rtl.cpp

Go to the documentation of this file.

/****************************************************************************
 *
 *   Copyright (c) 2013-2019 PX4 Development Team. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name PX4 nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/
/**
 * @file rtl.cpp
 *
 * Helper class to access RTL
 *
 * @author Julian Oes <julian@oes.ch>
 * @author Anton Babushkin <anton.babushkin@me.com>
 */

#include "rtl.h"
#include "navigator.h"
#include <dataman/dataman.h>


static constexpr float DELAY_SIGMA = 0.01f;

RTL::RTL(Navigator *navigator) :
    MissionBlock(navigator),
    ModuleParams(navigator)
{
}

void
RTL::on_inactive()
{
    // Reset RTL state.
    _rtl_state = RTL_STATE_NONE;

    find_RTL_destination();

}

void
RTL::find_RTL_destination()
{
    // get home position:
    home_position_s &home_landing_position = *_navigator->get_home_position();
    // get global position
    const vehicle_global_position_s &global_position = *_navigator->get_global_position();

    // set destination to home per default, then check if other valid landing spot is closer
    _destination.set(home_landing_position);
    // get distance to home position
    double dlat = home_landing_position.lat - global_position.lat;
    double dlon = home_landing_position.lon - global_position.lon;
    double min_dist_squared = dlat * dlat + dlon * dlon;

    _destination.type = RTL_DESTINATION_HOME;

    // consider the mission landing if not RTL_HOME type set
    if (rtl_type() != RTL_HOME && _navigator->get_mission_start_land_available()) {
        double mission_landing_lat = _navigator->get_mission_landing_lat();
        double mission_landing_lon = _navigator->get_mission_landing_lon();

        // compare home position to landing position to decide which is closer
        dlat = mission_landing_lat - global_position.lat;
        dlon = mission_landing_lon - global_position.lon;
        double dist_squared = dlat * dlat + dlon * dlon;

        // set destination to mission landing if closest or in RTL_LAND or RTL_MISSION (so not in RTL_CLOSEST)
        if (dist_squared < min_dist_squared || rtl_type() != RTL_CLOSEST) {
            min_dist_squared = dist_squared;
            _destination.lat = _navigator->get_mission_landing_lat();
            _destination.lon = _navigator->get_mission_landing_lon();
            _destination.alt = _navigator->get_mission_landing_alt();
            _destination.type = RTL_DESTINATION_MISSION_LANDING;

        }
    }

    // do not consider rally point if RTL type is set to RTL_MISSION, so exit function and use either home or mission landing
    if (rtl_type() == RTL_MISSION) {
        return;
    }

    // compare to safe landing positions
    mission_safe_point_s closest_safe_point {} ;
    mission_stats_entry_s stats;
    int ret = dm_read(DM_KEY_SAFE_POINTS, 0, &stats, sizeof(mission_stats_entry_s));
    int num_safe_points = 0;

    if (ret == sizeof(mission_stats_entry_s)) {
        num_safe_points = stats.num_items;
    }

    // check if a safe point is closer than home or landing
    int closest_index = 0;

    for (int current_seq = 1; current_seq <= num_safe_points; ++current_seq) {
        mission_safe_point_s mission_safe_point;

        if (dm_read(DM_KEY_SAFE_POINTS, current_seq, &mission_safe_point, sizeof(mission_safe_point_s)) !=
            sizeof(mission_safe_point_s)) {
            PX4_ERR("dm_read failed");
            continue;
        }

        // TODO: take altitude into account for distance measurement
        dlat = mission_safe_point.lat - global_position.lat;
        dlon = mission_safe_point.lon - global_position.lon;
        double dist_squared = dlat * dlat + dlon * dlon;

        if (dist_squared < min_dist_squared) {
            closest_index = current_seq;
            min_dist_squared = dist_squared;
            closest_safe_point = mission_safe_point;
        }
    }

    if (closest_index > 0) {
        _destination.type = RTL_DESTINATION_SAFE_POINT;

