189 lines
6.1 KiB
C++
189 lines
6.1 KiB
C++
/*******************************************************************************
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Module: FGPosition.cpp
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Author: Jon S. Berndt
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Date started: 01/05/99
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Purpose: Integrate the EOM to determine instantaneous position
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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 encapsulates the integration of rates and accelerations to get the
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current position of the aircraft.
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HISTORY
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--------------------------------------------------------------------------------
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01/05/99 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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********************************************************************************
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INCLUDES
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*******************************************************************************/
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#ifdef FGFS
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# include <Include/compiler.h>
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# ifdef FG_HAVE_STD_INCLUDES
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# include <cmath>
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# else
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# include <math.h>
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# endif
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#else
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# include <cmath>
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#endif
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#include "FGPosition.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 "FGRotation.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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FGPosition::FGPosition(FGFDMExec* fdmex) : FGModel(fdmex)
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{
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Name = "FGPosition";
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AccelN = AccelE = AccelD = 0.0;
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LongitudeDot = LatitudeDot = RadiusDot = 0.0;
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}
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FGPosition::~FGPosition(void)
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{
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}
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bool FGPosition:: Run(void)
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{
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float tanLat, cosLat;
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if (!FGModel::Run()) {
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GetState();
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T[1][1] = Q0*Q0 + Q1*Q1 - Q2*Q2 - Q3*Q3; // Page A-11
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T[1][2] = 2*(Q1*Q2 + Q0*Q3); // From
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T[1][3] = 2*(Q1*Q3 - Q0*Q2); // Reference [2]
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T[2][1] = 2*(Q1*Q2 - Q0*Q3);
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T[2][2] = Q0*Q0 - Q1*Q1 + Q2*Q2 - Q3*Q3;
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T[2][3] = 2*(Q2*Q3 + Q0*Q1);
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T[3][1] = 2*(Q1*Q3 + Q0*Q2);
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T[3][2] = 2*(Q2*Q3 - Q0*Q1);
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T[3][3] = Q0*Q0 - Q1*Q1 - Q2*Q2 + Q3*Q3;
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Fn = T[1][1]*Fx + T[2][1]*Fy + T[3][1]*Fz; // Eqn. 3.5
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Fe = T[1][2]*Fx + T[2][2]*Fy + T[3][2]*Fz; // From
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Fd = T[1][3]*Fx + T[2][3]*Fy + T[3][3]*Fz; // Reference [3]
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tanLat = tan(Latitude); // I made this up
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cosLat = cos(Latitude);
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lastAccelN = AccelN;
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lastAccelE = AccelE;
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lastAccelD = AccelD;
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Vn = T[1][1]*U + T[2][1]*V + T[3][1]*W;
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Ve = T[1][2]*U + T[2][2]*V + T[3][2]*W;
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Vd = T[1][3]*U + T[2][3]*V + T[3][3]*W;
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AccelN = invMass * Fn + invRadius * (Vn*Vd - Ve*Ve*tanLat); // Eqn. 3.6
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AccelE = invMass * Fe + invRadius * (Ve*Vd + Vn*Ve*tanLat); // From
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AccelD = invMass * Fd - invRadius * (Vn*Vn + Ve*Ve); // Reference [3]
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Vn += 0.5*dt*rate*(3.0*AccelN - lastAccelN); // Eqn. 3.7
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Ve += 0.5*dt*rate*(3.0*AccelE - lastAccelE); // From
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Vd += 0.5*dt*rate*(3.0*AccelD - lastAccelD); // Reference [3]
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Vee = Ve - OMEGAEARTH * (Radius) * cosLat; // From Eq. 3.8
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// Reference [3]
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lastLatitudeDot = LatitudeDot;
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lastLongitudeDot = LongitudeDot;
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lastRadiusDot = RadiusDot;
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if (cosLat != 0) LongitudeDot = Ve / (Radius * cosLat);
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LatitudeDot = Vn * invRadius;
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RadiusDot = -Vd;
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Longitude += 0.5*dt*rate*(LongitudeDot + lastLongitudeDot);
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Latitude += 0.5*dt*rate*(LatitudeDot + lastLatitudeDot);
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Radius += 0.5*dt*rate*(RadiusDot + lastRadiusDot);
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PutState();
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return false;
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} else {
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return true;
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}
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}
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void FGPosition::GetState(void)
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{
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dt = State->Getdt();
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Q0 = Rotation->GetQ0();
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Q1 = Rotation->GetQ1();
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Q2 = Rotation->GetQ2();
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Q3 = Rotation->GetQ3();
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Fx = Aircraft->GetFx();
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Fy = Aircraft->GetFy();
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Fz = Aircraft->GetFz();
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U = Translation->GetU();
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V = Translation->GetV();
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W = Translation->GetW();
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Latitude = State->Getlatitude();
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Longitude = State->Getlongitude();
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invMass = 1.0 / Aircraft->GetMass();
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invRadius = 1.0 / (State->Geth() + EARTHRAD);
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Radius = State->Geth() + EARTHRAD;
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}
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void FGPosition::PutState(void)
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{
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State->Setlatitude(Latitude);
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State->Setlongitude(Longitude);
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State->Seth(Radius - EARTHRAD);
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}
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