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UFO FDM patches from Jonathan Polley:

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I have finished working the bugs out of my "Enhanced" version of the Magic
Carpet FDM.  The UFO FDM works the same as the Magic Carpet with the
following exceptions:

The aircraft's pitch is determined by the Elevator setting (with a pitch
rate of 45 degrees per second).
Climb is forward velocity * sin(pitch)
Speed is forward velocity * soc(pitch)

Roll is tied to the aileron (again, with a roll rate of 45 degrees per
second)
Turn rate is sin(roll) * 45 degrees.

Yes, this does mean that turning is quite a bit more sluggish than
climbing.

If you are wondering why a UFO FDM, it is because it's best that I not
replace the existing magic carpet and this FDM does behave like a UFO (it
hovers, can spin and pitch while hovering, and does not obey the laws of
physics ;)
This commit is contained in:
david 2002-04-25 16:23:16 +00:00
parent 5166d46743
commit 18e36a3302
4 changed files with 223 additions and 0 deletions
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1
src/FDM/Makefile.am
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@ -12,6 +12,7 @@ libFlight_a_SOURCES = \
LaRCsim.cxx LaRCsim.hxx \
LaRCsimIC.cxx LaRCsimIC.hxx \
MagicCarpet.cxx MagicCarpet.hxx \
UFO.cxx UFO.hxx \
NullFDM.cxx NullFDM.hxx
if OLD_AUTOMAKE

173
src/FDM/UFO.cxx Normal file
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@ -0,0 +1,173 @@
// UFO.cxx -- interface to the "UFO" flight model
//
// Written by Curtis Olson, started October 1999.
// Slightly modified from MagicCarpet.cxx by Jonathan Polley, April 2002
//
// Copyright (C) 1999-2002 Curtis L. Olson - curt@flightgear.org
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//
#include <simgear/math/sg_geodesy.hxx>
#include <simgear/math/point3d.hxx>
#include <simgear/math/polar3d.hxx>
#include <Controls/controls.hxx>
#include <Main/globals.hxx>
#include <Main/fg_props.hxx>
#include "UFO.hxx"
FGUFO::FGUFO( double dt ) {
set_delta_t( dt );
}
FGUFO::~FGUFO() {
}
// Initialize the UFO flight model, dt is the time increment
// for each subsequent iteration through the EOM
void FGUFO::init() {
common_init();
}
// Run an iteration of the EOM (equations of motion)
void FGUFO::update( int multiloop ) {
// cout << "FGLaRCsim::update()" << endl;
double time_step = get_delta_t() * multiloop;
// read the throttle
double Throttle = globals->get_controls()->get_throttle( 0 );
// read the state of the control surfaces
double Aileron = globals->get_controls()->get_aileron();
double Elevator = globals->get_controls()->get_elevator();
// the velocity of the aircraft
double velocity = Throttle * 2000; // meters/sec
double old_pitch = get_Theta();
double pitch_rate = SGD_PI_4; // assume I will be pitching up
double target_pitch = -Elevator * SGD_PI_2;
// if I am pitching down
if (old_pitch > target_pitch)
// set the pitch rate to negative (down)
pitch_rate *= -1;
double pitch = old_pitch + (pitch_rate * time_step);
// if I am pitching up
if (pitch_rate > 0.0)
{
// clip the pitch at the limit
if ( pitch > target_pitch)
{
pitch = target_pitch;
}
}
// if I am pitching down
else if (pitch_rate < 0.0)
{
// clip the pitch at the limit
if ( pitch < target_pitch)
{
pitch = target_pitch;
}
}
double old_roll = get_Phi();
double roll_rate = SGD_PI_4;
double target_roll = Aileron * SGD_PI_2;
if (old_roll > target_roll)
roll_rate *= -1;
double roll = old_roll + (roll_rate * time_step);
// if I am rolling CW
if (roll_rate > 0.0)
{
// clip the roll at the limit
if ( roll > target_roll)
{
roll = target_roll;
}
}
// if I am rolling CCW
else if (roll_rate < 0.0)
{
// clip the roll at the limit
if ( roll < target_roll)
{
roll = target_roll;
}
}
// the vertical speed of the aircraft
double real_climb_rate = sin (pitch) * SG_METER_TO_FEET * velocity; // feet/sec
_set_Climb_Rate( -Elevator * 10.0 );
double climb = real_climb_rate * time_step;
// the lateral speed of the aircraft
double speed = cos (pitch) * velocity; // meters/sec
double dist = speed * time_step;
double kts = velocity * SG_METER_TO_NM * 3600.0;
_set_V_equiv_kts( kts );
_set_V_calibrated_kts( kts );
_set_V_ground_speed( kts );
// angle of turn
double turn_rate = sin(roll) * SGD_PI_4; // radians/sec
double turn = turn_rate * time_step;
// update (lon/lat) position
double lat2, lon2, az2;
if ( speed > SG_EPSILON ) {
geo_direct_wgs_84 ( get_Altitude(),
get_Latitude() * SGD_RADIANS_TO_DEGREES,
get_Longitude() * SGD_RADIANS_TO_DEGREES,
get_Psi() * SGD_RADIANS_TO_DEGREES,
dist, &lat2, &lon2, &az2 );
_set_Longitude( lon2 * SGD_DEGREES_TO_RADIANS );
_set_Latitude( lat2 * SGD_DEGREES_TO_RADIANS );
}
// cout << "lon error = " << fabs(end.x()*SGD_RADIANS_TO_DEGREES - lon2)
// << " lat error = " << fabs(end.y()*SGD_RADIANS_TO_DEGREES - lat2)
// << endl;
double sl_radius, lat_geoc;
sgGeodToGeoc( get_Latitude(), get_Altitude(), &sl_radius, &lat_geoc );
// update euler angles
_set_Euler_Angles( roll, pitch,
fmod(get_Psi() + turn, SGD_2PI) );
_set_Euler_Rates(0,0,0);
_set_Geocentric_Position( lat_geoc, get_Longitude(),
sl_radius + get_Altitude() + climb );
// cout << "sea level radius (ft) = " << sl_radius << endl;
// cout << "(setto) sea level radius (ft) = " << get_Sea_level_radius() << endl;
_set_Sea_level_radius( sl_radius * SG_METER_TO_FEET);
_set_Altitude( get_Altitude() + climb );
}

