1 // MRG.cxx - an electrically powered master reference gyro.
2 // Written by Vivian Meazza based on work by David Megginson, started 2006.
4 // This file is in the Public Domain and comes with no warranty.
9 #include <simgear/compiler.h>
10 #include <simgear/sg_inlines.h>
16 #include <math.h> // fabs()
18 #include <Main/fg_props.hxx>
19 #include <Main/util.hxx>
23 const double MasterReferenceGyro::gravity = -32.1740485564;
25 MasterReferenceGyro::MasterReferenceGyro ( SGPropertyNode *node ) :
26 _name(node->getStringValue("name", "master-reference-gyro")),
27 _num(node->getIntValue("number", 0))
31 MasterReferenceGyro::~MasterReferenceGyro ()
36 MasterReferenceGyro::init ()
44 _indicated_hdg_rate = 0;
45 _indicated_roll_rate = 0;
46 _indicated_pitch_rate = 0;
52 branch = "/instrumentation/" + _name;
54 _pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
55 _roll_in_node = fgGetNode("/orientation/roll-deg", true);
56 _hdg_in_node = fgGetNode("/orientation/heading-deg", true);
57 _hdg_mag_in_node = fgGetNode("/orientation/heading-magnetic-deg", true);
58 _pitch_rate_node = fgGetNode("/orientation/pitch-rate-degps", true);
59 _roll_rate_node = fgGetNode("/orientation/roll-rate-degps", true);
60 _yaw_rate_node = fgGetNode("/orientation/yaw-rate-degps", true);
61 //_g_in_node = fgGetNode("/accelerations/pilot/z-accel-fps_sec", true);
62 _g_in_node = fgGetNode("/accelerations/pilot-g", true);
63 _electrical_node = fgGetNode("/systems/electrical/outputs/MRG", true);
64 _hdg_mag_in_node = fgGetNode("/orientation/heading-magnetic-deg", true);
66 SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
67 _off_node = node->getChild("off-flag", 0, true);
68 _pitch_out_node = node->getChild("indicated-pitch-deg", 0, true);
69 _roll_out_node = node->getChild("indicated-roll-deg", 0, true);
70 _hdg_out_node = node->getChild("indicated-hdg-deg", 0, true);
71 _hdg_mag_out_node = node->getChild("indicated-mag-hdg-deg", 0, true);
72 _pitch_rate_out_node = node->getChild("indicated-pitch-rate-degps", 0, true);
73 _roll_rate_out_node = node->getChild("indicated-roll-rate-degps", 0, true);
74 _hdg_rate_out_node = node->getChild("indicated-hdg-rate-degps", 0, true);
75 _responsiveness_node = node->getChild("responsiveness", 0, true);
76 _error_out_node = node->getChild("heading-bug-error-deg", 0, true);
77 _hdg_input_source_node = node->getChild("heading-source", 0, true);
78 _fast_erect_node = node->getChild("fast-erect", 0, true);
80 _electrical_node->setDoubleValue(0);
81 _responsiveness_node->setDoubleValue(0.75);
82 _off_node->setBoolValue(false);
83 _hdg_input_source_node->setBoolValue(false);
84 _fast_erect_node->setBoolValue(false);
85 _g_in_node->setDoubleValue(1);
89 MasterReferenceGyro::bind ()
91 std::ostringstream temp;
94 branch = "/instrumentation/" + _name + "[" + temp.str() + "]";
96 fgTie((branch + "/serviceable").c_str(),
97 &_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
98 fgTie((branch + "/spin").c_str(),
99 &_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
103 MasterReferenceGyro::unbind ()
105 std::ostringstream temp;
108 branch = "/instrumentation/" + _name + "[" + temp.str() + "]";
110 fgUntie((branch + "/serviceable").c_str());
111 fgUntie((branch + "/spin").c_str());
115 MasterReferenceGyro::update (double dt)
118 if (!fgGetBool("/sim/fdm-initialized", false)) {
122 double indicated_roll = 0;
123 double indicated_pitch = 0;
124 double indicated_hdg = 0;
125 double indicated_roll_rate = 0;
126 double indicated_pitch_rate = 0;
127 double indicated_hdg_rate = 0;
129 double erect_time_factor = 1;
131 const double erect_time = 180;
132 const double max_g_error = 10.0;
134 //Get the spin from the gyro
135 _gyro.set_power_norm( _electrical_node->getDoubleValue()/24 );
137 double spin = _gyro.get_spin_norm();
139 // set the "off-flag"
140 if ( _electrical_node->getDoubleValue() > 0 && spin >= 0.25) {
141 _off_node->setBoolValue(false);
143 _off_node->setBoolValue(true);
147 // Get the input values
148 if(_hdg_input_source_node->getBoolValue()){
149 hdg = _hdg_in_node->getDoubleValue();
151 hdg = _hdg_mag_in_node->getDoubleValue();
154 double roll = _roll_in_node->getDoubleValue();
155 double pitch = _pitch_in_node->getDoubleValue();
156 double g = _g_in_node->getDoubleValue()/* / gravity*/;
158 double roll_rate = _yaw_rate_node->getDoubleValue();
159 double pitch_rate = _pitch_rate_node->getDoubleValue();
160 double yaw_rate = _yaw_rate_node->getDoubleValue();
162 //modulate the input by the spin rate
163 double responsiveness = spin * spin * spin * spin * spin * spin;
164 roll = fgGetLowPass( _last_roll, roll, responsiveness );
165 pitch = fgGetLowPass( _last_pitch , pitch, responsiveness );
167 if ((hdg - _last_hdg) > 180)
169 if ((hdg - _last_hdg) < -180)
172 hdg = fgGetLowPass( _last_hdg , hdg, responsiveness );
174 //but we need to filter the hdg and yaw_rate as well - yuk!
