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TJ:

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Annexed an IVSI (instantaneous ertical speed indicator), which bypasses a
limitation with Concorde :

- the cruise at Mach 2 must be with a slow climb rate of 50/60 ft/min
  (2h from 50000 ft).
- with /velocities/vertical-speed-fpm, the real climb rate (altimeter) varies :
  One must constantly (every 5-10 minutes) change the vertical speed hold of
  the autopilot between 10 ft/min and 200 ft/min.
  This is very annoying because not a constant offset : that could be a lack of
  sensitivity of /velocities/vertical-speed-fpm (FDM ?).

This new IVSI :
- Is an emulation with works with environment pressure : a real IVSI works with
  static pressure (with lag) + accelerometers.
  It is not forbidden to later upgrade to the real model.
- Doesn't require a tuning of the autopilot made with
  /velocities/vertical-speed-fpm (also tested with 737, 747) :
    Concorde's autoland works without update.
This commit is contained in:
ehofman 2005-06-25 08:46:58 +00:00
parent 4732b96861
commit 486b59a431
4 changed files with 345 additions and 1 deletions

3
src/Instrumentation/Makefile.am
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@ -21,6 +21,7 @@ libInstrumentation_a_SOURCES = \
slip_skid_ball.cxx slip_skid_ball.hxx \
transponder.cxx transponder.hxx \
turn_indicator.cxx turn_indicator.hxx \
vertical_speed_indicator.cxx vertical_speed_indicator.hxx
vertical_speed_indicator.cxx vertical_speed_indicator.hxx \
inst_vertical_speed_indicator.cxx inst_vertical_speed_indicator.hxx
INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/src

