149 lines
4.8 KiB
C++
149 lines
4.8 KiB
C++
// attitude_indicator.cxx - a vacuum-powered attitude indicator.
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// Written by David Megginson, started 2002.
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//
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// This file is in the Public Domain and comes with no warranty.
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// TODO:
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// - better spin-up
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#include <math.h> // fabs()
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#include "attitude_indicator.hxx"
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#include <Main/fg_props.hxx>
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#include <Main/util.hxx>
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AttitudeIndicator::AttitudeIndicator ()
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{
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}
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AttitudeIndicator::~AttitudeIndicator ()
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{
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}
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void
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AttitudeIndicator::init ()
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{
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// TODO: allow index of pump and AI
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// to be configured.
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_pitch_in_node = fgGetNode("/orientation/pitch-deg", true);
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_roll_in_node = fgGetNode("/orientation/roll-deg", true);
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_suction_node = fgGetNode("/systems/vacuum[0]/suction-inhg", true);
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_tumble_flag_node =
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fgGetNode("/instrumentation/attitude-indicator/config/tumble-flag",
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true);
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_caged_node =
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fgGetNode("/instrumentation/attitude-indicator/caged-flag", true);
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_tumble_node =
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fgGetNode("/instrumentation/attitude-indicator/tumble-norm", true);
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_pitch_int_node =
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fgGetNode("/instrumentation/attitude-indicator/internal-pitch-deg",
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true);
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_roll_int_node =
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fgGetNode("/instrumentation/attitude-indicator/internal-roll-deg",
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true);
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_pitch_out_node =
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fgGetNode("/instrumentation/attitude-indicator/indicated-pitch-deg",
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true);
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_roll_out_node =
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fgGetNode("/instrumentation/attitude-indicator/indicated-roll-deg",
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true);
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}
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void
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AttitudeIndicator::bind ()
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{
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fgTie("/instrumentation/attitude-indicator/serviceable",
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&_gyro, &Gyro::is_serviceable, &Gyro::set_serviceable);
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fgTie("/instrumentation/attitude-indicator/spin",
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&_gyro, &Gyro::get_spin_norm, &Gyro::set_spin_norm);
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}
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void
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AttitudeIndicator::unbind ()
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{
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fgUntie("/instrumentation/attitude-indicator/serviceable");
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fgUntie("/instrumentation/attitude-indicator/spin");
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}
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void
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AttitudeIndicator::update (double dt)
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{
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// If it's caged, it doesn't indicate
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if (_caged_node->getBoolValue()) {
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_roll_int_node->setDoubleValue(0.0);
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_pitch_int_node->setDoubleValue(0.0);
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return;
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}
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// Get the spin from the gyro
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_gyro.set_power_norm(_suction_node->getDoubleValue()/5.0);
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_gyro.update(dt);
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double spin = _gyro.get_spin_norm();
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// Calculate the responsiveness
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double responsiveness = spin * spin * spin * spin * spin * spin;
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// Get the indicated roll and pitch
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double roll = _roll_in_node->getDoubleValue();
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double pitch = _pitch_in_node->getDoubleValue();
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// Calculate the tumble for the
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// next pass.
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if (_tumble_flag_node->getBoolValue()) {
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double tumble = _tumble_node->getDoubleValue();
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if (fabs(roll) > 45.0) {
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double target = (fabs(roll) - 45.0) / 45.0;
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target *= target; // exponential past +-45 degrees
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if (roll < 0)
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target = -target;
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if (fabs(target) > fabs(tumble))
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tumble = target;
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if (tumble > 1.0)
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tumble = 1.0;
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else if (tumble < -1.0)
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tumble = -1.0;
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}
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// Reerect in 5 minutes
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double step = dt/300.0;
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if (tumble < -step)
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tumble += step;
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else if (tumble > step)
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tumble -= step;
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roll += tumble * 45;
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_tumble_node->setDoubleValue(tumble);
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}
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roll = fgGetLowPass(_roll_int_node->getDoubleValue(), roll,
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responsiveness);
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pitch = fgGetLowPass(_pitch_int_node->getDoubleValue(), pitch,
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responsiveness);
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// Assign the new values
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_roll_int_node->setDoubleValue(roll);
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_pitch_int_node->setDoubleValue(pitch);
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// add in a gyro underspin "error" if gyro is spinning too slowly
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const double spin_thresh = 0.8;
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const double max_roll_error = 40.0;
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const double max_pitch_error = 12.0;
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double roll_error;
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double pitch_error;
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if ( spin <= spin_thresh ) {
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double roll_error_factor = (spin_thresh - spin) / spin_thresh;
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double pitch_error_factor = (spin_thresh - spin) / spin_thresh;
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roll_error = roll_error_factor * roll_error_factor * max_roll_error;
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pitch_error = pitch_error_factor * pitch_error_factor * max_pitch_error;
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} else {
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roll_error = 0.0;
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pitch_error = 0.0;
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}
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_roll_out_node->setDoubleValue(roll + roll_error);
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_pitch_out_node->setDoubleValue(pitch + pitch_error);
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}
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// end of attitude_indicator.cxx
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