+++ /dev/null
-// steam.cxx - Steam Gauge Calculations
-//
-// Copyright (C) 2000 Alexander Perry - alex.perry@ieee.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.
-//
-// $Id$
-
-
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
-
-#include <simgear/compiler.h>
-
-#include STL_IOSTREAM
-
-#include <simgear/constants.h>
-#include <simgear/math/sg_types.hxx>
-#include <simgear/misc/props.hxx>
-
-#include <Main/fg_props.hxx>
-#include <Aircraft/aircraft.hxx>
-#ifdef FG_WEATHERCM
-# include <WeatherCM/FGLocalWeatherDatabase.h>
-#else
-# include <Environment/environment_mgr.hxx>
-# include <Environment/environment.hxx>
-#endif
-
-SG_USING_NAMESPACE(std);
-
-#include "radiostack.hxx"
-#include "steam.hxx"
-
-static bool isTied = false;
-
-
-\f
-////////////////////////////////////////////////////////////////////////
-// Constructor and destructor.
-////////////////////////////////////////////////////////////////////////
-
-FGSteam::FGSteam ()
- :
- the_ALT_ft(0.0),
- the_ALT_datum_mb(1013.0),
- the_TC_rad(0.0),
- the_TC_std(0.0),
- the_STATIC_inhg(29.92),
- the_VACUUM_inhg(0.0),
- the_VSI_fps(0.0),
- the_VSI_case(29.92),
- the_MH_deg(0.0),
- the_MH_degps(0.0),
- the_MH_err(0.0),
- the_DG_deg(0.0),
- the_DG_degps(0.0),
- the_DG_inhg(0.0),
- the_DG_err(0.0),
- _UpdateTimePending(1000000)
-{
-}
-
-FGSteam::~FGSteam ()
-{
-}
-
-void
-FGSteam::init ()
-{
- _heading_deg_node = fgGetNode("/orientation/heading-deg", true);
- _mag_var_deg_node = fgGetNode("/environment/magnetic-variation-deg", true);
- _mag_dip_deg_node = fgGetNode("/environment/magnetic-dip-deg", true);
- _engine_0_rpm_node = fgGetNode("/engines/engine[0]/rpm", true);
- _pressure_inhg_node = fgGetNode("environment/pressure-inhg", true);
-}
-
-void
-FGSteam::update (double dt_sec)
-{
- _UpdateTimePending += dt_sec;
- _CatchUp();
-}
-
-void
-FGSteam::bind ()
-{
- fgTie("/steam/airspeed-kt", this, &FGSteam::get_ASI_kias);
- fgSetArchivable("/steam/airspeed-kt");
- fgTie("/steam/altitude-ft", this, &FGSteam::get_ALT_ft);
- fgSetArchivable("/steam/altitude-ft");
- fgTie("/steam/altimeter-datum-mb", this,
- &FGSteam::get_ALT_datum_mb, &FGSteam::set_ALT_datum_mb,
- false); /* don't modify the value */
- fgSetArchivable("/steam/altimeter-datum-mb");
- fgTie("/steam/turn-rate", this, &FGSteam::get_TC_std);
- fgSetArchivable("/steam/turn-rate");
- fgTie("/steam/slip-skid",this, &FGSteam::get_TC_rad);
- fgSetArchivable("/steam/slip-skid");
- fgTie("/steam/vertical-speed-fps", this, &FGSteam::get_VSI_fps);
- fgSetArchivable("/steam/vertical-speed-fps");
- fgTie("/steam/gyro-compass-deg", this, &FGSteam::get_DG_deg);
- fgSetArchivable("/steam/gyro-compass-deg");
- // fgTie("/steam/adf-deg", FGSteam::get_HackADF_deg);
- // fgSetArchivable("/steam/adf-deg");
- fgTie("/steam/gyro-compass-error-deg", this,
- &FGSteam::get_DG_err, &FGSteam::set_DG_err,
- false); /* don't modify the value */
- fgSetArchivable("/steam/gyro-compass-error-deg");
- fgTie("/steam/mag-compass-deg", this, &FGSteam::get_MH_deg);
- fgSetArchivable("/steam/mag-compass-deg");
-}
-
-void
-FGSteam::unbind ()
-{
- fgUntie("/steam/airspeed-kt");
- fgUntie("/steam/altitude-ft");
- fgUntie("/steam/altimeter-datum-mb");
- fgUntie("/steam/turn-rate");
- fgUntie("/steam/slip-skid");
