PX4-Autopilot/src/modules/land_detector/LandDetector.cpp

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/*
 * @file LandDetector.cpp
 *
 * @author Johan Jansen <jnsn.johan@gmail.com>
 * @author Julian Oes <julian@oes.ch>
 */

#include "LandDetector.h"

using namespace time_literals;

namespace land_detector
{

LandDetector::LandDetector() :
	ModuleParams(nullptr),
	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::nav_and_controllers)
{
	_land_detected.ground_contact = true;
	_land_detected.maybe_landed = true;
	_land_detected.landed = true;
	_land_detected.in_ground_effect = true;
	_land_detected.in_descend = false;
	_land_detected.has_low_throttle = false;
	_land_detected.vertical_movement = false;
	_land_detected.horizontal_movement = false;
	_land_detected.close_to_ground_or_skipped_check = true;
	_land_detected.at_rest = true;
}

LandDetector::~LandDetector()
{
	perf_free(_cycle_perf);
}

void LandDetector::start()
{
	ScheduleDelayed(50_ms);
	_vehicle_local_position_sub.registerCallback();
}

void LandDetector::Run()
{
	// push backup schedule
	ScheduleDelayed(50_ms);

	perf_begin(_cycle_perf);

	if (_parameter_update_sub.updated() || (_land_detected.timestamp == 0)) {
		parameter_update_s param_update;
		_parameter_update_sub.copy(&param_update);

		updateParams();
		_update_params();

		_total_flight_time = static_cast<uint64_t>(_param_total_flight_time_high.get()) << 32;
		_total_flight_time |= static_cast<uint32_t>(_param_total_flight_time_low.get());
	}

	actuator_armed_s actuator_armed;

	if (_actuator_armed_sub.update(&actuator_armed)) {
		_armed = actuator_armed.armed;
	}

	vehicle_acceleration_s vehicle_acceleration;

	if (_vehicle_acceleration_sub.update(&vehicle_acceleration)) {
		_acceleration = matrix::Vector3f{vehicle_acceleration.xyz};
	}

	vehicle_angular_velocity_s vehicle_angular_velocity{};

	if (_vehicle_angular_velocity_sub.update(&vehicle_angular_velocity)) {
		_angular_velocity = matrix::Vector3f{vehicle_angular_velocity.xyz};

		static constexpr float GYRO_NORM_MAX = math::radians(3.f); // 3 degrees/second

		if (_angular_velocity.norm() > GYRO_NORM_MAX) {
			_time_last_move_detect_us = vehicle_angular_velocity.timestamp_sample;
		}
	}

	_vehicle_local_position_sub.update(&_vehicle_local_position);
	_vehicle_status_sub.update(&_vehicle_status);

	_update_topics();

	if (!_dist_bottom_is_observable) {
		// we consider the distance to the ground observable if the system is using a range sensor
		_dist_bottom_is_observable = _vehicle_local_position.dist_bottom_sensor_bitfield &
					     vehicle_local_position_s::DIST_BOTTOM_SENSOR_RANGE;
	}

	// Increase land detection time if not close to ground
	if (_dist_bottom_is_observable && !_vehicle_local_position.dist_bottom_valid) {
		_set_hysteresis_factor(3);

	} else {
		_set_hysteresis_factor(1);
	}

	const hrt_abstime now_us = hrt_absolute_time();

	_freefall_hysteresis.set_state_and_update(_get_freefall_state(), now_us);
	_ground_contact_hysteresis.set_state_and_update(_get_ground_contact_state(), now_us);
	_maybe_landed_hysteresis.set_state_and_update(_get_maybe_landed_state(), now_us);
	_landed_hysteresis.set_state_and_update(_get_landed_state(), now_us);
	_ground_effect_hysteresis.set_state_and_update(_get_ground_effect_state(), now_us);

	const bool freefallDetected = _freefall_hysteresis.get_state();
	const bool ground_contactDetected = _ground_contact_hysteresis.get_state();
	const bool maybe_landedDetected = _maybe_landed_hysteresis.get_state();
	const bool landDetected = _landed_hysteresis.get_state();
	const bool in_ground_effect = _ground_effect_hysteresis.get_state();

	UpdateVehicleAtRest();

	const bool at_rest = landDetected && _at_rest;

