PX4-Autopilot/src/modules/mc_pos_control/MulticopterPositionControl.cpp

/****************************************************************************
 *
 *   Copyright (c) 2013-2020 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:
 *
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 *    notice, this list of conditions and the following disclaimer.
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 *    used to endorse or promote products derived from this software
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#include "MulticopterPositionControl.hpp"

#include <float.h>
#include <lib/mathlib/mathlib.h>
#include <lib/matrix/matrix/math.hpp>
#include <px4_platform_common/events.h>
#include "PositionControl/ControlMath.hpp"

using namespace matrix;

MulticopterPositionControl::MulticopterPositionControl(bool vtol) :
	SuperBlock(nullptr, "MPC"),
	ModuleParams(nullptr),
	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::nav_and_controllers),
	_vehicle_attitude_setpoint_pub(vtol ? ORB_ID(mc_virtual_attitude_setpoint) : ORB_ID(vehicle_attitude_setpoint)),
	_vel_x_deriv(this, "VELD"),
	_vel_y_deriv(this, "VELD"),
	_vel_z_deriv(this, "VELD")
{
	parameters_update(true);
	_tilt_limit_slew_rate.setSlewRate(.2f);
	reset_setpoint_to_nan(_setpoint);
	_takeoff_status_pub.advertise();
}

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

bool MulticopterPositionControl::init()
{
	if (!_local_pos_sub.registerCallback()) {
		PX4_ERR("callback registration failed");
		return false;
	}

	_time_stamp_last_loop = hrt_absolute_time();
	ScheduleNow();

	return true;
}

void MulticopterPositionControl::parameters_update(bool force)
{
	// check for parameter updates
	if (_parameter_update_sub.updated() || force) {
		// clear update
		parameter_update_s pupdate;
		_parameter_update_sub.copy(&pupdate);

		// update parameters from storage
		ModuleParams::updateParams();
		SuperBlock::updateParams();

		int num_changed = 0;

		if (_param_sys_vehicle_resp.get() >= 0.f) {
			// make it less sensitive at the lower end
			float responsiveness = _param_sys_vehicle_resp.get() * _param_sys_vehicle_resp.get();

			num_changed += _param_mpc_acc_hor.commit_no_notification(math::lerp(1.f, 15.f, responsiveness));
			num_changed += _param_mpc_acc_hor_max.commit_no_notification(math::lerp(2.f, 15.f, responsiveness));
			num_changed += _param_mpc_man_y_max.commit_no_notification(math::lerp(80.f, 450.f, responsiveness));

			if (responsiveness > 0.6f) {
				num_changed += _param_mpc_man_y_tau.commit_no_notification(0.f);

			} else {
				num_changed += _param_mpc_man_y_tau.commit_no_notification(math::lerp(0.5f, 0.f, responsiveness / 0.6f));
			}

			if (responsiveness < 0.5f) {
				num_changed += _param_mpc_tiltmax_air.commit_no_notification(45.f);

			} else {
				num_changed += _param_mpc_tiltmax_air.commit_no_notification(math::min(MAX_SAFE_TILT_DEG, math::lerp(45.f, 70.f,
						(responsiveness - 0.5f) * 2.f)));
			}

			num_changed += _param_mpc_acc_down_max.commit_no_notification(math::lerp(0.8f, 15.f, responsiveness));
			num_changed += _param_mpc_acc_up_max.commit_no_notification(math::lerp(1.f, 15.f, responsiveness));
			num_changed += _param_mpc_jerk_max.commit_no_notification(math::lerp(2.f, 50.f, responsiveness));
			num_changed += _param_mpc_jerk_auto.commit_no_notification(math::lerp(1.f, 25.f, responsiveness));
		}

		if (_param_mpc_xy_vel_all.get() >= 0.f) {
			float xy_vel = _param_mpc_xy_vel_all.get();
			num_changed += _param_mpc_vel_manual.commit_no_notification(xy_vel);
			num_changed += _param_mpc_xy_cruise.commit_no_notification(xy_vel);
			num_changed += _param_mpc_xy_vel_max.commit_no_notification(xy_vel);
		}

