[Octave-cvsupdate] SF.net SVN: octave:[8502] trunk/octave-forge/main/control

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

Revision: 8502
          http://octave.svn.sourceforge.net/octave/?rev=8502&view=rev
Author:   paramaniac
Date:     2011-09-05 19:14:03 +0000 (Mon, 05 Sep 2011)
Log Message:
-----------
control: add pre-warping option to c2d and d2c

Modified Paths:
--------------
    trunk/octave-forge/main/control/doc/NEWS
    trunk/octave-forge/main/control/inst/@lti/c2d.m
    trunk/octave-forge/main/control/inst/@lti/d2c.m
    trunk/octave-forge/main/control/inst/@ss/__c2d__.m
    trunk/octave-forge/main/control/inst/@ss/__d2c__.m

Modified: trunk/octave-forge/main/control/doc/NEWS
===================================================================
--- trunk/octave-forge/main/control/doc/NEWS	2011-09-05 18:02:37 UTC (rev 8501)
+++ trunk/octave-forge/main/control/doc/NEWS	2011-09-05 19:14:03 UTC (rev 8502)
@@ -5,12 +5,13 @@
 ===============================================================================
 
 ** @lti/c2d
-   -- Support for "tustin" method added.
+   -- Support for "tustin" and "prewarp" method added.
    -- Improved Texinfo string.
 
 ** @lti/d2c
    -- Discrete to continuous-time conversion added.  However, support is
-      limited to state-space models and the zero-order hold and tustin methods.
+      limited to state-space models and the zero-order hold, tustin and pre-
+      warping methods.
    
 ** Conversion from descriptor to regular state-space is now performed by SLICOT
    routine SB10JD.  Better numerical results are to be expected over the

Modified: trunk/octave-forge/main/control/inst/@lti/c2d.m
===================================================================
--- trunk/octave-forge/main/control/inst/@lti/c2d.m	2011-09-05 18:02:37 UTC (rev 8501)
+++ trunk/octave-forge/main/control/inst/@lti/c2d.m	2011-09-05 19:14:03 UTC (rev 8502)
@@ -18,6 +18,7 @@
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {@var{sys} =} c2d (@var{sys}, @var{tsam})
 ## @deftypefnx {Function File} {@var{sys} =} c2d (@var{sys}, @var{tsam}, @var{method})
+## @deftypefnx {Function File} {@var{sys} =} c2d (@var{sys}, @var{tsam}, @var{"prewarp"}, @var{w0})
 ## Convert the continuous lti model into its discrete-time equivalent.
 ##
 ## @strong{Inputs}
@@ -29,11 +30,13 @@
 ## @item method
 ## Optional conversion method.  If not specified, default method @var{"zoh"}
 ## is taken.
-## @table @code
+## @table @var
 ## @item "zoh"
 ## Zero-order hold or matrix exponential.
 ## @item "tustin", "bilin"
 ## Bilinear transformation or Tustin approximation.
+## @item "prewarp"
+## Bilinear transformation with pre-warping at frequency @var{w0}.
 ## @end table
 ## @end table
 ##
@@ -48,9 +51,9 @@
 ## Created: October 2009
 ## Version: 0.2
 
-function sys = c2d (sys, tsam, method = "std")
+function sys = c2d (sys, tsam, method = "std", w0 = 0)
 
-  if (nargin < 2 || nargin > 3)
+  if (nargin < 2 || nargin > 4)
     print_usage ();
   endif
 
@@ -70,7 +73,7 @@
     error ("c2d: third argument is not a string");
   endif
 
-  sys = __c2d__ (sys, tsam, method);
+  sys = __c2d__ (sys, tsam, lower (method), w0);
   sys.tsam = tsam;
 
-endfunction
\ No newline at end of file
+endfunction

Modified: trunk/octave-forge/main/control/inst/@lti/d2c.m
===================================================================
--- trunk/octave-forge/main/control/inst/@lti/d2c.m	2011-09-05 18:02:37 UTC (rev 8501)
+++ trunk/octave-forge/main/control/inst/@lti/d2c.m	2011-09-05 19:14:03 UTC (rev 8502)
@@ -18,6 +18,7 @@
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {@var{sys} =} d2c (@var{sys})
 ## @deftypefnx {Function File} {@var{sys} =} d2c (@var{sys}, @var{method})
+## @deftypefnx {Function File} {@var{sys} =} d2c (@var{sys}, @var{"prewarp"}, @var{w0})
 ## Convert the discrete lti model into its continuous-time equivalent.
 ##
 ## @strong{Inputs}
@@ -27,11 +28,13 @@
 ## @item method
 ## Optional conversion method.  If not specified, default method @var{"zoh"}
 ## is taken.
-## @table @code
+## @table @var
 ## @item "zoh"
 ## Zero-order hold or matrix logarithm.
 ## @item "tustin", "bilin"
 ## Bilinear transformation or Tustin approximation.
+## @item "prewarp"
+## Bilinear transformation with pre-warping at frequency @var{w0}.
 ## @end table
 ## @end table
 ##
@@ -46,9 +49,9 @@
 ## Created: September 2011
 ## Version: 0.1
 