- fgUntie("/steam/vertical-speed-fps");
- fgUntie("/steam/gyro-compass-deg");
- fgUntie("/steam/gyro-compass-error-deg");
- fgUntie("/steam/mag-compass-deg");
-}
-
-
-\f
-////////////////////////////////////////////////////////////////////////
-// Declare the functions that read the variables
-////////////////////////////////////////////////////////////////////////
-
-double
-FGSteam::get_ALT_ft () const
-{
- return the_ALT_ft;
-}
-
-double
-FGSteam::get_ALT_datum_mb () const
-{
- return the_ALT_datum_mb;
-}
-
-void
-FGSteam::set_ALT_datum_mb (double datum_mb)
-{
- the_ALT_datum_mb = datum_mb;
-}
-
-double
-FGSteam::get_ASI_kias () const
-{
- return fgGetDouble("/velocities/airspeed-kt");
-}
-
-double
-FGSteam::get_VSI_fps () const
-{
- return the_VSI_fps;
-}
-
-double
-FGSteam::get_VACUUM_inhg () const
-{
- return the_VACUUM_inhg;
-}
-
-double
-FGSteam::get_MH_deg () const
-{
- return the_MH_deg;
-}
-
-double
-FGSteam::get_DG_deg () const
-{
- return the_DG_deg;
-}
-
-double
-FGSteam::get_DG_err () const
-{
- return the_DG_err;
-}
-
-void
-FGSteam::set_DG_err (double approx_magvar)
-{
- the_DG_err = approx_magvar;
-}
-
-double
-FGSteam::get_TC_rad () const
-{
- return the_TC_rad;
-}
-
-double
-FGSteam::get_TC_std () const
-{
- return the_TC_std;
-}
-
-
-\f
-////////////////////////////////////////////////////////////////////////
-// Recording the current time
-////////////////////////////////////////////////////////////////////////
-
-
-/* tc should be (elapsed_time_between_updates / desired_smoothing_time) */
-void FGSteam::set_lowpass ( double *outthe, double inthe, double tc )
-{
- if ( tc < 0.0 )
- { if ( tc < -1.0 )
- { /* time went backwards; kill the filter */
- (*outthe) = inthe;
- } else
- { /* ignore mildly negative time */
- }
- } else
- if ( tc < 0.2 )
- { /* Normal mode of operation; fast approximation to exp(-tc) */
- (*outthe) = (*outthe) * ( 1.0 - tc )
- + inthe * tc;
- } else
- if ( tc > 5.0 )
- { /* Huge time step; assume filter has settled */
- (*outthe) = inthe;
- } else
- { /* Moderate time step; non linear response */
- double keep = exp ( -tc );
- // printf ( "ARP: Keep is %f\n", keep );
- (*outthe) = (*outthe) * keep
- + inthe * ( 1.0 - keep );
- }
-}
-
-
-#define INHG_TO_MB 33.86388 /* Inches_of_mercury * INHG_TO_MB == millibars. */
-
-// Convert air pressure to altitude by ICAO Standard Atmosphere
-double pressInHgToAltFt(double p_inhg)
-{
- // Ref. Aviation Formulary, Ed Williams, www.best.com/~williams/avform.htm
- const double P_0 = 29.92126; // Std. MSL pressure, inHg. (=1013.25 mb)
- const double p_Tr = 0.2233609 * P_0; // Pressure at tropopause, same units.
- const double h_Tr = 36089.24; // Alt of tropopause, ft. (=11.0 km)
-
- if (p_inhg > p_Tr) // 0.0 to 11.0 km
- return (1.0 - pow((p_inhg / P_0), 1.0 / 5.2558797)) / 6.8755856e-6;
- return h_Tr + log10(p_inhg / p_Tr) / -4.806346e-5; // 11.0 to 20.0 km
- // We could put more code for higher altitudes here.
-}
-
-
-// Convert altitude to air pressure by ICAO Standard Atmosphere
-double altFtToPressInHg(double alt_ft)
-{
- // Ref. Aviation Formulary, Ed Williams, www.best.com/~williams/avform.htm
- const double P_0 = 29.92126; // Std. MSL pressure, inHg. (=1013.25 mb)
- const double p_Tr = 0.2233609 * P_0; // Pressure at tropopause, same units.
