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Updates to vacuum system model from Alex Perry.

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This commit is contained in:
curt 2000-03-22 21:59:59 +00:00
parent ae3a6fdff4
commit 863423054e
2 changed files with 58 additions and 15 deletions
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67
src/Cockpit/steam.cxx
View file

@ -57,6 +57,9 @@ double FGSteam::the_VSI_case = 29.92;
double FGSteam::the_VSI_fps = 0.0;
double FGSteam::get_VSI_fps() { _CatchUp(); return the_VSI_fps; }
double FGSteam::the_VACUUM_inhg = 0.0;
double FGSteam::get_VACUUM_inhg() { _CatchUp(); return the_VACUUM_inhg; }
double FGSteam::get_MH_deg () { return FGBFI::getHeading (); }
double FGSteam::get_DG_deg () { return FGBFI::getHeading (); }
@ -94,14 +97,15 @@ void FGSteam::set_lowpass ( double *outthe, double inthe, double 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 );
}
}
@ -116,16 +120,26 @@ void FGSteam::_CatchUp()
{ if ( _UpdatesPending != 0 )
{ double dt = _UpdatesPending * 1.0 / current_options.get_model_hz();
int i,j;
double d;
double d, the_ENGINE_rpm;
/*
Someone has called our update function and we haven't
incorporated this into our instrument modelling yet
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
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_ALT_ft = FGBFI::getAltitude();
the_ENGINE_rpm = FGBFI::getThrottle() * 26.0;
/**************************
This is just temporary, until the static source works,
so we just filter the actual value by one second to
account for the line impedance of the plumbing.
*/
set_lowpass ( & the_ALT_ft, FGBFI::getAltitude(), dt );
/**************************
First, we need to know what the static line is reporting,
@ -133,11 +147,11 @@ void FGSteam::_CatchUp()
*/
the_STATIC_inhg = 29.92;
i = (int) the_ALT_ft;
while ( i > 18000 )
{ the_STATIC_inhg /= 2;
i -= 18000;
while ( i > 9000 )
{ the_STATIC_inhg *= 0.707;
i -= 9000;
}
the_STATIC_inhg /= ( 1.0 + i / 18000.0 );
the_STATIC_inhg *= ( 1.0 - 0.293 * i / 9000.0 );
/*
NO alternate static source error (student feature),
@ -152,9 +166,34 @@ void FGSteam::_CatchUp()
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 */
set_lowpass ( & the_VSI_case, the_STATIC_inhg, dt/9.0 );
/**************************
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.
*/
/**************************
Finished updates, now clear the timer

6
src/Cockpit/steam.hxx
View file

@ -67,8 +67,12 @@ public:
static double get_TC_radps ();
static double get_VSI_fps ();
// Engine Gauges
static double get_VACUUM_inhg ();
private:
static double the_ALT_ft, the_STATIC_inhg;
static double the_ALT_ft;
static double the_STATIC_inhg, the_VACUUM_inhg;
static double the_VSI_fps, the_VSI_case;
static int _UpdatesPending;