[Octave-cvsupdate] SF.net SVN: octave:[7704] trunk/octave-forge/main/control/inst

[<par...@us...>]

Revision: 7704
          http://octave.svn.sourceforge.net/octave/?rev=7704&view=rev
Author:   paramaniac
Date:     2010-09-12 23:03:20 +0000 (Sun, 12 Sep 2010)

Log Message:
-----------
control: add new sminreal implementation and tests

Modified Paths:
--------------
    trunk/octave-forge/main/control/inst/@lti/sminreal.m
    trunk/octave-forge/main/control/inst/issample.m
    trunk/octave-forge/main/control/inst/ltimodels.m

Modified: trunk/octave-forge/main/control/inst/@lti/sminreal.m
===================================================================
--- trunk/octave-forge/main/control/inst/@lti/sminreal.m	2010-09-11 20:50:58 UTC (rev 7703)
+++ trunk/octave-forge/main/control/inst/@lti/sminreal.m	2010-09-12 23:03:20 UTC (rev 7704)
@@ -1,4 +1,4 @@
-## Copyright (C) 2009   Lukas F. Reichlin
+## Copyright (C) 2009 - 2010   Lukas F. Reichlin
 ##
 ## This file is part of LTI Syncope.
 ##
@@ -17,44 +17,91 @@
 
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {@var{sys} =} sminreal (@var{sys})
-## Perform state-space model reduction based on structure,
-## i.e. retain only states which are both controllable and observable.
+## @deftypefnx {Function File} {@var{sys} =} sminreal (@var{sys}, @var{tol})
+## Perform state-space model reduction based on structure.
+## Remove states which have no influence on the input-output behaviour.
 ## The physical meaning of the states is retained.
+##
+## @strong{Inputs}
+## @table @var
+## @item sys
+## State-space model.
+## @item tol
+## Optional tolerance for controllability and observability. 
+## Entries of the state-space matrices whose moduli are less or equal to @var{tol}
+## are assumed to be zero. Default value is 0.
+## @end table
+##
+## @strong{Outputs}
+## @table @var
+## @item sys
+## Reduced state-space model.
+## @end table
+##
+## @seealso{minreal}
 ## @end deftypefn
 
-## Algorithm based on sysmin by A. Scottedward Hodel
 ## Author: Lukas Reichlin <luk...@gm...>
 ## Created: October 2009
-## Version: 0.1
+## Version: 0.2
 
-function sys = sminreal (sys)
+function sys = sminreal (sys, tol = 0)
 
+  if (nargin > 2)  # sminreal () not possible (inside @lti)
+    print_usage ();
+  endif
+
   if (! isa (sys, "ss"))
     warning ("sminreal: system not in state-space form");
     sys = ss (sys);
   endif
 
-  [cflg, Uc] = isctrb (sys);
-  [oflg, Uo] = isobsv (sys);
+  if (! (isreal (tol) && isscalar (tol) && (tol >= 0)))
+    error ("sminreal: second argument is not a valid tolerance");
+  endif
 
-  xc = find (max (abs (Uc.')) != 0);
-  xo = find (max (abs (Uo.')) != 0);
-  st_idx = intersect (xc, xo);
+  [a, b, c] = ssdata (sys);
 
+  a = abs (a) > tol;
+  b = abs (b) > tol;
+  c = abs (c) > tol;
+
+  co_idx = __controllable_states__ (a, b);
+  ob_idx = __controllable_states__ (a.', c.');
+
+  st_idx = intersect (co_idx, ob_idx);
+
   sys = __sysprune__ (sys, ":", ":", st_idx);
 
-  warning ("sminreal: use result with caution");
-
 endfunction
 
 
-## FIXME: algorithm returns wrong result for the example below
-##
-## P = ss (-2, 3, 4, 5)
-## C = inv (P)
-## L = P * C
-## Ls = sminreal (L)
-## bode (Ls)
-## 
-## Obviously, both magnitude and phase should be straight lines at 0 dB and 0 deg
-## In this case, sminreal shouldn't remove any states of L
\ No newline at end of file
+function c_idx = __controllable_states__ (a, b)
+
+  n = rows (a);  # number of states
+  a = a & ! eye (n);  # set diagonal entries to zero
+
+  c_vec = any (b, 2);  # states directly controllable
+  c_idx = find (c_vec);  # indices of directly controllable states
+  c_idx_new = 0;  # any vector of length > 0 possible
+
+  while (all (length (c_idx) != [0, n] && length(c_idx_new) != 0))
+
+    u_idx = find (! c_vec);  # indices of uncontrollable states
+
+    #{
+    ## debug code
+    a(u_idx, :)
+    repmat (c_vec.', length (u_idx), 1)
+    a(u_idx, :) & repmat (c_vec.', length (u_idx), 1)
+    any (a(u_idx, :) & repmat (c_vec.', length (u_idx), 1), 2)
+    find (any (a(u_idx, :) & repmat (c_vec.', length (u_idx), 1), 2))
+    #}
+
+    c_idx_new = u_idx (find (any (a(u_idx, :) & repmat (c_vec.', length (u_idx), 1), 2)));
+    c_idx = union (c_idx, c_idx_new);
+    c_vec(c_idx_new) = 1;
+
+  endwhile
+
+endfunction

Modified: trunk/octave-forge/main/control/inst/issample.m
===================================================================
--- trunk/octave-forge/main/control/inst/issample.m	2010-09-11 20:50:58 UTC (rev 7703)
+++ trunk/octave-forge/main/control/inst/issample.m	2010-09-12 23:03:20 UTC (rev 7704)
@@ -35,9 +35,9 @@
     print_usage (); 
   endif
 
-  if (flg == 0)  # allow -1 and 0
+  if (flg == 0)  # refuse -1 and 0
     bool = (isreal (tsam) && isscalar (tsam) && (tsam > 0));       
-  else  # refuse -1 and 0
+  else  # allow -1 and 0
     bool = (isreal (tsam) && isscalar (tsam) && (tsam >= 0 || tsam == -1));
   endif
 

Modified: trunk/octave-forge/main/control/inst/ltimodels.m
===================================================================
--- trunk/octave-forge/main/control/inst/ltimodels.m	2010-09-11 20:50:58 UTC (rev 7703)
+++ trunk/octave-forge/main/control/inst/ltimodels.m	2010-09-12 23:03:20 UTC (rev 7704)
@@ -249,6 +249,36 @@
 #%!assert (M, Me, 1e-4);
 
 
+## ss: sminreal
+%!shared B, C
+%!
+%! A = ss (-2, 3, 4, 5);
+%! B = A / A;
+%! C = sminreal (B);  # no states should be removed
+%!
+%!assert (C.a, B.a);
+%!assert (C.b, B.b);
+%!assert (C.c, B.c);
+%!assert (C.d, B.d);
+
+%!shared A, B, D, E
+%!
+%! A = ss (-1, 1, 1, 0);
+%! B = ss (-2, 3, 4, 5);
+%! C = [A, B];
+%! D = sminreal (C(:, 1));
+%! E = sminreal (C(:, 2));
+%!
+%!assert (D.a, A.a);
+%!assert (D.b, A.b);
+%!assert (D.c, A.c);
+%!assert (D.d, A.d);
+%!assert (E.a, B.a);
+%!assert (E.b, B.b);
+%!assert (E.c, B.c);
+%!assert (E.d, B.d);
+
+
 ## mtimes
 %!shared sysmat, sysmat_exp
 %! sys1 = ss ([0, 1; -3, -2], [0; 1], [-5, 1], [2]);


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