FixedwingRateControl.cpp

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#include "FixedwingRateControl.hpp"

using namespace time_literals;
using namespace matrix;

using math::constrain;
using math::interpolate;
using math::radians;

FixedwingRateControl::FixedwingRateControl(bool vtol) :
	ModuleParams(nullptr),
	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::nav_and_controllers),
	_actuator_controls_status_pub(vtol ? ORB_ID(actuator_controls_status_1) : ORB_ID(actuator_controls_status_0)),
	_vehicle_torque_setpoint_pub(vtol ? ORB_ID(vehicle_torque_setpoint_virtual_fw) : ORB_ID(vehicle_torque_setpoint)),
	_vehicle_thrust_setpoint_pub(vtol ? ORB_ID(vehicle_thrust_setpoint_virtual_fw) : ORB_ID(vehicle_thrust_setpoint)),
	_loop_perf(perf_alloc(PC_ELAPSED, MODULE_NAME": cycle"))
{
	_handle_param_vt_fw_difthr_en = param_find("VT_FW_DIFTHR_EN");

	/* fetch initial parameter values */
	parameters_update();

	_rate_ctrl_status_pub.advertise();
}

FixedwingRateControl::~FixedwingRateControl()
{
	perf_free(_loop_perf);
}

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

	return true;
}

int
FixedwingRateControl::parameters_update()
{
	const Vector3f rate_p = Vector3f(_param_fw_rr_p.get(), _param_fw_pr_p.get(), _param_fw_yr_p.get());
	const Vector3f rate_i = Vector3f(_param_fw_rr_i.get(), _param_fw_pr_i.get(), _param_fw_yr_i.get());
	const Vector3f rate_d = Vector3f(_param_fw_rr_d.get(), _param_fw_pr_d.get(), _param_fw_yr_d.get());

	_rate_control.setGains(rate_p, rate_i, rate_d);

	_rate_control.setIntegratorLimit(
		Vector3f(_param_fw_rr_imax.get(), _param_fw_pr_imax.get(), _param_fw_yr_imax.get()));

	_rate_control.setFeedForwardGain(
		// set FF gains to 0 as we add the FF control outside of the rate controller
		Vector3f(0.f, 0.f, 0.f));

	if (_handle_param_vt_fw_difthr_en != PARAM_INVALID) {
		param_get(_handle_param_vt_fw_difthr_en, &_param_vt_fw_difthr_en);
	}


	return PX4_OK;
}

void
FixedwingRateControl::vehicle_manual_poll()
{
	if (_vcontrol_mode.flag_control_manual_enabled && _in_fw_or_transition_wo_tailsitter_transition) {

		// Always copy the new manual setpoint, even if it wasn't updated, to fill the actuators with valid values
		if (_manual_control_setpoint_sub.copy(&_manual_control_setpoint)) {

			if (_vcontrol_mode.flag_control_rates_enabled &&
			    !_vcontrol_mode.flag_control_attitude_enabled) {

				// RATE mode we need to generate the rate setpoint from manual user inputs

				if (_vehicle_status.is_vtol_tailsitter && _vehicle_status.vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING) {
					// the rate_sp must always be published in body (hover) frame
					_rates_sp.roll = _manual_control_setpoint.yaw * radians(_param_fw_acro_z_max.get());
					_rates_sp.yaw = -_manual_control_setpoint.roll * radians(_param_fw_acro_x_max.get());

				} else {
					_rates_sp.roll = _manual_control_setpoint.roll * radians(_param_fw_acro_x_max.get());
					_rates_sp.yaw = _manual_control_setpoint.yaw * radians(_param_fw_acro_z_max.get());
				}

				_rates_sp.timestamp = hrt_absolute_time();
				_rates_sp.pitch = -_manual_control_setpoint.pitch * radians(_param_fw_acro_y_max.get());
				_rates_sp.thrust_body[0] = (_manual_control_setpoint.throttle + 1.f) * .5f;

				_rate_sp_pub.publish(_rates_sp);

			} else {
				// Manual/direct control, filled in FW-frame. Note that setpoints will get transformed to body frame prior publishing.

