JSBSim Flight Dynamics Model  1.0 (02 March 2017)
An Open Source Flight Dynamics and Control Software Library in C++
FGInertial.cpp
1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
2 
3  Module: FGInertial.cpp
4  Author: Jon S. Berndt
5  Date started: 09/13/00
6  Purpose: Encapsulates the inertial frame forces (coriolis and centrifugal)
7 
8  ------------- Copyright (C) 2000 Jon S. Berndt (jon@jsbsim.org) -------------
9 
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
13  version.
14 
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
18  details.
19 
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.
23 
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.
26 
27 FUNCTIONAL DESCRIPTION
28 --------------------------------------------------------------------------------
29 
30 HISTORY
31 --------------------------------------------------------------------------------
32 09/13/00 JSB Created
33 
34 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35 INCLUDES
36 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
37 
38 #include "FGInertial.h"
39 #include "FGFDMExec.h"
40 #include <iostream>
41 
42 using namespace std;
43 
44 namespace JSBSim {
45 
46 IDENT(IdSrc,"$Id: FGInertial.cpp,v 1.31 2014/05/17 15:24:37 jberndt Exp $");
47 IDENT(IdHdr,ID_INERTIAL);
48 
49 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
50 CLASS IMPLEMENTATION
51 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
52 
53 
54 FGInertial::FGInertial(FGFDMExec* fgex) : FGModel(fgex)
55 {
56  Name = "FGInertial";
57 
58  // Earth defaults
59  RotationRate = 0.00007292115;
60 // RotationRate = 0.000072921151467;
61  GM = 14.0764417572E15; // WGS84 value
62  C2_0 = -4.84165371736E-04; // WGS84 value for the C2,0 coefficient
63  J2 = 1.08262982E-03; // WGS84 value for J2
64  a = 20925646.32546; // WGS84 semimajor axis length in feet
65 // a = 20902254.5305; // Effective Earth radius for a sphere
66  b = 20855486.5951; // WGS84 semiminor axis length in feet
67  RadiusReference = a;
68 
69  // Lunar defaults
70  /*
71  RotationRate = 0.0000026617;
72  GM = 1.7314079E14; // Lunar GM
73  RadiusReference = 5702559.05; // Equatorial radius
74  C2_0 = 0; // value for the C2,0 coefficient
75  J2 = 2.033542482111609E-4; // value for J2
76  a = 5702559.05; // semimajor axis length in feet
77  b = 5695439.63; // semiminor axis length in feet
78  */
79 
80  vOmegaPlanet = FGColumnVector3( 0.0, 0.0, RotationRate );
81  gAccelReference = GM/(RadiusReference*RadiusReference);
82  gAccel = GM/(RadiusReference*RadiusReference);
83 
84  bind();
85 
86  Debug(0);
87 }
88 
89 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
90 
91 FGInertial::~FGInertial(void)
92 {
93  Debug(1);
94 }
95 
96 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
97 
98 bool FGInertial::InitModel(void)
99 {
100  return FGModel::InitModel();
101 }
102 
103 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
104 
105 bool FGInertial::Run(bool Holding)
106 {
107  // Fast return if we have nothing to do ...
108  if (FGModel::Run(Holding)) return true;
109  if (Holding) return false;
110 
111  // Gravitation accel
112  gAccel = GetGAccel(in.Radius);
113 
114  return false;
115 }
116 
117 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
118 
119 double FGInertial::GetGAccel(double r) const
120 {
121  return GM/(r*r);
122 }
123 
124 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
125 //
126 // Calculate the WGS84 gravitation value in ECEF frame. Pass in the ECEF position
127 // via the position parameter. The J2Gravity value returned is in ECEF frame,
128 // and therefore may need to be expressed (transformed) in another frame,
129 // depending on how it is used. See Stevens and Lewis eqn. 1.4-16.
130 
131 FGColumnVector3 FGInertial::GetGravityJ2(const FGColumnVector3& position) const
132 {
133  FGColumnVector3 J2Gravity;
134 
135  // Gravitation accel
136  double r = position.Magnitude();
137  double sinLat = sin(in.Latitude);
138 
139  double adivr = a/r;
140  double preCommon = 1.5*J2*adivr*adivr;
141  double xy = 1.0 - 5.0*(sinLat*sinLat);
142  double z = 3.0 - 5.0*(sinLat*sinLat);
143  double GMOverr2 = GM/(r*r);
144 
145  J2Gravity(1) = -GMOverr2 * ((1.0 + (preCommon * xy)) * position(eX)/r);
146  J2Gravity(2) = -GMOverr2 * ((1.0 + (preCommon * xy)) * position(eY)/r);
147  J2Gravity(3) = -GMOverr2 * ((1.0 + (preCommon * z)) * position(eZ)/r);
148 
149  return J2Gravity;
150 }
151 
152 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
153 
154 void FGInertial::bind(void)
155 {
156  PropertyManager->Tie("inertial/sea-level-radius_ft", this, &FGInertial::GetRefRadius);
157 }
158 
159 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
160 // The bitmasked value choices are as follows:
161 // unset: In this case (the default) JSBSim would only print
162 // out the normally expected messages, essentially echoing
163 // the config files as they are read. If the environment
164 // variable is not set, debug_lvl is set to 1 internally
165 // 0: This requests JSBSim not to output any messages
166 // whatsoever.
167 // 1: This value explicity requests the normal JSBSim
168 // startup messages
169 // 2: This value asks for a message to be printed out when
170 // a class is instantiated
171 // 4: When this value is set, a message is displayed when a
172 // FGModel object executes its Run() method
173 // 8: When this value is set, various runtime state variables
174 // are printed out periodically
175 // 16: When set various parameters are sanity checked and
176 // a message is printed out when they go out of bounds
177 
178 void FGInertial::Debug(int from)
179 {
180  if (debug_lvl <= 0) return;
181 
182  if (debug_lvl & 1) { // Standard console startup message output
183  if (from == 0) { // Constructor
184 
185  }
186  }
187  if (debug_lvl & 2 ) { // Instantiation/Destruction notification
188  if (from == 0) cout << "Instantiated: FGInertial" << endl;
189  if (from == 1) cout << "Destroyed: FGInertial" << endl;
190  }
191  if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
192  }
193  if (debug_lvl & 8 ) { // Runtime state variables
194  }
195  if (debug_lvl & 16) { // Sanity checking
196  }
197  if (debug_lvl & 64) {
198  if (from == 0) { // Constructor
199  cout << IdSrc << endl;
200  cout << IdHdr << endl;
201  }
202  }
203 }
204 }
STL namespace.
virtual bool Run(bool Holding)
Runs the model; called by the Executive.
Definition: FGModel.cpp:92
void Tie(const std::string &name, bool *pointer, bool useDefault=true)
Tie a property to an external bool variable.
bool Run(bool Holding)
Runs the Inertial model; called by the Executive Can pass in a value indicating if the executive is d...
Definition: FGInertial.cpp:105
This class implements a 3 element column vector.
double Magnitude(void) const
Length of the vector.