src/Instrumentation/mrg.cxx

   1 // MRG.cxx - an electrically powered master reference gyro.
   2 // Written by Vivian Meazza based on work by David Megginson, started 2006.
   3 //
   4 // This file is in the Public Domain and comes with no warranty.
   5
   6 // TODO:
   7 // - better spin-up
   8
   9 #include <simgear/compiler.h>
  10 #include <simgear/sg_inlines.h>
  11
  12
  13 #include <iostream>
  14 #include <string>
  15 #include <sstream>
  16 #include <math.h>       // fabs()
  17
  18 #include <Main/fg_props.hxx>
  19 #include <Main/util.hxx>
  20
  21 #include "mrg.hxx"
  22
  23
  24 MasterReferenceGyro::MasterReferenceGyro ( SGPropertyNode *node ) :
  25         _name(node->getStringValue("name", "master-reference-gyro")),
  26         _num(node->getIntValue("number", 0))
  27 {
  28 }
  29
  30 MasterReferenceGyro::~MasterReferenceGyro ()
  31 {
  32 }
  33
  34 void
  35 MasterReferenceGyro::init ()
  36 {
  37         _last_hdg = 0;
  38         _last_roll = 0;
  39         _last_pitch = 0;
  40         _indicated_hdg = 0;
  41         _indicated_roll = 0;
  42         _indicated_pitch = 0;
  43         _indicated_hdg_rate = 0;
  44         _indicated_roll_rate = 0;
  45         _indicated_pitch_rate = 0;
  46
  47         string branch;
  48         branch = "/instrumentation/" + _name;
  49
  50         _pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
  51         _roll_in_node = fgGetNode("/orientation/roll-deg", true);
  52         _hdg_in_node = fgGetNode("/orientation/heading-deg", true);
  53         _hdg_mag_in_node = fgGetNode("/orientation/heading-magnetic-deg", true);
  54         _pitch_rate_node = fgGetNode("/orientation/pitch-rate-degps", true);
  55         _roll_rate_node = fgGetNode("/orientation/roll-rate-degps", true);
  56         _yaw_rate_node = fgGetNode("/orientation/yaw-rate-degps", true);
  57         _g_in_node =   fgGetNode("/accelerations/pilot-g", true);
  58         _electrical_node = fgGetNode("/systems/electrical/outputs/MRG", true);
  59         _hdg_mag_in_node = fgGetNode("/orientation/heading-magnetic-deg", true);
  60
  61         SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
  62         _off_node = node->getChild("off-flag", 0, true);
  63         _pitch_out_node = node->getChild("indicated-pitch-deg", 0, true);
  64         _roll_out_node = node->getChild("indicated-roll-deg", 0, true);
  65         _hdg_out_node = node->getChild("indicated-hdg-deg", 0, true);
  66         _hdg_mag_out_node = node->getChild("indicated-mag-hdg-deg", 0, true);
  67         _pitch_rate_out_node = node->getChild("indicated-pitch-rate-degps", 0, true);
  68         _roll_rate_out_node = node->getChild("indicated-roll-rate-degps", 0, true);
  69         _hdg_rate_out_node = node->getChild("indicated-hdg-rate-degps", 0, true);
  70         _responsiveness_node = node->getChild("responsiveness", 0, true);
  71         _error_out_node = node->getChild("heading-bug-error-deg", 0, true);
  72         _hdg_input_source_node = node->getChild("heading-source", 0, true);
  73