				_vehicle_torque_setpoint.xyz[0] = math::constrain(_manual_control_setpoint.roll * _param_fw_man_r_sc.get() +
								  _param_trim_roll.get(), -1.f, 1.f);
				_vehicle_torque_setpoint.xyz[1] = math::constrain(-_manual_control_setpoint.pitch * _param_fw_man_p_sc.get() +
								  _param_trim_pitch.get(), -1.f, 1.f);
				_vehicle_torque_setpoint.xyz[2] = math::constrain(_manual_control_setpoint.yaw * _param_fw_man_y_sc.get() +
								  _param_trim_yaw.get(), -1.f, 1.f);

				_vehicle_thrust_setpoint.xyz[0] = math::constrain((_manual_control_setpoint.throttle + 1.f) * .5f, 0.f, 1.f);
			}
		}
	}
}

void
FixedwingRateControl::vehicle_land_detected_poll()
{
	if (_vehicle_land_detected_sub.updated()) {
		vehicle_land_detected_s vehicle_land_detected {};

		if (_vehicle_land_detected_sub.copy(&vehicle_land_detected)) {
			_landed = vehicle_land_detected.landed;
		}
	}
}

float FixedwingRateControl::get_airspeed_and_update_scaling()
{
	_airspeed_validated_sub.update();
	const bool airspeed_valid = PX4_ISFINITE(_airspeed_validated_sub.get().calibrated_airspeed_m_s)
				    && (hrt_elapsed_time(&_airspeed_validated_sub.get().timestamp) < 1_s);

	// if no airspeed measurement is available out best guess is to use the trim airspeed
	float airspeed = _param_fw_airspd_trim.get();

	if ((_param_fw_arsp_mode.get() == 0) && airspeed_valid) {
		/* prevent numerical drama by requiring 0.5 m/s minimal speed */
		airspeed = math::max(0.5f, _airspeed_validated_sub.get().calibrated_airspeed_m_s);

	} else {
		// VTOL: if we have no airspeed available and we are in hover mode then assume the lowest airspeed possible
		// this assumption is good as long as the vehicle is not hovering in a headwind which is much larger
		// than the stall airspeed
		if (_vehicle_status.is_vtol && _vehicle_status.vehicle_type == vehicle_status_s::VEHICLE_TYPE_ROTARY_WING
		    && !_vehicle_status.in_transition_mode) {
			airspeed = _param_fw_airspd_stall.get();
		}
	}

	/*
	 * For scaling our actuators using anything less than the stall
	 * speed doesn't make any sense - its the strongest reasonable deflection we
	 * want to do in flight and it's the baseline a human pilot would choose.
	 *
	 * Forcing the scaling to this value allows reasonable handheld tests.
	 */
	const float airspeed_constrained = constrain(constrain(airspeed, _param_fw_airspd_stall.get(),
					   _param_fw_airspd_max.get()), 0.1f, 1000.0f);

	_airspeed_scaling = (_param_fw_arsp_scale_en.get()) ? (_param_fw_airspd_trim.get() / airspeed_constrained) : 1.0f;

	return airspeed;
}

void FixedwingRateControl::Run()
{
	if (should_exit()) {
		_vehicle_angular_velocity_sub.unregisterCallback();
		exit_and_cleanup();
		return;
	}

	perf_begin(_loop_perf);

	// only run controller if angular velocity changed
	if (_vehicle_angular_velocity_sub.updated() || (hrt_elapsed_time(&_last_run) > 20_ms)) { //TODO rate!

		// only update parameters if they changed
		bool params_updated = _parameter_update_sub.updated();

		// check for parameter updates
		if (params_updated) {
			// clear update
			parameter_update_s pupdate;
			_parameter_update_sub.copy(&pupdate);

			// update parameters from storage
			updateParams();
			parameters_update();
		}

		float dt = 0.f;

		static constexpr float DT_MIN = 0.002f;
		static constexpr float DT_MAX = 0.04f;

		vehicle_angular_velocity_s vehicle_angular_velocity{};

		if (_vehicle_angular_velocity_sub.copy(&vehicle_angular_velocity)) {
			dt = math::constrain((vehicle_angular_velocity.timestamp_sample - _last_run) * 1e-6f, DT_MIN, DT_MAX);
			_last_run = vehicle_angular_velocity.timestamp_sample;
		}

		if (dt < DT_MIN || dt > DT_MAX) {
			const hrt_abstime time_now_us = hrt_absolute_time();
			dt = math::constrain((time_now_us - _last_run) * 1e-6f, DT_MIN, DT_MAX);
			_last_run = time_now_us;
		}

		vehicle_angular_velocity_s angular_velocity{};
		_vehicle_angular_velocity_sub.copy(&angular_velocity);

		Vector3f rates(angular_velocity.xyz);
		Vector3f angular_accel{angular_velocity.xyz_derivative};

