px4_autopilot/EKF/control.cpp

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/**
 * @file control.cpp
 * Control functions for ekf attitude and position estimator.
 *
 * @author Paul Riseborough <p_riseborough@live.com.au>
 *
 */

#include "ekf.h"

void Ekf::controlFusionModes()
{
    // Determine the vehicle status
    calculateVehicleStatus();

    // optical flow fusion mode selection logic
    _control_status.flags.opt_flow = false;

    // GPS fusion mode selection logic
    // To start use GPS we need angular alignment completed, the local NED origin set and fresh GPS data
    if (!_control_status.flags.gps) {
        if (_control_status.flags.angle_align && (_time_last_imu - _time_last_gps) < 5e5 && _NED_origin_initialised && (_time_last_imu - _last_gps_fail_us > 5e6)) {
            _control_status.flags.gps = true;
            resetPosition();
            resetVelocity();
        }
    }

    // decide when to start using optical flow data
    if (!_control_status.flags.opt_flow) {
        // TODO optical flow start logic
    }

    // handle the case when we are relying on GPS fusion and lose it
    if (_control_status.flags.gps && !_control_status.flags.opt_flow) {
        // We are relying on GPS aiding to constrain attitude drift so after 10 seconds without aiding we need to do something
        if ((_time_last_imu - _time_last_pos_fuse > 10e6) && (_time_last_imu - _time_last_vel_fuse > 10e6)) {
            if (_time_last_imu - _time_last_gps > 5e5) {
                // if we don't have gps then we need to switch to the non-aiding mode, zero the veloity states
                // and set the synthetic GPS position to the current estimate
                _control_status.flags.gps = false;
                _last_known_posNE(0) = _state.pos(0);
                _last_known_posNE(1) = _state.pos(1);
                _state.vel.setZero();
            } else {
                // Reset states to the last GPS measurement
                resetPosition();
                resetVelocity();
            }
        }
    }

    // handle the case when we are relying on optical flow fusion and lose it
    if (_control_status.flags.opt_flow && !_control_status.flags.gps) {
        // TODO
    }

    // Determine if we should use simple magnetic heading fusion which works better when there are large external disturbances
    // or the more accurate 3-axis fusion
    if (!_control_status.flags.armed) {
        // always use simple mag fusion for initial startup
        _control_status.flags.mag_hdg = true;
        _control_status.flags.mag_3D = false;
    } else {
        if (_control_status.flags.in_air) {
            // always use 3-axis mag fusion when airborne
            _control_status.flags.mag_hdg = false;
            _control_status.flags.mag_3D = true;
        } else {
            // always use simple heading fusion when on the ground
            _control_status.flags.mag_hdg = true;
            _control_status.flags.mag_3D = false;
        }
    }
}

void Ekf::calculateVehicleStatus()
{
    // determine if the vehicle is armed
    _control_status.flags.armed = _vehicle_armed;

    // record vertical position whilst disarmed to use as a height change reference
    if (!_control_status.flags.armed) {
        _last_disarmed_posD = _state.pos(2);
    }

    // Transition to in-air occurs when armed and when altitude has increased sufficiently from the altitude at arming
    if (!_control_status.flags.in_air && _control_status.flags.armed && (_state.pos(2) - _last_disarmed_posD) < -1.0f) {
        _control_status.flags.in_air = true;
    }

    // Transition to on-ground occurs when disarmed.
    if (_control_status.flags.in_air && !_control_status.flags.armed) {
        _control_status.flags.in_air = false;
    }
}