		if (_param_mpc_z_vel_all.get() >= 0.f) {
			float z_vel = _param_mpc_z_vel_all.get();
			num_changed += _param_mpc_z_v_auto_up.commit_no_notification(z_vel);
			num_changed += _param_mpc_z_vel_max_up.commit_no_notification(z_vel);
			num_changed += _param_mpc_z_v_auto_dn.commit_no_notification(z_vel * 0.75f);
			num_changed += _param_mpc_z_vel_max_dn.commit_no_notification(z_vel * 0.75f);
			num_changed += _param_mpc_tko_speed.commit_no_notification(z_vel * 0.6f);
			num_changed += _param_mpc_land_speed.commit_no_notification(z_vel * 0.5f);
		}

		if (num_changed > 0) {
			param_notify_changes();
		}

		if (_param_mpc_tiltmax_air.get() > MAX_SAFE_TILT_DEG) {
			_param_mpc_tiltmax_air.set(MAX_SAFE_TILT_DEG);
			_param_mpc_tiltmax_air.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Tilt constrained to safe value\t");
			/* EVENT
			 * @description <param>MPC_TILTMAX_AIR</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_tilt_set"), events::Log::Warning,
					    "Maximum tilt limit has been constrained to a safe value", MAX_SAFE_TILT_DEG);
		}

		if (_param_mpc_tiltmax_lnd.get() > _param_mpc_tiltmax_air.get()) {
			_param_mpc_tiltmax_lnd.set(_param_mpc_tiltmax_air.get());
			_param_mpc_tiltmax_lnd.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Land tilt has been constrained by max tilt\t");
			/* EVENT
			 * @description <param>MPC_TILTMAX_LND</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_land_tilt_set"), events::Log::Warning,
					    "Land tilt limit has been constrained by maximum tilt", _param_mpc_tiltmax_air.get());
		}

		_control.setPositionGains(Vector3f(_param_mpc_xy_p.get(), _param_mpc_xy_p.get(), _param_mpc_z_p.get()));
		_control.setVelocityGains(
			Vector3f(_param_mpc_xy_vel_p_acc.get(), _param_mpc_xy_vel_p_acc.get(), _param_mpc_z_vel_p_acc.get()),
			Vector3f(_param_mpc_xy_vel_i_acc.get(), _param_mpc_xy_vel_i_acc.get(), _param_mpc_z_vel_i_acc.get()),
			Vector3f(_param_mpc_xy_vel_d_acc.get(), _param_mpc_xy_vel_d_acc.get(), _param_mpc_z_vel_d_acc.get()));
		_control.setHorizontalThrustMargin(_param_mpc_thr_xy_marg.get());

		// Check that the design parameters are inside the absolute maximum constraints
		if (_param_mpc_xy_cruise.get() > _param_mpc_xy_vel_max.get()) {
			_param_mpc_xy_cruise.set(_param_mpc_xy_vel_max.get());
			_param_mpc_xy_cruise.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Cruise speed has been constrained by max speed\t");
			/* EVENT
			 * @description <param>MPC_XY_CRUISE</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_cruise_set"), events::Log::Warning,
					    "Cruise speed has been constrained by maximum speed", _param_mpc_xy_vel_max.get());
		}

		if (_param_mpc_vel_manual.get() > _param_mpc_xy_vel_max.get()) {
			_param_mpc_vel_manual.set(_param_mpc_xy_vel_max.get());
			_param_mpc_vel_manual.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Manual speed has been constrained by max speed\t");
			/* EVENT
			 * @description <param>MPC_VEL_MANUAL</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_man_vel_set"), events::Log::Warning,
					    "Manual speed has been constrained by maximum speed", _param_mpc_xy_vel_max.get());
		}

		if (_param_mpc_z_v_auto_up.get() > _param_mpc_z_vel_max_up.get()) {
			_param_mpc_z_v_auto_up.set(_param_mpc_z_vel_max_up.get());
			_param_mpc_z_v_auto_up.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Ascent speed has been constrained by max speed\t");
			/* EVENT
			 * @description <param>MPC_Z_V_AUTO_UP</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_up_vel_set"), events::Log::Warning,
					    "Ascent speed has been constrained by max speed", _param_mpc_z_vel_max_up.get());
		}

