# include <config.h>
#endif
-#if defined( FG_HAVE_NATIVE_SGI_COMPILERS )
-# include <iostream.h>
-#else
-# include <iostream>
-#endif
+#include <simgear/compiler.h>
+
+#include STL_IOSTREAM
#include <simgear/constants.h>
-#include <simgear/math/fg_types.hxx>
-#include <Main/options.hxx>
-#include <Main/bfi.hxx>
+#include <simgear/math/sg_types.hxx>
+#include <simgear/misc/props.hxx>
-FG_USING_NAMESPACE(std);
+#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
////////////////////////////////////////////////////////////////////////
-// Declare the functions that read the variables
+// Constructor and destructor.
////////////////////////////////////////////////////////////////////////
-// Anything that reads the BFI directly is not implemented at all!
-
+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)
+{
+}
-double FGSteam::the_STATIC_inhg = 29.92;
-double FGSteam::the_ALT_ft = 0.0;
-double FGSteam::get_ALT_ft() { _CatchUp(); return the_ALT_ft; }
+FGSteam::~FGSteam ()
+{
+}
-double FGSteam::get_ASI_kias() { return FGBFI::getAirspeed(); }
+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);
+}
-double FGSteam::the_VSI_case = 29.92;
-double FGSteam::the_VSI_fps = 0.0;
-double FGSteam::get_VSI_fps() { _CatchUp(); return the_VSI_fps; }
+void
+FGSteam::update (double dt_sec)
+{
+ _UpdateTimePending += dt_sec;
+ _CatchUp();
+}
-double FGSteam::get_MH_deg () { return FGBFI::getHeading (); }
-double FGSteam::get_DG_deg () { return FGBFI::getHeading (); }
+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");
+}
-double FGSteam::get_TC_rad () { return FGBFI::getSideSlip (); }
-double FGSteam::get_TC_radps () { return FGBFI::getRoll (); }
+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
////////////////////////////////////////////////////////////////////////
-// Recording the current time
+// Declare the functions that read the variables
////////////////////////////////////////////////////////////////////////
+double
+FGSteam::get_ALT_ft () const
+{
+ return the_ALT_ft;
+}
-int FGSteam::_UpdatesPending = 9999; /* Forces filter to reset */
+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;
+}
-void FGSteam::update ( int timesteps )
+double
+FGSteam::get_TC_std () const
{
- _UpdatesPending += timesteps;
+ 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 )
}
} else
if ( tc < 0.2 )
- { /* Normal mode of operation */
+ { /* Normal mode of operation; fast approximation to exp(-tc) */
(*outthe) = (*outthe) * ( 1.0 - tc )
+ inthe * tc;
} else
- if ( tc > 5 )
+ if ( tc > 5.0 )
{ /* Huge time step; assume filter has settled */
(*outthe) = inthe;
} else
{ /* Moderate time step; non linear response */
- tc = exp ( -tc );
- (*outthe) = (*outthe) * ( 1.0 - tc )
- + inthe * tc;
+ 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 ( _UpdatesPending != 0 )
- { double dt = _UpdatesPending * 1.0 / current_options.get_model_hz();
- int i,j;
- double d;
- /*
- Someone has called our update function and we haven't
- incorporated this into our instrument modelling yet
+{
+ 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.
*/
/**************************
- This is just temporary
+ 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.
*/
- the_ALT_ft = FGBFI::getAltitude();
+ 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 );
/**************************
- First, we need to know what the static line is reporting,
- which is a whole simulation area in itself. For now, we cheat.
+ 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.
*/
- the_STATIC_inhg = 29.92;
- i = (int) the_ALT_ft;
- while ( i > 18000 )
- { the_STATIC_inhg /= 2;
- i -= 18000;
+ 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;
}
- the_STATIC_inhg /= ( 1.0 + i / 18000.0 );
+
+ /**************************
+ 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 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 capability for a fixed non-zero reading when level.
NO capability to have a scaling error of maybe a factor of two.
*/
- set_lowpass ( & the_VSI_case, the_STATIC_inhg, dt/9.0 );
the_VSI_fps = ( the_VSI_case - the_STATIC_inhg )
- * 7000.0; /* manual scaling factor */
+ * 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
*/
- _UpdatesPending = 0;
+ _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