1 // UFO.cxx -- interface to the "UFO" flight model
3 // Written by Curtis Olson, started October 1999.
4 // Slightly modified from MagicCarpet.cxx by Jonathan Polley, April 2002
6 // Copyright (C) 1999-2002 Curtis L. Olson - curt@flightgear.org
8 // This program is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU General Public License as
10 // published by the Free Software Foundation; either version 2 of the
11 // License, or (at your option) any later version.
13 // This program is distributed in the hope that it will be useful, but
14 // WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 // General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 #include <simgear/math/sg_geodesy.hxx>
25 #include <simgear/math/point3d.hxx>
26 #include <simgear/math/polar3d.hxx>
28 #include <Controls/controls.hxx>
29 #include <Main/globals.hxx>
30 #include <Main/fg_props.hxx>
35 FGUFO::FGUFO( double dt ) {
44 // Initialize the UFO flight model, dt is the time increment
45 // for each subsequent iteration through the EOM
51 // Run an iteration of the EOM (equations of motion)
52 void FGUFO::update( int multiloop ) {
53 // cout << "FGLaRCsim::update()" << endl;
55 double time_step = get_delta_t() * multiloop;
58 double Throttle = globals->get_controls()->get_throttle( 0 );
60 // read the state of the control surfaces
61 double Aileron = globals->get_controls()->get_aileron();
62 double Elevator = globals->get_controls()->get_elevator();
64 // the velocity of the aircraft
65 double velocity = Throttle * 2000; // meters/sec
67 double old_pitch = get_Theta();
68 double pitch_rate = SGD_PI_4; // assume I will be pitching up
69 double target_pitch = -Elevator * SGD_PI_2;
71 // if I am pitching down
72 if (old_pitch > target_pitch)
73 // set the pitch rate to negative (down)
76 double pitch = old_pitch + (pitch_rate * time_step);
78 // if I am pitching up
81 // clip the pitch at the limit
82 if ( pitch > target_pitch)
87 // if I am pitching down
88 else if (pitch_rate < 0.0)
90 // clip the pitch at the limit
91 if ( pitch < target_pitch)
97 double old_roll = get_Phi();
98 double roll_rate = SGD_PI_4;
99 double target_roll = Aileron * SGD_PI_2;
101 if (old_roll > target_roll)
104 double roll = old_roll + (roll_rate * time_step);
106 // if I am rolling CW
109 // clip the roll at the limit
110 if ( roll > target_roll)
115 // if I am rolling CCW
116 else if (roll_rate < 0.0)
118 // clip the roll at the limit
119 if ( roll < target_roll)
125 // the vertical speed of the aircraft
126 double real_climb_rate = sin (pitch) * SG_METER_TO_FEET * velocity; // feet/sec
127 _set_Climb_Rate( -Elevator * 10.0 );
128 double climb = real_climb_rate * time_step;
130 // the lateral speed of the aircraft
131 double speed = cos (pitch) * velocity; // meters/sec
132 double dist = speed * time_step;
133 double kts = velocity * SG_METER_TO_NM * 3600.0;
134 _set_V_equiv_kts( kts );
135 _set_V_calibrated_kts( kts );
136 _set_V_ground_speed( kts );
139 double turn_rate = sin(roll) * SGD_PI_4; // radians/sec
140 double turn = turn_rate * time_step;
142 // update (lon/lat) position
143 double lat2, lon2, az2;
144 if ( speed > SG_EPSILON ) {
145 geo_direct_wgs_84 ( get_Altitude(),
146 get_Latitude() * SGD_RADIANS_TO_DEGREES,
147 get_Longitude() * SGD_RADIANS_TO_DEGREES,
148 get_Psi() * SGD_RADIANS_TO_DEGREES,
149 dist, &lat2, &lon2, &az2 );
151 _set_Longitude( lon2 * SGD_DEGREES_TO_RADIANS );
152 _set_Latitude( lat2 * SGD_DEGREES_TO_RADIANS );
155 // cout << "lon error = " << fabs(end.x()*SGD_RADIANS_TO_DEGREES - lon2)
156 // << " lat error = " << fabs(end.y()*SGD_RADIANS_TO_DEGREES - lat2)
159 double sl_radius, lat_geoc;
160 sgGeodToGeoc( get_Latitude(), get_Altitude(), &sl_radius, &lat_geoc );
162 // update euler angles
163 _set_Euler_Angles( roll, pitch,
164 fmod(get_Psi() + turn, SGD_2PI) );
165 _set_Euler_Rates(0,0,0);
167 _set_Geocentric_Position( lat_geoc, get_Longitude(),
168 sl_radius + get_Altitude() + climb );
169 // cout << "sea level radius (ft) = " << sl_radius << endl;
170 // cout << "(setto) sea level radius (ft) = " << get_Sea_level_radius() << endl;
171 _set_Sea_level_radius( sl_radius * SG_METER_TO_FEET);
172 _set_Altitude( get_Altitude() + climb );