		if (_param_mpc_z_v_auto_dn.get() > _param_mpc_z_vel_max_dn.get()) {
			_param_mpc_z_v_auto_dn.set(_param_mpc_z_vel_max_dn.get());
			_param_mpc_z_v_auto_dn.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Descent speed has been constrained by max speed\t");
			/* EVENT
			 * @description <param>MPC_Z_V_AUTO_DN</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_down_vel_set"), events::Log::Warning,
					    "Descent speed has been constrained by max speed", _param_mpc_z_vel_max_dn.get());
		}

		if (_param_mpc_thr_hover.get() > _param_mpc_thr_max.get() ||
		    _param_mpc_thr_hover.get() < _param_mpc_thr_min.get()) {
			_param_mpc_thr_hover.set(math::constrain(_param_mpc_thr_hover.get(), _param_mpc_thr_min.get(),
						 _param_mpc_thr_max.get()));
			_param_mpc_thr_hover.commit();
			mavlink_log_critical(&_mavlink_log_pub, "Hover thrust has been constrained by min/max\t");
			/* EVENT
			 * @description <param>MPC_THR_HOVER</param> is set to {1:.0}.
			 */
			events::send<float>(events::ID("mc_pos_ctrl_hover_thrust_set"), events::Log::Warning,
					    "Hover thrust has been constrained by min/max thrust", _param_mpc_thr_hover.get());
		}

		if (!_param_mpc_use_hte.get() || !_hover_thrust_initialized) {
			_control.setHoverThrust(_param_mpc_thr_hover.get());
			_hover_thrust_initialized = true;
		}

		// initialize vectors from params and enforce constraints
		_param_mpc_tko_speed.set(math::min(_param_mpc_tko_speed.get(), _param_mpc_z_vel_max_up.get()));
		_param_mpc_land_speed.set(math::min(_param_mpc_land_speed.get(), _param_mpc_z_vel_max_dn.get()));

		_takeoff.setSpoolupTime(_param_mpc_spoolup_time.get());
		_takeoff.setTakeoffRampTime(_param_mpc_tko_ramp_t.get());
		_takeoff.generateInitialRampValue(_param_mpc_z_vel_p_acc.get());
	}
}

PositionControlStates MulticopterPositionControl::set_vehicle_states(const vehicle_local_position_s
		&vehicle_local_position)
{
	PositionControlStates states;

	// only set position states if valid and finite
	if (PX4_ISFINITE(vehicle_local_position.x) && PX4_ISFINITE(vehicle_local_position.y)
	    && vehicle_local_position.xy_valid) {
		states.position(0) = vehicle_local_position.x;
		states.position(1) = vehicle_local_position.y;

	} else {
		states.position(0) = NAN;
		states.position(1) = NAN;
	}

	if (PX4_ISFINITE(vehicle_local_position.z) && vehicle_local_position.z_valid) {
		states.position(2) = vehicle_local_position.z;

	} else {
		states.position(2) = NAN;
	}

	if (PX4_ISFINITE(vehicle_local_position.vx) && PX4_ISFINITE(vehicle_local_position.vy)
	    && vehicle_local_position.v_xy_valid) {
		states.velocity(0) = vehicle_local_position.vx;
		states.velocity(1) = vehicle_local_position.vy;
		states.acceleration(0) = _vel_x_deriv.update(vehicle_local_position.vx);
		states.acceleration(1) = _vel_y_deriv.update(vehicle_local_position.vy);

	} else {
		states.velocity(0) = NAN;
		states.velocity(1) = NAN;
		states.acceleration(0) = NAN;
		states.acceleration(1) = NAN;

		// reset derivatives to prevent acceleration spikes when regaining velocity
		_vel_x_deriv.reset();
		_vel_y_deriv.reset();
	}

	if (PX4_ISFINITE(vehicle_local_position.vz) && vehicle_local_position.v_z_valid) {
		states.velocity(2) = vehicle_local_position.vz;
		states.acceleration(2) = _vel_z_deriv.update(states.velocity(2));