        // There is a safe point closer than home/mission landing
        // TODO: handle all possible mission_safe_point.frame cases
        switch (closest_safe_point.frame) {
        case 0: // MAV_FRAME_GLOBAL
            _destination.lat = closest_safe_point.lat;
            _destination.lon = closest_safe_point.lon;
            _destination.alt = closest_safe_point.alt;
            _destination.yaw = home_landing_position.yaw;
            break;

        case 3: // MAV_FRAME_GLOBAL_RELATIVE_ALT
            _destination.lat = closest_safe_point.lat;
            _destination.lon = closest_safe_point.lon;
            _destination.alt = closest_safe_point.alt + home_landing_position.alt; // alt of safe point is rel to home
            _destination.yaw = home_landing_position.yaw;
            break;

        default:
            mavlink_log_critical(_navigator->get_mavlink_log_pub(), "RTL: unsupported MAV_FRAME");
            break;
        }
    }

}

int
RTL::rtl_type() const
{
    return _param_rtl_type.get();
}

void
RTL::on_activation()
{

    // output the correct message, depending on where the RTL destination is
    switch (_destination.type) {
    case RTL_DESTINATION_HOME:
        mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: landing at home position.");
        break;

    case RTL_DESTINATION_MISSION_LANDING:
        mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: landing at mission landing.");
        break;

    case RTL_DESTINATION_SAFE_POINT:
        mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: landing at safe landing point.");
        break;
    }

    const vehicle_global_position_s &global_position = *_navigator->get_global_position();

    _rtl_alt = calculate_return_alt_from_cone_half_angle((float)_param_rtl_cone_half_angle_deg.get());

    if (_navigator->get_land_detected()->landed) {
        // For safety reasons don't go into RTL if landed.
        _rtl_state = RTL_STATE_LANDED;

    } else if ((_destination.type == RTL_DESTINATION_MISSION_LANDING) && _navigator->on_mission_landing()) {
        // RTL straight to RETURN state, but mission will takeover for landing.

    } else if ((global_position.alt < _destination.alt + _param_rtl_return_alt.get()) || _rtl_alt_min) {

        // If lower than return altitude, climb up first.
        // If rtl_alt_min is true then forcing altitude change even if above.
        _rtl_state = RTL_STATE_CLIMB;

    } else {
        // Otherwise go straight to return
        _rtl_state = RTL_STATE_RETURN;
    }

    set_rtl_item();
}

void
RTL::on_active()
{
    if (_rtl_state != RTL_STATE_LANDED && is_mission_item_reached()) {
        advance_rtl();
        set_rtl_item();
    }
}

void
RTL::set_return_alt_min(bool min)
{
    _rtl_alt_min = min;
}

void
RTL::set_rtl_item()
{
    // RTL_TYPE: mission landing.
    // Landing using planned mission landing, fly to DO_LAND_START instead of returning _destination.
    // After reaching DO_LAND_START, do nothing, let navigator takeover with mission landing.
    if (_destination.type == RTL_DESTINATION_MISSION_LANDING) {
        if (_rtl_state > RTL_STATE_CLIMB) {
            if (_navigator->start_mission_landing()) {
                mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: using mission landing");
                return;

            } else {
                // Otherwise use regular RTL.
                mavlink_log_critical(_navigator->get_mavlink_log_pub(), "RTL: unable to use mission landing");
            }
        }
    }

    _navigator->set_can_loiter_at_sp(false);

    const vehicle_global_position_s &gpos = *_navigator->get_global_position();

    position_setpoint_triplet_s *pos_sp_triplet = _navigator->get_position_setpoint_triplet();

    // Check if we are pretty close to the destination already.
    const float destination_dist = get_distance_to_next_waypoint(_destination.lat, _destination.lon, gpos.lat, gpos.lon);

    // Compute the loiter altitude.
    const float loiter_altitude = math::min(_destination.alt + _param_rtl_descend_alt.get(), gpos.alt);

    switch (_rtl_state) {
    case RTL_STATE_CLIMB: {

            _mission_item.nav_cmd = NAV_CMD_WAYPOINT;
            _mission_item.lat = gpos.lat;
            _mission_item.lon = gpos.lon;
            _mission_item.altitude = _rtl_alt;
            _mission_item.altitude_is_relative = false;
            _mission_item.yaw = _navigator->get_local_position()->yaw;
            _mission_item.acceptance_radius = _navigator->get_acceptance_radius();
            _mission_item.time_inside = 0.0f;
            _mission_item.autocontinue = true;
            _mission_item.origin = ORIGIN_ONBOARD;

            mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: climb to %d m (%d m above destination)",
                             (int)ceilf(_rtl_alt), (int)ceilf(_rtl_alt - _destination.alt));
            break;
        }

    case RTL_STATE_RETURN: {

            // Don't change altitude.
            _mission_item.nav_cmd = NAV_CMD_WAYPOINT;
            _mission_item.lat = _destination.lat;
            _mission_item.lon = _destination.lon;
            _mission_item.altitude = _rtl_alt;
            _mission_item.altitude_is_relative = false;

