src/Instrumentation/attitude_indicator.cxx

   1 // attitude_indicator.cxx - a vacuum-powered attitude indicator.
   2 // Written by David Megginson, started 2002.
   3 //
   4 // This file is in the Public Domain and comes with no warranty.
   5
   6 // TODO:
   7 // - tumble
   8 // - better spin-up
   9
  10 #include "attitude_indicator.hxx"
  11 #include <Main/fg_props.hxx>
  12
  13
  14 AttitudeIndicator::AttitudeIndicator ()
  15 {
  16 }
  17
  18 AttitudeIndicator::~AttitudeIndicator ()
  19 {
  20 }
  21
  22 void
  23 AttitudeIndicator::init ()
  24 {
  25                                 // TODO: allow index of pump and AI
  26                                 // to be configured.
  27     _serviceable_node =
  28         fgGetNode("/instrumentation/attitude-indicator/serviceable", true);
  29     _spin_node = fgGetNode("/instrumentation/attitude-indicator/spin", true);
  30     _pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
  31     _roll_in_node = fgGetNode("/orientation/roll-deg", true);
  32     _suction_node = fgGetNode("/systems/vacuum[0]/suction-inhg", true);
  33     _pitch_out_node =
  34         fgGetNode("/instrumentation/attitude-indicator/indicated-pitch-deg",
  35                   true);
  36     _roll_out_node =
  37         fgGetNode("/instrumentation/attitude-indicator/indicated-roll-deg",
  38                   true);
  39 }
  40
  41 void
  42 AttitudeIndicator::bind ()
  43 {
  44 }
  45
  46 void
  47 AttitudeIndicator::unbind ()
  48 {
  49 }
  50
  51 void
  52 AttitudeIndicator::update (double dt)
  53 {
  54                                 // First, calculate the bogo-spin from 0 to 1.
  55                                 // All numbers are made up.
  56
  57     double spin = _spin_node->getDoubleValue();
  58     spin -= 0.005 * dt;         // spin decays every 0.5% every second.
  59
  60                                 // spin increases up to 25% every second
  61                                 // if suction is available and the gauge
  62                                 // is serviceable.
  63     if (_serviceable_node->getBoolValue()) {
  64         double suction = _suction_node->getDoubleValue();
  65         double step = 0.25 * (suction / 5.0) * dt;
  66         if ((spin + step) <= (suction / 5.0))
  67             spin += step;
  68     }
  69     if (spin > 1.0)
  70         spin = 1.0;
  71     else if (spin < 0.0)
  72         spin = 0.0;
  73     _spin_node->setDoubleValue(spin);
  74
  75                                 // Next, calculate the indicated roll
  76                                 // and pitch, introducing errors.
  77     double factor = 1.0 - ((1.0 - spin) * (1.0 - spin) * (1.0 - spin));
  78     double roll = _roll_in_node->getDoubleValue();
  79     double pitch = _pitch_in_node->getDoubleValue();
  80     roll = 35 + (factor * (roll - 35));
  81     pitch = 15 + (factor * (pitch - 15));
  82
  83     _roll_out_node->setDoubleValue(roll);
  84     _pitch_out_node->setDoubleValue(pitch);
  85 }
  86
  87 // end of attitude_indicator.cxx