	} else {
		states.velocity(2) = NAN;
		states.acceleration(2) = NAN;

		// reset derivative to prevent acceleration spikes when regaining velocity
		_vel_z_deriv.reset();
	}

	states.yaw = vehicle_local_position.heading;

	return states;
}

void MulticopterPositionControl::Run()
{
	if (should_exit()) {
		_local_pos_sub.unregisterCallback();
		exit_and_cleanup();
		return;
	}

	// reschedule backup
	ScheduleDelayed(100_ms);

	parameters_update(false);

	perf_begin(_cycle_perf);
	vehicle_local_position_s vehicle_local_position;

	if (_local_pos_sub.update(&vehicle_local_position)) {
		const float dt =
			math::constrain(((vehicle_local_position.timestamp_sample - _time_stamp_last_loop) * 1e-6f), 0.002f, 0.04f);
		_time_stamp_last_loop = vehicle_local_position.timestamp_sample;

		// set _dt in controllib Block for BlockDerivative
		setDt(dt);

		if (_vehicle_control_mode_sub.updated()) {
			const bool previous_position_control_enabled = _vehicle_control_mode.flag_multicopter_position_control_enabled;

			if (_vehicle_control_mode_sub.update(&_vehicle_control_mode)) {
				if (!previous_position_control_enabled && _vehicle_control_mode.flag_multicopter_position_control_enabled) {
					_time_position_control_enabled = _vehicle_control_mode.timestamp;

				} else if (previous_position_control_enabled && !_vehicle_control_mode.flag_multicopter_position_control_enabled) {
					// clear existing setpoint when controller is no longer active
					reset_setpoint_to_nan(_setpoint);
				}
			}
		}

		_vehicle_land_detected_sub.update(&_vehicle_land_detected);

		if (_param_mpc_use_hte.get()) {
			hover_thrust_estimate_s hte;

			if (_hover_thrust_estimate_sub.update(&hte)) {
				if (hte.valid) {
					_control.updateHoverThrust(hte.hover_thrust);
				}
			}
		}

		_trajectory_setpoint_sub.update(&_setpoint);

		// adjust existing (or older) setpoint with any EKF reset deltas
		if ((_setpoint.timestamp != 0) && (_setpoint.timestamp < vehicle_local_position.timestamp)) {
			if (vehicle_local_position.vxy_reset_counter != _vxy_reset_counter) {
				_setpoint.vx += vehicle_local_position.delta_vxy[0];
				_setpoint.vy += vehicle_local_position.delta_vxy[1];
			}

			if (vehicle_local_position.vz_reset_counter != _vz_reset_counter) {
				_setpoint.vz += vehicle_local_position.delta_vz;
			}

			if (vehicle_local_position.xy_reset_counter != _xy_reset_counter) {
				_setpoint.x += vehicle_local_position.delta_xy[0];
				_setpoint.y += vehicle_local_position.delta_xy[1];
			}

			if (vehicle_local_position.z_reset_counter != _z_reset_counter) {
				_setpoint.z += vehicle_local_position.delta_z;
			}

			if (vehicle_local_position.heading_reset_counter != _heading_reset_counter) {
				_setpoint.yaw = wrap_pi(_setpoint.yaw + vehicle_local_position.delta_heading);
			}
		}

		if (vehicle_local_position.vxy_reset_counter != _vxy_reset_counter) {
			_vel_x_deriv.reset();
			_vel_y_deriv.reset();
		}

		if (vehicle_local_position.vz_reset_counter != _vz_reset_counter) {
			_vel_z_deriv.reset();
		}

		// save latest reset counters
		_vxy_reset_counter = vehicle_local_position.vxy_reset_counter;
		_vz_reset_counter = vehicle_local_position.vz_reset_counter;
		_xy_reset_counter = vehicle_local_position.xy_reset_counter;
		_z_reset_counter = vehicle_local_position.z_reset_counter;
		_heading_reset_counter = vehicle_local_position.heading_reset_counter;


