 endif |
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95 |
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96 ## check tol dimensions |
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97 if (! isscalar (tol)) |
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98 error ("is_controllable: tol(%dx%d) must be a scalar", ... |
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99 rows (tol), columns (tol)); |
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100 elseif (! is_sample (tol)) |
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101 error ("is_controllable: tol=%e must be positive",tol); |
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102 endif |
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103 |
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104 ## check dimensions compatibility |
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105 n = issquare (a); |
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106 [nr, nc] = size (b); |
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107 |
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108 if (n == 0 || n != nr || nc == 0) |
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109 warning ("is_controllable: a=(%dx%d), b(%dx%d)",rows(a),columns(a),nr,nc); |
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110 retval = 0; |
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111 else |
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112 ## call block-krylov subspace routine to get an orthogonal basis |
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113 ## of the controllable subspace. |
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114 [U, H, Ucols] = krylov (a, b, n, tol, 1); |
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115 retval = (Ucols == n); |
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116 endif |
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117 |
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118 endfunction |