            // Use destination yaw if close to _destination.
            // Check if we are pretty close to the destination already.
            if (destination_dist < _param_rtl_min_dist.get()) {
                _mission_item.yaw = _destination.yaw;

            } else {
                // Use current heading to _destination.
                _mission_item.yaw = get_bearing_to_next_waypoint(gpos.lat, gpos.lon, _destination.lat, _destination.lon);
            }

            _mission_item.acceptance_radius = _navigator->get_acceptance_radius();
            _mission_item.time_inside = 0.0f;
            _mission_item.autocontinue = true;
            _mission_item.origin = ORIGIN_ONBOARD;

            mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: return at %d m (%d m above destination)",
                             (int)ceilf(_mission_item.altitude), (int)ceilf(_mission_item.altitude - _destination.alt));

            break;
        }

    case RTL_STATE_TRANSITION_TO_MC: {
            set_vtol_transition_item(&_mission_item, vtol_vehicle_status_s::VEHICLE_VTOL_STATE_MC);
            break;
        }

    case RTL_STATE_DESCEND: {
            _mission_item.nav_cmd = NAV_CMD_WAYPOINT;
            _mission_item.lat = _destination.lat;
            _mission_item.lon = _destination.lon;
            _mission_item.altitude = loiter_altitude;
            _mission_item.altitude_is_relative = false;

            // Except for vtol which might be still off here and should point towards this location.
            const float d_current = get_distance_to_next_waypoint(gpos.lat, gpos.lon, _mission_item.lat, _mission_item.lon);

            if (_navigator->get_vstatus()->is_vtol && (d_current > _navigator->get_acceptance_radius())) {
                _mission_item.yaw = get_bearing_to_next_waypoint(gpos.lat, gpos.lon, _mission_item.lat, _mission_item.lon);

            } else {
                _mission_item.yaw = _destination.yaw;
            }

            _mission_item.acceptance_radius = _navigator->get_acceptance_radius();
            _mission_item.time_inside = 0.0f;
            _mission_item.autocontinue = true;
            _mission_item.origin = ORIGIN_ONBOARD;

            // Disable previous setpoint to prevent drift.
            pos_sp_triplet->previous.valid = false;

            mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: descend to %d m (%d m above destination)",
                             (int)ceilf(_mission_item.altitude), (int)ceilf(_mission_item.altitude - _destination.alt));
            break;
        }

    case RTL_STATE_LOITER: {
            const bool autoland = (_param_rtl_land_delay.get() > FLT_EPSILON);

            // Don't change altitude.
            _mission_item.lat = _destination.lat;
            _mission_item.lon = _destination.lon;
            _mission_item.altitude = loiter_altitude;
            _mission_item.altitude_is_relative = false;
            _mission_item.yaw = _destination.yaw;
            _mission_item.loiter_radius = _navigator->get_loiter_radius();
            _mission_item.acceptance_radius = _navigator->get_acceptance_radius();
            _mission_item.time_inside = math::max(_param_rtl_land_delay.get(), 0.0f);
            _mission_item.autocontinue = autoland;
            _mission_item.origin = ORIGIN_ONBOARD;

            _navigator->set_can_loiter_at_sp(true);

            if (autoland && (get_time_inside(_mission_item) > FLT_EPSILON)) {
                _mission_item.nav_cmd = NAV_CMD_LOITER_TIME_LIMIT;
                mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: loiter %.1fs",
                                 (double)get_time_inside(_mission_item));

