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[project @ 2004-02-17 02:34:33 by jwe]
author jwe
date Tue, 17 Feb 2004 02:34:33 +0000
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1 ## Copyright (C) 1996, 1998 Auburn University. All rights reserved.
2 ##
3 ## This file is part of Octave.
4 ##
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by the
7 ## Free Software Foundation; either version 2, or (at your option) any
8 ## later version.
9 ##
10 ## Octave is distributed in the hope that it will be useful, but WITHOUT
11 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 ## for more details.
14 ##
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, write to the Free
17 ## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA.
18
19 ## -*- texinfo -*-
20 ## @deftypefn {Function File} {} tf (@var{num}, @var{den}, @var{tsam}, @var{inname}, @var{outname})
21 ## build system data structure from transfer function format data
22 ##
23 ## @strong{Inputs}
24 ## @table @var
25 ## @item num
26 ## @itemx den
27 ## coefficients of numerator/denominator polynomials
28 ## @item tsam
29 ## sampling interval. default: 0 (continuous time)
30 ## @item inname
31 ## @itemx outname
32 ## input/output signal names; may be a string or cell array with a single string
33 ## entry.
34 ## @end table
35 ##
36 ## @strong{Outputs}
37 ## @var{sys} = system data structure
38 ##
39 ## @strong{Example}
40 ## @example
41 ## octave:1> sys=tf([2 1],[1 2 1],0.1);
42 ## octave:2> sysout(sys)
43 ## Input(s)
44 ## 1: u_1
45 ## Output(s):
46 ## 1: y_1 (discrete)
47 ## Sampling interval: 0.1
48 ## transfer function form:
49 ## 2*z^1 + 1
50 ## -----------------
51 ## 1*z^2 + 2*z^1 + 1
52 ## @end example
53 ## @end deftypefn
54
55 ## Author: R. Bruce Tenison <btenison@eng.auburn.edu>
56 ## Created: July 29, 1994
57 ## Name changed to TF2SYS July 1995
58 ## updated for new system data structure format July 1996
59
60 function outsys = tf (num, den, tsam, inname, outname)
61
62 ## Test for the correct number of input arguments
63 if ((nargin < 2) || (nargin > 5))
64 usage ("outsys = tf (num, den [, tsam, inname, outname])");
65 return
66 endif
67
68 ## check input format
69 if( ! ( (isvector(num) || isscalar(num)) && ...
70 (isvector(den) || isscalar(den))) )
71 error(["num (",num2str(rows(num)),"x",num2str(columns(num)), ...
72 ") and den (",num2str(rows(den)),"x",num2str(columns(den)), ...
73 ") must be vectors"])
74 endif
75
76 ## strip leading zero coefficients
77 num = __tfl__ (num);
78 den = __tfl__ (den);
79
80 if (length(num) > length(den))
81 error("# of poles (%d) < # of zeros (%d)",length(den)-1, length(num)-1);
82 endif
83
84 ## check sampling interval (if any)
85 if(nargin <= 2) tsam = 0; # default
86 elseif (isempty(tsam)) tsam = 0; endif
87 if ( (! (isscalar(tsam) && (imag(tsam) == 0) )) || (tsam < 0) )
88 error("tsam must be a positive real scalar")
89 endif
90
91 outsys.num = num;
92 outsys.den = den;
93
94 ## Set the system vector: active = 0(tf), updated = [1 0 0];
95 outsys.sys = [0, 1, 0, 0];
96
97 ## Set defaults
98 outsys.tsam = tsam;
99 outsys.n = length(den)-1;
100 outsys.nz = 0;
101 outsys.yd = 0; # assume discrete-time
102 ## check discrete time
103 if(tsam > 0)
104 [outsys.n,outsys.nz] = swap(outsys.n, outsys.nz);
105 outsys.yd = 1;
106 endif
107
108 outsys.inname = __sysdefioname__ (1, "u");
109 outsys.outname = __sysdefioname__ (1, "y");
110 outsys.stname = __sysdefstname__ (outsys.n, outsys.nz);
111
112 ## Set name of input
113 if (nargin > 3)
114 ## make sure it's a cell array of a single string
115 if(!isempty(inname))
116 if(!iscell(inname)) inname = {inname}; endif
117 if( !is_signal_list(inname) )
118 error("inname must be a string or cell array of strings");
119 endif
120 if(length(inname) > 1)
121 warning("tf: %d input names provided; first used",length(inname));
122 inname = inname(1);
123 endif
124 outsys = syssetsignals(outsys,"in",inname);
125 endif
126 endif
127
128 ## Set name of output
129 if (nargin > 4)
130 if(!isempty(outname))
131 if(!iscell(outname)) outname = {outname}; endif
132 if(!is_signal_list(outname))
133 error("outname must be a string or a cell array of strings");
134 endif
135 if(length(outname) > 1)
136 warning("tf: %d output names provided; first used",length(outname));
137 outname = outname(1);
138 endif
139 outsys = syssetsignals(outsys,"out",outname);
140 endif
141 endif
142
143 endfunction