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1 ## Copyright (C) 1996,1998 Auburn University. All Rights Reserved |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by the |
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7 ## Free Software Foundation; either version 2, or (at your option) any |
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8 ## later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but WITHOUT |
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11 ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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12 ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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13 ## for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, write to the Free |
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17 ## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File } { @var{sys} = } tf2sys( @var{num}, @var{den} @{, @var{tsam}, @var{inname}, @var{outname} @}) |
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21 ## build system data structure from transfer function format data |
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22 ## |
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23 ## @strong{Inputs} |
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24 ## @table @var |
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25 ## @item num, den |
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26 ## coefficients of numerator/denominator polynomials |
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27 ## @item tsam |
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28 ## sampling interval. default: 0 (continuous time) |
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29 ## @item inname, outname |
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30 ## input/output signal names; may be a string or list with a single string |
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31 ## entry. |
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32 ## @end table |
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33 ## |
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34 ## @strong{Outputs} |
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35 ## @var{sys} = system data structure |
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36 ## |
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37 ## @strong{Example} |
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38 ## @example |
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39 ## octave:1> sys=tf2sys([2 1],[1 2 1],0.1); |
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40 ## octave:2> sysout(sys) |
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41 ## Input(s) |
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42 ## 1: u_1 |
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43 ## Output(s): |
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44 ## 1: y_1 (discrete) |
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45 ## Sampling interval: 0.1 |
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46 ## transfer function form: |
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47 ## 2*z^1 + 1 |
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48 ## ----------------- |
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49 ## 1*z^2 + 2*z^1 + 1 |
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50 ## @end example |
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51 ## @end deftypefn |
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52 |
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53 function outsys = tf2sys(num,den,tsam,inname,outname) |
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54 ## Written by R. Bruce Tenison July 29, 1994 |
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55 ## Name changed to TF2SYS July 1995 |
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56 ## updated for new system data structure format July 1996 |
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57 |
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58 save_val = implicit_str_to_num_ok; |
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59 implicit_str_to_num_ok = 1; |
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60 |
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61 ## Test for the correct number of input arguments |
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62 if ((nargin < 2) || (nargin > 5)) |
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63 usage('outsys=tf2sys(num,den[,tsam,inname,outname])'); |
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64 return |
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65 endif |
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66 |
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67 ## check input format |
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68 if( ! ( (is_vector(num) || is_scalar(num)) && ... |
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69 (is_vector(den) || is_scalar(den))) ) |
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70 error(['num (',num2str(rows(num)),'x',num2str(columns(num)), ... |
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71 ') and den (',num2str(rows(den)),'x',num2str(columns(den)), ... |
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72 ') must be vectors']) |
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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 = tf2sysl(num); |
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77 den = tf2sysl(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) tsam = 0; # default |
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85 elseif (isempty(tsam)) tsam = 0; endif |
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86 if ( (! (is_scalar(tsam) && (imag(tsam) == 0) )) || (tsam < 0) ) |
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87 error('tsam must be a positive real scalar') |
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88 endif |
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89 |
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90 outsys.num = num; |
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91 outsys.den = den; |
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92 |
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93 ## Set the system vector: active = 0(tf), updated = [1 0 0]; |
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94 outsys.sys = [0, 1, 0, 0]; |
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95 |
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96 ## Set defaults |
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97 outsys.tsam = tsam; |
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98 outsys.n = length(den)-1; |
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99 outsys.nz = 0; |
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100 outsys.yd = 0; # assume discrete-time |
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101 ## check discrete time |
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102 if(tsam > 0) |
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103 [outsys.n,outsys.nz] = swap(outsys.n, outsys.nz); |
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104 outsys.yd = 1; |
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105 endif |
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106 |
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107 outsys.inname = sysdefioname(1,"u"); |
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108 outsys.outname = sysdefioname(1,"y"); |
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109 outsys.stname = sysdefstname(outsys.n,outsys.nz); |
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110 |
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111 ## Set name of input |
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112 if (nargin > 3) |
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113 ## make sure its a list of a single string |
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114 if(!isempty(inname)) |
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115 if(!is_list(inname)) inname = list(inname); endif |
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116 if( !is_signal_list(inname) ) |
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117 error("inname must be a string or list of strings"); |
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118 endif |
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119 if(length(inname) > 1) |
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120 warning("tf2sys: %d input names provided; first used",length(inname)); |
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121 inname = inname(1); |
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122 endif |
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123 outsys = syssetsignals(outsys,"in",inname); |
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124 endif |
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125 endif |
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126 |
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127 ## Set name of output |
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128 if (nargin > 4) |
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129 if(!isempty(outname)) |
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130 if(!is_list(outname)) outname = list(outname); endif |
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131 if(!is_signal_list(outname)) |
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132 error("outname must be a string or a list of strings"); |
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133 endif |
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134 if(length(outname) > 1) |
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135 warning("tf2sys: %d output names provided; first used",length(outname)); |
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136 outname = outname(1); |
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137 endif |
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138 outsys = syssetsignals(outsys,"out",outname); |
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139 endif |
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140 endif |
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141 |
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142 implicit_str_to_num_ok = save_val; |
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143 endfunction |
