PX4-Autopilot/src/lib/runway_takeoff/RunwayTakeoff.cpp

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/**
 * @file RunwayTakeoff.cpp
 * Runway takeoff handling for fixed-wing UAVs with steerable wheels.
 *
 * @author Roman Bapst <roman@px4.io>
 * @author Andreas Antener <andreas@uaventure.com>
 */

#include <stdbool.h>
#include <stdint.h>
#include <math.h>

#include "RunwayTakeoff.h"
#include <controllib/blocks.hpp>
#include <controllib/block/BlockParam.hpp>
#include <mavlink/mavlink_log.h>
#include <mathlib/mathlib.h>

namespace runwaytakeoff
{

RunwayTakeoff::RunwayTakeoff() :
	SuperBlock(NULL, "RWTO"),
	_state(),
	_initialized(false),
	_initialized_time(0),
	_init_yaw(0),
	_climbout(false),
	_throttle_ramp_time(2 * 1e6),
	_start_wp(),
	_runway_takeoff_enabled(this, "TKOFF"),
	_heading_mode(this, "HDG"),
	_nav_alt(this, "NAV_ALT"),
	_takeoff_throttle(this, "MAX_THR"),
	_runway_pitch_sp(this, "PSP"),
	_max_takeoff_pitch(this, "MAX_PITCH"),
	_max_takeoff_roll(this, "MAX_ROLL"),
	_min_airspeed_scaling(this, "AIRSPD_SCL"),
	_airspeed_min(this, "FW_AIRSPD_MIN", false),
	_climbout_diff(this, "FW_CLMBOUT_DIFF", false)
{

	updateParams();
}

RunwayTakeoff::~RunwayTakeoff()
{

}

void RunwayTakeoff::init(float yaw, double current_lat, double current_lon)
{
	_init_yaw = yaw;
	_initialized = true;
	_state = RunwayTakeoffState::THROTTLE_RAMP;
	_initialized_time = hrt_absolute_time();
	_climbout = true; // this is true until climbout is finished
	_start_wp(0) = (float)current_lat;
	_start_wp(1) = (float)current_lon;
}

void RunwayTakeoff::update(float airspeed, float alt_agl,
			   double current_lat, double current_lon, int mavlink_fd)
{

	switch (_state) {
	case RunwayTakeoffState::THROTTLE_RAMP:
		if (hrt_elapsed_time(&_initialized_time) > _throttle_ramp_time) {
			_state = RunwayTakeoffState::CLAMPED_TO_RUNWAY;
		}

		break;

	case RunwayTakeoffState::CLAMPED_TO_RUNWAY:
		if (airspeed > _airspeed_min.get() * _min_airspeed_scaling.get()) {
			_state = RunwayTakeoffState::TAKEOFF;
			mavlink_log_info(mavlink_fd, "#Takeoff airspeed reached");
		}

		break;

	case RunwayTakeoffState::TAKEOFF:
		if (alt_agl > _nav_alt.get()) {
			_state = RunwayTakeoffState::CLIMBOUT;

			/*
			 * If we started in heading hold mode, move the navigation start WP to the current location now.
			 * The navigator will take this as starting point to navigate towards the takeoff WP.
			 */
			if (_heading_mode.get() == 0) {
				_start_wp(0) = (float)current_lat;
				_start_wp(1) = (float)current_lon;
			}

			mavlink_log_info(mavlink_fd, "#Climbout");
		}

		break;

	case RunwayTakeoffState::CLIMBOUT:
		if (alt_agl > _climbout_diff.get()) {
			_climbout = false;
			_state = RunwayTakeoffState::FLY;
			mavlink_log_info(mavlink_fd, "#Navigating to waypoint");
		}

		break;

	default:
		break;
	}
}

/*
 * Returns true as long as we're below navigation altitude
 */
bool RunwayTakeoff::controlYaw()
{
	// keep controlling yaw directly until we start navigation
	return _state < RunwayTakeoffState::CLIMBOUT;
}

/*
 * Returns pitch setpoint to use.
 *
 * Limited (parameter) as long as the plane is on runway. Otherwise
 * use the one from TECS
 */
float RunwayTakeoff::getPitch(float tecsPitch)
{
	if (_state <= RunwayTakeoffState::CLAMPED_TO_RUNWAY) {
		return math::radians(_runway_pitch_sp.get());
	}

	return tecsPitch;
}

/*
 * Returns the roll setpoint to use.
 */
float RunwayTakeoff::getRoll(float navigatorRoll)
{
	// until we have enough ground clearance, set roll to 0
	if (_state < RunwayTakeoffState::CLIMBOUT) {
		return 0.0f;
	}

	// allow some roll during climbout
	else if (_state < RunwayTakeoffState::FLY) {
		return math::constrain(navigatorRoll,
				       math::radians(-_max_takeoff_roll.get()),
				       math::radians(_max_takeoff_roll.get()));
	}

	return navigatorRoll;
}

/*
 * Returns the yaw setpoint to use.
 *
 * In heading hold mode (_heading_mode == 0), it returns initial yaw as long as it's on the
 * runway. When it has enough ground clearance we start navigation towards WP.
 */
float RunwayTakeoff::getYaw(float navigatorYaw)
{
	if (_heading_mode.get() == 0 && _state < RunwayTakeoffState::CLIMBOUT) {
		return _init_yaw;

	} else {
		return navigatorYaw;
	}
}

/*
 * Returns the throttle setpoint to use.
 *
 * Ramps up in the beginning, until it lifts off the runway it is set to
 * parameter value, then it returns the TECS throttle.
 */
float RunwayTakeoff::getThrottle(float tecsThrottle)
{
	switch (_state) {
	case RunwayTakeoffState::THROTTLE_RAMP: {
			float throttle = hrt_elapsed_time(&_initialized_time) / (float)_throttle_ramp_time *
					 _takeoff_throttle.get();
			return throttle < _takeoff_throttle.get() ?
			       throttle :
			       _takeoff_throttle.get();
		}

	case RunwayTakeoffState::CLAMPED_TO_RUNWAY:
		return _takeoff_throttle.get();

	default:
		return tecsThrottle;
	}
}

bool RunwayTakeoff::resetIntegrators()
{
	// reset integrators if we're still on runway
	return _state < RunwayTakeoffState::TAKEOFF;
}

/*
 * Returns the minimum pitch for TECS to use.
 *
 * In climbout we either want what was set on the waypoint (sp_min) but at least
 * the climbtout minimum pitch (parameter).
 * Otherwise use the minimum that is enforced generally (parameter).
 */
float RunwayTakeoff::getMinPitch(float sp_min, float climbout_min, float min)
{
	if (_state < RunwayTakeoffState::FLY) {
		return math::max(sp_min, climbout_min);
	}

	else {
		return min;
	}
}

/*
 * Returns the maximum pitch for TECS to use.
 *
 * Limited by parameter (if set) until climbout is done.
 */
float RunwayTakeoff::getMaxPitch(float max)
{
	// use max pitch from parameter if set (> 0.1)
	if (_state < RunwayTakeoffState::FLY && _max_takeoff_pitch.get() > 0.1f) {
		return _max_takeoff_pitch.get();
	}

	else {
		return max;
	}
}

/*
 * Returns the "previous" (start) WP for navigation.
 */
math::Vector<2> RunwayTakeoff::getStartWP()
{
	return _start_wp;
}

void RunwayTakeoff::reset()
{
	_initialized = false;
	_state = RunwayTakeoffState::THROTTLE_RAMP;
}

}