FixedWingPositionControl: Use reference model for all auto modes except when in vtol transition

msg/VehicleAttitudeSetpoint.msg

@@ -17,4 +17,4 @@ bool reset_integral	# Reset roll/pitch/yaw integrals (navigation logic change)
 
 bool fw_control_yaw_wheel	# control heading with steering wheel (used for auto takeoff on runway)
 
-# TOPICS vehicle_attitude_setpoint mc_virtual_attitude_setpoint fw_virtual_attitude_setpoint
+# TOPICS vehicle_attitude_setpoint mc_virtual_attitude_setpoint fw_virtual_attitude_setpoint vehicle_attitude_reference_setpoint fw_virtual_vehicle_attitude_reference_setpoint

msg/VehicleRatesSetpoint.msg

@@ -5,6 +5,8 @@ float32 roll		# [rad/s] roll rate setpoint
 float32 pitch		# [rad/s] pitch rate setpoint
 float32 yaw		# [rad/s] yaw rate setpoint
 
+float32[3] accel_feedforward # [rad/s²] angular acceleration feedforward
+
 # For clarification: For multicopters thrust_body[0] and thrust[1] are usually 0 and thrust[2] is the negative throttle demand.
 # For fixed wings thrust_x is the throttle demand and thrust_y, thrust_z will usually be zero.
 float32[3] thrust_body	# Normalized thrust command in body NED frame [-1,1]

src/lib/mathlib/math/filter/second_order_reference_model.hpp

@@ -41,8 +41,12 @@
 
 #pragma once
 
+#include <float.h>
+#include <math.h>
+
 #include <px4_platform_common/defines.h>
-#include <matrix/SquareMatrix.hpp>
+
+#include "lib/matrix/matrix/math.hpp"
 
 namespace math
 {
@@ -150,9 +154,6 @@ public:
 		// take a step forward from the last state (and input), update the filter states
 		integrateStates(time_step, last_state_sample_, last_rate_sample_);
 
-		// instantaneous acceleration from current input / state
-		filter_accel_ = calculateInstantaneousAcceleration(state_sample, rate_sample);
-
 		// store the current samples
 		last_state_sample_ = state_sample;
 		last_rate_sample_ = rate_sample;
@@ -174,7 +175,7 @@ public:
 		last_rate_sample_ = rate;
 	}
 
-private:
+protected:
 
 	// A conservative multiplier (>=2) on sample frequency to bound the maximum time step
 	static constexpr float kSampleRateMultiplier = 4.0f;
@@ -247,7 +248,7 @@ private:
 	 * @param[in] state_sample [units]
 	 * @param[in] rate_sample [units/s]
 	 */
-	void integrateStatesForwardEuler(const float time_step, const T &state_sample, const T &rate_sample)
+	virtual void integrateStatesForwardEuler(const float time_step, const T &state_sample, const T &rate_sample)
 	{
 		// general notation for what follows:
 		// c: continuous
@@ -278,6 +279,9 @@ private:
 
 		// discrete state transition
 		transitionStates(state_matrix, input_matrix, state_sample, rate_sample);
+
+		// instantaneous acceleration from current input / state
+		filter_accel_ = calculateInstantaneousAcceleration(state_sample, rate_sample);
 	}
 
 	/**
@@ -324,6 +328,9 @@ private:
 
 		// discrete state transition
 		transitionStates(state_matrix, input_matrix, state_sample, rate_sample);
+
+		// instantaneous acceleration from current input / state
+		filter_accel_ = calculateInstantaneousAcceleration(state_sample, rate_sample);
 	}
 
 	/**

src/modules/fw_att_control/CMakeLists.txt

@@ -36,8 +36,8 @@ px4_add_module(
 	MAIN fw_att_control
 	SRCS
 		FixedwingAttitudeControl.cpp
-		FixedwingAttitudeControl.hpp
 
+		att_ref_model.cpp
 		ecl_controller.cpp
 		ecl_pitch_controller.cpp
 		ecl_roll_controller.cpp

src/modules/fw_att_control/FixedwingAttitudeControl.cpp

@@ -119,16 +119,6 @@ FixedwingAttitudeControl::vehicle_manual_poll(const float yaw_body)
 	}
 }
 
-void
-FixedwingAttitudeControl::vehicle_attitude_setpoint_poll()
-{
-	if (_att_sp_sub.update(&_att_sp)) {
-		_rates_sp.thrust_body[0] = _att_sp.thrust_body[0];
-		_rates_sp.thrust_body[1] = _att_sp.thrust_body[1];
-		_rates_sp.thrust_body[2] = _att_sp.thrust_body[2];
-	}
-}
-
 void
 FixedwingAttitudeControl::vehicle_land_detected_poll()
 {
@@ -260,7 +250,16 @@ void FixedwingAttitudeControl::Run()
 
 		vehicle_manual_poll(euler_angles.psi());
 
-		vehicle_attitude_setpoint_poll();
+		// attitude setpoint poll
+		_reference_model.update();
+
+		_att_sp = _reference_model.getOutput();
+		matrix::Vector2f vel_feedforward = _reference_model.getRateFeedforward();
+		matrix::Vector2f acc_feedforward = _reference_model.getTorqueFeedforward();
+
+		_rates_sp.thrust_body[0] = _att_sp.thrust_body[0];
+		_rates_sp.thrust_body[1] = _att_sp.thrust_body[1];
+		_rates_sp.thrust_body[2] = _att_sp.thrust_body[2];
 
 		// 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);
@@ -383,10 +382,14 @@ void FixedwingAttitudeControl::Run()
 					}
 
