1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
6 Purpose: Integrate the EOM to determine instantaneous position
9 ------------- Copyright (C) 1999 Jon S. Berndt (jsb@hal-pc.org) -------------
11 This program is free software; you can redistribute it and/or modify it under
12 the terms of the GNU General Public License as published by the Free Software
13 Foundation; either version 2 of the License, or (at your option) any later
16 This program is distributed in the hope that it will be useful, but WITHOUT
17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
18 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
21 You should have received a copy of the GNU General Public License along with
22 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
23 Place - Suite 330, Boston, MA 02111-1307, USA.
25 Further information about the GNU General Public License can also be found on
26 the world wide web at http://www.gnu.org.
28 FUNCTIONAL DESCRIPTION
29 --------------------------------------------------------------------------------
30 This class encapsulates the integration of rates and accelerations to get the
31 current position of the aircraft.
34 --------------------------------------------------------------------------------
37 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
38 COMMENTS, REFERENCES, and NOTES
39 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
40 [1] Cooke, Zyda, Pratt, and McGhee, "NPSNET: Flight Simulation Dynamic Modeling
41 Using Quaternions", Presence, Vol. 1, No. 4, pp. 404-420 Naval Postgraduate
43 [2] D. M. Henderson, "Euler Angles, Quaternions, and Transformation Matrices",
45 [3] Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
46 NASA-Ames", NASA CR-2497, January 1975
47 [4] Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
48 Wiley & Sons, 1979 ISBN 0-471-03032-5
49 [5] Bernard Etkin, "Dynamics of Flight, Stability and Control", Wiley & Sons,
50 1982 ISBN 0-471-08936-2
52 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
54 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
57 # include <simgear/compiler.h>
58 # ifdef SG_HAVE_STD_INCLUDES
70 #include "FGPosition.h"
71 #include "FGAtmosphere.h"
73 #include "FGFDMExec.h"
75 #include "FGAircraft.h"
76 #include "FGTranslation.h"
77 #include "FGRotation.h"
78 #include "FGAuxiliary.h"
81 static const char *IdSrc = "$Header$";
82 static const char *IdHdr = ID_POSITION;
84 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
86 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
88 extern float globalTriNormal[3];
89 extern double globalSceneryAltitude;
90 extern double globalSeaLevelRadius;
92 FGPosition::FGPosition(FGFDMExec* fdmex) : FGModel(fdmex),
99 LongitudeDot = LatitudeDot = RadiusDot = 0.0;
100 lastLongitudeDot = lastLatitudeDot = lastRadiusDot = 0.0;
101 Longitude = Latitude = 0.0;
102 gamma = Vt = Vground = 0.0;
103 h = 3.0; // Est. height of aircraft cg off runway
104 SeaLevelRadius = EARTHRAD; // For initialization ONLY
105 Radius = SeaLevelRadius + h;
106 RunwayRadius = SeaLevelRadius;
107 DistanceAGL = Radius - RunwayRadius; // Geocentric
108 vRunwayNormal(3) = -1.0; // Initialized for standalone mode
111 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
113 FGPosition::~FGPosition(void) {}
115 /*************************************************************************** Run
116 Purpose: Called on a schedule to perform Positioning algorithms
117 Notes: [TP] Make sure that -Vt <= hdot <= Vt, which, of course, should always
119 [JB] Run in standalone mode, SeaLevelRadius will be EARTHRAD. In FGFS,
120 SeaLevelRadius is stuffed from FGJSBSim in JSBSim.cxx each pass.
123 bool FGPosition:: Run(void) {
127 if (!FGModel::Run()) {
130 Vground = sqrt( vVel(eNorth)*vVel(eNorth) + vVel(eEast)*vVel(eEast) );
132 invMass = 1.0 / Aircraft->GetMass();
133 Radius = h + SeaLevelRadius;
134 invRadius = 1.0 / Radius;
136 cosLat = cos(Latitude);
137 if (cosLat != 0) LongitudeDot = vVel(eEast) / (Radius * cosLat);
139 LatitudeDot = vVel(eNorth) * invRadius;
140 RadiusDot = -vVel(eDown);
142 Longitude += 0.5*dt*rate*(LongitudeDot + lastLongitudeDot);
143 Latitude += 0.5*dt*rate*(LatitudeDot + lastLatitudeDot);
144 Radius += 0.5*dt*rate*(RadiusDot + lastRadiusDot);
146 h = Radius - SeaLevelRadius; // Geocentric
148 DistanceAGL = Radius - RunwayRadius; // Geocentric
150 hoverb = DistanceAGL/b;
153 hdot_Vt = RadiusDot/Vt;
154 if (fabs(hdot_Vt) <= 1) gamma = asin(hdot_Vt);
159 lastLatitudeDot = LatitudeDot;
160 lastLongitudeDot = LongitudeDot;
161 lastRadiusDot = RadiusDot;
170 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
172 void FGPosition::GetState(void) {
175 vUVW = Translation->GetUVW();
176 Vt = Translation->GetVt();
177 vVel = State->GetTb2l()*vUVW;
178 vVelDot = State->GetTb2l() * Translation->GetUVWdot();
180 b = Aircraft->GetWingSpan();
184 void FGPosition::Seth(double tt) {
186 Radius = h + SeaLevelRadius;
187 DistanceAGL = Radius - RunwayRadius; // Geocentric
190 void FGPosition::SetDistanceAGL(double tt) {
192 Radius = RunwayRadius + DistanceAGL;
193 h = Radius - SeaLevelRadius;