  74         _electrical_node->setDoubleValue(0);
  75         _responsiveness_node->setDoubleValue(0.75);
  76         _off_node->setBoolValue(false);
  77         _hdg_input_source_node->setBoolValue(false);
  78 }
  79
  80 void
  81 MasterReferenceGyro::bind ()
  82 {
  83         std::ostringstream temp;
  84         string branch;
  85         temp << _num;
  86         branch = "/instrumentation/" + _name + "[" + temp.str() + "]";
  87
  88         fgTie((branch + "/serviceable").c_str(),
  89                 &_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
  90         fgTie((branch + "/spin").c_str(),
  91                 &_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
  92 }
  93
  94 void
  95 MasterReferenceGyro::unbind ()
  96 {
  97         std::ostringstream temp;
  98         string branch;
  99         temp << _num;
 100         branch = "/instrumentation/" + _name + "[" + temp.str() + "]";
 101
 102         fgUntie((branch + "/serviceable").c_str());
 103         fgUntie((branch + "/spin").c_str());
 104 }
 105
 106 void
 107 MasterReferenceGyro::update (double dt)
 108 {
 109         double indicated_roll = 0;
 110         double indicated_pitch = 0;
 111         double indicated_hdg = 0;
 112         double indicated_roll_rate = 0;
 113         double indicated_pitch_rate = 0;
 114         double indicated_hdg_rate = 0;
 115
 116         // Get the spin from the gyro
 117         _gyro.set_power_norm( _electrical_node->getDoubleValue()/24 );
 118         _gyro.update(dt);
 119         double spin = _gyro.get_spin_norm();
 120
 121         // set the "off-flag"
 122         if ( _electrical_node->getDoubleValue() == 0 ) {
 123                 _off_node->setBoolValue(true);
 124         } else if ( spin == 1 ) {
 125                 _off_node->setBoolValue(false);
 126         } else {
 127                 _off_node->setBoolValue(true);
 128         }
 129
 130         // Get the input values
 131         double hdg = _hdg_mag_in_node->getDoubleValue();
 132
 133         if(_hdg_input_source_node->getBoolValue())
 134                 hdg = _hdg_in_node->getDoubleValue();
 135
 136         double roll = _roll_in_node->getDoubleValue();
 137         double pitch = _pitch_in_node->getDoubleValue();
 138
 139         double roll_rate = _yaw_rate_node->getDoubleValue();
 140         double pitch_rate = _yaw_rate_node->getDoubleValue();
 141         double yaw_rate = _yaw_rate_node->getDoubleValue();
 142         double g = _g_in_node->getDoubleValue();
 143
 144         //modulate the input by the spin rate
 145         double responsiveness = spin * spin * spin * spin * spin * spin;
 146         roll = fgGetLowPass( _last_roll, roll, responsiveness );
 147         pitch = fgGetLowPass( _last_pitch , pitch, responsiveness );
 148
 149         if ((hdg - _last_hdg) > 180)
 150                 _last_hdg += 360;
 151         if ((hdg - _last_hdg) < -180)
 152                 _last_hdg -= 360;
 153
 154         hdg = fgGetLowPass( _last_hdg , hdg, responsiveness );
 155
 156         //but we need to filter the hdg and yaw_rate as well - yuk!