254
src/Instrumentation/inst_vertical_speed_indicator.cxx Normal file
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@ -0,0 +1,254 @@
// inst_vertical_speed_indicator.cxx
// -- Instantaneous VSI (emulation calibrated to standard atmosphere).
//
// Started September 2004.
//
// Copyright (C) 2004
//
// 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/interpolater.hxx>
#include "inst_vertical_speed_indicator.hxx"
#include <Main/fg_props.hxx>
#include <Main/util.hxx>
// Altitude based on pressure difference from sea level.
//
// See http://www.pdas.com/programs/atmos.f90, the tables match exactly
// environment.cxx (Standard 1976).
// Example :
// - at 27900 m the level is 20 km :
// geopotential altitude 27.9 x 6369 / ( 27.9 + 6369) = 27.778 km.
// - deltah = 27.778 - 20 = 7.778 km and tbase 216.65 degK.
// - delta = 5.403295E-2 x exp( -34.163195 x 7.778 / 216.65 ) = 0.016.
// - pressure = (1 - delta ) x 29.92 = 29.44 inhg.
// - to construct the tables, round delta to 3 digits.
// altitude ft, pressure step inHG
static double pressure_data[][2] = {
{ 0.00, 3.33 }, // guess !
{ 2952.76, 3.05 },
{ 5905.51, 2.81 },
{ 8858.27, 2.55 },
{ 11811.02, 2.33 },
{ 14763.78, 2.13 },
{ 17716.54, 1.91 },
{ 20669.29, 1.77 },
{ 23622.05, 1.58 },
{ 26574.80, 1.49 },
{ 29527.56, 1.20 },
{ 32480.31, 1.14 },
{ 35433.07, 1.05 },
{ 38385.83, 0.90 },
{ 41338.58, 0.80 },
{ 44291.34, 0.69 },
{ 47244.09, 0.60 },
{ 50196.85, 0.51 },
{ 53149.61, 0.45 },
{ 56102.36, 0.39 },
{ 59055.12, 0.33 },
{ 62007.87, 0.30 },
{ 64960.63, 0.26 },
{ 67913.39, 0.21 },
{ 70866.14, 0.18 },
{ 73818.90, 0.18 },
{ 76771.65, 0.15 },
{ 79724.41, 0.12 },
{ 82677.17, 0.12 },
{ 85629.92, 0.09 },
{ 88582.68, 0.09 },
{ 91535.43, 0.06 },
{ 94488.19, 0.06 },
{ 97440.94, 0.06 },
{ 100393.70, 0.06 },
{ -1, -1 }
};
// pressure difference inHG, altitude ft
static double altitude_data[][2] = {
{ 0.00, 0.00 },
{ 3.05, 2952.76 },
{ 5.86, 5905.51 },
{ 8.41, 8858.27 },
{ 10.74, 11811.02 },
{ 12.87, 14763.78 },
{ 14.78, 17716.54 },
{ 16.55, 20669.29 },
{ 18.13, 23622.05 },
{ 19.62, 26574.80 },
{ 20.82, 29527.56 },
{ 21.96, 32480.31 },
{ 23.01, 35433.07 },
{ 23.91, 38385.83 },
{ 24.71, 41338.58 },
{ 25.40, 44291.34 },
{ 26.00, 47244.09 },
{ 26.51, 50196.85 },
{ 26.96, 53149.61 },
{ 27.35, 56102.36 },
{ 27.68, 59055.12 },
{ 27.98, 62007.87 },
{ 28.24, 64960.63 },
{ 28.45, 67913.39 },
{ 28.63, 70866.14 },
{ 28.81, 73818.90 },
{ 28.96, 76771.65 },
{ 29.08, 79724.41 },
{ 29.20, 82677.17 },
{ 29.29, 85629.92 },
{ 29.38, 88582.68 },
{ 29.44, 91535.43 },
{ 29.50, 94488.19 },
{ 29.56, 97440.94 },
{ 29.62, 100393.70 },
{ -1, -1 }
};
// SI constants
#define SEA_LEVEL_INHG 29.92
// A higher number means more responsive.
#define RESPONSIVENESS 5.0
// External environment
#define MAX_INHG_PER_S 0.0002
InstVerticalSpeedIndicator::InstVerticalSpeedIndicator ( SGPropertyNode *node ) :
_internal_pressure_inhg( SEA_LEVEL_INHG ),
_internal_sea_inhg( SEA_LEVEL_INHG ),
_pressure_table(new SGInterpTable),
_altitude_table(new SGInterpTable),
_speed_ft_per_s( 0 )
{
for (int i = 0; pressure_data[i][0] != -1; i++)
_pressure_table->addEntry( pressure_data[i][0], pressure_data[i][1] );
for (int i = 0; altitude_data[i][0] != -1; i++)
_altitude_table->addEntry( altitude_data[i][0], altitude_data[i][1] );
int i;
for ( i = 0; i < node->nChildren(); ++i ) {
SGPropertyNode *child = node->getChild(i);
string cname = child->getName();
string cval = child->getStringValue();
if ( cname == "name" ) {
name = cval;
} else if ( cname == "number" ) {
num = child->getIntValue();
} else {
SG_LOG( SG_INSTR, SG_WARN, "Error in inst-vertical-speed-indicator config logic" );
if ( name.length() ) {
SG_LOG( SG_INSTR, SG_WARN, "Section = " << name );
}
}
}
}
InstVerticalSpeedIndicator::~InstVerticalSpeedIndicator ()
{
delete _pressure_table;
delete _altitude_table;
}
void InstVerticalSpeedIndicator::init ()
{
_serviceable_node =
fgGetNode("/instrumentation/inst-vertical-speed-indicator/serviceable", true);
_freeze_node =
fgGetNode("/sim/freeze/master", true);
// A real IVSI is operated by static pressure changes.
// It operates like a conventional VSI, except that an internal sensor
// detects load factors, to momentarily alters the static pressure
// (with lag).
// It appears lag free at subsonic speed; at high altitude indication may
// be less than 1/3 of actual conditions.
_pressure_node =
fgGetNode("/environment/pressure-inhg", true);
_sea_node =
fgGetNode("/environment/pressure-sea-level-inhg", true);
_speed_up_node =
fgGetNode("/sim/speed-up", true);
_speed_node =
fgGetNode("/instrumentation/inst-vertical-speed-indicator/indicated-speed-fps",
true);
_speed_min_node =
fgGetNode("/instrumentation/inst-vertical-speed-indicator/indicated-speed-fpm",
true);
// Initialize at ambient pressure
_internal_pressure_inhg = _pressure_node->getDoubleValue();
}
void InstVerticalSpeedIndicator::update (double dt)
{
if (_serviceable_node->getBoolValue())
{
// avoids hang, when freeze
if( !_freeze_node->getBoolValue() )
{
double pressure_inhg = _pressure_node->getDoubleValue();
double sea_inhg = _sea_node->getDoubleValue();
double speed_up = _speed_up_node->getDoubleValue();
// must work by speed up
if( speed_up > 1 )
{
dt *= speed_up;
}
// limit effect of external environment
double rate_sea_inhg_per_s = ( sea_inhg - _internal_sea_inhg ) / dt;
if( rate_sea_inhg_per_s > - MAX_INHG_PER_S && rate_sea_inhg_per_s < MAX_INHG_PER_S )
{
double rate_inhg_per_s = ( pressure_inhg - _internal_pressure_inhg ) / dt;
// IVSI determines alone the current altitude, without altimeter setting.
// Altimeter setting is 29.92 above 10000 or 18000 ft.
// Below this level, the slope is slightly wrong.
double altitude_ft = _altitude_table->interpolate( SEA_LEVEL_INHG - pressure_inhg );
double slope_inhg = _pressure_table->interpolate( altitude_ft );
double last_speed_ft_per_s = _speed_ft_per_s;
// slope at 900 m
_speed_ft_per_s = - rate_inhg_per_s * 2952.75591 / slope_inhg;
// filter noise
_speed_ft_per_s = fgGetLowPass( last_speed_ft_per_s, _speed_ft_per_s,
dt * RESPONSIVENESS );
}
_speed_node->setDoubleValue( _speed_ft_per_s );
_speed_min_node->setDoubleValue( _speed_ft_per_s * 60.0 );
// backup
_internal_pressure_inhg = pressure_inhg;
_internal_sea_inhg = sea_inhg;
}
}
}
// end of inst_vertical_speed_indicator.cxx

