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 - http://www.flightgear.org/~curt
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>
34 const double throttle_damp = 0.2;
35 const double aileron_damp = 0.05;
36 const double elevator_damp = 0.05;
37 const double rudder_damp = 0.4;
39 FGUFO::FGUFO( double dt )
53 // Initialize the UFO flight model, dt is the time increment
54 // for each subsequent iteration through the EOM
60 // Run an iteration of the EOM (equations of motion)
61 void FGUFO::update( double dt ) {
62 // cout << "FGLaRCsim::update()" << endl;
67 double time_step = dt;
70 double th = globals->get_controls()->get_throttle( 0 );
71 if ( globals->get_controls()->get_brake_left() > 0.0
72 || globals->get_controls()->get_brake_right() > 0.0 )
76 Throttle = th * throttle_damp + Throttle * (1 - throttle_damp);
78 // read the state of the control surfaces
79 Aileron = globals->get_controls()->get_aileron() * aileron_damp
80 + Aileron * (1 - aileron_damp);
81 Elevator = globals->get_controls()->get_elevator() * elevator_damp
82 + Elevator * (1 - elevator_damp);
83 Rudder = globals->get_controls()->get_rudder() * rudder_damp
84 + Rudder * (1 - rudder_damp);
86 // the velocity of the aircraft
87 double velocity = Throttle * 2000; // meters/sec
89 double old_pitch = get_Theta();
90 double pitch_rate = SGD_PI_4; // assume I will be pitching up
91 double target_pitch = -Elevator * SGD_PI_2;
93 // if I am pitching down
94 if (old_pitch > target_pitch)
95 // set the pitch rate to negative (down)
98 double pitch = old_pitch + (pitch_rate * time_step);
100 // if I am pitching up
101 if (pitch_rate > 0.0)
103 // clip the pitch at the limit
104 if ( pitch > target_pitch)
106 pitch = target_pitch;
109 // if I am pitching down
110 else if (pitch_rate < 0.0)
112 // clip the pitch at the limit
113 if ( pitch < target_pitch)
115 pitch = target_pitch;
119 double old_roll = get_Phi();
120 double roll_rate = SGD_PI_4;
121 double target_roll = Aileron * SGD_PI_2;
123 if (old_roll > target_roll)
126 double roll = old_roll + (roll_rate * time_step);
128 // if I am rolling CW
131 // clip the roll at the limit
132 if ( roll > target_roll)
137 // if I am rolling CCW
138 else if (roll_rate < 0.0)
140 // clip the roll at the limit
141 if ( roll < target_roll)
147 // the vertical speed of the aircraft
148 double real_climb_rate = sin (pitch) * SG_METER_TO_FEET * velocity; // feet/sec
149 _set_Climb_Rate( -Elevator * 10.0 );
150 double climb = real_climb_rate * time_step;
152 // the lateral speed of the aircraft
153 double speed = cos (pitch) * velocity; // meters/sec
154 double dist = speed * time_step;
155 double kts = velocity * SG_METER_TO_NM * 3600.0;
156 _set_V_equiv_kts( kts );
157 _set_V_calibrated_kts( kts );
158 _set_V_ground_speed( kts );
161 double turn_rate = sin(roll) * SGD_PI_4; // radians/sec
162 double turn = turn_rate * time_step;
163 double yaw = fabs(Rudder) < .2 ? 0.0 : Rudder / (25 + fabs(speed) * .1);
165 // update (lon/lat) position
166 double lat2, lon2, az2;
167 if ( fabs(speed) > SG_EPSILON ) {
168 geo_direct_wgs_84 ( get_Altitude(),
169 get_Latitude() * SGD_RADIANS_TO_DEGREES,
170 get_Longitude() * SGD_RADIANS_TO_DEGREES,
171 get_Psi() * SGD_RADIANS_TO_DEGREES,
172 dist, &lat2, &lon2, &az2 );
174 _set_Longitude( lon2 * SGD_DEGREES_TO_RADIANS );
175 _set_Latitude( lat2 * SGD_DEGREES_TO_RADIANS );
178 // cout << "lon error = " << fabs(end.x()*SGD_RADIANS_TO_DEGREES - lon2)
179 // << " lat error = " << fabs(end.y()*SGD_RADIANS_TO_DEGREES - lat2)
182 double sl_radius, lat_geoc;
183 sgGeodToGeoc( get_Latitude(), get_Altitude(), &sl_radius, &lat_geoc );
185 // update euler angles
186 _set_Euler_Angles( roll, pitch,
187 fmod(get_Psi() + turn + yaw, SGD_2PI) );
188 _set_Euler_Rates(0,0,0);
190 _set_Geocentric_Position( lat_geoc, get_Longitude(),
191 sl_radius + get_Altitude() + climb );
192 // cout << "sea level radius (ft) = " << sl_radius << endl;
193 // cout << "(setto) sea level radius (ft) = " << get_Sea_level_radius() << endl;
194 _set_Sea_level_radius( sl_radius * SG_METER_TO_FEET);
195 _set_Altitude( get_Altitude() + climb );