PX4-Autopilot/src/modules/ekf2/Utility/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);

	/*
	 * Packs the boolean flags into a bit field
	 */
	static uint8_t prefltFailBoolToBitMask(bool heading_failed, bool horiz_vel_failed, bool vert_vel_failed,
					       bool height_failed);

	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;
};