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

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/**
 * @file FixedwingLandDetector.cpp
 *
 * @author Johan Jansen <jnsn.johan@gmail.com>
 * @author Lorenz Meier <lorenz@px4.io>
 * @author Julian Oes <julian@oes.ch>
 */

#include <px4_config.h>
#include <px4_defines.h>
#include <cmath>
#include <drivers/drv_hrt.h>

#include "FixedwingLandDetector.h"


namespace land_detector
{

FixedwingLandDetector::FixedwingLandDetector() :
	_paramHandle(),
	_params(),
	_controlStateSub(-1),
	_armingSub(-1),
	_airspeedSub(-1),
	_controlState{},
	_arming{},
	_airspeed{},
	_velocity_xy_filtered(0.0f),
	_velocity_z_filtered(0.0f),
	_airspeed_filtered(0.0f),
	_accel_horz_lp(0.0f)
{
	_paramHandle.maxVelocity = param_find("LNDFW_VEL_XY_MAX");
	_paramHandle.maxClimbRate = param_find("LNDFW_VEL_Z_MAX");
	_paramHandle.maxAirSpeed = param_find("LNDFW_AIRSPD_MAX");
	_paramHandle.maxIntVelocity = param_find("LNDFW_VELI_MAX");
}

void FixedwingLandDetector::_initialize_topics()
{
	_controlStateSub = orb_subscribe(ORB_ID(control_state));
	_armingSub = orb_subscribe(ORB_ID(actuator_armed));
	_airspeedSub = orb_subscribe(ORB_ID(airspeed));
}

void FixedwingLandDetector::_update_topics()
{
	_orb_update(ORB_ID(control_state), _controlStateSub, &_controlState);
	_orb_update(ORB_ID(actuator_armed), _armingSub, &_arming);
	_orb_update(ORB_ID(airspeed), _airspeedSub, &_airspeed);
}

void FixedwingLandDetector::_update_params()
{
	param_get(_paramHandle.maxVelocity, &_params.maxVelocity);
	param_get(_paramHandle.maxClimbRate, &_params.maxClimbRate);
	param_get(_paramHandle.maxAirSpeed, &_params.maxAirSpeed);
	param_get(_paramHandle.maxIntVelocity, &_params.maxIntVelocity);
}

float FixedwingLandDetector::_get_max_altitude()
{
	// TODO
	// This means no altitude limit as the limit
	// is always current position plus 1000 meters
	return -_controlState.z_pos + 1000;
}

bool FixedwingLandDetector::_get_freefall_state()
{
	// TODO
	return false;
}
bool FixedwingLandDetector::_get_ground_contact_state()
{

	// TODO
	return false;
}

bool FixedwingLandDetector::_get_maybe_landed_state()
{

	// TODO
	return false;
}

bool FixedwingLandDetector::_get_landed_state()
{
	// only trigger flight conditions if we are armed
	if (!_arming.armed) {
		return true;
	}

	bool landDetected = false;

	if (hrt_elapsed_time(&_controlState.timestamp) < 500 * 1000) {
		float val = 0.97f * _velocity_xy_filtered + 0.03f * sqrtf(_controlState.x_vel *
				_controlState.x_vel + _controlState.y_vel * _controlState.y_vel);

		if (PX4_ISFINITE(val)) {
			_velocity_xy_filtered = val;
		}

		val = 0.99f * _velocity_z_filtered + 0.01f * fabsf(_controlState.z_vel);

		if (PX4_ISFINITE(val)) {
			_velocity_z_filtered = val;
		}

		_airspeed_filtered = 0.95f * _airspeed_filtered + 0.05f * _airspeed.true_airspeed_m_s;

		// a leaking lowpass prevents biases from building up, but
		// gives a mostly correct response for short impulses
		_accel_horz_lp = _accel_horz_lp * 0.8f + _controlState.horz_acc_mag * 0.18f;

		// crude land detector for fixedwing
		landDetected = _velocity_xy_filtered < _params.maxVelocity
			       && _velocity_z_filtered < _params.maxClimbRate
			       && _airspeed_filtered < _params.maxAirSpeed
			       && _accel_horz_lp < _params.maxIntVelocity;

	} else {
		// Control state topic has timed out and we need to assume we're landed.
		landDetected = true;
	}

	return landDetected;
}

} // namespace land_detector