175 responsiveness = 0.1 / (spin * spin * spin * spin * spin * spin);
176 yaw_rate = fgGetLowPass( _last_yaw_rate , yaw_rate, responsiveness );
177 g = fgGetLowPass( _last_g , g, 1.5);
180 // store the new values
184 _last_roll_rate = roll_rate;
185 _last_pitch_rate = pitch_rate;
186 _last_yaw_rate = yaw_rate;
189 //the gyro only erects inside limits
190 if ( fabs ( yaw_rate ) <= 5
191 && g <= 1.5 && g >= -0.5){
193 if ( !_fast_erect_node->getBoolValue() ){
194 erect_time_factor = 1;
196 erect_time_factor = 2;
199 _g_error -= (max_g_error/(erect_time * 0.33)) * dt * erect_time_factor;
201 _g_error += (max_g_error /(erect_time * 0.33)) * dt * 2;
203 //SG_LOG(SG_GENERAL, SG_ALERT,_num <<
204 // " g input " << _g_in_node->getDoubleValue() * gravity
205 // <<" _erect_time " << _erect_time
206 // << " yaw " << yaw_rate
207 // << " pitch " << _pitch_rate_node->getDoubleValue()
208 // << " roll " << _roll_rate_node->getDoubleValue());
212 //cout << "_g_error "<< _g_error << endl;
213 _g_error = SGMiscd::clip(_g_error, 0, 10);
214 // cout << "_g_error clip "<< _g_error << endl;
215 indicated_roll = _last_roll + _g_error;
216 indicated_pitch = _last_pitch + _g_error;
217 indicated_hdg = _last_hdg + _g_error;
218 indicated_roll_rate = _last_roll_rate;
219 indicated_pitch_rate = _last_pitch_rate;
220 indicated_hdg_rate = _last_yaw_rate;
221 // calculate the difference between the indicated heading
222 // and the selected heading for use with an autopilot
223 static SGPropertyNode *bnode
224 = fgGetNode( "/autopilot/settings/heading-bug-deg", false );
227 double diff = bnode->getDoubleValue() - indicated_hdg;
228 if ( diff < -180.0 ) { diff += 360.0; }
229 if ( diff > 180.0 ) { diff -= 360.0; }
230 _error_out_node->setDoubleValue( diff );
231 //SG_LOG(SG_GENERAL, SG_ALERT,
232 //"autopilot input " << bnode->getDoubleValue()
233 //<< " output " << _error_out_node->getDoubleValue()<<);
237 double factor = _responsiveness_node->getDoubleValue() * dt;
239 indicated_roll = fgGetLowPass( _indicated_roll, indicated_roll, factor );
240 indicated_pitch = fgGetLowPass( _indicated_pitch , indicated_pitch, factor );
241 //indicated_hdg = fgGetLowPass( _indicated_hdg , indicated_hdg, factor );
243 indicated_roll_rate = fgGetLowPass( _indicated_roll_rate, indicated_roll_rate, factor );
244 indicated_pitch_rate = fgGetLowPass( _indicated_pitch_rate , indicated_pitch_rate, factor );
245 indicated_hdg_rate = fgGetLowPass( _indicated_hdg_rate , indicated_hdg_rate, factor );
247 // store the new values
248 _indicated_roll = indicated_roll;
249 _indicated_pitch = indicated_pitch;
250 _indicated_hdg = indicated_hdg;
252 _indicated_roll_rate = indicated_roll_rate;
253 _indicated_pitch_rate = indicated_pitch_rate;
254 _indicated_hdg_rate = indicated_hdg_rate;
256 // add in a gyro underspin "error" if gyro is spinning too slowly
257 const double spin_thresh = 0.8;
258 const double max_roll_error = 40.0;
259 const double max_pitch_error = 12.0;
260 const double max_hdg_error = 140.0;
265 if ( spin <= spin_thresh ) {
266 double roll_error_factor = ( spin_thresh - spin ) / spin_thresh;
267 double pitch_error_factor = ( spin_thresh - spin ) / spin_thresh;
268 double hdg_error_factor = ( spin_thresh - spin ) / spin_thresh;
269 roll_error = roll_error_factor * roll_error_factor * max_roll_error;
270 pitch_error = pitch_error_factor * pitch_error_factor * max_pitch_error;
271 hdg_error = hdg_error_factor * hdg_error_factor * max_hdg_error;
278 _roll_out_node->setDoubleValue( _indicated_roll + roll_error );
279 _pitch_out_node->setDoubleValue( _indicated_pitch + pitch_error );
280 _hdg_out_node->setDoubleValue( _indicated_hdg + hdg_error );
281 _pitch_rate_out_node ->setDoubleValue( _indicated_pitch_rate );
282 _roll_rate_out_node ->setDoubleValue( _indicated_roll_rate );
283 _hdg_rate_out_node ->setDoubleValue( _indicated_hdg_rate );