		PositionControlStates states{set_vehicle_states(vehicle_local_position)};


		if (_vehicle_control_mode.flag_multicopter_position_control_enabled) {
			// set failsafe setpoint if there hasn't been a new
			// trajectory setpoint since position control started
			if ((_setpoint.timestamp < _time_position_control_enabled)
			    && (vehicle_local_position.timestamp_sample > _time_position_control_enabled)) {

				_setpoint = generateFailsafeSetpoint(vehicle_local_position.timestamp_sample, states);
			}
		}

		if (_vehicle_control_mode.flag_multicopter_position_control_enabled
		    && (_setpoint.timestamp >= _time_position_control_enabled)) {

			// update vehicle constraints and handle smooth takeoff
			_vehicle_constraints_sub.update(&_vehicle_constraints);

			// fix to prevent the takeoff ramp to ramp to a too high value or get stuck because of NAN
			// TODO: this should get obsolete once the takeoff limiting moves into the flight tasks
			if (!PX4_ISFINITE(_vehicle_constraints.speed_up) || (_vehicle_constraints.speed_up > _param_mpc_z_vel_max_up.get())) {
				_vehicle_constraints.speed_up = _param_mpc_z_vel_max_up.get();
			}

			if (_vehicle_control_mode.flag_control_offboard_enabled) {

				const bool want_takeoff = _vehicle_control_mode.flag_armed
							  && (vehicle_local_position.timestamp_sample < _setpoint.timestamp + 1_s);

				if (want_takeoff && PX4_ISFINITE(_setpoint.z)
				    && (_setpoint.z < states.position(2))) {

					_vehicle_constraints.want_takeoff = true;

				} else if (want_takeoff && PX4_ISFINITE(_setpoint.vz)
					   && (_setpoint.vz < 0.f)) {

					_vehicle_constraints.want_takeoff = true;

				} else if (want_takeoff && PX4_ISFINITE(_setpoint.acceleration[2])
					   && (_setpoint.acceleration[2] < 0.f)) {

					_vehicle_constraints.want_takeoff = true;

				} else {
					_vehicle_constraints.want_takeoff = false;
				}

				// override with defaults
				_vehicle_constraints.speed_up = _param_mpc_z_vel_max_up.get();
				_vehicle_constraints.speed_down = _param_mpc_z_vel_max_dn.get();
			}

			// handle smooth takeoff
			_takeoff.updateTakeoffState(_vehicle_control_mode.flag_armed, _vehicle_land_detected.landed,
						    _vehicle_constraints.want_takeoff,
						    _vehicle_constraints.speed_up, false, vehicle_local_position.timestamp_sample);

			const bool not_taken_off             = (_takeoff.getTakeoffState() < TakeoffState::rampup);
			const bool flying                    = (_takeoff.getTakeoffState() >= TakeoffState::flight);
			const bool flying_but_ground_contact = (flying && _vehicle_land_detected.ground_contact);

			if (!flying) {
				_control.setHoverThrust(_param_mpc_thr_hover.get());
			}

			// make sure takeoff ramp is not amended by acceleration feed-forward
			if (_takeoff.getTakeoffState() == TakeoffState::rampup) {
				_setpoint.acceleration[2] = NAN;
			}

			if (not_taken_off || flying_but_ground_contact) {
				// we are not flying yet and need to avoid any corrections
				reset_setpoint_to_nan(_setpoint);
				_setpoint.timestamp = vehicle_local_position.timestamp_sample;
				Vector3f(0.f, 0.f, 100.f).copyTo(_setpoint.acceleration); // High downwards acceleration to make sure there's no thrust

				// prevent any integrator windup
				_control.resetIntegral();
			}

			// limit tilt during takeoff ramupup
			const float tilt_limit_deg = (_takeoff.getTakeoffState() < TakeoffState::flight)
						     ? _param_mpc_tiltmax_lnd.get() : _param_mpc_tiltmax_air.get();
			_control.setTiltLimit(_tilt_limit_slew_rate.update(math::radians(tilt_limit_deg), dt));

			const float speed_up = _takeoff.updateRamp(dt,
					       PX4_ISFINITE(_vehicle_constraints.speed_up) ? _vehicle_constraints.speed_up : _param_mpc_z_vel_max_up.get());
			const float speed_down = PX4_ISFINITE(_vehicle_constraints.speed_down) ? _vehicle_constraints.speed_down :
						 _param_mpc_z_vel_max_dn.get();

