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61 lines
2.0 KiB
61 lines
2.0 KiB
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% Ryan Steindl based on Robotics Toolbox for MATLAB (v6 and v9)
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%
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% Copyright (C) 1993-2011, by Peter I. Corke
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%
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% This file is part of The Robotics Toolbox for MATLAB (RTB).
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%
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% RTB is free software: you can redistribute it and/or modify
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% it under the terms of the GNU Lesser General Public License as published by
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% the Free Software Foundation, either version 3 of the License, or
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% (at your option) any later version.
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%
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% RTB is distributed in the hope that it will be useful,
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% but WITHOUT ANY WARRANTY; without even the implied warranty of
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% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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% GNU Lesser General Public License for more details.
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%
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% You should have received a copy of the GNU Leser General Public License
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% along with RTB. If not, see <http://www.gnu.org/licenses/>.
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%
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% http://www.petercorke.com
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function q = scale(Q, r)
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%Quaternion.scale Interpolate rotations expressed by quaternion objects
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%
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% QI = Q.scale(R) is a unit-quaternion that interpolates between identity for R=0
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% to Q for R=1. This is a spherical linear interpolation (slerp) that can
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% be interpretted as interpolation along a great circle arc on a sphere.
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%
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% If R is a vector QI is a cell array of quaternions, each element
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% corresponding to sequential elements of R.
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%
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% See also ctraj, Quaternion.interp.
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q2 = double(Q);
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if any(r<0) || (r>1)
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error('r out of range');
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end
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q1 = [1 0 0 0]; % identity quaternion
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theta = acos(q1*q2');
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if length(r) == 1
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if theta == 0
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q = Q;
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else
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q = unit(Quaternion( (sin((1-r)*theta) * q1 + sin(r*theta) * q2) / sin(theta) ));
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end
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else
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count = 1;
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for R=r(:)'
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if theta == 0
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qq = Q;
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else
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qq = Quaternion( (sin((1-r)*theta) * q1 + sin(r*theta) * q2) / sin(theta) ).unit;
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end
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q(count) = qq;
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count = count + 1;
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end
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end
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end
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