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1 ## Copyright (C) 1996 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} {} lsim (@var{sys}, @var{u}, @var{t}, @var{x0}) |
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21 ## Produce output for a linear simulation of a system |
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22 ## |
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23 ## Produces a plot for the output of the system, sys. |
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24 ## |
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25 ## U is an array that contains the system's inputs. Each row in u |
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26 ## corresponds to a different time step. Each column in u corresponds to a |
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27 ## different input. T is an array that contains the time index of the |
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28 ## system. T should be regularly spaced. If initial conditions are required |
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29 ## on the system, the x0 vector should be added to the argument list. |
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30 ## |
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31 ## When the lsim function is invoked with output parameters: |
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32 ## [y,x] = lsim(sys,u,t,[x0]) |
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33 ## a plot is not displayed, however, the data is returned in y = system output |
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34 ## and x = system states. |
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35 ## @end deftypefn |
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36 |
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37 ## Author: David Clem |
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38 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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39 ## Created: July 1995 |
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40 ## modified by John Ingram for system format August 1996 |
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41 |
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42 function [y, x] = lsim (sys, u, t, x0) |
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43 |
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44 if((nargin < 3)||(nargin > 4)) |
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45 usage("[y,x] = lsim(sys,u,t[,x0])"); |
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46 endif |
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47 |
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48 if(!isstruct(sys)) |
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49 error("sys must be in system data structure"); |
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50 endif |
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51 |
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52 sys = sysupdate(sys,"ss"); |
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53 |
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54 [ncstates, ndstates, nin, nout] = sysdimensions(sys); |
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55 [a,b,c,d] = sys2ss(sys); |
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56 |
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57 if (nargin == 3) x0 = zeros(columns(a),1); endif |
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58 |
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59 if(rows(u) ~= length(t)) |
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60 error("lsim: There should be an input value (row) for each time instant"); |
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61 endif |
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62 if(columns(u) ~= columns(d)) |
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63 error("lsim: U and d should have the same number of inputs"); |
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64 endif |
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65 if(columns(x0) > 1) |
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66 error("lsim: Initial condition vector should have only one column"); |
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67 endif |
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68 if(rows(x0) > rows(a)) |
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69 error("lsim: Initial condition vector is too large"); |
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70 endif |
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71 |
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72 Ts = 0; |
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73 t(2)-t(1); |
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74 u=u'; |
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75 n = max(size(t)); |
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76 |
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77 for ii = 1:(n-1) |
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78 |
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79 ## check if step size changed |
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80 ## XXX FIXME XXX -- this is probably not the best test, but it is |
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81 ## better than a test for exact equality. |
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82 if (abs (t(ii+1) - t(ii) - Ts) > 10 * eps) |
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83 Ts = t(ii+1) - t(ii); |
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84 ## [F,G] = c2d(a,b,Ts); |
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85 dsys = c2d(sys, Ts); |
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86 [F,G] = sys2ss(dsys); |
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87 endif |
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88 |
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89 x(:,ii) = x0; |
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90 x0 = F*x0 + G*u(:,ii); |
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91 endfor |
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92 |
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93 ## pick up last point |
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94 x(:,n) = x0; |
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95 |
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96 y = c*x + d*u; |
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97 if(nargout == 0) |
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98 plot(t,y); |
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99 y=[]; |
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100 x=[]; |
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101 endif |
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102 endfunction |