			// Allow ramping from zero thrust on takeoff
			const float minimum_thrust = flying ? _param_mpc_thr_min.get() : 0.f;

			_control.setThrustLimits(minimum_thrust, _param_mpc_thr_max.get());

			_control.setVelocityLimits(
				_param_mpc_xy_vel_max.get(),
				math::min(speed_up, _param_mpc_z_vel_max_up.get()), // takeoff ramp starts with negative velocity limit
				math::max(speed_down, 0.f));

			_control.setInputSetpoint(_setpoint);

			// update states
			if (!PX4_ISFINITE(_setpoint.z)
			    && PX4_ISFINITE(_setpoint.vz) && (fabsf(_setpoint.vz) > FLT_EPSILON)
			    && PX4_ISFINITE(vehicle_local_position.z_deriv) && vehicle_local_position.z_valid && vehicle_local_position.v_z_valid) {
				// A change in velocity is demanded and the altitude is not controlled.
				// Set velocity to the derivative of position
				// because it has less bias but blend it in across the landing speed range
				//  <  MPC_LAND_SPEED: ramp up using altitude derivative without a step
				//  >= MPC_LAND_SPEED: use altitude derivative
				float weighting = fminf(fabsf(_setpoint.vz) / _param_mpc_land_speed.get(), 1.f);
				states.velocity(2) = vehicle_local_position.z_deriv * weighting + vehicle_local_position.vz * (1.f - weighting);
			}

			_control.setState(states);

			// Run position control
			if (!_control.update(dt)) {
				// Failsafe
				_vehicle_constraints = {0, NAN, NAN, false, {}}; // reset constraints

				_control.setInputSetpoint(generateFailsafeSetpoint(vehicle_local_position.timestamp_sample, states));
				_control.setVelocityLimits(_param_mpc_xy_vel_max.get(), _param_mpc_z_vel_max_up.get(), _param_mpc_z_vel_max_dn.get());
				_control.update(dt);
			}

			// Publish internal position control setpoints
			// on top of the input/feed-forward setpoints these containt the PID corrections
			// This message is used by other modules (such as Landdetector) to determine vehicle intention.
			vehicle_local_position_setpoint_s local_pos_sp{};
			_control.getLocalPositionSetpoint(local_pos_sp);
			local_pos_sp.timestamp = hrt_absolute_time();
			_local_pos_sp_pub.publish(local_pos_sp);

			// Publish attitude setpoint output
			vehicle_attitude_setpoint_s attitude_setpoint{};
			_control.getAttitudeSetpoint(attitude_setpoint);
			attitude_setpoint.timestamp = hrt_absolute_time();
			_vehicle_attitude_setpoint_pub.publish(attitude_setpoint);

		} else {
			// an update is necessary here because otherwise the takeoff state doesn't get skipped with non-altitude-controlled modes
			_takeoff.updateTakeoffState(_vehicle_control_mode.flag_armed, _vehicle_land_detected.landed, false, 10.f, true,
						    vehicle_local_position.timestamp_sample);
		}

		// Publish takeoff status
		const uint8_t takeoff_state = static_cast<uint8_t>(_takeoff.getTakeoffState());

		if (takeoff_state != _takeoff_status_pub.get().takeoff_state
		    || !isEqualF(_tilt_limit_slew_rate.getState(), _takeoff_status_pub.get().tilt_limit)) {
			_takeoff_status_pub.get().takeoff_state = takeoff_state;
			_takeoff_status_pub.get().tilt_limit = _tilt_limit_slew_rate.getState();
			_takeoff_status_pub.get().timestamp = hrt_absolute_time();
			_takeoff_status_pub.update();
		}
	}

