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1 ## Copyright (C) 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 |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License 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, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {} qderiv (omega) |
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21 ## Derivative of a quaternion. |
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22 ## |
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23 ## Let Q be a quaternion to transform a vector from a fixed frame to |
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24 ## a rotating frame. If the rotating frame is rotating about the |
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25 ## [x, y, z] axes at angular rates [wx, wy, wz], then the derivative |
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26 ## of Q is given by |
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27 ## |
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28 ## @example |
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29 ## Q' = qderivmat (omega) * Q |
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30 ## @end example |
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31 ## |
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32 ## If the passive convention is used (rotate the frame, not the vector), |
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33 ## then |
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34 ## |
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35 ## @example |
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36 ## Q' = -qderivmat (omega) * Q |
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37 ## @end example |
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38 ## @end deftypefn |
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39 |
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40 ## Author: A. S. Hodel <a.s.hodel@eng.auburn.edu> |
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41 ## Adapted-By: jwe |
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42 |
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43 function Dmat = qderivmat (Omega) |
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44 |
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45 Omega = vec (Omega); |
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46 |
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47 if (length (Omega) != 3) |
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48 error ("qderivmat: Omega must be a length 3 vector"); |
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49 endif |
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50 |
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51 Dmat = 0.5 * [ 0.0, Omega(3), -Omega(2), Omega(1); |
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52 -Omega(3), 0.0, Omega(1), Omega(2); |
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53 Omega(2), -Omega(1), 0.0, Omega(3); |
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54 -Omega(1), -Omega(2), -Omega(3), 0.0 ]; |
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55 endfunction |
