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1 ## Copyright (C) 1996, 1998, 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} {} tf (@var{num}, @var{den}, @var{tsam}, @var{inname}, @var{outname}) |
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22 ## build system data structure from transfer function format data |
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23 ## |
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24 ## @strong{Inputs} |
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25 ## @table @var |
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26 ## @item num |
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27 ## @itemx den |
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28 ## coefficients of numerator/denominator polynomials |
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29 ## @item tsam |
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30 ## sampling interval. default: 0 (continuous time) |
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31 ## @item inname |
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32 ## @itemx outname |
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33 ## input/output signal names; may be a string or cell array with a single string |
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34 ## entry. |
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35 ## @end table |
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36 ## |
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37 ## @strong{Outputs} |
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38 ## @var{sys} = system data structure |
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39 ## |
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40 ## @strong{Example} |
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41 ## @example |
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42 ## octave:1> sys=tf([2 1],[1 2 1],0.1); |
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43 ## octave:2> sysout(sys) |
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44 ## Input(s) |
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45 ## 1: u_1 |
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46 ## Output(s): |
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47 ## 1: y_1 (discrete) |
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48 ## Sampling interval: 0.1 |
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49 ## transfer function form: |
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50 ## 2*z^1 + 1 |
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51 ## ----------------- |
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52 ## 1*z^2 + 2*z^1 + 1 |
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53 ## @end example |
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54 ## @end deftypefn |
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55 |
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56 ## Author: R. Bruce Tenison <btenison@eng.auburn.edu> |
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57 ## Created: July 29, 1994 |
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58 ## Name changed to TF2SYS July 1995 |
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59 ## updated for new system data structure format July 1996 |
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60 |
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61 function outsys = tf (num, den, tsam, inname, outname) |
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62 |
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63 ## Test for the correct number of input arguments |
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64 if (nargin < 2 || nargin > 5) |
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65 print_usage (); |
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66 endif |
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67 |
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68 ## check input format |
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69 if (! ((isvector (num) || isscalar (num)) |
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70 && (isvector (den) || isscalar (den)))) |
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71 error ("num (%dx%d) and den (%dx%d) must be vectors", |
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72 rows (num), columns (num), rows (den), columns (den)); |
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73 endif |
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74 |
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75 ## strip leading zero coefficients |
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76 num = __tfl__ (num); |
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77 den = __tfl__ (den); |
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78 |
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79 if (length (num) > length (den)) |
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80 error ("# of poles (%d) < # of zeros (%d)", length(den)-1, length(num)-1); |
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81 endif |
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82 |
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83 ## check sampling interval (if any) |
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84 if (nargin <= 2) |
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85 tsam = 0; # default |
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86 elseif (isempty (tsam)) |
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87 tsam = 0; |
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88 endif |
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89 if (! (isscalar (tsam) && imag (tsam) == 0) || tsam < 0) |
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90 error ("tsam must be a positive real scalar") |
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91 endif |
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92 |
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93 outsys.num = num; |
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94 outsys.den = den; |
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95 |
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96 ## Set the system vector: active = 0(tf), updated = [1 0 0]; |
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97 outsys.sys = [0, 1, 0, 0]; |
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98 |
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99 ## Set defaults |
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100 outsys.tsam = tsam; |
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101 outsys.n = length (den) - 1; |
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102 outsys.nz = 0; |
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103 outsys.yd = 0; # assume discrete-time |
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104 ## check discrete time |
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105 if (tsam > 0) |
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106 [outsys.n, outsys.nz] = swap (outsys.n, outsys.nz); |
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107 outsys.yd = 1; |
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108 endif |
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109 |
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110 outsys.inname = __sysdefioname__ (1, "u"); |
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111 outsys.outname = __sysdefioname__ (1, "y"); |
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112 outsys.stname = __sysdefstname__ (outsys.n, outsys.nz); |
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113 |
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114 ## Set name of input |
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115 if (nargin > 3) |
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116 ## make sure it's a cell array of a single string |
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117 if (! isempty (inname)) |
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118 if (! iscell (inname)) |
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119 inname = {inname}; |
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120 endif |
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121 if (! is_signal_list (inname)) |
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122 error ("inname must be a string or cell array of strings"); |
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123 endif |
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124 if (length (inname) > 1) |
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125 warning ("tf: %d input names provided; first used", length (inname)); |
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126 inname = inname(1); |
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127 endif |
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128 outsys = syssetsignals (outsys, "in", inname); |
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129 endif |
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130 endif |
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131 |
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132 ## Set name of output |
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133 if (nargin > 4) |
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134 if (! isempty (outname)) |
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135 if (! iscell (outname)) |
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136 outname = {outname}; |
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137 endif |
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138 if (! is_signal_list (outname)) |
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139 error ("outname must be a string or a cell array of strings"); |
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140 endif |
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141 if (length (outname) > 1) |
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142 warning ("tf: %d output names provided; first used", length(outname)); |
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143 outname = outname(1); |
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144 endif |
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145 outsys = syssetsignals (outsys, "out", outname); |
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146 endif |
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147 endif |
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148 |
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149 endfunction |