	// publish at 1 Hz, very first time, or when the result has changed
	if ((hrt_elapsed_time(&_land_detected.timestamp) >= 1_s) ||
	    (_land_detected.landed != landDetected) ||
	    (_land_detected.freefall != freefallDetected) ||
	    (_land_detected.maybe_landed != maybe_landedDetected) ||
	    (_land_detected.ground_contact != ground_contactDetected) ||
	    (_land_detected.in_ground_effect != in_ground_effect) ||
	    (_land_detected.at_rest != at_rest)) {

		if (!landDetected && _land_detected.landed && _takeoff_time == 0) { /* only set take off time once, until disarming */
			// We did take off
			_takeoff_time = now_us;
		}

		_land_detected.landed = landDetected;
		_land_detected.freefall = freefallDetected;
		_land_detected.maybe_landed = maybe_landedDetected;
		_land_detected.ground_contact = ground_contactDetected;
		_land_detected.in_ground_effect = in_ground_effect;
		_land_detected.in_descend = _get_in_descend();
		_land_detected.has_low_throttle = _get_has_low_throttle();
		_land_detected.horizontal_movement = _get_horizontal_movement();
		_land_detected.vertical_movement = _get_vertical_movement();
		_land_detected.close_to_ground_or_skipped_check = _get_close_to_ground_or_skipped_check();
		_land_detected.at_rest = at_rest;
		_land_detected.timestamp = hrt_absolute_time();
		_vehicle_land_detected_pub.publish(_land_detected);
	}

	// set the flight time when disarming (not necessarily when landed, because all param changes should
	// happen on the same event and it's better to set/save params while not in armed state)
	if (_takeoff_time != 0 && !_armed && _previous_armed_state) {
		_total_flight_time += now_us - _takeoff_time;
		_takeoff_time = 0;

		uint32_t flight_time = (_total_flight_time >> 32) & 0xffffffff;

		_param_total_flight_time_high.set(flight_time);
		_param_total_flight_time_high.commit_no_notification();

		flight_time = _total_flight_time & 0xffffffff;

		_param_total_flight_time_low.set(flight_time);
		_param_total_flight_time_low.commit_no_notification();
	}

	_previous_armed_state = _armed;

	perf_end(_cycle_perf);

	if (should_exit()) {
		ScheduleClear();
		exit_and_cleanup();
	}
}

void LandDetector::UpdateVehicleAtRest()
{
	if (_sensor_selection_sub.updated()) {
		sensor_selection_s sensor_selection{};
		_sensor_selection_sub.copy(&sensor_selection);

		if (sensor_selection.gyro_device_id != _device_id_gyro) {

			bool gyro_status_found = false;

			// find corresponding vehicle_imu_status instance
			for (uint8_t imu_instance = 0; imu_instance < 4; imu_instance++) {
				uORB::Subscription imu_status_sub{ORB_ID(vehicle_imu_status), imu_instance};

				vehicle_imu_status_s imu_status{};
				imu_status_sub.copy(&imu_status);

				if ((imu_status.gyro_device_id != 0) && (imu_status.gyro_device_id == sensor_selection.gyro_device_id)) {
					_vehicle_imu_status_sub.ChangeInstance(imu_instance);
					_device_id_gyro = sensor_selection.gyro_device_id;
					gyro_status_found = true;
					break;
				}
			}

			if (!gyro_status_found) {
				PX4_WARN("IMU status not found for gyro %" PRId32, sensor_selection.gyro_device_id);
			}
		}
	}

	vehicle_imu_status_s imu_status;

	if (_vehicle_imu_status_sub.update(&imu_status)) {
		static constexpr float GYRO_VIBE_METRIC_MAX = 0.02f; // gyro_vibration_metric * dt * 4.0e4f > is_moving_scaler)
		static constexpr float ACCEL_VIBE_METRIC_MAX = 1.2f; // accel_vibration_metric * dt * 2.1e2f > is_moving_scaler

		if ((imu_status.gyro_vibration_metric > GYRO_VIBE_METRIC_MAX)
		    || (imu_status.accel_vibration_metric > ACCEL_VIBE_METRIC_MAX)) {

			_time_last_move_detect_us = imu_status.timestamp;
		}
	}

	_at_rest = (hrt_elapsed_time(&_time_last_move_detect_us) > 1_s);
}

} // namespace land_detector