PreFlightChecker.hpp

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/**
 * @file PreFlightChecker.hpp
 * Class handling the EKF2 innovation pre flight checks
 *
 * First call the update(...) function and then get the results
 * using the hasXxxFailed() getters
 */

#pragma once

#include <uORB/topics/vehicle_status.h>
#include <uORB/topics/ekf2_innovations.h>

#include <matrix/matrix/math.hpp>

#include "InnovationLpf.hpp"

using matrix::Vector2f;

class PreFlightChecker
{
public:
    PreFlightChecker() = default;
    ~PreFlightChecker() = default;

    /*
     * Reset all the internal states of the class to their default value
     */
    void reset();

    /*
     * Update the internal states
     * @param dt the sampling time
     * @param innov the ekf2_innovation_s struct containing the current innovations
     */
    void update(float dt, const ekf2_innovations_s &innov);

    /*
     * If set to true, the checker will use a less conservative heading innovation check
     */
    void setVehicleCanObserveHeadingInFlight(bool val) { _can_observe_heading_in_flight = val; }

    void setUsingGpsAiding(bool val) { _is_using_gps_aiding = val; }
    void setUsingFlowAiding(bool val) { _is_using_flow_aiding = val; }
    void setUsingEvPosAiding(bool val) { _is_using_ev_pos_aiding = val; }

    bool hasHeadingFailed() const { return _has_heading_failed; }
    bool hasHorizVelFailed() const { return _has_horiz_vel_failed; }
    bool hasVertVelFailed() const { return _has_vert_vel_failed; }
    bool hasHeightFailed() const { return _has_height_failed; }

    /*
     * Overall state of the pre fligh checks
     * @return true if any of the check failed
     */
    bool hasFailed() const { return hasHorizFailed() || hasVertFailed(); }

    /*
     * Horizontal checks overall result
     * @return true if one of the horizontal checks failed
     */
    bool hasHorizFailed() const { return _has_heading_failed || _has_horiz_vel_failed; }

    /*
     * Vertical checks overall result
     * @return true if one of the vertical checks failed
     */
    bool hasVertFailed() const { return _has_vert_vel_failed || _has_height_failed; }

    /*
     * Check if the innovation fails the test
     * To pass the test, the following conditions should be true:
     * innov <= test_limit
     * innov_lpf <= 2 * test_limit
     * @param innov the current unfiltered innovation
     * @param innov_lpf the low-pass filtered innovation
     * @param test_limit the magnitude test limit
     * @return true if the check failed the test, false otherwise
     */
    static bool checkInnovFailed(float innov, float innov_lpf, float test_limit);

    /*
     * Check if the a innovation of a 2D vector fails the test
     * To pass the test, the following conditions should be true:
     * innov <= test_limit
     * innov_lpf <= 2 * test_limit
     * @param innov the current unfiltered innovation
     * @param innov_lpf the low-pass filtered innovation
     * @param test_limit the magnitude test limit
     * @return true if the check failed the test, false otherwise
     */
    static bool checkInnov2DFailed(const Vector2f &innov, const Vector2f &innov_lpf, float test_limit);

    static constexpr float sq(float var) { return var * var; }

private:
    bool preFlightCheckHeadingFailed(const ekf2_innovations_s &innov, float alpha);
    float selectHeadingTestLimit();

    bool preFlightCheckHorizVelFailed(const ekf2_innovations_s &innov, float alpha);
    bool preFlightCheckVertVelFailed(const ekf2_innovations_s &innov, float alpha);
    bool preFlightCheckHeightFailed(const ekf2_innovations_s &innov, float alpha);

    void resetPreFlightChecks();

    bool _has_heading_failed{};
    bool _has_horiz_vel_failed{};
    bool _has_vert_vel_failed{};
    bool _has_height_failed{};

    bool _can_observe_heading_in_flight{};
    bool _is_using_gps_aiding{};
    bool _is_using_flow_aiding{};
    bool _is_using_ev_pos_aiding{};

    // Low-pass filters for innovation pre-flight checks
    InnovationLpf _filter_vel_n_innov;  ///< Preflight low pass filter N axis velocity innovations (m/sec)
    InnovationLpf _filter_vel_e_innov;  ///< Preflight low pass filter E axis velocity innovations (m/sec)
    InnovationLpf _filter_vel_d_innov;  ///< Preflight low pass filter D axis velocity innovations (m/sec)
    InnovationLpf _filter_hgt_innov;    ///< Preflight low pass filter height innovation (m)
    InnovationLpf _filter_heading_innov;    ///< Preflight low pass filter heading innovation magntitude (rad)
    InnovationLpf _filter_flow_x_innov; ///< Preflight low pass filter optical flow innovation (rad)
    InnovationLpf _filter_flow_y_innov; ///< Preflight low pass filter optical flow innovation (rad)

    // Preflight low pass filter time constant inverse (1/sec)
    static constexpr float _innov_lpf_tau_inv = 0.2f;
    // Maximum permissible velocity innovation to pass pre-flight checks (m/sec)
    static constexpr float _vel_innov_test_lim = 0.5f;
    // Maximum permissible height innovation to pass pre-flight checks (m)
    static constexpr float _hgt_innov_test_lim = 1.5f;
    // Maximum permissible yaw innovation to pass pre-flight checks when aiding inertial nav using NE frame observations (rad)
    static constexpr float _nav_heading_innov_test_lim = 0.25f;
    // Maximum permissible yaw innovation to pass pre-flight checks when not aiding inertial nav using NE frame observations (rad)
    static constexpr float _heading_innov_test_lim = 0.52f;
    // Maximum permissible flow innovation to pass pre-flight checks
    static constexpr float _flow_innov_test_lim = 0.1f;
    // Preflight velocity innovation spike limit (m/sec)
    static constexpr float _vel_innov_spike_lim = 2.0f * _vel_innov_test_lim;
    // Preflight position innovation spike limit (m)
    static constexpr float _hgt_innov_spike_lim = 2.0f * _hgt_innov_test_lim;
    // Preflight flow innovation spike limit (rad)
    static constexpr float _flow_innov_spike_lim = 2.0f * _flow_innov_test_lim;
};