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 --------------------------------------------------------------------------------
37 --------------------------------------------------------------------------------
40 ********************************************************************************
41 COMMENTS, REFERENCES, and NOTES
42 ********************************************************************************
43 [1] Cooke, Zyda, Pratt, and McGhee, "NPSNET: Flight Simulation Dynamic Modeling
44 Using Quaternions", Presence, Vol. 1, No. 4, pp. 404-420 Naval Postgraduate
46 [2] D. M. Henderson, "Euler Angles, Quaternions, and Transformation Matrices",
48 [3] Richard E. McFarland, "A Standard Kinematic Model for Flight Simulation at
49 NASA-Ames", NASA CR-2497, January 1975
50 [4] Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics",
51 Wiley & Sons, 1979 ISBN 0-471-03032-5
52 [5] Bernard Etkin, "Dynamics of Flight, Stability and Control", Wiley & Sons,
53 1982 ISBN 0-471-08936-2
55 The order of rotations used in this class corresponds to a 3-2-1 sequence,
56 or Y-P-R, or Z-Y-X, if you prefer.
58 ********************************************************************************
60 *******************************************************************************/
62 #include "FGRotation.h"
64 /*******************************************************************************
65 ************************************ CODE **************************************
66 *******************************************************************************/
69 FGRotation::FGRotation(void) : FGModel()
71 strcpy(Name, "FGRotation");
72 Q0dot = Q1dot = Q2dot = Q3dot = 0.0;
76 FGRotation::~FGRotation(void)
81 bool FGRotation::Run(void)
83 float L2, N1, iQtot, sum;
85 if (!FGModel::Run()) {
92 L2 = L + Ixz*P*Q - (Izz-Iyy)*R*Q;
93 N1 = N - (Iyy-Ixx)*P*Q - Ixz*R*Q;
95 Pdot = (L2*Izz - N1*Ixz) / (Ixx*Izz - Ixz*Ixz);
96 Qdot = (M - (Ixx-Izz)*P*R - Ixz*(P*P - R*R))/Iyy;
97 Rdot = (N1*Ixx + L2*Ixz) / (Ixx*Izz - Ixz*Ixz);
99 P += dt*(lastPdot + Pdot)/2.0;
100 Q += dt*(lastQdot + Qdot)/2.0;
101 R += dt*(lastRdot + Rdot)/2.0;
108 Q0dot = -0.5*(Q1*P + Q2*Q + Q3*R);
109 Q1dot = 0.5*(Q0*P + Q2*R - Q3*Q);
110 Q2dot = 0.5*(Q0*Q + Q3*P - Q1*R);
111 Q3dot = 0.5*(Q0*R + Q1*Q - Q2*P);
113 Q0 += 0.5*dt*(lastQ0dot + Q0dot);
114 Q1 += 0.5*dt*(lastQ1dot + Q1dot);
115 Q2 += 0.5*dt*(lastQ2dot + Q2dot);
116 Q3 += 0.5*dt*(lastQ3dot + Q3dot);
118 sum = Q0*Q0 + Q1*Q1 + Q2*Q2 + Q3*Q3;
120 iQtot = 1.0 / sqrt(sum);
130 phi = atan2(T[2][3], T[3][3]);
132 tht = asin(-T[1][3]);
137 psi = atan2(T[1][2], T[1][1]);
139 if (psi < 0.0) psi += 2*M_PI;
148 void FGRotation::GetState(void)
155 Pdot = State->GetPdot();
156 Qdot = State->GetQdot();
157 Rdot = State->GetRdot();
163 Ixx = State->GetIxx();
164 Iyy = State->GetIyy();
165 Izz = State->GetIzz();
166 Ixz = State->GetIxz();
173 for (int r=1;r<=3;r++)
174 for (int c=1;c<=3;c++)
175 T[r][c] = State->GetT(r,c);
179 void FGRotation::PutState(void)
189 State->SetQ0123(Q0, Q1, Q2, Q3);