PX4-Autopilot/src/modules/land_detector/LandDetector.h

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/**
 * @file LandDetector.h
Land detector interface for multicopter, fixedwing and VTOL implementations.
 *
 * @author Johan Jansen <jnsn.johan@gmail.com>
 * @author Julian Oes <julian@oes.ch>
 * @author Lorenz Meier <lorenz@px4.io>
 */

#pragma once

#include <px4_workqueue.h>
#include <systemlib/hysteresis/hysteresis.h>
#include <systemlib/param/param.h>
#include <uORB/uORB.h>
#include <uORB/topics/vehicle_land_detected.h>

namespace land_detector
{


class LandDetector
{
public:
	enum class LandDetectionState {
		FLYING = 0,
		LANDED = 1,
		FREEFALL = 2,
		GROUND_CONTACT = 3
	};

	LandDetector();
	virtual ~LandDetector();

	/**
	 * @return true if this task is currently running.
	 */
	inline bool is_running() const
	{
		return _taskIsRunning;
	}


	/**
	 * @return current state.
	 */
	LandDetectionState get_state() const
	{
		return _state;
	}

	/**
	 * Tells the task that it should exit.
	 */
	void stop();

	/**
	 * Get the work queue going.
	 */
	int start();

protected:
	/**
	 * Called once to initialize uORB topics.
	 */
	virtual void _initialize_topics() = 0;

	/**
	 * Update uORB topics.
	 */
	virtual void _update_topics() = 0;


	/**
	 * Update parameters.
	 */
	virtual void _update_params() = 0;

	/**
	 * @return true if UAV is in a landed state.
	 */
	virtual bool _get_landed_state() = 0;

	/**
	 * @return true if UAV is touching ground but not landed
	 */
	virtual bool _get_ground_contact_state()  = 0;

	/**
	 * @return true if UAV is in free-fall state.
	 */
	virtual bool _get_freefall_state() = 0;

	/**
	 *  @return maximum altitude that can be reached
	 */
	virtual float _get_max_altitude() = 0;

	/**
	 * Convenience function for polling uORB subscriptions.
	 *
	 * @return true if there was new data and it was successfully copied
	 */
	static bool _orb_update(const struct orb_metadata *meta, int handle, void *buffer);

	/** Run main land detector loop at this rate in Hz. */
	static constexpr uint32_t LAND_DETECTOR_UPDATE_RATE_HZ = 50;

	/** Time in us that landing conditions have to hold before triggering a land. */
	static constexpr uint64_t LAND_DETECTOR_TRIGGER_TIME_US = 1500000;

	/** Time in us that ground contact condition have to hold before triggering contact ground */
	static constexpr uint64_t GROUND_CONTACT_TRIGGER_TIME_US = 1000000;

	/** Time interval in us in which wider acceptance thresholds are used after arming. */
	static constexpr uint64_t LAND_DETECTOR_ARM_PHASE_TIME_US = 2000000;

	orb_advert_t _landDetectedPub;
	struct vehicle_land_detected_s _landDetected;

	int _parameterSub;

	LandDetectionState _state;

	systemlib::Hysteresis _freefall_hysteresis;
	systemlib::Hysteresis _landed_hysteresis;
	systemlib::Hysteresis _ground_contact_hysteresis;

	float _altitude_max;

private:
	static void _cycle_trampoline(void *arg);

	void _cycle();

	void _check_params(const bool force);

	void _update_state();

	bool _taskShouldExit;
	bool _taskIsRunning;

	param_t _p_total_flight_time_high;
	param_t _p_total_flight_time_low;
	uint64_t _total_flight_time; ///< in microseconds
	hrt_abstime _takeoff_time;


	struct work_s	_work;
};


} // namespace land_detector