176 lines
4.8 KiB
C++
176 lines
4.8 KiB
C++
/*******************************************************************************
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Module: FGRotation.cpp
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Author: Jon Berndt
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Date started: 12/02/98
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Purpose: Integrates the rotational EOM
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Called by: FGFDMExec
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------------- Copyright (C) 1999 Jon S. Berndt (jsb@hal-pc.org) -------------
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any later
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version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc., 59 Temple
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Place - Suite 330, Boston, MA 02111-1307, USA.
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Further information about the GNU General Public License can also be found on
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the world wide web at http://www.gnu.org.
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FUNCTIONAL DESCRIPTION
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--------------------------------------------------------------------------------
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This class integrates the rotational EOM.
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HISTORY
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--------------------------------------------------------------------------------
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12/02/98 JSB Created
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********************************************************************************
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COMMENTS, REFERENCES, and NOTES
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********************************************************************************
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[1] Cooke, Zyda, Pratt, and McGhee, "NPSNET: Flight Simulation Dynamic Modeling
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Using Quaternions", Presence, Vol. 1, No. 4, pp. 404-420 Naval Postgraduate
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School, January 1994
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[2] D. M. Henderson, "Euler Angles, Quaternions, and Transformation Matrices",
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JSC 12960, July 1977
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[3] Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
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NASA-Ames", NASA CR-2497, January 1975
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[4] Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
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Wiley & Sons, 1979 ISBN 0-471-03032-5
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[5] Bernard Etkin, "Dynamics of Flight, Stability and Control", Wiley & Sons,
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1982 ISBN 0-471-08936-2
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The order of rotations used in this class corresponds to a 3-2-1 sequence,
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or Y-P-R, or Z-Y-X, if you prefer.
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********************************************************************************
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INCLUDES
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*******************************************************************************/
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#include "FGRotation.h"
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#include "FGAtmosphere.h"
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#include "FGState.h"
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#include "FGFDMExec.h"
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#include "FGFCS.h"
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#include "FGAircraft.h"
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#include "FGTranslation.h"
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#include "FGPosition.h"
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#include "FGAuxiliary.h"
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#include "FGOutput.h"
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/*******************************************************************************
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************************************ CODE **************************************
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*******************************************************************************/
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FGRotation::FGRotation(FGFDMExec* fdmex) : FGModel(fdmex)
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{
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strcpy(Name, "FGRotation");
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Q0dot = Q1dot = Q2dot = Q3dot = 0.0;
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Pdot = Qdot = Rdot = 0.0;
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}
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FGRotation::~FGRotation(void)
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{
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}
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bool FGRotation::Run(void)
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{
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float L2, N1, iQtot, sum;
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if (!FGModel::Run()) {
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GetState();
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lastPdot = Pdot;
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lastQdot = Qdot;
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lastRdot = Rdot;
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L2 = L + Ixz*P*Q - (Izz-Iyy)*R*Q;
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N1 = N - (Iyy-Ixx)*P*Q - Ixz*R*Q;
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Pdot = (L2*Izz - N1*Ixz) / (Ixx*Izz - Ixz*Ixz);
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Qdot = (M - (Ixx-Izz)*P*R - Ixz*(P*P - R*R))/Iyy;
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Rdot = (N1*Ixx + L2*Ixz) / (Ixx*Izz - Ixz*Ixz);
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P += dt*rate*(lastPdot + Pdot)/2.0;
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Q += dt*rate*(lastQdot + Qdot)/2.0;
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R += dt*rate*(lastRdot + Rdot)/2.0;
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lastQ0dot = Q0dot;
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lastQ1dot = Q1dot;
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lastQ2dot = Q2dot;
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lastQ3dot = Q3dot;
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Q0dot = -0.5*(Q1*P + Q2*Q + Q3*R);
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Q1dot = 0.5*(Q0*P + Q2*R - Q3*Q);
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Q2dot = 0.5*(Q0*Q + Q3*P - Q1*R);
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Q3dot = 0.5*(Q0*R + Q1*Q - Q2*P);
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Q0 += 0.5*dt*rate*(lastQ0dot + Q0dot);
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Q1 += 0.5*dt*rate*(lastQ1dot + Q1dot);
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Q2 += 0.5*dt*rate*(lastQ2dot + Q2dot);
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Q3 += 0.5*dt*rate*(lastQ3dot + Q3dot);
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sum = Q0*Q0 + Q1*Q1 + Q2*Q2 + Q3*Q3;
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iQtot = 1.0 / sqrt(sum);
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Q0 *= iQtot;
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Q1 *= iQtot;
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Q2 *= iQtot;
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Q3 *= iQtot;
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if (T[3][3] == 0)
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phi = 0.0;
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else
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phi = atan2(T[2][3], T[3][3]);
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tht = asin(-T[1][3]);
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if (T[1][1] == 0.0)
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psi = 0.0;
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else
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psi = atan2(T[1][2], T[1][1]);
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if (psi < 0.0) psi += 2*M_PI;
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PutState();
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} else {
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}
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return false;
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}
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void FGRotation::GetState(void)
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{
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dt = State->Getdt();
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L = Aircraft->GetL();
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M = Aircraft->GetM();
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N = Aircraft->GetN();
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Ixx = Aircraft->GetIxx();
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Iyy = Aircraft->GetIyy();
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Izz = Aircraft->GetIzz();
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Ixz = Aircraft->GetIxz();
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for (int r=1;r<=3;r++)
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for (int c=1;c<=3;c++)
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T[r][c] = Position->GetT(r,c);
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}
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void FGRotation::PutState(void)
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{
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}
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