1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 Module: FGAuxiliary.cpp
4 Author: Tony Peden, Jon Berndt
6 Purpose: Calculates additional parameters needed by the visual system, etc.
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 calculates various auxiliary parameters.
33 Anderson, John D. "Introduction to Flight", 3rd Edition, McGraw-Hill, 1989
36 --------------------------------------------------------------------------------
39 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
41 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
43 #include "FGAuxiliary.h"
44 #include "FGTranslation.h"
45 #include "FGRotation.h"
46 #include "FGAtmosphere.h"
48 #include "FGFDMExec.h"
50 #include "FGAircraft.h"
51 #include "FGPosition.h"
53 #include "FGInertial.h"
54 #include "FGMatrix33.h"
55 #include "FGColumnVector3.h"
56 #include "FGColumnVector4.h"
58 static const char *IdSrc = "$Id$";
59 static const char *IdHdr = ID_AUXILIARY;
61 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
63 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
66 FGAuxiliary::FGAuxiliary(FGFDMExec* fdmex) : FGModel(fdmex),
71 vcas = veas = mach = qbar = pt = 0;
75 if (debug_lvl & 2) cout << "Instantiated: " << Name << endl;
78 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
80 FGAuxiliary::~FGAuxiliary()
82 if (debug_lvl & 2) cout << "Destroyed: FGAuxiliary" << endl;
85 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
87 bool FGAuxiliary::Run()
91 if (!FGModel::Run()) {
93 if (mach < 1) { //calculate total pressure assuming isentropic flow
94 pt=p*pow((1 + 0.2*mach*mach),3.5);
96 // shock in front of pitot tube, we'll assume its normal and use
97 // the Rayleigh Pitot Tube Formula, i.e. the ratio of total
98 // pressure behind the shock to the static pressure in front
100 B = 5.76*mach*mach/(5.6*mach*mach - 0.8);
102 // The denominator above is zero for Mach ~ 0.38, for which
103 // we'll never be here, so we're safe
105 D = (2.8*mach*mach-0.4)*0.4167;
109 A = pow(((pt-p)/psl+1),0.28571);
110 vcas = sqrt(7*psl/rhosl*(A-1));
111 veas = sqrt(2*qbar/rhosl);
113 // Pilot sensed accelerations are calculated here. This is used
114 // for the coordinated turn ball instrument. Motion base platforms sometimes
115 // use the derivative of pilot sensed accelerations as the driving parameter,
116 // rather than straight accelerations.
118 // The theory behind pilot-sensed calculations is presented:
120 // For purposes of discussion and calculation, assume for a minute that the
121 // pilot is in space and motionless in inertial space. She will feel
122 // no accelerations. If the aircraft begins to accelerate along any axis or
123 // axes (without rotating), the pilot will sense those accelerations. If
124 // any rotational moment is applied, the pilot will sense an acceleration
125 // due to that motion in the amount:
127 // [wdot X R] + [w X (w X R)]
132 // wdot = omegadot, the rotational acceleration rate vector
133 // w = omega, the rotational rate vector
134 // R = the vector from the aircraft CG to the pilot eyepoint
136 // The sum total of these two terms plus the acceleration of the aircraft
137 // body axis gives the acceleration the pilot senses in inertial space.
138 // In the presence of a large body such as a planet, a gravity field also
139 // provides an accelerating attraction. This acceleration can be transformed
140 // from the reference frame of the planet so as to be expressed in the frame
141 // of reference of the aircraft. This gravity field accelerating attraction
142 // is felt by the pilot as a force on her tushie as she sits in her aircraft
143 // on the runway awaiting takeoff clearance.
145 // In JSBSim the acceleration of the body frame in inertial space is given
146 // by the F = ma relation. If the vForces vector is divided by the aircraft
147 // mass, the acceleration vector is calculated. The term wdot is equivalent
148 // to the JSBSim vPQRdot vector, and the w parameter is equivalent to vPQR.
149 // The radius R is calculated below in the vector vToEyePt.
151 vToEyePt = Aircraft->GetXYZep() - MassBalance->GetXYZcg();
153 vPilotAccel = Aircraft->GetBodyAccel()
154 + Rotation->GetPQRdot() * vToEyePt
155 + Rotation->GetPQR() * (Rotation->GetPQR() * vToEyePt)
156 + Inertial->GetGravity();
158 earthPosAngle += State->Getdt()*Inertial->omega();
165 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
167 double FGAuxiliary::GetHeadWind(void)
171 psiw = Atmosphere->GetWindPsi();
172 psi = Rotation->Getpsi();
173 vw = Atmosphere->GetWindNED().Magnitude();
175 return vw*cos(psiw - psi);
178 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
180 double FGAuxiliary::GetCrossWind(void)
184 psiw = Atmosphere->GetWindPsi();
185 psi = Rotation->Getpsi();
186 vw = Atmosphere->GetWindNED().Magnitude();
188 return vw*sin(psiw - psi);
191 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
193 FGColumnVector3 FGAuxiliary::GetNpilot(void)
195 return vPilotAccel/Inertial->gravity();
198 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
200 double FGAuxiliary::GetNpilot(int idx)
202 return (vPilotAccel/Inertial->gravity())(idx);
205 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
207 void FGAuxiliary::GetState(void)
209 qbar = Translation->Getqbar();
210 mach = Translation->GetMach();
211 p = Atmosphere->GetPressure();
212 rhosl = Atmosphere->GetDensitySL();
213 psl = Atmosphere->GetPressureSL();
216 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
218 void FGAuxiliary::Debug(void)
220 //TODO: Add your source code here