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;
27 MasterReferenceGyro::MasterReferenceGyro ( SGPropertyNode *node ) :
28 _name(node->getStringValue("name", "master-reference-gyro")),
29 _num(node->getIntValue("number", 0))
33 MasterReferenceGyro::~MasterReferenceGyro ()
38 MasterReferenceGyro::init ()
46 _indicated_hdg_rate = 0;
47 _indicated_roll_rate = 0;
48 _indicated_pitch_rate = 0;
54 branch = "/instrumentation/" + _name;
56 _pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
57 _roll_in_node = fgGetNode("/orientation/roll-deg", true);
58 _hdg_in_node = fgGetNode("/orientation/heading-deg", true);
59 _hdg_mag_in_node = fgGetNode("/orientation/heading-magnetic-deg", true);
60 _pitch_rate_node = fgGetNode("/orientation/pitch-rate-degps", true);
61 _roll_rate_node = fgGetNode("/orientation/roll-rate-degps", true);
62 _yaw_rate_node = fgGetNode("/orientation/yaw-rate-degps", true);
63 //_g_in_node = fgGetNode("/accelerations/pilot/z-accel-fps_sec", true);
64 _g_in_node = fgGetNode("/accelerations/pilot-g", true);
65 _electrical_node = fgGetNode("/systems/electrical/outputs/MRG", true);
66 _hdg_mag_in_node = fgGetNode("/orientation/heading-magnetic-deg", true);
68 SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
69 _off_node = node->getChild("off-flag", 0, true);
70 _pitch_out_node = node->getChild("indicated-pitch-deg", 0, true);
71 _roll_out_node = node->getChild("indicated-roll-deg", 0, true);
72 _hdg_out_node = node->getChild("indicated-hdg-deg", 0, true);
73 _hdg_mag_out_node = node->getChild("indicated-mag-hdg-deg", 0, true);
74 _pitch_rate_out_node = node->getChild("indicated-pitch-rate-degps", 0, true);
75 _roll_rate_out_node = node->getChild("indicated-roll-rate-degps", 0, true);
76 _hdg_rate_out_node = node->getChild("indicated-hdg-rate-degps", 0, true);
77 _responsiveness_node = node->getChild("responsiveness", 0, true);
78 _error_out_node = node->getChild("heading-bug-error-deg", 0, true);
79 _hdg_input_source_node = node->getChild("heading-source", 0, true);
80 _fast_erect_node = node->getChild("fast-erect", 0, true);
82 _electrical_node->setDoubleValue(0);
83 _responsiveness_node->setDoubleValue(0.75);
84 _off_node->setBoolValue(false);
85 _hdg_input_source_node->setBoolValue(false);
86 _fast_erect_node->setBoolValue(false);
87 _g_in_node->setDoubleValue(1);
91 MasterReferenceGyro::bind ()
93 std::ostringstream temp;
96 branch = "/instrumentation/" + _name + "[" + temp.str() + "]";
98 fgTie((branch + "/serviceable").c_str(),
99 &_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
100 fgTie((branch + "/spin").c_str(),
101 &_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
105 MasterReferenceGyro::unbind ()
107 std::ostringstream temp;
110 branch = "/instrumentation/" + _name + "[" + temp.str() + "]";
112 fgUntie((branch + "/serviceable").c_str());
113 fgUntie((branch + "/spin").c_str());
117 MasterReferenceGyro::update (double dt)
120 if (!fgGetBool("/sim/fdm-initialized", false)) {
124 double indicated_roll = 0;
125 double indicated_pitch = 0;
126 double indicated_hdg = 0;
127 double indicated_roll_rate = 0;
128 double indicated_pitch_rate = 0;
129 double indicated_hdg_rate = 0;
131 double erect_time_factor = 1;
133 const double erect_time = 180;
134 const double max_g_error = 10.0;
136 //Get the spin from the gyro
137 _gyro.set_power_norm( _electrical_node->getDoubleValue()/24 );
139 double spin = _gyro.get_spin_norm();
141 // set the "off-flag"
142 if ( _electrical_node->getDoubleValue() > 0 && spin >= 0.25) {
143 _off_node->setBoolValue(false);
145 _off_node->setBoolValue(true);
149 // Get the input values
150 if(_hdg_input_source_node->getBoolValue()){
151 hdg = _hdg_in_node->getDoubleValue();
153 hdg = _hdg_mag_in_node->getDoubleValue();
156 double roll = _roll_in_node->getDoubleValue();
157 double pitch = _pitch_in_node->getDoubleValue();
158 double g = _g_in_node->getDoubleValue()/* / gravity*/;
160 double roll_rate = _yaw_rate_node->getDoubleValue();
161 double pitch_rate = _pitch_rate_node->getDoubleValue();
162 double yaw_rate = _yaw_rate_node->getDoubleValue();
164 //modulate the input by the spin rate
165 double responsiveness = spin * spin * spin * spin * spin * spin;
166 roll = fgGetLowPass( _last_roll, roll, responsiveness );
167 pitch = fgGetLowPass( _last_pitch , pitch, responsiveness );
169 if ((hdg - _last_hdg) > 180)
171 if ((hdg - _last_hdg) < -180)
174 hdg = fgGetLowPass( _last_hdg , hdg, responsiveness );
176 //but we need to filter the hdg and yaw_rate as well - yuk!
