1 // flight.c -- a general interface to the various flight models
3 // Written by Curtis Olson, started May 1997.
5 // Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 // (Log is kept at end of this file)
28 #include "LaRCsim.hxx"
30 #include <Debug/logstream.hxx>
31 #include <FDM/External/external.hxx>
32 #include <FDM/LaRCsim/ls_interface.h>
33 #include <Include/fg_constants.h>
34 #include <Math/fg_geodesy.hxx>
35 #include <Time/timestamp.hxx>
38 // base_fdm_state is the internal state that is updated in integer
39 // multiples of "dt". This leads to "jitter" with respect to the real
40 // world time, so we introduce cur_fdm_state which is extrapolated by
41 // the difference between sim time and real world time
43 FGState cur_fdm_state;
44 FGState base_fdm_state;
47 // Extrapolate fdm based on time_offset (in usec)
48 void FGState::extrapolate( int time_offset ) {
49 double dt = time_offset / 1000000.0;
50 cout << "extrapolating FDM by dt = " << dt << endl;
52 double lat = geodetic_position_v[0] + geocentric_rates_v[0] * dt;
53 double lat_geoc = geocentric_position_v[0] + geocentric_rates_v[0] * dt;
55 double lon = geodetic_position_v[1] + geocentric_rates_v[1] * dt;
56 double lon_geoc = geocentric_position_v[1] + geocentric_rates_v[1] * dt;
58 double alt = geodetic_position_v[2] + geocentric_rates_v[2] * dt;
59 double radius = geocentric_position_v[2] + geocentric_rates_v[2] * dt;
61 geodetic_position_v[0] = lat;
62 geocentric_position_v[0] = lat_geoc;
64 geodetic_position_v[1] = lon;
65 geocentric_position_v[1] = lon_geoc;
67 geodetic_position_v[2] = alt;
68 geocentric_position_v[2] = radius;
72 // Initialize the flight model parameters
73 int fgFDMInit(int model, FGState& f, double dt) {
74 double save_alt = 0.0;
76 FG_LOG( FG_FLIGHT ,FG_INFO, "Initializing flight model" );
80 if ( model == FGState::FG_SLEW ) {
82 } else if ( model == FGState::FG_LARCSIM ) {
84 // lets try to avoid really screwing up the LaRCsim model
85 if ( base_fdm_state.get_Altitude() < -9000.0 ) {
86 save_alt = base_fdm_state.get_Altitude();
87 base_fdm_state.set_Altitude( 0.0 );
90 // translate FG to LaRCsim structure
91 FGState_2_LaRCsim(base_fdm_state);
96 FG_LOG( FG_FLIGHT, FG_INFO, "FG pos = " <<
97 base_fdm_state.get_Latitude() );
99 // translate LaRCsim back to FG structure
100 fgLaRCsim_2_FGState(base_fdm_state);
102 // but lets restore our original bogus altitude when we are done
103 if ( save_alt < -9000.0 ) {
104 base_fdm_state.set_Altitude( save_alt );
106 } else if ( model == FGState::FG_EXTERNAL ) {
107 fgExternalInit(base_fdm_state);
109 FG_LOG( FG_FLIGHT, FG_WARN,
110 "Unimplemented flight model == " << model );
113 // set valid time for this record
114 base_fdm_state.stamp_time();
122 // Run multiloop iterations of the flight model
123 int fgFDMUpdate(int model, FGState& f, int multiloop, int time_offset) {
124 double time_step, start_elev, end_elev;
126 // printf("Altitude = %.2f\n", FG_Altitude * 0.3048);
128 // set valid time for this record
129 base_fdm_state.stamp_time();
131 time_step = (1.0 / DEFAULT_MODEL_HZ) * multiloop;
132 start_elev = base_fdm_state.get_Altitude();
134 if ( model == FGState::FG_SLEW ) {
135 // fgSlewUpdate(f, multiloop);
136 } else if ( model == FGState::FG_LARCSIM ) {
137 fgLaRCsimUpdate(base_fdm_state, multiloop);
138 // extrapolate position based on actual time
139 // f = extrapolate_fdm( base_fdm_state, time_offset );
141 } else if ( model == FGState::FG_EXTERNAL ) {
142 // fgExternalUpdate(f, multiloop);
146 f.extrapolate( current - base_fdm_state.get_time_stamp() );
148 FG_LOG( FG_FLIGHT, FG_WARN,
149 "Unimplemented flight model == " << model );
152 end_elev = base_fdm_state.get_Altitude();
154 if ( time_step > 0.0 ) {
156 base_fdm_state.set_Climb_Rate( (end_elev - start_elev) / time_step );
163 // Set the altitude (force)
164 void fgFDMForceAltitude(int model, double alt_meters) {
165 double sea_level_radius_meters;
168 // Set the FG variables first
169 fgGeodToGeoc( base_fdm_state.get_Latitude(), alt_meters,
170 &sea_level_radius_meters, &lat_geoc);
172 base_fdm_state.set_Altitude( alt_meters * METER_TO_FEET );
173 base_fdm_state.set_Radius_to_vehicle( base_fdm_state.get_Altitude() +
174 (sea_level_radius_meters *
177 // additional work needed for some flight models
178 if ( model == FGState::FG_LARCSIM ) {
179 ls_ForceAltitude( base_fdm_state.get_Altitude() );
184 // Set the local ground elevation
185 void fgFDMSetGroundElevation(int model, double ground_meters) {
186 base_fdm_state.set_Runway_altitude( ground_meters * METER_TO_FEET );
187 cur_fdm_state.set_Runway_altitude( ground_meters * METER_TO_FEET );
192 // Revision 1.14 1999/02/01 21:33:31 curt
193 // Renamed FlightGear/Simulator/Flight to FlightGear/Simulator/FDM since
194 // Jon accepted my offer to do this and thought it was a good idea.
