PX4-Autopilot/src/modules/fw_pos_control_l1/landingslope.cpp

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

#include "landingslope.h"

#include <px4_config.h>
#include <stdlib.h>
#include <errno.h>
#include <math.h>
#include <unistd.h>
#include <mathlib/mathlib.h>

Landingslope::Landingslope() :
	_landing_slope_angle_rad(0.0f),
	_flare_relative_alt(0.0f),
	_motor_lim_relative_alt(0.0f),
	_H1_virt(0.0f),
	_H0(0.0f),
	_d1(0.0f),
	_flare_constant(0.0f),
	_flare_length(0.0f),
	_horizontal_slope_displacement(0.0f)
{
}

void Landingslope::update(float landing_slope_angle_rad_new,
			  float flare_relative_alt_new,
			  float motor_lim_relative_alt_new,
			  float H1_virt_new)
{

	_landing_slope_angle_rad = landing_slope_angle_rad_new;
	_flare_relative_alt = flare_relative_alt_new;
	_motor_lim_relative_alt = motor_lim_relative_alt_new;
	_H1_virt = H1_virt_new;

	calculateSlopeValues();
}

void Landingslope::calculateSlopeValues()
{
	_H0 =  _flare_relative_alt + _H1_virt;
	_d1 = _flare_relative_alt / tanf(_landing_slope_angle_rad);
	_flare_constant = (_H0 * _d1) / _flare_relative_alt;
	_flare_length = - logf(_H1_virt / _H0) * _flare_constant;
	_horizontal_slope_displacement = (_flare_length - _d1);
}

float Landingslope::getLandingSlopeRelativeAltitude(float wp_landing_distance)
{
	return Landingslope::getLandingSlopeRelativeAltitude(wp_landing_distance, _horizontal_slope_displacement,
			_landing_slope_angle_rad);
}

float Landingslope::getLandingSlopeRelativeAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp,
		float bearing_airplane_currwp)
{
	/* If airplane is in front of waypoint return slope altitude, else return waypoint altitude */
	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f)) {
		return getLandingSlopeRelativeAltitude(wp_landing_distance);

	} else {
		return 0.0f;
	}
}

float Landingslope::getLandingSlopeAbsoluteAltitude(float wp_landing_distance, float wp_altitude)
{
	return Landingslope::getLandingSlopeAbsoluteAltitude(wp_landing_distance, wp_altitude, _horizontal_slope_displacement,
			_landing_slope_angle_rad);
}

float Landingslope::getLandingSlopeAbsoluteAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp,
		float bearing_airplane_currwp, float wp_altitude)
{
	/* If airplane is in front of waypoint return slope altitude, else return waypoint altitude */
	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f)) {
		return getLandingSlopeAbsoluteAltitude(wp_landing_distance, wp_altitude);

	} else {
		return wp_altitude;
	}
}

float Landingslope::getFlareCurveRelativeAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp,
		float bearing_airplane_currwp)
{
	/* If airplane is in front of waypoint return flare curve altitude, else return waypoint altitude */
	if (fabsf(bearing_airplane_currwp - bearing_lastwp_currwp) < math::radians(90.0f)) {
		return _H0 * expf(-math::max(0.0f, _flare_length - wp_landing_distance) / _flare_constant) - _H1_virt;

	} else {
		return 0.0f;
	}
}

float Landingslope::getFlareCurveAbsoluteAltitudeSave(float wp_landing_distance, float bearing_lastwp_currwp,
		float bearing_airplane_currwp, float wp_landing_altitude)
{

	return wp_landing_altitude + getFlareCurveRelativeAltitudeSave(wp_landing_distance, bearing_lastwp_currwp,
			bearing_airplane_currwp);
}