- const double h_Tr = 36089.24; // Alt of tropopause, ft. (=11.0 km)
-
- if (alt_ft < h_Tr) // 0.0 to 11.0 km
- return P_0 * pow(1.0 - 6.8755856e-6 * alt_ft, 5.2558797);
- return p_Tr * exp(-4.806346e-5 * (alt_ft - h_Tr)); // 11.0 to 20.0 km
- // We could put more code for higher altitudes here.
-}
-
-
-\f
-////////////////////////////////////////////////////////////////////////
-// Here the fun really begins
-////////////////////////////////////////////////////////////////////////
-
-
-void FGSteam::_CatchUp()
-{
- if ( _UpdateTimePending != 0 )
- {
- double dt = _UpdateTimePending;
- double AccN, AccE, AccU;
- /* int i, j; */
- double d, the_ENGINE_rpm;
-
- /**************************
- Someone has called our update function and
- it turns out that we are running somewhat behind.
- Here, we recalculate everything for a 'dt' second step.
- */
-
- /**************************
- The ball responds to the acceleration vector in the body
- frame, only the components perpendicular to the longitudinal
- axis of the aircraft. This is only related to actual
- side slip for a symmetrical aircraft which is not touching
- the ground and not changing its attitude. Math simplifies
- by assuming (for small angles) arctan(x)=x in radians.
- Obvious failure mode is the absence of liquid in the
- tube, which is there to damp the motion, so that instead
- the ball will bounce around, hitting the tube ends.
- More subtle flaw is having it not move or a travel limit
- occasionally due to some dirt in the tube or on the ball.
- */
- // cout << current_aircraft.fdm_state->get_A_Z_pilot() << endl;
- // cout << "Ay = " << current_aircraft.fdm_state->get_A_Y_pilot()
- // << " Az = " << current_aircraft.fdm_state->get_A_Z_pilot() << endl;
- d = -current_aircraft.fdm_state->get_A_Z_pilot();
- if ( d < 1 ) d = 1;
- set_lowpass ( & the_TC_rad,
- current_aircraft.fdm_state->get_A_Y_pilot () / d,
- dt );
-
- /**************************
- The rate of turn indication is from an electric gyro.
- We should have it spin up with the master switch.
- It is mounted at a funny angle so that it detects
- both rate of bank (i.e. rolling into and out of turns)
- and the rate of turn (i.e. how fast heading is changing).
- */
- set_lowpass ( & the_TC_std,
- current_aircraft.fdm_state->get_Phi_dot ()
- * SGD_RADIANS_TO_DEGREES / 20.0 +
- current_aircraft.fdm_state->get_Psi_dot ()
- * SGD_RADIANS_TO_DEGREES / 3.0 , dt );
-
- /**************************
- We want to know the pilot accelerations,
- to compute the magnetic compass errors.
- */
- AccN = current_aircraft.fdm_state->get_V_dot_north();
- AccE = current_aircraft.fdm_state->get_V_dot_east();
- AccU = current_aircraft.fdm_state->get_V_dot_down()
- - 9.81 * SG_METER_TO_FEET;
- if ( fabs(the_TC_rad) > 0.2 /* 2.0 */ )
- { /* Massive sideslip jams it; it stops turning */
- the_MH_degps = 0.0;
- the_MH_err = _heading_deg_node->getDoubleValue() - the_MH_deg;
- } else
- { double MagDip, MagVar, CosDip;
- double FrcN, FrcE, FrcU, AccTot;
- double EdgN, EdgE, EdgU;
- double TrqN, TrqE, TrqU, Torque;
- /* Find a force vector towards exact magnetic north */
- MagVar = _mag_var_deg_node->getDoubleValue()
- / SGD_RADIANS_TO_DEGREES;
- MagDip = _mag_var_deg_node->getDoubleValue()
- / SGD_RADIANS_TO_DEGREES;
- CosDip = cos ( MagDip );
- FrcN = CosDip * cos ( MagVar );
- FrcE = CosDip * sin ( MagVar );
- FrcU = sin ( MagDip );
- /* Rotation occurs around acceleration axis,
- but axis magnitude is irrelevant. So compute it. */
- AccTot = AccN*AccN + AccE*AccE + AccU*AccU;
- if ( AccTot > 1.0 ) AccTot = sqrt ( AccTot );
- else AccTot = 1.0;
- /* Force applies to north marking on compass card */
- EdgN = cos ( the_MH_err / SGD_RADIANS_TO_DEGREES );
- EdgE = sin ( the_MH_err / SGD_RADIANS_TO_DEGREES );
- EdgU = 0.0;
- /* Apply the force to the edge to get torques */
- TrqN = EdgE * FrcU - EdgU * FrcE;
- TrqE = EdgU * FrcN - EdgN * FrcU;
- TrqU = EdgN * FrcE - EdgE * FrcN;
- /* Select the component parallel to the axis */
- Torque = ( TrqN * AccN +
- TrqE * AccE +
- TrqU * AccU ) * 5.0 / AccTot;
- /* The magnetic compass has angular momentum,
- so we apply a torque to it and wait */
- if ( dt < 1.0 )
- { the_MH_degps= the_MH_degps * (1.0 - dt) - Torque;
- the_MH_err += dt * the_MH_degps;
- }
- if ( the_MH_err > 180.0 ) the_MH_err -= 360.0; else
- if ( the_MH_err < -180.0 ) the_MH_err += 360.0;
- the_MH_deg = _heading_deg_node->getDoubleValue() - the_MH_err;
- }
-
- /**************************
- This is not actually correct, but provides a
- scaling capability for the vacuum pump later on.