-function sys = d2c (sys, method = "std")
+function sys = d2c (sys, method = "std", w0 = 0)
 
-  if (nargin == 0 || nargin > 2)
+  if (nargin == 0 || nargin > 3)
     print_usage ();
   endif
 
@@ -64,7 +67,7 @@
     error ("d2c: second argument is not a string");
   endif
 
-  sys = __d2c__ (sys, sys.tsam, method);
+  sys = __d2c__ (sys, sys.tsam, lower (method), w0);
   sys.tsam = 0;
 
 endfunction

Modified: trunk/octave-forge/main/control/inst/@ss/__c2d__.m
===================================================================
--- trunk/octave-forge/main/control/inst/@ss/__c2d__.m	2011-09-05 18:02:37 UTC (rev 8501)
+++ trunk/octave-forge/main/control/inst/@ss/__c2d__.m	2011-09-05 19:14:03 UTC (rev 8502)
@@ -22,10 +22,10 @@
 ## Created: October 2009
 ## Version: 0.2
 
-function sys = __c2d__ (sys, tsam, method = "zoh")
+function sys = __c2d__ (sys, tsam, method = "zoh", w0 = 0)
 
-  switch (method)
-    case {"zoh", "std"}
+  switch (method(1))
+    case {"z", "s"}                # {"zoh", "std"}
       [sys.a, sys.b, sys.c, sys.d, sys.e] = __dss2ss__ (sys.a, sys.b, sys.c, sys.d, sys.e);
       [n, m] = size (sys.b);       # n: states, m: inputs
       ## TODO: use SLICOT MB05OD
@@ -33,13 +33,16 @@
       sys.a = tmp (1:n, 1:n);      # F
       sys.b = tmp (1:n, n+(1:m));  # G
 
-    case {"tustin", "bilin"}
+    case {"t", "b", "p"}           # {"tustin", "bilin", "prewarp"}
+      if (method(1) == "p")        # prewarping
+        beta = w0 / tan (w0*tsam/2);
+      else
+        beta = 2/tsam;
+      endif
       [sys.a, sys.b, sys.c, sys.d, sys.e] = __dss2ss__ (sys.a, sys.b, sys.c, sys.d, sys.e);
-      [sys.a, sys.b, sys.c, sys.d] = slab04md (sys.a, sys.b, sys.c, sys.d, 1, 2/tsam, false);
+      [sys.a, sys.b, sys.c, sys.d] = slab04md (sys.a, sys.b, sys.c, sys.d, 1, beta, false);
       ## TODO: descriptor case
 
-    ## TODO: case "prewarp"
-
     otherwise
       error ("ss: c2d: %s is an invalid or missing method", method);
   endswitch

Modified: trunk/octave-forge/main/control/inst/@ss/__d2c__.m
===================================================================
--- trunk/octave-forge/main/control/inst/@ss/__d2c__.m	2011-09-05 18:02:37 UTC (rev 8501)
+++ trunk/octave-forge/main/control/inst/@ss/__d2c__.m	2011-09-05 19:14:03 UTC (rev 8502)
@@ -22,10 +22,10 @@
 ## Created: September 2011
 ## Version: 0.1
 
-function sys = __d2c__ (sys, tsam, method = "zoh")
+function sys = __d2c__ (sys, tsam, method = "zoh", w0 = 0)
 
-  switch (method)
-    case {"zoh", "std"}
+  switch (method(1))
+    case {"z", "s"}                # {"zoh", "std"}
       [sys.a, sys.b, sys.c, sys.d, sys.e] = __dss2ss__ (sys.a, sys.b, sys.c, sys.d, sys.e);
       [n, m] = size (sys.b);       # n: states, m: inputs
       tmp = logm ([sys.a, sys.b; zeros(m,n), eye(m)]) / tsam;
@@ -35,13 +35,16 @@
       sys.a = real (tmp(1:n, 1:n));
       sys.b = real (tmp(1:n, n+1:n+m));
 
-    case {"tustin", "bilin"}
+    case {"t", "b", "p"}           # {"tustin", "bilin", "prewarp"}
+      if (method(1) == "p")        # prewarping
+        beta = w0 / tan (w0*tsam/2);
+      else
+        beta = 2/tsam;
+      endif
       [sys.a, sys.b, sys.c, sys.d, sys.e] = __dss2ss__ (sys.a, sys.b, sys.c, sys.d, sys.e);
-      [sys.a, sys.b, sys.c, sys.d] = slab04md (sys.a, sys.b, sys.c, sys.d, 1, 2/tsam, true);
+      [sys.a, sys.b, sys.c, sys.d] = slab04md (sys.a, sys.b, sys.c, sys.d, 1, beta, true);
       ## TODO: descriptor case
 
-    ## TODO: case "prewarp"
-
     otherwise
       error ("ss: d2c: %s is an invalid or missing method", method);
   endswitch

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