1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
6 Purpose: Encapsulates the inertial frame forces (coriolis and centrifugal)
8 ------------- Copyright (C) 2000 Jon S. Berndt (jon@jsbsim.org) -------------
10 This program is free software; you can redistribute it and/or modify it under
11 the terms of the GNU Lesser General Public License as published by the Free Software
12 Foundation; either version 2 of the License, or (at your option) any later
15 This program is distributed in the hope that it will be useful, but WITHOUT
16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
20 You should have received a copy of the GNU Lesser General Public License along with
21 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
22 Place - Suite 330, Boston, MA 02111-1307, USA.
24 Further information about the GNU Lesser General Public License can also be found on
25 the world wide web at http://www.gnu.org.
27 FUNCTIONAL DESCRIPTION
28 --------------------------------------------------------------------------------
31 --------------------------------------------------------------------------------
34 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
38 #include "FGInertial.h"
39 #include "FGFDMExec.h"
40 #include "FGPropagate.h"
41 #include "FGMassBalance.h"
48 static const char *IdSrc = "$Id: FGInertial.cpp,v 1.18 2010/03/28 05:57:00 jberndt Exp $";
49 static const char *IdHdr = ID_INERTIAL;
51 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
53 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
56 FGInertial::FGInertial(FGFDMExec* fgex) : FGModel(fgex)
61 RotationRate = 0.00007292115;
62 GM = 14.07644180E15; // WGS84 value
63 RadiusReference = 20925650.00; // Equatorial radius (WGS84)
64 C2_0 = -4.84165371736E-04; // WGS84 value for the C2,0 coefficient
65 J2 = 1.0826266836E-03; // WGS84 value for J2
66 a = 20925646.3255; // WGS84 semimajor axis length in feet
67 b = 20855486.5951; // WGS84 semiminor axis length in feet
72 RotationRate = 0.0000026617;
73 GM = 1.7314079E14; // Lunar GM
74 RadiusReference = 5702559.05; // Equatorial radius
75 C2_0 = 0; // value for the C2,0 coefficient
76 J2 = 2.033542482111609E-4; // value for J2
77 a = 5702559.05; // semimajor axis length in feet
78 b = 5695439.63; // semiminor axis length in feet
82 gAccelReference = GM/(RadiusReference*RadiusReference);
83 gAccel = GM/(RadiusReference*RadiusReference);
90 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
92 FGInertial::~FGInertial(void)
97 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
99 bool FGInertial::InitModel(void)
101 if (!FGModel::InitModel()) return false;
108 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
110 bool FGInertial::Run(void)
112 // Fast return if we have nothing to do ...
113 if (FGModel::Run()) return true;
114 if (FDMExec->Holding()) return false;
119 double r = Propagate->GetRadius();
120 gAccel = GetGAccel(r);
121 earthPosAngle += FDMExec->GetDeltaT()*RotationRate;
128 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
130 double FGInertial::GetGAccel(double r) const
135 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
137 // Calculate the WGS84 gravitation value in ECEF frame. Pass in the ECEF position
138 // via the position parameter. The J2Gravity value returned is in ECEF frame,
139 // and therefore may need to be expressed (transformed) in another frame,
140 // depending on how it is used. See Stevens and Lewis eqn. 1.4-16.
142 FGColumnVector3 FGInertial::GetGravityJ2(FGColumnVector3 position) const
144 FGColumnVector3 J2Gravity;
147 double r = position.Magnitude();
148 double lat = Propagate->GetLatitude();
149 double sinLat = sin(lat);
151 double preCommon = 1.5*J2*(a/r)*(a/r);
152 double xy = 1.0 - 5.0*(sinLat*sinLat);
153 double z = 3.0 - 5.0*(sinLat*sinLat);
154 double GMOverr2 = GM/(r*r);
156 J2Gravity(1) = -GMOverr2 * ((1.0 + (preCommon * xy)) * position(eX)/r);
157 J2Gravity(2) = -GMOverr2 * ((1.0 + (preCommon * xy)) * position(eY)/r);
158 J2Gravity(3) = -GMOverr2 * ((1.0 + (preCommon * z)) * position(eZ)/r);
163 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
165 void FGInertial::bind(void)
167 PropertyManager->Tie("position/epa-rad", this, &FGInertial::GetEarthPositionAngle);
170 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
171 // The bitmasked value choices are as follows:
172 // unset: In this case (the default) JSBSim would only print
173 // out the normally expected messages, essentially echoing
174 // the config files as they are read. If the environment
175 // variable is not set, debug_lvl is set to 1 internally
176 // 0: This requests JSBSim not to output any messages
178 // 1: This value explicity requests the normal JSBSim
180 // 2: This value asks for a message to be printed out when
181 // a class is instantiated
182 // 4: When this value is set, a message is displayed when a
183 // FGModel object executes its Run() method
184 // 8: When this value is set, various runtime state variables
185 // are printed out periodically
186 // 16: When set various parameters are sanity checked and
187 // a message is printed out when they go out of bounds
189 void FGInertial::Debug(int from)
191 if (debug_lvl <= 0) return;
193 if (debug_lvl & 1) { // Standard console startup message output
194 if (from == 0) { // Constructor
198 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
199 if (from == 0) cout << "Instantiated: FGInertial" << endl;
200 if (from == 1) cout << "Destroyed: FGInertial" << endl;
202 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
204 if (debug_lvl & 8 ) { // Runtime state variables
206 if (debug_lvl & 16) { // Sanity checking
208 if (debug_lvl & 64) {
209 if (from == 0) { // Constructor
210 cout << IdSrc << endl;
211 cout << IdHdr << endl;