- When we have a real engine model, we can ask it.
- */
- the_ENGINE_rpm = _engine_0_rpm_node->getDoubleValue();
-
- /**************************
- First, we need to know what the static line is reporting,
- which is a whole simulation area in itself.
- We filter the actual value by one second to
- account for the line impedance of the plumbing.
- */
-#ifdef FG_WEATHERCM
- sgVec3 plane_pos = { cur_fdm_state->get_Latitude(),
- cur_fdm_state->get_Longitude(),
- cur_fdm_state->get_Altitude() * SG_FEET_TO_METER };
- double static_inhg = WeatherDatabase->get(plane_pos).AirPressure *
- (0.01 / INHG_TO_MB);
-#else
- double static_inhg = _pressure_inhg_node->getDoubleValue();
-#endif
-
- set_lowpass ( & the_STATIC_inhg, static_inhg, dt );
-
- /*
- NO alternate static source error (student feature),
- NO possibility of blockage (instructor feature),
- NO slip-induced error, important for C172 for example.
- */
-
- /**************************
- Altimeter.
- ICAO standard atmosphere MSL pressure is 1013.25 mb, and pressure
- gradient is about 28 ft per mb at MSL increasing to about 32 at
- 5000 and 38 at 10000 ft.
- Standard altimeters apply the subscale offset to the output altitude,
- not to the input pressure; I don't know exactly what pressure gradient
- they assume for this. I choose to make it accurate at low altitudes.
- Remember, we are trying to simulate a real altimeter, not an ideal one.
- */
- set_lowpass ( & the_ALT_ft,
- pressInHgToAltFt(the_STATIC_inhg) +
- (the_ALT_datum_mb - 1013.25) * 28.0, /* accurate at low alt. */
- dt * 10 ); /* smoothing time 0.1 s */
-
- /**************************
- The VSI case is a low-pass filter of the static line pressure.
- The instrument reports the difference, scaled to approx ft.
- NO option for student to break glass when static source fails.
- NO capability for a fixed non-zero reading when level.
- NO capability to have a scaling error of maybe a factor of two.
- */
- the_VSI_fps = ( the_VSI_case - the_STATIC_inhg )
- * 10000.0; /* manual scaling factor */
- set_lowpass ( & the_VSI_case, the_STATIC_inhg, dt/6.0 );
-
- /**************************
- The engine driven vacuum pump is directly attached
- to the engine shaft, so each engine rotation pumps
- a fixed volume. The amount of air in that volume
- is determined by the vacuum line's internal pressure.
- The instruments are essentially leaking air like
- a fixed source impedance from atmospheric pressure.
- The regulator provides a digital limit setting,
- which is open circuit unless the pressure drop is big.
- Thus, we can compute the vacuum line pressure directly.
- We assume that there is negligible reservoir space.
