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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
28 #include <simgear/math/sg_geodesy.hxx>
29 #include <simgear/math/point3d.hxx>
30 #include <simgear/math/polar3d.hxx>
32 #include <Aircraft/controls.hxx>
33 #include <Main/globals.hxx>
34 #include <Main/fg_props.hxx>
38 const double throttle_damp = 0.2;
39 const double aileron_damp = 0.05;
40 const double elevator_damp = 0.05;
41 const double elevator_trim_damp = 0.05;
42 const double rudder_damp = 0.4;
44 FGUFO::FGUFO( double dt )
50 Speed_Max(fgGetNode("/engines/engine/speed-max-mps", true))
60 // Initialize the UFO flight model, dt is the time increment
61 // for each subsequent iteration through the EOM
64 if (Speed_Max->getDoubleValue() < 0.01)
65 Speed_Max->setDoubleValue(2000.0);
69 // Run an iteration of the EOM (equations of motion)
70 void FGUFO::update( double dt ) {
71 // cout << "FGLaRCsim::update()" << endl;
76 double time_step = dt;
79 double th = globals->get_controls()->get_throttle( 0 );
80 if ( globals->get_controls()->get_brake_left() > 0.5
81 || globals->get_controls()->get_brake_right() > 0.5 )
85 Throttle = th * throttle_damp + Throttle * (1 - throttle_damp);
87 // read the state of the control surfaces
88 Aileron = globals->get_controls()->get_aileron() * aileron_damp
89 + Aileron * (1 - aileron_damp);
90 Elevator = globals->get_controls()->get_elevator() * elevator_damp
91 + Elevator * (1 - elevator_damp);
92 Elevator_Trim = globals->get_controls()->get_elevator_trim()
94 + Elevator_Trim * (1 - elevator_trim_damp);
95 Rudder = globals->get_controls()->get_rudder() * rudder_damp
96 + Rudder * (1 - rudder_damp);
98 // the velocity of the aircraft
99 double velocity = Throttle * Speed_Max->getDoubleValue(); // meters/sec
101 double old_pitch = get_Theta();
102 double pitch_rate = SGD_PI_4; // assume I will be pitching up
103 double target_pitch = (-Elevator - Elevator_Trim) * SGD_PI_2;
105 // if I am pitching down
106 if (old_pitch > target_pitch)
107 // set the pitch rate to negative (down)
110 double pitch = old_pitch + (pitch_rate * time_step);
112 // if I am pitching up
113 if (pitch_rate > 0.0)
115 // clip the pitch at the limit
116 if ( pitch > target_pitch)
118 pitch = target_pitch;
121 // if I am pitching down
122 else if (pitch_rate < 0.0)
124 // clip the pitch at the limit
125 if ( pitch < target_pitch)
127 pitch = target_pitch;
131 double old_roll = get_Phi();
132 double roll_rate = SGD_PI_4;
133 double target_roll = Aileron * SGD_PI_2;
135 if (old_roll > target_roll)
138 double roll = old_roll + (roll_rate * time_step);
140 // if I am rolling CW
143 // clip the roll at the limit
144 if ( roll > target_roll)
149 // if I am rolling CCW
150 else if (roll_rate < 0.0)
152 // clip the roll at the limit
153 if ( roll < target_roll)
159 // the vertical speed of the aircraft
160 double real_climb_rate = sin (pitch) * SG_METER_TO_FEET * velocity; // feet/sec
161 _set_Climb_Rate( -Elevator * 10.0 );
162 double climb = real_climb_rate * time_step;
164 // the lateral speed of the aircraft
165 double speed = cos (pitch) * velocity; // meters/sec
166 double dist = speed * time_step;
167 double kts = velocity * SG_METER_TO_NM * 3600.0;
168 _set_V_equiv_kts( kts );
169 _set_V_calibrated_kts( kts );
170 _set_V_ground_speed( kts );
173 double turn_rate = sin(roll) * SGD_PI_4; // radians/sec
174 double turn = turn_rate * time_step;
175 double yaw = fabs(Rudder) < .2 ? 0.0 : Rudder / (25 + fabs(speed) * .1);
177 // update (lon/lat) position
178 double lat2, lon2, az2;
179 if ( fabs(speed) > SG_EPSILON ) {
180 geo_direct_wgs_84 ( get_Altitude(),
181 get_Latitude() * SGD_RADIANS_TO_DEGREES,
182 get_Longitude() * SGD_RADIANS_TO_DEGREES,
183 get_Psi() * SGD_RADIANS_TO_DEGREES,
184 dist, &lat2, &lon2, &az2 );
186 _set_Longitude( lon2 * SGD_DEGREES_TO_RADIANS );
187 _set_Latitude( lat2 * SGD_DEGREES_TO_RADIANS );
190 // cout << "lon error = " << fabs(end.x()*SGD_RADIANS_TO_DEGREES - lon2)
191 // << " lat error = " << fabs(end.y()*SGD_RADIANS_TO_DEGREES - lat2)
194 double sl_radius, lat_geoc;
195 sgGeodToGeoc( get_Latitude(), get_Altitude(), &sl_radius, &lat_geoc );
197 // update euler angles
198 double heading = fmod(get_Psi() + turn + yaw, SGD_2PI);
199 _set_Euler_Angles(roll, pitch, heading);
200 _set_Euler_Rates(0,0,0);
202 _set_Geocentric_Position( lat_geoc, get_Longitude(),
203 sl_radius + get_Altitude() + climb );
204 // cout << "sea level radius (ft) = " << sl_radius << endl;
205 // cout << "(setto) sea level radius (ft) = " << get_Sea_level_radius() << endl;
206 _update_ground_elev_at_pos();
207 _set_Sea_level_radius( sl_radius * SG_METER_TO_FEET);
208 _set_Altitude( get_Altitude() + climb );
209 _set_Altitude_AGL( get_Altitude() - get_Runway_altitude() );
211 set_V_north(cos(heading) * velocity * SG_METER_TO_FEET);
212 set_V_east(sin(heading) * velocity * SG_METER_TO_FEET);
213 set_V_down(-real_climb_rate);