            } else {
                _mission_item.nav_cmd = NAV_CMD_LOITER_UNLIMITED;
                mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: completed, loitering");
            }

            break;
        }

    case RTL_STATE_LAND: {
            // Land at destination.
            _mission_item.nav_cmd = NAV_CMD_LAND;
            _mission_item.lat = _destination.lat;
            _mission_item.lon = _destination.lon;
            _mission_item.yaw = _destination.yaw;
            _mission_item.altitude = _destination.alt;
            _mission_item.altitude_is_relative = false;
            _mission_item.acceptance_radius = _navigator->get_acceptance_radius();
            _mission_item.time_inside = 0.0f;
            _mission_item.autocontinue = true;
            _mission_item.origin = ORIGIN_ONBOARD;

            mavlink_and_console_log_info(_navigator->get_mavlink_log_pub(), "RTL: land at destination");
            break;
        }

    case RTL_STATE_LANDED: {
            set_idle_item(&_mission_item);
            set_return_alt_min(false);
            break;
        }

    default:
        break;
    }

    reset_mission_item_reached();

    // Execute command if set. This is required for commands like VTOL transition.
    if (!item_contains_position(_mission_item)) {
        issue_command(_mission_item);
    }

    // Convert mission item to current position setpoint and make it valid.
    mission_apply_limitation(_mission_item);

    if (mission_item_to_position_setpoint(_mission_item, &pos_sp_triplet->current)) {
        _navigator->set_position_setpoint_triplet_updated();
    }
}

void
RTL::advance_rtl()
{
    switch (_rtl_state) {
    case RTL_STATE_CLIMB:
        _rtl_state = RTL_STATE_RETURN;
        break;

    case RTL_STATE_RETURN:

        // Descend to desired altitude if delay is set, directly land otherwise
        if (_param_rtl_land_delay.get() < -DELAY_SIGMA || _param_rtl_land_delay.get() > DELAY_SIGMA) {
            _rtl_state = RTL_STATE_DESCEND;

        } else {
            _rtl_state = RTL_STATE_LAND;
        }

        if (_navigator->get_vstatus()->is_vtol
            && _navigator->get_vstatus()->vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING) {
            _rtl_state = RTL_STATE_TRANSITION_TO_MC;
        }

        break;

    case RTL_STATE_TRANSITION_TO_MC:
        _rtl_state = RTL_STATE_RETURN;
        break;

    case RTL_STATE_DESCEND:

        // Only go to land if autoland is enabled.
        if (_param_rtl_land_delay.get() < -DELAY_SIGMA || _param_rtl_land_delay.get() > DELAY_SIGMA) {
            _rtl_state = RTL_STATE_LOITER;

        } else {
            _rtl_state = RTL_STATE_LAND;
        }

        break;

    case RTL_STATE_LOITER:
        _rtl_state = RTL_STATE_LAND;
        break;

    case RTL_STATE_LAND:
        _rtl_state = RTL_STATE_LANDED;
        break;

    default:
        break;
    }
}


float RTL::calculate_return_alt_from_cone_half_angle(float cone_half_angle_deg)
{
    const vehicle_global_position_s &gpos = *_navigator->get_global_position();

    // horizontal distance to destination
    const float destination_dist = get_distance_to_next_waypoint(_destination.lat, _destination.lon, gpos.lat, gpos.lon);

    float rtl_altitude;

    if (destination_dist <= _param_rtl_min_dist.get()) {
        rtl_altitude = _destination.alt + _param_rtl_descend_alt.get();

    } else if (gpos.alt > _destination.alt + _param_rtl_return_alt.get() || cone_half_angle_deg >= 90.0f) {
        rtl_altitude = gpos.alt;

    } else if (cone_half_angle_deg <= 0) {
        rtl_altitude = _destination.alt + _param_rtl_return_alt.get();

    } else {

        // constrain cone half angle to meaningful values. All other cases are already handled above.
        const float cone_half_angle_rad = math::radians(math::constrain(cone_half_angle_deg, 1.0f, 89.0f));

        // minimum height above destination required
        float height_above_destination_min = destination_dist / tanf(cone_half_angle_rad);

        // minimum altitude we need in order to be within the user defined cone
        const float altitude_min = math::constrain(height_above_destination_min + _destination.alt, _destination.alt,
                       _destination.alt + _param_rtl_return_alt.get());

        if (gpos.alt < altitude_min) {
            rtl_altitude = altitude_min;

        } else {
            rtl_altitude = gpos.alt;
        }
    }

    // always demand altitude which is higher or equal the RTL descend altitude
    rtl_altitude = math::max(rtl_altitude, _destination.alt + _param_rtl_descend_alt.get());

    return rtl_altitude;
}