46
src/FDM/UFO.hxx Normal file
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@ -0,0 +1,46 @@
// UFO.hxx -- interface to the "UFO" flight model
//
// Written by Curtis Olson, started October 1999.
// Slightly modified from MagicCarpet.hxx by Jonathan Polley, April 2002
//
// Copyright (C) 1999-2002 Curtis L. Olson - curt@flightgear.org
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//
#ifndef _UFO_HXX
#define _UFO_HXX
#include "flight.hxx"
class FGUFO: public FGInterface {
public:
FGUFO( double dt );
~FGUFO();
// reset flight params to a specific position
void init();
// update position based on inputs, positions, velocities, etc.
void update( int multiloop );
};
#endif // _UFO_HXX

3
src/Main/fg_init.cxx
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@ -89,6 +89,7 @@
#include <FDM/JSBSim/JSBSim.hxx>
#include <FDM/LaRCsim.hxx>
#include <FDM/MagicCarpet.hxx>
#include <FDM/UFO.hxx>
#include <FDM/NullFDM.hxx>
#include <FDM/YASim/YASim.hxx>
#include <Include/general.hxx>
@ -586,6 +587,8 @@ void fgInitFDM() {
cur_fdm_state = new FGBalloonSim( dt );
} else if ( model == "magic" ) {
cur_fdm_state = new FGMagicCarpet( dt );
} else if ( model == "ufo" ) {
cur_fdm_state = new FGUFO( dt );
} else if ( model == "external" ) {
cur_fdm_state = new FGExternal( dt );
} else if ( model.find("network,") == 0 ) {