85
src/Instrumentation/inst_vertical_speed_indicator.hxx Normal file
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@ -0,0 +1,85 @@
// inst_vertical_speed_indicator.hxx -- Instantaneous VSI (emulation calibrated to standard atmosphere).
//
// Started September 2004.
//
// Copyright (C) 2004
//
// 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 __INST_VERTICAL_SPEED_INDICATOR_HXX
#define __INST_VERTICAL_SPEED_INDICATOR_HXX 1
#ifndef __cplusplus
# error This library requires C++
#endif
#include <simgear/props/props.hxx>
#include <simgear/structure/subsystem_mgr.hxx>
class SGInterpTable;
/**
* Model an instantaneous VSI tied to the external pressure.
*
* Input properties:
*
* /instrumentation/inst-vertical-speed-indicator/serviceable
* /environment/pressure-inhg
* /environment/pressure-sea-level-inhg
* /sim/speed-up
* /sim/freeze/master
*
* Output properties:
*
* /instrumentation/inst-vertical-speed-indicator/indicated-speed-fps
* /instrumentation/inst-vertical-speed-indicator/indicated-speed-fpm
*/
class InstVerticalSpeedIndicator : public SGSubsystem
{
public:
InstVerticalSpeedIndicator ( SGPropertyNode *node );
virtual ~InstVerticalSpeedIndicator ();
virtual void init ();
virtual void update (double dt);
private:
double _internal_pressure_inhg;
double _internal_sea_inhg;
double _speed_ft_per_s;
string name;
int num;
SGPropertyNode_ptr _serviceable_node;
SGPropertyNode_ptr _freeze_node;
SGPropertyNode_ptr _pressure_node;
SGPropertyNode_ptr _sea_node;
SGPropertyNode_ptr _speed_up_node;
SGPropertyNode_ptr _speed_node;
SGPropertyNode_ptr _speed_min_node;
SGInterpTable * _pressure_table;
SGInterpTable * _altitude_table;
};
#endif // __INST_VERTICAL_SPEED_INDICATOR_HXX

4
src/Instrumentation/instrument_mgr.cxx
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@ -35,6 +35,7 @@
#include "transponder.hxx"
#include "turn_indicator.hxx"
#include "vertical_speed_indicator.hxx"
#include "inst_vertical_speed_indicator.hxx" // (TJ)
FGInstrumentMgr::FGInstrumentMgr ()
@ -147,6 +148,9 @@ bool FGInstrumentMgr::build ()
} else if ( name == "vertical-speed-indicator" ) {
set_subsystem( "instrument" + temp.str(),
new VerticalSpeedIndicator( node ) );
} else if ( name == "inst-vertical-speed-indicator" ) { // (TJ)
set_subsystem( "instrument" + temp.str(),
new InstVerticalSpeedIndicator( node ) );
} else {
SG_LOG( SG_ALL, SG_ALERT, "Unknown top level section: "
<< name );