1 // attitude_indicator.cxx - a vacuum-powered attitude indicator.
2 // Written by David Megginson, started 2002.
4 // This file is in the Public Domain and comes with no warranty.
9 #include <math.h> // fabs()
11 #include "attitude_indicator.hxx"
12 #include <Main/fg_props.hxx>
13 #include <Main/util.hxx>
16 AttitudeIndicator::AttitudeIndicator ( SGPropertyNode *node )
18 name("attitude-indicator"),
20 vacuum_system("/systems/vacuum")
23 for ( i = 0; i < node->nChildren(); ++i ) {
24 SGPropertyNode *child = node->getChild(i);
25 string cname = child->getName();
26 string cval = child->getStringValue();
27 if ( cname == "name" ) {
29 } else if ( cname == "number" ) {
30 num = (int) child->getDoubleValue();
31 } else if ( cname == "vacuum-system" ) {
34 SG_LOG( SG_INSTR, SG_WARN, "Error in attitude-indicator config logic" );
35 if ( name.length() ) {
36 SG_LOG( SG_INSTR, SG_WARN, "Section = " << name );
42 AttitudeIndicator::AttitudeIndicator ()
46 AttitudeIndicator::~AttitudeIndicator ()
51 AttitudeIndicator::init ()
54 branch = "/instrumentation/" + name;
55 vacuum_system += "/suction-inhg";
57 SGPropertyNode *node = fgGetNode(branch.c_str(), num, true );
59 _pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
60 _roll_in_node = fgGetNode("/orientation/roll-deg", true);
61 _suction_node = fgGetNode(vacuum_system.c_str(), true);
62 SGPropertyNode *cnode = node->getChild("config", 0, true);
63 _tumble_flag_node = cnode->getChild("tumble-flag", 0, true);
64 _caged_node = node->getChild("caged-flag", 0, true);
65 _tumble_node = node->getChild("tumble-norm", 0, true);
66 _pitch_int_node = node->getChild("internal-pitch-deg", 0, true);
67 _roll_int_node = node->getChild("internal-roll-deg", 0, true);
68 _pitch_out_node = node->getChild("indicated-pitch-deg", 0, true);
69 _roll_out_node = node->getChild("indicated-roll-deg", 0, true);
73 AttitudeIndicator::bind ()
76 branch = "/instrumentation/" + name + "/serviceable";
79 &_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
80 branch = "/instrumentation/" + name + "/spin";
82 &_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
86 AttitudeIndicator::unbind ()
89 branch = "/instrumentation/" + name + "/serviceable";
91 fgUntie(branch.c_str());
92 branch = "/instrumentation/" + name + "/spin";
93 fgUntie(branch.c_str());
97 AttitudeIndicator::update (double dt)
99 // If it's caged, it doesn't indicate
100 if (_caged_node->getBoolValue()) {
101 _roll_int_node->setDoubleValue(0.0);
102 _pitch_int_node->setDoubleValue(0.0);
106 // Get the spin from the gyro
107 _gyro.set_power_norm(_suction_node->getDoubleValue()/5.0);
109 double spin = _gyro.get_spin_norm();
111 // Calculate the responsiveness
112 double responsiveness = spin * spin * spin * spin * spin * spin;
114 // Get the indicated roll and pitch
115 double roll = _roll_in_node->getDoubleValue();
116 double pitch = _pitch_in_node->getDoubleValue();
118 // Calculate the tumble for the
120 if (_tumble_flag_node->getBoolValue()) {
121 double tumble = _tumble_node->getDoubleValue();
122 if (fabs(roll) > 45.0) {
123 double target = (fabs(roll) - 45.0) / 45.0;
124 target *= target; // exponential past +-45 degrees
128 if (fabs(target) > fabs(tumble))
133 else if (tumble < -1.0)
136 // Reerect in 5 minutes
137 double step = dt/300.0;
140 else if (tumble > step)
144 _tumble_node->setDoubleValue(tumble);
147 roll = fgGetLowPass(_roll_int_node->getDoubleValue(), roll,
149 pitch = fgGetLowPass(_pitch_int_node->getDoubleValue(), pitch,
152 // Assign the new values
153 _roll_int_node->setDoubleValue(roll);
154 _pitch_int_node->setDoubleValue(pitch);
156 // add in a gyro underspin "error" if gyro is spinning too slowly
157 const double spin_thresh = 0.8;
158 const double max_roll_error = 40.0;
159 const double max_pitch_error = 12.0;
162 if ( spin <= spin_thresh ) {
163 double roll_error_factor = (spin_thresh - spin) / spin_thresh;
164 double pitch_error_factor = (spin_thresh - spin) / spin_thresh;
165 roll_error = roll_error_factor * roll_error_factor * max_roll_error;
166 pitch_error = pitch_error_factor * pitch_error_factor * max_pitch_error;
172 _roll_out_node->setDoubleValue(roll + roll_error);
173 _pitch_out_node->setDoubleValue(pitch + pitch_error);
176 // end of attitude_indicator.cxx