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1 ## Copyright (C) 1996, 2000, 2002, 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} {[@var{y}, @var{x}] =} lsim (@var{sys}, @var{u}, @var{t}, @var{x0}) |
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22 ## Produce output for a linear simulation of a system; produces |
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23 ## a plot for the output of the system, @var{sys}. |
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24 ## |
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25 ## @var{u} is an array that contains the system's inputs. Each row in @var{u} |
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26 ## corresponds to a different time step. Each column in @var{u} corresponds to a |
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27 ## different input. @var{t} is an array that contains the time index of the |
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28 ## system; @var{t} should be regularly spaced. If initial conditions are required |
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29 ## on the system, the @var{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 a plot is not displayed; |
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32 ## however, the data is returned in @var{y} (system output) |
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33 ## and @var{x} (system states). |
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34 ## @end deftypefn |
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35 |
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36 ## Author: David Clem |
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37 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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38 ## Created: July 1995 |
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39 ## modified by John Ingram for system format August 1996 |
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40 |
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41 function [y, x] = lsim (sys, u, t, x0) |
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42 |
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43 if (nargin < 3 || nargin > 4) |
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44 print_usage (); |
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45 endif |
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46 |
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47 if (! isstruct (sys)) |
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48 error ("sys must be in system data structure"); |
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49 endif |
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50 |
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51 sys = sysupdate (sys,"ss"); |
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52 |
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53 [ncstates, ndstates, nin, nout] = sysdimensions (sys); |
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54 [a, b, c, d] = sys2ss (sys); |
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55 |
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56 if (nargin == 3) |
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57 x0 = zeros (columns (a), 1); |
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58 endif |
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59 |
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60 if (rows (u) != length (t)) |
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61 error ("lsim: There should be an input value (row) for each time instant"); |
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62 endif |
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63 if (columns (u) != columns (d)) |
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64 error ("lsim: U and d should have the same number of inputs"); |
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65 endif |
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66 if (columns (x0) > 1) |
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67 error ("lsim: Initial condition vector should have only one column"); |
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68 endif |
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69 if (rows (x0) > rows p(a)) |
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70 error ("lsim: Initial condition vector is too large"); |
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71 endif |
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72 |
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73 Ts = 0; |
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74 t(2)-t(1); |
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75 u=u'; |
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76 n = max (size (t)); |
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77 |
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78 for ii = 1:(n-1) |
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79 |
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80 ## check if step size changed |
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81 ## FIXME -- this is probably not the best test, but it is |
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82 ## better than a test for exact equality. |
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83 if (abs (t(ii+1) - t(ii) - Ts) > 10 * eps) |
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84 Ts = t(ii+1) - t(ii); |
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85 ## [F,G] = c2d(a,b,Ts); |
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86 dsys = c2d (sys, Ts); |
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87 [F, G] = sys2ss (dsys); |
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88 endif |
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89 |
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90 x(:,ii) = x0; |
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91 x0 = F*x0 + G*u(:,ii); |
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92 endfor |
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93 |
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94 ## pick up last point |
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95 x(:,n) = x0; |
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96 |
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97 y = c*x + d*u; |
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98 if (nargout == 0) |
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99 plot (t, y); |
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100 y = []; |
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101 x = []; |
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102 endif |
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103 |
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104 endfunction |