- NO failure of the pump supported (yet)
- */
- the_VACUUM_inhg = the_STATIC_inhg *
- the_ENGINE_rpm / ( the_ENGINE_rpm + 10000.0 );
- if ( the_VACUUM_inhg > 5.0 )
- the_VACUUM_inhg = 5.0;
-
-/*
-> I was merely going to do the engine rpm driven vacuum pump for both
-> the AI and DG, have the gyros spin down down in power off descents,
-> have it tumble when you exceed the usual pitch or bank limits,
-> put in those insidious turning errors ... for now anyway.
-*/
- if ( _UpdateTimePending > 999999 )
- the_DG_err = fgGetDouble("/environment/magnetic-variation-deg");
- the_DG_degps = 0.01; /* HACK! */
- if (dt<1.0) the_DG_err += dt * the_DG_degps;
- the_DG_deg = _heading_deg_node->getDoubleValue() - the_DG_err;
-
- /**************************
- Finished updates, now clear the timer
- */
- _UpdateTimePending = 0;
- } else {
- // cout << "0 Updates pending" << endl;
- }
-}
-
-\f
-////////////////////////////////////////////////////////////////////////
-// Everything below is a transient hack; expect it to disappear
-////////////////////////////////////////////////////////////////////////
-
-double FGSteam::get_HackOBS1_deg () const
-{
- return current_radiostack->get_navcom1()->get_nav_radial();
-}
-
-double FGSteam::get_HackOBS2_deg () const
-{
- return current_radiostack->get_navcom2()->get_nav_radial();
-}
-
-
-// end of steam.cxx
+++ /dev/null
-// steam.hxx - Steam Gauge Indications
-//
-// Started by Alex Perry
-//
-// Copyright (C) 2000 Alexander Perry - alex.perry@ieee.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.
-//
-// $Id$
-
-
-#ifndef FG_STEAM
-#define FG_STEAM
-
-
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
-
-#include <simgear/compiler.h>
-
-#include <Main/fgfs.hxx>
-
-#include <time.h>
-#include STL_STRING
-
-SG_USING_NAMESPACE(std);
-
-
-/**
- * STEAM GAUGES
- *
- * This class is a mapping layer, which retrieves information from the
- * property manager (which reports truthful and ideal values) and
- * generates all the instrument errors and inaccuracies that pilots
- * (err) love, of course. Please report any missing flaws (!).
- *
- * These should be used to operate cockpit instruments,
- * and autopilot features where these are slaved thus.
- * They should not be used for other simulation purposes.
- */
-class FGSteam : public FGSubsystem
-{
-public:
-
- FGSteam ();
- virtual ~FGSteam ();
-
- virtual void init ();
-
- virtual void update (double dt_sec);
-
- virtual void bind ();
-
- virtual void unbind ();
-
- // Position
- virtual double get_ALT_ft () const;
- virtual double get_TC_rad () const;
- virtual double get_MH_deg () const;
- virtual double get_DG_deg () const;
- virtual double get_DG_err () const;
- virtual void set_DG_err(double approx_magvar);
-
- // Velocities
- virtual double get_ASI_kias () const;
- virtual double get_TC_std () const;
- virtual double get_VSI_fps () const;
-
- // Engine Gauges
- virtual double get_VACUUM_inhg () const;
-
- // Atmosphere
- virtual double get_ALT_datum_mb () const;
- virtual void set_ALT_datum_mb(double datum_mb);
-
- // Hacks ... temporary stuff
- // static double get_HackVOR1_deg ();
- virtual double get_HackOBS1_deg () const;
- // static double get_HackGS_deg ();
- // static double get_HackVOR2_deg ();
- virtual double get_HackOBS2_deg () const;
-
-
-private:
-
- void _CatchUp ();
- void set_lowpass ( double *outthe, double inthe, double tc );
-
- double the_ALT_ft;
- double the_ALT_datum_mb;
- double the_TC_rad, the_TC_std;
- double the_STATIC_inhg, the_VACUUM_inhg;
- double the_VSI_fps, the_VSI_case;
- double the_MH_deg, the_MH_degps, the_MH_err;
- double the_DG_deg, the_DG_degps, the_DG_inhg, the_DG_err;
-
- double _UpdateTimePending;
-
- SGPropertyNode_ptr _heading_deg_node;
- SGPropertyNode_ptr _mag_var_deg_node;
- SGPropertyNode_ptr _mag_dip_deg_node;
- SGPropertyNode_ptr _engine_0_rpm_node;
- SGPropertyNode_ptr _pressure_inhg_node;
-
-};
-
-
-#endif // FG_STEAM
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