 157         responsiveness = 0.1 / (spin * spin * spin * spin * spin * spin);
 158         yaw_rate = fgGetLowPass( _last_yaw_rate , yaw_rate, responsiveness );
 159         g = fgGetLowPass( _last_g , yaw_rate, 0.15 );
 160
 161         // store the new values
 162         _last_roll = roll;
 163         _last_pitch = pitch;
 164         _last_hdg = hdg;
 165         _last_roll_rate = roll_rate;
 166         _last_pitch_rate = pitch_rate;
 167         _last_yaw_rate = yaw_rate;
 168         _last_g = g;
 169
 170         //the gyro only erects inside limits
 171         if ( fabs ( yaw_rate ) <= 5
 172                         && (_g_in_node->getDoubleValue() <= 1.5
 173                         || _g_in_node->getDoubleValue() >= -0.5) ) {
 174                 indicated_roll = _last_roll;
 175                 indicated_pitch = _last_pitch;
 176                 indicated_hdg = _last_hdg;
 177                 indicated_roll_rate = _last_roll_rate;
 178                 indicated_pitch_rate = _last_pitch_rate;
 179                 indicated_hdg_rate = _last_yaw_rate;
 180         } else {
 181                 indicated_roll_rate = 0;
 182                 indicated_pitch_rate = 0;
 183                 indicated_hdg_rate = 0;
 184         }
 185
 186         // calculate the difference between the indicated heading
 187         // and the selected heading for use with an autopilot
 188         static SGPropertyNode *bnode
 189                 = fgGetNode( "/autopilot/settings/heading-bug-deg", false );
 190
 191         if ( bnode ) {
 192                 double diff = bnode->getDoubleValue() - indicated_hdg;
 193                 if ( diff < -180.0 ) { diff += 360.0; }
 194                 if ( diff > 180.0 ) { diff -= 360.0; }
 195                 _error_out_node->setDoubleValue( diff );
 196                 //SG_LOG(SG_GENERAL, SG_ALERT,
 197                 //"autopilot input " << bnode->getDoubleValue()
 198                 //<< " output " << _error_out_node->getDoubleValue()<<);
 199         }
 200
 201         //smooth the output
 202         double factor = _responsiveness_node->getDoubleValue() * dt;
 203
 204         indicated_roll = fgGetLowPass( _indicated_roll, indicated_roll, factor );
 205         indicated_pitch = fgGetLowPass( _indicated_pitch , indicated_pitch, factor );
 206         //indicated_hdg = fgGetLowPass( _indicated_hdg , indicated_hdg, factor );
 207
 208         indicated_roll_rate = fgGetLowPass( _indicated_roll_rate, indicated_roll_rate, factor );
 209         indicated_pitch_rate = fgGetLowPass( _indicated_pitch_rate , indicated_pitch_rate, factor );
 210         indicated_hdg_rate = fgGetLowPass( _indicated_hdg_rate , indicated_hdg_rate, factor );
 211
 212         // store the new values
 213         _indicated_roll = indicated_roll;
 214         _indicated_pitch = indicated_pitch;
 215         _indicated_hdg = indicated_hdg;
 216
 217         _indicated_roll_rate = indicated_roll_rate;
 218         _indicated_pitch_rate = indicated_pitch_rate;
 219         _indicated_hdg_rate = indicated_hdg_rate;
 220
 221         // add in a gyro underspin "error" if gyro is spinning too slowly
 222         const double spin_thresh = 0.8;
 223         const double max_roll_error = 40.0;
 224         const double max_pitch_error = 12.0;
 225         const double max_hdg_error = 140.0;
 226         double roll_error;
 227         double pitch_error;
 228         double hdg_error;
 229
 230         if ( spin <= spin_thresh ) {
 231                 double roll_error_factor        = ( spin_thresh - spin ) / spin_thresh;
 232                 double pitch_error_factor       = ( spin_thresh - spin ) / spin_thresh;
 233                 double hdg_error_factor         = ( spin_thresh - spin ) / spin_thresh;
 234                 roll_error      = roll_error_factor * roll_error_factor * max_roll_error;
 235                 pitch_error = pitch_error_factor * pitch_error_factor * max_pitch_error;
 236                 hdg_error       = hdg_error_factor * hdg_error_factor * max_hdg_error;
 237         } else {
 238                 roll_error = 0.0;
 239                 pitch_error = 0.0;
 240                 hdg_error = 0.0;
 241         }
 242
 243         _roll_out_node->setDoubleValue( _indicated_roll + roll_error );
 244         _pitch_out_node->setDoubleValue( _indicated_pitch + pitch_error );
 245         _hdg_out_node->setDoubleValue( _indicated_hdg + hdg_error );
 246         _pitch_rate_out_node ->setDoubleValue( _indicated_pitch_rate );
 247         _roll_rate_out_node ->setDoubleValue( _indicated_roll_rate );
 248         _hdg_rate_out_node ->setDoubleValue( _indicated_hdg_rate );
 249 }
 250
 251 // end of mrg.cxx