PreFlightChecker.cpp

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/**
 * @file PreFlightCheckHelper.cpp
 * Class handling the EKF2 innovation pre flight checks
 */

#include "PreFlightChecker.hpp"

void PreFlightChecker::update(const float dt, const ekf2_innovations_s &innov)
{
    const float alpha = InnovationLpf::computeAlphaFromDtAndTauInv(dt, _innov_lpf_tau_inv);

    _has_heading_failed = preFlightCheckHeadingFailed(innov, alpha);
    _has_horiz_vel_failed = preFlightCheckHorizVelFailed(innov, alpha);
    _has_vert_vel_failed = preFlightCheckVertVelFailed(innov, alpha);
    _has_height_failed = preFlightCheckHeightFailed(innov, alpha);
}

bool PreFlightChecker::preFlightCheckHeadingFailed(const ekf2_innovations_s &innov, const float alpha)
{
    const float heading_test_limit = selectHeadingTestLimit();
    const float heading_innov_spike_lim = 2.0f * heading_test_limit;

    const float heading_innov_lpf = _filter_heading_innov.update(innov.heading_innov, alpha, heading_innov_spike_lim);

    return checkInnovFailed(innov.heading_innov, heading_innov_lpf, heading_test_limit);
}

float PreFlightChecker::selectHeadingTestLimit()
{
    // Select the max allowed heading innovaton depending on whether we are not aiding navigation using
    // observations in the NE reference frame and if the vehicle can use GPS course to realign in flight (fixedwing sideslip fusion).
    const bool is_ne_aiding = _is_using_gps_aiding || _is_using_ev_pos_aiding;

    return (is_ne_aiding && !_can_observe_heading_in_flight)
           ? _nav_heading_innov_test_lim // more restrictive test limit
           : _heading_innov_test_lim; // less restrictive test limit
}

bool PreFlightChecker::preFlightCheckHorizVelFailed(const ekf2_innovations_s &innov, const float alpha)
{
    bool has_failed = false;

    if (_is_using_gps_aiding || _is_using_ev_pos_aiding) {
        const Vector2f vel_ne_innov = Vector2f(innov.vel_pos_innov);
        Vector2f vel_ne_innov_lpf;
        vel_ne_innov_lpf(0) = _filter_vel_n_innov.update(vel_ne_innov(0), alpha, _vel_innov_spike_lim);
        vel_ne_innov_lpf(1) = _filter_vel_n_innov.update(vel_ne_innov(1), alpha, _vel_innov_spike_lim);
        has_failed |= checkInnov2DFailed(vel_ne_innov, vel_ne_innov_lpf, _vel_innov_test_lim);
    }

    if (_is_using_flow_aiding) {
        const Vector2f flow_innov = Vector2f(innov.flow_innov);
        Vector2f flow_innov_lpf;
        flow_innov_lpf(0) = _filter_flow_x_innov.update(flow_innov(0), alpha, _flow_innov_spike_lim);
        flow_innov_lpf(1) = _filter_flow_x_innov.update(flow_innov(1), alpha, _flow_innov_spike_lim);
        has_failed |= checkInnov2DFailed(flow_innov, flow_innov_lpf, _flow_innov_test_lim);
    }

    return has_failed;
}

bool PreFlightChecker::preFlightCheckVertVelFailed(const ekf2_innovations_s &innov, const float alpha)
{
    const float vel_d_innov = innov.vel_pos_innov[2];
    const float vel_d_innov_lpf = _filter_vel_d_innov.update(vel_d_innov, alpha, _vel_innov_spike_lim);
    return checkInnovFailed(vel_d_innov, vel_d_innov_lpf, _vel_innov_test_lim);
}

bool PreFlightChecker::preFlightCheckHeightFailed(const ekf2_innovations_s &innov, const float alpha)
{
    const float hgt_innov = innov.vel_pos_innov[5];
    const float hgt_innov_lpf = _filter_hgt_innov.update(hgt_innov, alpha, _hgt_innov_spike_lim);
    return checkInnovFailed(hgt_innov, hgt_innov_lpf, _hgt_innov_test_lim);
}

bool PreFlightChecker::checkInnovFailed(const float innov, const float innov_lpf, const float test_limit)
{
    return fabsf(innov_lpf) > test_limit || fabsf(innov) > 2.0f * test_limit;
}

bool PreFlightChecker::checkInnov2DFailed(const Vector2f &innov, const Vector2f &innov_lpf, const float test_limit)
{
    return innov_lpf.norm_squared() > sq(test_limit)
           || innov.norm_squared() > sq(2.0f * test_limit);
}

void PreFlightChecker::reset()
{
    _is_using_gps_aiding = false;
    _is_using_flow_aiding = false;
    _is_using_ev_pos_aiding = false;
    _has_heading_failed = false;
    _has_horiz_vel_failed = false;
    _has_vert_vel_failed = false;
    _has_height_failed = false;
    _filter_vel_n_innov.reset();
    _filter_vel_e_innov.reset();
    _filter_vel_d_innov.reset();
    _filter_hgt_innov.reset();
    _filter_heading_innov.reset();
    _filter_flow_x_innov.reset();
    _filter_flow_y_innov.reset();
}