	perf_end(_cycle_perf);
}

vehicle_local_position_setpoint_s MulticopterPositionControl::generateFailsafeSetpoint(const hrt_abstime &now,
		const PositionControlStates &states)
{
	// do not warn while we are disarmed, as we might not have valid setpoints yet
	bool warn = _vehicle_control_mode.flag_armed && ((now - _last_warn) > 2_s);

	if (warn) {
		PX4_WARN("invalid setpoints");
		_last_warn = now;
	}

	vehicle_local_position_setpoint_s failsafe_setpoint{};
	reset_setpoint_to_nan(failsafe_setpoint);
	failsafe_setpoint.timestamp = now;

	if (PX4_ISFINITE(states.velocity(0)) && PX4_ISFINITE(states.velocity(1))) {
		// don't move along xy
		failsafe_setpoint.vx = failsafe_setpoint.vy = 0.f;

		if (warn) {
			PX4_WARN("Failsafe: stop and wait");
		}

	} else {
		// descend with land speed since we can't stop
		failsafe_setpoint.acceleration[0] = failsafe_setpoint.acceleration[1] = 0.f;
		failsafe_setpoint.vz = _param_mpc_land_speed.get();

		if (warn) {
			PX4_WARN("Failsafe: blind land");
		}
	}

	if (PX4_ISFINITE(states.velocity(2))) {
		// don't move along z if we can stop in all dimensions
		if (!PX4_ISFINITE(failsafe_setpoint.vz)) {
			failsafe_setpoint.vz = 0.f;
		}

	} else {
		// emergency descend with a bit below hover thrust
		failsafe_setpoint.vz = NAN;
		failsafe_setpoint.acceleration[2] = .3f;

		if (warn) {
			PX4_WARN("Failsafe: blind descent");
		}
	}

	return failsafe_setpoint;
}

void MulticopterPositionControl::reset_setpoint_to_nan(vehicle_local_position_setpoint_s &setpoint)
{
	setpoint.timestamp = 0;
	setpoint.x = setpoint.y = setpoint.z = NAN;
	setpoint.yaw = setpoint.yawspeed = NAN;
	setpoint.vx = setpoint.vy = setpoint.vz = NAN;
	setpoint.acceleration[0] = setpoint.acceleration[1] = setpoint.acceleration[2] = NAN;
	setpoint.thrust[0] = setpoint.thrust[1] = setpoint.thrust[2] = NAN;
}

int MulticopterPositionControl::task_spawn(int argc, char *argv[])
{
	bool vtol = false;

	if (argc > 1) {
		if (strcmp(argv[1], "vtol") == 0) {
			vtol = true;
		}
	}

	MulticopterPositionControl *instance = new MulticopterPositionControl(vtol);

	if (instance) {
		_object.store(instance);
		_task_id = task_id_is_work_queue;

		if (instance->init()) {
			return PX4_OK;
		}

	} else {
		PX4_ERR("alloc failed");
	}

	delete instance;
	_object.store(nullptr);
	_task_id = -1;

	return PX4_ERROR;
}

int MulticopterPositionControl::custom_command(int argc, char *argv[])
{
	return print_usage("unknown command");
}

int MulticopterPositionControl::print_usage(const char *reason)
{
	if (reason) {
		PX4_WARN("%s\n", reason);
	}

	PRINT_MODULE_DESCRIPTION(
		R"DESCR_STR(
### Description
The controller has two loops: a P loop for position error and a PID loop for velocity error.
Output of the velocity controller is thrust vector that is split to thrust direction
(i.e. rotation matrix for multicopter orientation) and thrust scalar (i.e. multicopter thrust itself).

The controller doesn't use Euler angles for its work, they are generated only for more human-friendly control and
logging.
)DESCR_STR");

	PRINT_MODULE_USAGE_NAME("mc_pos_control", "controller");
	PRINT_MODULE_USAGE_COMMAND("start");
	PRINT_MODULE_USAGE_ARG("vtol", "VTOL mode", true);
	PRINT_MODULE_USAGE_DEFAULT_COMMANDS();

	return 0;
}

extern "C" __EXPORT int mc_pos_control_main(int argc, char *argv[])
{
	return MulticopterPositionControl::main(argc, argv);
}