196 // Revision 1.13 1999/01/27 04:48:39 curt
197 // Set the runway height in cur_fdm_state as well as base_fdm_state.
199 // Revision 1.12 1999/01/20 13:42:22 curt
200 // Tweaked FDM interface.
201 // Testing check sum support for NMEA serial output.
203 // Revision 1.11 1999/01/19 17:52:06 curt
204 // Working on being able to extrapolate a new position and orientation
205 // based on a position, orientation, and time offset.
207 // Revision 1.10 1999/01/09 13:37:32 curt
208 // Convert fgTIMESTAMP to FGTimeStamp which holds usec instead of ms.
210 // Revision 1.9 1999/01/08 19:27:37 curt
211 // Fixed AOA reading on HUD.
212 // Continued work on time jitter compensation.
214 // Revision 1.8 1999/01/08 03:23:51 curt
215 // Beginning work on compensating for sim time vs. real world time "jitter".
217 // Revision 1.7 1998/12/18 23:37:07 curt
218 // Collapsed out the FGState variables not currently needed. They are just
219 // commented out and can be readded easily at any time. The point of this
220 // exersize is to determine which variables were or were not currently being
223 // Revision 1.6 1998/12/05 15:54:11 curt
224 // Renamed class fgFLIGHT to class FGState as per request by JSB.
226 // Revision 1.5 1998/12/04 01:29:39 curt
227 // Stubbed in a new flight model called "External" which is expected to be driven
228 // from some external source.
230 // Revision 1.4 1998/12/03 01:16:40 curt
231 // Converted fgFLIGHT to a class.
233 // Revision 1.3 1998/11/06 21:18:03 curt
234 // Converted to new logstream debugging facility. This allows release
235 // builds with no messages at all (and no performance impact) by using
236 // the -DFG_NDEBUGNDEBUG flag.
238 // Revision 1.2 1998/10/16 23:27:40 curt
241 // Revision 1.1 1998/10/16 20:16:41 curt
242 // Renamed flight.[ch] to flight.[ch]xx
244 // Revision 1.19 1998/09/29 14:57:38 curt
245 // c++-ified comments.
247 // Revision 1.18 1998/09/29 02:02:40 curt
248 // Added a rate of climb calculation.
250 // Revision 1.17 1998/08/24 20:09:07 curt
253 // Revision 1.16 1998/08/22 14:49:55 curt
254 // Attempting to iron out seg faults and crashes.
255 // Did some shuffling to fix a initialization order problem between view
256 // position, scenery elevation.
258 // Revision 1.15 1998/07/30 23:44:36 curt
259 // Beginning to add support for multiple flight models.
261 // Revision 1.14 1998/07/12 03:08:27 curt
262 // Added fgFlightModelSetAltitude() to force the altitude to something
263 // other than the current altitude. LaRCsim doesn't let you do this by just
264 // changing FG_Altitude.
266 // Revision 1.13 1998/04/25 22:06:28 curt
267 // Edited cvs log messages in source files ... bad bad bad!
269 // Revision 1.12 1998/04/21 16:59:33 curt
270 // Integrated autopilot.
271 // Prepairing for C++ integration.
273 // Revision 1.11 1998/04/18 04:14:04 curt
274 // Moved fg_debug.c to it's own library.
276 // Revision 1.10 1998/02/07 15:29:37 curt
277 // Incorporated HUD changes and struct/typedef changes from Charlie Hotchkiss
278 // <chotchkiss@namg.us.anritsu.com>
280 // Revision 1.9 1998/01/27 00:47:53 curt
281 // Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
282 // system and commandline/config file processing code.
284 // Revision 1.8 1998/01/19 19:27:03 curt
285 // Merged in make system changes from Bob Kuehne <rpk@sgi.com>
286 // This should simplify things tremendously.
288 // Revision 1.7 1998/01/19 18:40:23 curt
289 // Tons of little changes to clean up the code and to remove fatal errors
290 // when building with the c++ compiler.
292 // Revision 1.6 1998/01/19 18:35:43 curt
293 // Minor tweaks and fixes for cygwin32.
295 // Revision 1.5 1997/12/30 20:47:37 curt
296 // Integrated new event manager with subsystem initializations.
298 // Revision 1.4 1997/12/10 22:37:42 curt
299 // Prepended "fg" on the name of all global structures that didn't have it yet.
300 // i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
302 // Revision 1.3 1997/08/27 03:30:04 curt
303 // Changed naming scheme of basic shared structures.
305 // Revision 1.2 1997/05/29 22:39:57 curt
306 // Working on incorporating the LaRCsim flight model.
308 // Revision 1.1 1997/05/29 02:35:04 curt