1 /*******************************************************************************
6 Purpose: Integrates the rotational EOM
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 integrates the rotational EOM.
33 --------------------------------------------------------------------------------
36 ********************************************************************************
37 COMMENTS, REFERENCES, and NOTES
38 ********************************************************************************
39 [1] Cooke, Zyda, Pratt, and McGhee, "NPSNET: Flight Simulation Dynamic Modeling
40 Using Quaternions", Presence, Vol. 1, No. 4, pp. 404-420 Naval Postgraduate
42 [2] D. M. Henderson, "Euler Angles, Quaternions, and Transformation Matrices",
44 [3] Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
45 NASA-Ames", NASA CR-2497, January 1975
46 [4] Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
47 Wiley & Sons, 1979 ISBN 0-471-03032-5
48 [5] Bernard Etkin, "Dynamics of Flight, Stability and Control", Wiley & Sons,
49 1982 ISBN 0-471-08936-2
51 The order of rotations used in this class corresponds to a 3-2-1 sequence,
52 or Y-P-R, or Z-Y-X, if you prefer.
54 ********************************************************************************
56 *******************************************************************************/
58 #include "FGRotation.h"
59 #include "FGAtmosphere.h"
61 #include "FGFDMExec.h"
63 #include "FGAircraft.h"
64 #include "FGTranslation.h"
65 #include "FGPosition.h"
66 #include "FGAuxiliary.h"
69 /*******************************************************************************
70 ************************************ CODE **************************************
71 *******************************************************************************/
74 FGRotation::FGRotation(FGFDMExec* fdmex) : FGModel(fdmex)
76 strcpy(Name, "FGRotation");
77 Q0dot = Q1dot = Q2dot = Q3dot = 0.0;
78 Pdot = Qdot = Rdot = 0.0;
82 FGRotation::~FGRotation(void)
87 bool FGRotation::Run(void)
89 float L2, N1, iQtot, sum;
91 if (!FGModel::Run()) {
98 L2 = L + Ixz*P*Q - (Izz-Iyy)*R*Q;
99 N1 = N - (Iyy-Ixx)*P*Q - Ixz*R*Q;
101 Pdot = (L2*Izz - N1*Ixz) / (Ixx*Izz - Ixz*Ixz);
102 Qdot = (M - (Ixx-Izz)*P*R - Ixz*(P*P - R*R))/Iyy;
103 Rdot = (N1*Ixx + L2*Ixz) / (Ixx*Izz - Ixz*Ixz);
105 P += dt*rate*(lastPdot + Pdot)/2.0;
106 Q += dt*rate*(lastQdot + Qdot)/2.0;
107 R += dt*rate*(lastRdot + Rdot)/2.0;
114 Q0dot = -0.5*(Q1*P + Q2*Q + Q3*R);
115 Q1dot = 0.5*(Q0*P + Q2*R - Q3*Q);
116 Q2dot = 0.5*(Q0*Q + Q3*P - Q1*R);
117 Q3dot = 0.5*(Q0*R + Q1*Q - Q2*P);
119 Q0 += 0.5*dt*rate*(lastQ0dot + Q0dot);
120 Q1 += 0.5*dt*rate*(lastQ1dot + Q1dot);
121 Q2 += 0.5*dt*rate*(lastQ2dot + Q2dot);
122 Q3 += 0.5*dt*rate*(lastQ3dot + Q3dot);
124 sum = Q0*Q0 + Q1*Q1 + Q2*Q2 + Q3*Q3;
126 iQtot = 1.0 / sqrt(sum);
136 phi = atan2(T[2][3], T[3][3]);
138 tht = asin(-T[1][3]);
143 psi = atan2(T[1][2], T[1][1]);
145 if (psi < 0.0) psi += 2*M_PI;
154 void FGRotation::GetState(void)
158 L = Aircraft->GetL();
159 M = Aircraft->GetM();
160 N = Aircraft->GetN();
162 Ixx = Aircraft->GetIxx();
163 Iyy = Aircraft->GetIyy();
164 Izz = Aircraft->GetIzz();
165 Ixz = Aircraft->GetIxz();
167 for (int r=1;r<=3;r++)
168 for (int c=1;c<=3;c++)
169 T[r][c] = Position->GetT(r,c);
173 void FGRotation::PutState(void)