		// Tailsitter: rotate setpoint from hover to fixed-wing frame (controller is in fixed-wing frame, interface in hover)
		if (_vehicle_status.is_vtol_tailsitter) {
			rates = Vector3f(-angular_velocity.xyz[2], angular_velocity.xyz[1], angular_velocity.xyz[0]);
			angular_accel = Vector3f(-angular_velocity.xyz_derivative[2], angular_velocity.xyz_derivative[1],
						 angular_velocity.xyz_derivative[0]);
		}

		// vehicle status update must be before the vehicle_control_mode poll, otherwise rate sp are not published during whole transition
		_vehicle_status_sub.update(&_vehicle_status);
		const bool is_in_transition_except_tailsitter = _vehicle_status.in_transition_mode
				&& !_vehicle_status.is_vtol_tailsitter;
		const bool is_fixed_wing = _vehicle_status.vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING;
		_in_fw_or_transition_wo_tailsitter_transition =  is_fixed_wing || is_in_transition_except_tailsitter;

		_vehicle_control_mode_sub.update(&_vcontrol_mode);

		vehicle_land_detected_poll();

		vehicle_manual_poll();
		vehicle_land_detected_poll();

		/* if we are in rotary wing mode, do nothing */
		if (_vehicle_status.vehicle_type == vehicle_status_s::VEHICLE_TYPE_ROTARY_WING && !_vehicle_status.is_vtol) {
			perf_end(_loop_perf);
			return;
		}

		if (_vcontrol_mode.flag_control_rates_enabled) {

			const float airspeed = get_airspeed_and_update_scaling();

			/* reset integrals where needed */
			if (_rates_sp.reset_integral) {
				_rate_control.resetIntegral();
			}

			// Reset integrators if the aircraft is on ground or not in a state where the fw attitude controller is run
			if (_landed || !_in_fw_or_transition_wo_tailsitter_transition) {

				_rate_control.resetIntegral();
			}

			// Update saturation status from control allocation feedback
			// TODO: send the unallocated value directly for better anti-windup
			Vector3<bool> diffthr_enabled(
				_param_vt_fw_difthr_en & static_cast<int32_t>(VTOLFixedWingDifferentialThrustEnabledBit::ROLL_BIT),
				_param_vt_fw_difthr_en & static_cast<int32_t>(VTOLFixedWingDifferentialThrustEnabledBit::PITCH_BIT),
				_param_vt_fw_difthr_en & static_cast<int32_t>(VTOLFixedWingDifferentialThrustEnabledBit::YAW_BIT)
			);

			if (_vehicle_status.is_vtol_tailsitter) {
				// Swap roll and yaw
				diffthr_enabled.swapRows(0, 2);
			}

			// saturation handling for axis controlled by differential thrust (VTOL only)
			control_allocator_status_s control_allocator_status;

			// Set saturation flags for VTOL differential thrust feature
			// If differential thrust is enabled in an axis, assume it's the only torque authority and only update saturation using matrix 0 allocating the motors.
			if (_control_allocator_status_subs[0].update(&control_allocator_status)) {
				for (size_t i = 0; i < 3; i++) {
					if (diffthr_enabled(i)) {
						_rate_control.setPositiveSaturationFlag(i, control_allocator_status.unallocated_torque[i] > FLT_EPSILON);
						_rate_control.setNegativeSaturationFlag(i, control_allocator_status.unallocated_torque[i] < -FLT_EPSILON);
					}
				}
			}

			// Set saturation flags for control surface controlled axes
			if (_control_allocator_status_subs[_vehicle_status.is_vtol ? 1 : 0].update(&control_allocator_status)) {
				for (size_t i = 0; i < 3; i++) {
					if (!diffthr_enabled(i)) {
						_rate_control.setPositiveSaturationFlag(i, control_allocator_status.unallocated_torque[i] > FLT_EPSILON);
						_rate_control.setNegativeSaturationFlag(i, control_allocator_status.unallocated_torque[i] < -FLT_EPSILON);
					}
				}
			}

			/* bi-linear interpolation over airspeed for actuator trim scheduling */
			float trim_roll = _param_trim_roll.get();
			float trim_pitch = _param_trim_pitch.get();
			float trim_yaw = _param_trim_yaw.get();

			if (airspeed < _param_fw_airspd_trim.get()) {
				trim_roll += interpolate(airspeed, _param_fw_airspd_min.get(), _param_fw_airspd_trim.get(),
							 _param_fw_dtrim_r_vmin.get(),
							 0.0f);
				trim_pitch += interpolate(airspeed, _param_fw_airspd_min.get(), _param_fw_airspd_trim.get(),
							  _param_fw_dtrim_p_vmin.get(),
							  0.0f);
				trim_yaw += interpolate(airspeed, _param_fw_airspd_min.get(), _param_fw_airspd_trim.get(),
							_param_fw_dtrim_y_vmin.get(),
							0.0f);

