Updates to vacuum system model from Alex Perry.

diff --git a/src/Cockpit/steam.cxx b/src/Cockpit/steam.cxx
index 0d8ca2547bc70b574933cff4607815ac716a81d2..860e8e90015d4a862533afc389897207fbed62cd 100644 (file)
--- a/src/Cockpit/steam.cxx
+++ b/src/Cockpit/steam.cxx
@@ -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 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 = FGBFI::getThrottle() * 26.0;
 
        /**************************
-       This is just temporary
+       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.
        */
-       the_ALT_ft = FGBFI::getAltitude();
+       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 

diff --git a/src/Cockpit/steam.hxx b/src/Cockpit/steam.hxx
index adc2228758fc70eccfaf6b9026e000c62849ef12..2254dc7fc4f2222c6b25377c2eb7c788dd664413 100644 (file)
--- a/src/Cockpit/steam.hxx
+++ b/src/Cockpit/steam.hxx
@@ -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;