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%MTIMES Multiply two quaternion objects % % Invoked by the * operator, handle two cases: % % q1*q2 standard quaternion multiplication % q1*v rotate vector v by quaternion % q1*s multiply vector v by scalar % Copyright (C) 1999-2008, by Peter I. Corke % % This file is part of The Robotics Toolbox for Matlab (RTB). % % RTB is free software: you can redistribute it and/or modify % it under the terms of the GNU Lesser General Public License as published by % the Free Software Foundation, either version 3 of the License, or % (at your option) any later version. % % RTB is distributed in the hope that it will be useful, % but WITHOUT ANY WARRANTY; without even the implied warranty of % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the % GNU Lesser General Public License for more details. % % You should have received a copy of the GNU Leser General Public License % along with RTB. If not, see <http://www.gnu.org/licenses/>. function qp = mtimes(q1, q2) if isa(q1, 'quaternion') & isa(q2, 'quaternion') %QQMUL Multiply unit-quaternion by unit-quaternion % % QQ = qqmul(Q1, Q2) % % Return a product of unit-quaternions. % % See also: TR2Q % Copyright (C) 1993 Peter Corke % decompose into scalar and vector components s1 = q1.s; v1 = q1.v; s2 = q2.s; v2 = q2.v; % form the product qp = quaternion([s1*s2-v1*v2' s1*v2+s2*v1+cross(v1,v2)]); elseif isa(q1, 'quaternion') & isa(q2, 'double'), %QVMUL Multiply vector by unit-quaternion % % VT = qvmul(Q, V) % % Rotate the vector V by the unit-quaternion Q. % % See also: QQMUL, QINV % Copyright (C) 1993 Peter Corke % MOD HISTORY % fixed error in q-v product, added inv(q1) on RHS if length(q2) == 3, qp = q1 * quaternion([0 q2(:)']) * inv(q1); qp = qp.v; elseif length(q2) == 1, qp = quaternion( double(q1)*q2); else error('quaternion-vector product: must be a 3-vector or scalar'); end elseif isa(q2, 'quaternion') & isa(q1, 'double'), if length(q1) == 3, qp = q2 * quaternion([0 q1(:)']) * inv(q2); qp = qp.v; elseif length(q1) == 1, qp = quaternion( double(q2)*q1); else error('quaternion-vector product: must be a 3-vector or scalar'); end end