Landingslope.cpp

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

#include "Landingslope.hpp"

#include <mathlib/mathlib.h>

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);

    }

    return 0.0f;
}

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;

    }

    return 0.0f;
}

/**
 *
 * @return Relative altitude of point on landing slope at distance to landing waypoint=wp_landing_distance
 */
float Landingslope::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
 */
float Landingslope::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
 */
float Landingslope::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;
}