range_finder_consistency_check.hpp

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/**
 * @file range_finder_consistency_check.hpp
 * @brief Compute statistical tests of the range finder data
 * using the estimated velocity as a reference in order to detect sensor faults
 */

#ifndef EKF_RANGE_FINDER_CONSISTENCY_CHECK_HPP
#define EKF_RANGE_FINDER_CONSISTENCY_CHECK_HPP

#include <mathlib/math/filter/AlphaFilter.hpp>

class RangeFinderConsistencyCheck final
{
public:
	RangeFinderConsistencyCheck() = default;
	~RangeFinderConsistencyCheck() = default;

	void update(float dist_bottom, float dist_bottom_var, float vz, float vz_var, bool horizontal_motion, uint64_t time_us);

	void setGate(float gate) { _gate = gate; }

	float getTestRatio() const { return _test_ratio; }
	float getSignedTestRatioLpf() const { return _signed_test_ratio_lpf.getState(); }
	float getInnov() const { return _innov; }
	float getInnovVar() const { return _innov_var; }
	bool isKinematicallyConsistent() const { return _is_kinematically_consistent; }

private:
	void updateConsistency(float vz, uint64_t time_us);

	uint64_t _time_last_update_us{};
	float _dist_bottom_prev{};

	float _test_ratio{};
	AlphaFilter<float> _signed_test_ratio_lpf{}; // average signed test ratio used to detect a bias in the data
	float _gate{.2f};
	float _innov{};
	float _innov_var{};

	bool _is_kinematically_consistent{true};
	uint64_t _time_last_inconsistent_us{};
	uint64_t _time_last_horizontal_motion{};

	static constexpr float _signed_test_ratio_tau = 2.f;

	static constexpr float _min_vz_for_valid_consistency = .5f;
	static constexpr uint64_t _consistency_hyst_time_us = 1e6;
};

#endif // !EKF_RANGE_FINDER_CONSISTENCY_CHECK_HPP