FixedwingLandDetector.cpp

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/**
 * @file FixedwingLandDetector.cpp
 *
 * @author Johan Jansen <jnsn.johan@gmail.com>
 * @author Lorenz Meier <lorenz@px4.io>
 * @author Julian Oes <julian@oes.ch>
 */

#include "FixedwingLandDetector.h"

namespace land_detector
{

FixedwingLandDetector::FixedwingLandDetector()
{
    // Use Trigger time when transitioning from in-air (false) to landed (true) / ground contact (true).
    _landed_hysteresis.set_hysteresis_time_from(false, LANDED_TRIGGER_TIME_US);
    _landed_hysteresis.set_hysteresis_time_from(true, FLYING_TRIGGER_TIME_US);
}

void FixedwingLandDetector::_update_topics()
{
    LandDetector::_update_topics();
    _airspeed_sub.update(&_airspeed);
}

bool FixedwingLandDetector::_get_landed_state()
{
    // Only trigger flight conditions if we are armed.
    if (!_actuator_armed.armed) {
        return true;
    }

    bool landDetected = false;

    if (hrt_elapsed_time(&_vehicle_local_position.timestamp) < 500_ms) {

        // Horizontal velocity complimentary filter.
        float val = 0.97f * _velocity_xy_filtered + 0.03f * sqrtf(_vehicle_local_position.vx * _vehicle_local_position.vx +
                _vehicle_local_position.vy * _vehicle_local_position.vy);

        if (PX4_ISFINITE(val)) {
            _velocity_xy_filtered = val;
        }

        // Vertical velocity complimentary filter.
        val = 0.99f * _velocity_z_filtered + 0.01f * fabsf(_vehicle_local_position.vz);

        if (PX4_ISFINITE(val)) {
            _velocity_z_filtered = val;
        }

        _airspeed_filtered = 0.95f * _airspeed_filtered + 0.05f * _airspeed.true_airspeed_m_s;

        // A leaking lowpass prevents biases from building up, but
        // gives a mostly correct response for short impulses.
        const matrix::Vector3f accel{_vehicle_acceleration.xyz};
        const float acc_hor = sqrtf(accel(0) * accel(0) + accel(1) * accel(1));

        _xy_accel_filtered = _xy_accel_filtered * 0.8f + acc_hor * 0.18f;

        // Crude land detector for fixedwing.
        landDetected = _airspeed_filtered       < _param_lndfw_airspd.get()
                   && _velocity_xy_filtered < _param_lndfw_vel_xy_max.get()
                   && _velocity_z_filtered  < _param_lndfw_vel_z_max.get()
                   && _xy_accel_filtered    < _param_lndfw_xyaccel_max.get();

    } else {
        // Control state topic has timed out and we need to assume we're landed.
        landDetected = true;
    }

    return landDetected;
}

} // namespace land_detector