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     _pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
  30     _roll_in_node = fgGetNode("/orientation/roll-deg", true);
  31     _suction_node = fgGetNode("/systems/vacuum[0]/suction-inhg", true);
  32     _pitch_out_node =
  33         fgGetNode("/instrumentation/attitude-indicator/indicated-pitch-deg",
  34                   true);
  35     _roll_out_node =
  36         fgGetNode("/instrumentation/attitude-indicator/indicated-roll-deg",
  37                   true);
  38 }
  39
  40 void
  41 AttitudeIndicator::bind ()
  42 {
  43 }
  44
  45 void
  46 AttitudeIndicator::unbind ()
  47 {
  48 }
  49
  50 void
  51 AttitudeIndicator::update (double dt)
  52 {
  53                                 // First, calculate the bogo-spin from 0 to 1.
  54                                 // All numbers are made up.
  55
  56     _spin -= 0.005 * dt;         // spin decays every 0.5% every second.
  57
  58                                 // spin increases up to 25% every second
  59                                 // if suction is available and the gauge
  60                                 // is serviceable.
  61     if (_serviceable_node->getBoolValue()) {
  62         double suction = _suction_node->getDoubleValue();
  63         double step = 0.25 * (suction / 5.0) * dt;
  64         if ((_spin + step) <= (suction / 5.0))
  65             _spin += step;
  66     }
  67     if (_spin > 1.0)
  68         _spin = 1.0;
  69     else if (_spin < 0.0)
  70         _spin = 0.0;
  71
  72                                 // Next, calculate the indicated roll
  73                                 // and pitch, introducing errors.
  74     double factor = 1.0 - ((1.0 - _spin) * (1.0 - _spin));
  75     double roll = _roll_in_node->getDoubleValue();
  76     double pitch = _pitch_in_node->getDoubleValue();
  77     roll = 35 + (factor * (roll - 35));
  78     pitch = 15 + (factor * (pitch - 15));
  79
  80     _roll_out_node->setDoubleValue(roll);
  81     _pitch_out_node->setDoubleValue(pitch);
  82 }
  83
  84 // end of attitude_indicator.cxx