PX4-Autopilot/src/modules/fw_pos_control_l1/Landingslope.hpp

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/*
 * @file landingslope.h
 *
 * @author Thomas Gubler <thomasgubler@gmail.com>
 */

#ifndef LANDINGSLOPE_H_
#define LANDINGSLOPE_H_

#include <math.h>

class Landingslope
{
private:
	/* see Documentation/fw_landing.png for a plot of the landing slope */
	float _landing_slope_angle_rad{0.0f};		/**< phi in the plot */
	float _flare_relative_alt{0.0f};		/**< h_flare,rel in the plot */
	float _motor_lim_relative_alt{0.0f};
	float _H1_virt{0.0f};				/**< H1 in the plot */
	float _H0{0.0f};				/**< h_flare,rel + H1 in the plot */
	float _d1{0.0f};				/**< d1 in the plot */
	float _flare_constant{0.0f};
	float _flare_length{0.0f};			/**< d1 + delta d in the plot */
	float _horizontal_slope_displacement{0.0f};	/**< delta d in the plot */

	void calculateSlopeValues();

public:
	Landingslope() = default;
	~Landingslope() = default;

	/**
	 *
	 * @return relative altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
	 */
	float getLandingSlopeRelativeAltitude(float wp_landing_distance);

	/**
	 *
	 * @return relative altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
	 * Performs check if aircraft is in front of waypoint to avoid climbout
	 */
	float getLandingSlopeRelativeAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp,
			float bearing_airplane_currwp);

	/**
	 *
	 * @return Relative altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
	 */
	__EXPORT static float getLandingSlopeRelativeAltitude(float wp_landing_distance, float horizontal_slope_displacement,
			float landing_slope_angle_rad)
	{
		// flare_relative_alt is negative
		return (wp_landing_distance - horizontal_slope_displacement) * tanf(landing_slope_angle_rad);
	}

	/**
	 *
	 * @return Absolute altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
	 */
	__EXPORT static float getLandingSlopeAbsoluteAltitude(float wp_landing_distance, float wp_landing_altitude,
			float horizontal_slope_displacement, float landing_slope_angle_rad)
	{
		return getLandingSlopeRelativeAltitude(wp_landing_distance, horizontal_slope_displacement,
						       landing_slope_angle_rad) + wp_landing_altitude;
	}

	/**
	 *
	 * @return distance to landing waypoint of point on landing slope at altitude=slope_altitude
	 */
	__EXPORT static float getLandingSlopeWPDistance(float slope_altitude, float wp_landing_altitude,
			float horizontal_slope_displacement, float landing_slope_angle_rad)
	{
		return (slope_altitude - wp_landing_altitude) / tanf(landing_slope_angle_rad) + horizontal_slope_displacement;

	}

	float getFlareCurveRelativeAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp,
						float bearing_airplane_currwp);

	void update(float landing_slope_angle_rad_new,
		    float flare_relative_alt_new,
		    float motor_lim_relative_alt_new,
		    float H1_virt_new);


	float landing_slope_angle_rad() { return _landing_slope_angle_rad; }
	float flare_relative_alt() { return _flare_relative_alt; }
	float motor_lim_relative_alt() { return _motor_lim_relative_alt; }
	float flare_length() { return _flare_length; }
	float horizontal_slope_displacement() { return _horizontal_slope_displacement; }

};


#endif /* LANDINGSLOPE_H_ */