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tim |
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/* |
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* Copyright (C) 2000-2004 Object Oriented Parallel Simulation Engine (OOPSE) project |
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* |
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* Contact: oopse@oopse.org |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public License |
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* as published by the Free Software Foundation; either version 2.1 |
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* of the License, or (at your option) any later version. |
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* All we ask is that proper credit is given for our work, which includes |
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* - but is not limited to - adding the above copyright notice to the beginning |
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* of your source code files, and to any copyright notice that you may distribute |
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* with programs based on this work. |
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* |
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* This program 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 Lesser General Public License |
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* along with this program; if not, write to the Free Software |
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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* |
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*/ |
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#include "DLM.hpp" |
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namespace oopse { |
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void DLM::doRotate(StuntDouble* sd, Vector3d& ji, double dt) { |
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double dt2 = 0.5 * dt; |
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double angle; |
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RotMat3x3d A = sd->getA(); |
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Mat3x3d I = sd->getI(); |
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// use the angular velocities to propagate the rotation matrix a full time step |
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if (sd->isLinear()) { |
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int i = sd->linearAxis(); |
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int j = (i+1)%3; |
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int k = (i+2)%3; |
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angle = dt2 * ji[j] / I(j, j); |
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rotateStep( k, i, angle, ji, A ); |
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angle = dt * ji[k] / I(k, k); |
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rotateStep( i, j, angle, ji, A); |
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angle = dt2 * ji[j] / I(j, j); |
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rotateStep( k, i, angle, ji, A ); |
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} else { |
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// rotate about the x-axis |
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angle = dt2 * ji[0] / I(0, 0); |
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rotateStep( 1, 2, angle, ji, A ); |
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// rotate about the y-axis |
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angle = dt2 * ji[1] / I(1, 1); |
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rotateStep( 2, 0, angle, ji, A ); |
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// rotate about the z-axis |
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angle = dt * ji[2] / I(2, 2); |
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sd->addZangle(angle); |
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rotateStep( 0, 1, angle, ji, A); |
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// rotate about the y-axis |
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angle = dt2 * ji[1] / I(1, 1); |
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rotateStep( 2, 0, angle, ji, A ); |
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// rotate about the x-axis |
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angle = dt2 * ji[0] / I(0, 0); |
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rotateStep( 1, 2, angle, ji, A ); |
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} |
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sd->setA( A ); |
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} |
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void DLM::rotateStep(int axes1, int axes2, double angle, Vector3d& ji, RotMat3x3d& A) { |
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int i, j, k; |
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double sinAngle; |
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double cosAngle; |
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double angleSqr; |
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double angleSqrOver4; |
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double top, bottom; |
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RotMat3x3d tempA(A); // initialize the tempA |
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Vector3d tempJ(0.0); |
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RotMat3x3d rot = RotMat3x3d::identity(); // initalize rot as a unit matrix |
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// use a small angle aproximation for sin and cosine |
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angleSqr = angle * angle; |
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angleSqrOver4 = angleSqr / 4.0; |
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top = 1.0 - angleSqrOver4; |
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bottom = 1.0 + angleSqrOver4; |
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cosAngle = top / bottom; |
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sinAngle = angle / bottom; |
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rot(axes1, axes1) = cosAngle; |
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rot(axes2, axes2) = cosAngle; |
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rot(axes1, axes2) = sinAngle; |
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rot(axes2, axes1) = -sinAngle; |
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// rotate the momentum acoording to: ji[] = rot[][] * ji[] |
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ji = rot * ji; |
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// rotate the Rotation matrix acording to: |
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// A[][] = A[][] * transpose(rot[][]) |
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// transpose(A[][]) = transpose(A[][]) * transpose(rot[][]) |
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A = rot * A; //? A = A* rot.transpose(); |
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} |
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} |
