PX4-Autopilot/src/modules/navigator/rtl.cpp

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/**
 * @file navigator_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 <cfloat>

#include <mathlib/mathlib.h>
#include <systemlib/mavlink_log.h>

using math::max;
using math::min;

static constexpr float DELAY_SIGMA = 0.01f;

RTL::RTL(Navigator *navigator, const char *name) :
	MissionBlock(navigator, name),
	_param_return_alt(this, "RTL_RETURN_ALT", false),
	_param_descend_alt(this, "RTL_DESCEND_ALT", false),
	_param_land_delay(this, "RTL_LAND_DELAY", false),
	_param_rtl_min_dist(this, "RTL_MIN_DIST", false),
	_param_rtl_land_type(this, "RTL_LAND_TYPE", false)
{
}

void
RTL::on_inactive()
{
	// reset RTL state
	_rtl_state = RTL_STATE_NONE;
}

bool
RTL::mission_landing_required()
{
	// returns true if navigator should use planned mission landing
	return (_param_rtl_land_type.get() == 1);
}

void
RTL::on_activation()
{
	if (_navigator->get_land_detected()->landed) {
		// for safety reasons don't go into RTL if landed
		_rtl_state = RTL_STATE_LANDED;

	} else if (mission_landing_required() && _navigator->on_mission_landing()) {
		// RTL straight to RETURN state, but mission will takeover for landing
		_rtl_state = RTL_STATE_RETURN;

	} else if ((_navigator->get_global_position()->alt < _navigator->get_home_position()->alt + _param_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 HOME
	// do nothing, let navigator takeover with mission landing
	if (mission_landing_required()) {
		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 home_position_s &home = *_navigator->get_home_position();
	const vehicle_global_position_s &gpos = *_navigator->get_global_position();

	position_setpoint_triplet_s *pos_sp_triplet = _navigator->get_position_setpoint_triplet();

	switch (_rtl_state) {
	case RTL_STATE_CLIMB: {

			// check if we are pretty close to home already
			const float home_dist = get_distance_to_next_waypoint(home.lat, home.lon, gpos.lat, gpos.lon);

			// if we are close to home we do not climb as high, otherwise we climb to return alt
			float climb_alt = home.alt + _param_return_alt.get();

			// we are close to home, limit climb to min
			if (home_dist < _param_rtl_min_dist.get()) {
				climb_alt = home.alt + _param_descend_alt.get();
			}

			_mission_item.nav_cmd = NAV_CMD_WAYPOINT;
			_mission_item.lat = gpos.lat;
			_mission_item.lon = gpos.lon;
			_mission_item.altitude = climb_alt;
			_mission_item.altitude_is_relative = false;
			_mission_item.yaw = NAN;
			_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 home)",
						     (int)(climb_alt), (int)(climb_alt - _navigator->get_home_position()->alt));
			break;
		}

	case RTL_STATE_RETURN: {

			// don't change altitude
			_mission_item.nav_cmd = NAV_CMD_WAYPOINT;
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.altitude = gpos.alt;
			_mission_item.altitude_is_relative = false;

			// use home yaw if close to home
			/* check if we are pretty close to home already */
			const float home_dist = get_distance_to_next_waypoint(home.lat, home.lon, gpos.lat, gpos.lon);

			if (home_dist < _param_rtl_min_dist.get()) {
				_mission_item.yaw = home.yaw;

			} else {
				// use current heading to home
				_mission_item.yaw = get_bearing_to_next_waypoint(gpos.lat, gpos.lon, home.lat, home.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 home)",
						     (int)(_mission_item.altitude), (int)(_mission_item.altitude - home.alt));

			break;
		}

	case RTL_STATE_TRANSITION_TO_MC: {
			_mission_item.nav_cmd = NAV_CMD_DO_VTOL_TRANSITION;
			_mission_item.params[0] = vtol_vehicle_status_s::VEHICLE_VTOL_STATE_MC;
			break;
		}

	case RTL_STATE_DESCEND: {
			_mission_item.nav_cmd = NAV_CMD_WAYPOINT;
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.altitude = min(home.alt + _param_descend_alt.get(), gpos.alt);
			_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 = home.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 home)",
						     (int)(_mission_item.altitude), (int)(_mission_item.altitude - home.alt));
			break;
		}

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

			// don't change altitude
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.altitude = gpos.alt;
			_mission_item.altitude_is_relative = false;
			_mission_item.yaw = home.yaw;
			_mission_item.loiter_radius = _navigator->get_loiter_radius();
			_mission_item.acceptance_radius = _navigator->get_acceptance_radius();
			_mission_item.time_inside = max(_param_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 home position
			_mission_item.nav_cmd = NAV_CMD_LAND;
			_mission_item.lat = home.lat;
			_mission_item.lon = home.lon;
			_mission_item.yaw = home.yaw;
			_mission_item.altitude = home.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_log_critical(_navigator->get_mavlink_log_pub(), "RTL: land at home");
			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:
		_rtl_state = RTL_STATE_DESCEND;

		if (_navigator->get_vstatus()->is_vtol && !_navigator->get_vstatus()->is_rotary_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_land_delay.get() < -DELAY_SIGMA || _param_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;
	}
}