177 responsiveness = 0.1 / (spin * spin * spin * spin * spin * spin);
178 yaw_rate = fgGetLowPass( _last_yaw_rate , yaw_rate, responsiveness );
179 g = fgGetLowPass( _last_g , g, 1.5);
182 // store the new values
186 _last_roll_rate = roll_rate;
187 _last_pitch_rate = pitch_rate;
188 _last_yaw_rate = yaw_rate;
191 //the gyro only erects inside limits
192 if ( fabs ( yaw_rate ) <= 5
193 && g <= 1.5 && g >= -0.5){
195 if ( !_fast_erect_node->getBoolValue() ){
196 erect_time_factor = 1;
198 erect_time_factor = 2;
201 _g_error -= (max_g_error/(erect_time * 0.33)) * dt * erect_time_factor;
203 _g_error += (max_g_error /(erect_time * 0.33)) * dt * 2;
205 //SG_LOG(SG_INSTR, SG_ALERT,_num <<
206 // " g input " << _g_in_node->getDoubleValue() * gravity
207 // <<" _erect_time " << _erect_time
208 // << " yaw " << yaw_rate
209 // << " pitch " << _pitch_rate_node->getDoubleValue()
210 // << " roll " << _roll_rate_node->getDoubleValue());
214 //cout << "_g_error "<< _g_error << endl;
215 _g_error = SGMiscd::clip(_g_error, 0, 10);
216 // cout << "_g_error clip "<< _g_error << endl;
217 indicated_roll = _last_roll + _g_error;
218 indicated_pitch = _last_pitch + _g_error;
219 indicated_hdg = _last_hdg + _g_error;
220 indicated_roll_rate = _last_roll_rate;
221 indicated_pitch_rate = _last_pitch_rate;
222 indicated_hdg_rate = _last_yaw_rate;
223 // calculate the difference between the indicated heading
224 // and the selected heading for use with an autopilot
225 static SGPropertyNode *bnode
226 = fgGetNode( "/autopilot/settings/heading-bug-deg", false );
229 double diff = bnode->getDoubleValue() - indicated_hdg;
230 if ( diff < -180.0 ) { diff += 360.0; }
231 if ( diff > 180.0 ) { diff -= 360.0; }
232 _error_out_node->setDoubleValue( diff );
233 //SG_LOG(SG_INSTR, SG_ALERT,
234 //"autopilot input " << bnode->getDoubleValue()
235 //<< " output " << _error_out_node->getDoubleValue()<<);
239 double factor = _responsiveness_node->getDoubleValue() * dt;
241 indicated_roll = fgGetLowPass( _indicated_roll, indicated_roll, factor );
242 indicated_pitch = fgGetLowPass( _indicated_pitch , indicated_pitch, factor );
243 //indicated_hdg = fgGetLowPass( _indicated_hdg , indicated_hdg, factor );
245 indicated_roll_rate = fgGetLowPass( _indicated_roll_rate, indicated_roll_rate, factor );
246 indicated_pitch_rate = fgGetLowPass( _indicated_pitch_rate , indicated_pitch_rate, factor );
247 indicated_hdg_rate = fgGetLowPass( _indicated_hdg_rate , indicated_hdg_rate, factor );
249 // store the new values
250 _indicated_roll = indicated_roll;
251 _indicated_pitch = indicated_pitch;
252 _indicated_hdg = indicated_hdg;
254 _indicated_roll_rate = indicated_roll_rate;
255 _indicated_pitch_rate = indicated_pitch_rate;
256 _indicated_hdg_rate = indicated_hdg_rate;
258 // add in a gyro underspin "error" if gyro is spinning too slowly
259 const double spin_thresh = 0.8;
260 const double max_roll_error = 40.0;
261 const double max_pitch_error = 12.0;
262 const double max_hdg_error = 140.0;
267 if ( spin <= spin_thresh ) {
268 double roll_error_factor = ( spin_thresh - spin ) / spin_thresh;
269 double pitch_error_factor = ( spin_thresh - spin ) / spin_thresh;
270 double hdg_error_factor = ( spin_thresh - spin ) / spin_thresh;
271 roll_error = roll_error_factor * roll_error_factor * max_roll_error;
272 pitch_error = pitch_error_factor * pitch_error_factor * max_pitch_error;
273 hdg_error = hdg_error_factor * hdg_error_factor * max_hdg_error;
280 _roll_out_node->setDoubleValue( _indicated_roll + roll_error );
281 _pitch_out_node->setDoubleValue( _indicated_pitch + pitch_error );
282 _hdg_out_node->setDoubleValue( _indicated_hdg + hdg_error );
283 _pitch_rate_out_node ->setDoubleValue( _indicated_pitch_rate );
284 _roll_rate_out_node ->setDoubleValue( _indicated_roll_rate );
285 _hdg_rate_out_node ->setDoubleValue( _indicated_hdg_rate );