			} else {
				trim_roll += interpolate(airspeed, _param_fw_airspd_trim.get(), _param_fw_airspd_max.get(), 0.0f,
							 _param_fw_dtrim_r_vmax.get());
				trim_pitch += interpolate(airspeed, _param_fw_airspd_trim.get(), _param_fw_airspd_max.get(), 0.0f,
							  _param_fw_dtrim_p_vmax.get());
				trim_yaw += interpolate(airspeed, _param_fw_airspd_trim.get(), _param_fw_airspd_max.get(), 0.0f,
							_param_fw_dtrim_y_vmax.get());
			}

			if (_vcontrol_mode.flag_control_rates_enabled) {
				_rates_sp_sub.update(&_rates_sp);

				Vector3f body_rates_setpoint = Vector3f(_rates_sp.roll, _rates_sp.pitch, _rates_sp.yaw);

				// Tailsitter: rotate setpoint from hover to fixed-wing frame (controller is in fixed-wing frame, interface in hover)
				if (_vehicle_status.is_vtol_tailsitter) {
					body_rates_setpoint = Vector3f(-_rates_sp.yaw, _rates_sp.pitch, _rates_sp.roll);
				}

				/* Run attitude RATE controllers which need the desired attitudes from above, add trim */
				const Vector3f angular_acceleration_setpoint = _rate_control.update(rates, body_rates_setpoint, angular_accel, dt,
						_landed);

				float roll_feedforward = _param_fw_rr_ff.get() * _airspeed_scaling * body_rates_setpoint(0);
				float roll_u = angular_acceleration_setpoint(0) * _airspeed_scaling * _airspeed_scaling + roll_feedforward;
				_vehicle_torque_setpoint.xyz[0] = PX4_ISFINITE(roll_u) ? math::constrain(roll_u + trim_roll, -1.f, 1.f) : trim_roll;

				float pitch_feedforward = _param_fw_pr_ff.get() * _airspeed_scaling * body_rates_setpoint(1);
				float pitch_u = angular_acceleration_setpoint(1) * _airspeed_scaling * _airspeed_scaling + pitch_feedforward;
				_vehicle_torque_setpoint.xyz[1] = PX4_ISFINITE(pitch_u) ? math::constrain(pitch_u + trim_pitch, -1.f, 1.f) : trim_pitch;

				const float yaw_feedforward = _param_fw_yr_ff.get() * _airspeed_scaling * body_rates_setpoint(2);
				float yaw_u = angular_acceleration_setpoint(2) * _airspeed_scaling * _airspeed_scaling + yaw_feedforward;

				_vehicle_torque_setpoint.xyz[2] = PX4_ISFINITE(yaw_u) ? math::constrain(yaw_u + trim_yaw, -1.f, 1.f) : trim_yaw;

				if (!PX4_ISFINITE(roll_u) || !PX4_ISFINITE(pitch_u) || !PX4_ISFINITE(yaw_u)) {
					_rate_control.resetIntegral();
				}

				/* throttle passed through if it is finite */
				_vehicle_thrust_setpoint.xyz[0] = PX4_ISFINITE(_rates_sp.thrust_body[0]) ? _rates_sp.thrust_body[0] : 0.0f;

				/* scale effort by battery status */
				if (_param_fw_bat_scale_en.get() && _vehicle_thrust_setpoint.xyz[0] > 0.1f) {

					if (_battery_status_sub.updated()) {
						battery_status_s battery_status{};

						if (_battery_status_sub.copy(&battery_status) && battery_status.connected && battery_status.scale > 0.f) {
							_battery_scale = battery_status.scale;
						}
					}

					_vehicle_thrust_setpoint.xyz[0] *= _battery_scale;
				}
			}

			// publish rate controller status
			rate_ctrl_status_s rate_ctrl_status{};
			_rate_control.getRateControlStatus(rate_ctrl_status);
			rate_ctrl_status.timestamp = hrt_absolute_time();

			_rate_ctrl_status_pub.publish(rate_ctrl_status);

		} else {
			// full manual
			_rate_control.resetIntegral();
		}

		// Add feed-forward from roll control output to yaw control output
		// This can be used to counteract the adverse yaw effect when rolling the plane
		_vehicle_torque_setpoint.xyz[2] = math::constrain(_vehicle_torque_setpoint.xyz[2] + _param_fw_rll_to_yaw_ff.get() *
						  _vehicle_torque_setpoint.xyz[0], -1.f, 1.f);

		// Tailsitter: rotate back to body frame from airspeed frame
		if (_vehicle_status.is_vtol_tailsitter) {
			const float helper = _vehicle_torque_setpoint.xyz[0];
			_vehicle_torque_setpoint.xyz[0] = _vehicle_torque_setpoint.xyz[2];
			_vehicle_torque_setpoint.xyz[2] = -helper;
		}

		/* Only publish if any of the proper modes are enabled */
		if (_vcontrol_mode.flag_control_rates_enabled ||
		    _vcontrol_mode.flag_control_attitude_enabled ||
		    _vcontrol_mode.flag_control_manual_enabled) {
			{
				_vehicle_thrust_setpoint.timestamp = hrt_absolute_time();
				_vehicle_thrust_setpoint.timestamp_sample = angular_velocity.timestamp_sample;
				_vehicle_thrust_setpoint_pub.publish(_vehicle_thrust_setpoint);

				_vehicle_torque_setpoint.timestamp = hrt_absolute_time();
				_vehicle_torque_setpoint.timestamp_sample = angular_velocity.timestamp_sample;
				_vehicle_torque_setpoint_pub.publish(_vehicle_torque_setpoint);
			}
		}

		updateActuatorControlsStatus(dt);

		// Manual flaps/spoilers control, also active in VTOL Hover. Is handled and published in FW Position controller/VTOL module if Auto.
		if (_vcontrol_mode.flag_control_manual_enabled) {

			// Flaps control
			float flaps_control = 0.f; // default to no flaps

			/* map flaps by default to manual if valid */
			if (PX4_ISFINITE(_manual_control_setpoint.flaps)) {
				flaps_control = math::max(_manual_control_setpoint.flaps, 0.f); // do not consider negative switch settings
			}

			normalized_unsigned_setpoint_s flaps_setpoint;
			flaps_setpoint.timestamp = hrt_absolute_time();
			flaps_setpoint.normalized_setpoint = flaps_control;
			_flaps_setpoint_pub.publish(flaps_setpoint);

			// Spoilers control
			float spoilers_control = 0.f; // default to no spoilers

			switch (_param_fw_spoilers_man.get()) {
			case 0:
				break;

			case 1:
				// do not consider negative switch settings
				spoilers_control = PX4_ISFINITE(_manual_control_setpoint.flaps) ? math::max(_manual_control_setpoint.flaps, 0.f) : 0.f;
				break;

			case 2:
				// do not consider negative switch settings
				spoilers_control = PX4_ISFINITE(_manual_control_setpoint.aux1) ? math::max(_manual_control_setpoint.aux1, 0.f) : 0.f;
				break;
			}

			normalized_unsigned_setpoint_s spoilers_setpoint;
			spoilers_setpoint.timestamp = hrt_absolute_time();
			spoilers_setpoint.normalized_setpoint = spoilers_control;
			_spoilers_setpoint_pub.publish(spoilers_setpoint);
		}
	}

	// backup schedule
	ScheduleDelayed(20_ms);

	perf_end(_loop_perf);
}

void FixedwingRateControl::updateActuatorControlsStatus(float dt)
{
	for (int i = 0; i < 3; i++) {

		// We assume that the attitude is actuated by control surfaces
		// consuming power only when they move
		const float control_signal = _vehicle_torque_setpoint.xyz[i] - _control_prev[i];
		_control_prev[i] = _vehicle_torque_setpoint.xyz[i];

		_control_energy[i] += control_signal * control_signal * dt;
	}

	_energy_integration_time += dt;

	if (_energy_integration_time > 500e-3f) {

		actuator_controls_status_s status;
		status.timestamp = _vehicle_torque_setpoint.timestamp;

		for (int i = 0; i < 3; i++) {
			status.control_power[i] = _control_energy[i] / _energy_integration_time;
			_control_energy[i] = 0.f;
		}

		_actuator_controls_status_pub.publish(status);
		_energy_integration_time = 0.f;
	}
}

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

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

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

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

	PRINT_MODULE_DESCRIPTION(
		R"DESCR_STR(
### Description
fw_rate_control is the fixed-wing rate controller.

)DESCR_STR");

	PRINT_MODULE_USAGE_NAME("fw_rate_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 fw_rate_control_main(int argc, char *argv[])
{
	return FixedwingRateControl::main(argc, argv);
}