 					/* Publish the rate setpoint for analysis once available */
-					_rates_sp.roll = body_rates_setpoint(0);
-					_rates_sp.pitch = body_rates_setpoint(1);
+					_rates_sp.roll = body_rates_setpoint(0) + vel_feedforward(0);
+					_rates_sp.pitch = body_rates_setpoint(1) + vel_feedforward(1);
 					_rates_sp.yaw = body_rates_setpoint(2);
 
+					_rates_sp.accel_feedforward[0] = acc_feedforward(0);
+					_rates_sp.accel_feedforward[1] = acc_feedforward(1);
+					_rates_sp.accel_feedforward[2] = 0.f;
+
 					_rates_sp.timestamp = hrt_absolute_time();
 
 					_rate_sp_pub.publish(_rates_sp);
@@ -415,6 +418,7 @@ void FixedwingAttitudeControl::Run()
 		} else {
 			// full manual
 			_wheel_ctrl.reset_integrator();
+			_reference_model.reset();
 
 			_landing_gear_wheel.normalized_wheel_setpoint = PX4_ISFINITE(_manual_control_setpoint.yaw) ?
 					_manual_control_setpoint.yaw : 0.f;

src/modules/fw_att_control/FixedwingAttitudeControl.hpp

@@ -34,6 +34,7 @@
 #pragma once
 
 #include <drivers/drv_hrt.h>
+#include "att_ref_model.h"
 #include "ecl_pitch_controller.h"
 #include "ecl_roll_controller.h"
 #include "ecl_wheel_controller.h"
@@ -98,7 +99,6 @@ private:
 
 	uORB::SubscriptionInterval _parameter_update_sub{ORB_ID(parameter_update), 1_s};
 
-	uORB::Subscription _att_sp_sub{ORB_ID(vehicle_attitude_setpoint)};			/**< vehicle attitude setpoint */
 	uORB::Subscription _autotune_attitude_control_status_sub{ORB_ID(autotune_attitude_control_status)};
 	uORB::Subscription _local_pos_sub{ORB_ID(vehicle_local_position)};			/**< local position subscription */
 	uORB::Subscription _manual_control_setpoint_sub{ORB_ID(manual_control_setpoint)};	/**< notification of manual control updates */
@@ -164,9 +164,10 @@ private:
 	ECL_YawController _yaw_ctrl;
 	ECL_WheelController _wheel_ctrl;
 
+	FixedwingAttitudeReferenceModel _reference_model;
+
 	void parameters_update();
 	void vehicle_manual_poll(const float yaw_body);
-	void vehicle_attitude_setpoint_poll();
 	void vehicle_land_detected_poll();
 	float get_airspeed_constrained();
 };

src/modules/fw_att_control/att_ref_model.cpp

@@ -0,0 +1,140 @@
+#include "att_ref_model.h"
+
+#include <px4_platform_common/log.h>
+
+#include <lib/mathlib/mathlib.h>
+#include "lib/slew_rate/SlewRate.hpp"
+
+float REFERENCE_MODEL_DAMPING{1.f};
+
+FixedwingAttitudeReferenceModel::FixedwingAttitudeReferenceModel() :
+	ModuleParams(nullptr)
+{
+	parameters_update();
+}
+
+void FixedwingAttitudeReferenceModel::update()
+{
+	parameters_update();
+
+	/* We check if the attitude setpoint topic got updated externally, put in throughput mode,
+	 if attitude reference got updated, but into filter mode. If none, keep the current mode.
+	 If both put throughput mode for safety. */
+	_att_sp_sub.update();
+
+	if (_att_sp_sub.get().timestamp > _last_att_setpoint_timestamp) {
+		if (_mode == ModelMode::MODELMODE_FILTERING) {
+			PX4_INFO("FixedWingAttitudeReferenceModel: Switch to throughput mode");
+		}
+
+		_mode = ModelMode::MODELMODE_THROUGHPUT;
+
+	} else if (_att_ref_sp_sub.updated()) {
+		_att_ref_sp_sub.update();
+
+		if (_mode == ModelMode::MODELMODE_THROUGHPUT) {
+			PX4_INFO("FixedWingAttitudeReferenceModel: Switch to filtering mode");
+		}
+
+		_mode = ModelMode::MODELMODE_FILTERING;
+
+	}
+
+	hrt_abstime now = hrt_absolute_time();
+
+	_attitiude_rate_feedforward_output = matrix::Vector2f{};
+	_attitiude_torque_feedforward_output = matrix::Vector2f{};
+
+	if (_mode == ModelMode::MODELMODE_FILTERING) {
+
+		if (!_is_initialized) {
+
+			_is_initialized = true;
+			_roll_ref_model.reset(_att_ref_sp_sub.get().roll_body);
+			_pitch_ref_model.reset(_att_ref_sp_sub.get().pitch_body);
+
+		} else {
+			if (_att_ref_sp_sub.get().timestamp > _last_update_timestamp) {
+				_roll_ref_model.update(static_cast<float>(_att_ref_sp_sub.get().timestamp - _last_update_timestamp) / 1_s,
+						       _last_attitude_reference_setpoint.roll_body);
+				_pitch_ref_model.update(static_cast<float>(_att_ref_sp_sub.get().timestamp - _last_update_timestamp) / 1_s,
+							_last_attitude_reference_setpoint.pitch_body);
+				_last_update_timestamp = _att_ref_sp_sub.get().timestamp;
+			}
+
+			_roll_ref_model.update(static_cast<float>(math::max(now - _last_update_timestamp, static_cast<hrt_abstime>(0U))) / 1_s,
+					       _att_ref_sp_sub.get().roll_body);
+			_pitch_ref_model.update(static_cast<float>(math::max(now - _last_update_timestamp, static_cast<hrt_abstime>(0U))) / 1_s,
+						_att_ref_sp_sub.get().pitch_body);
+
+		}
+
+		_last_attitude_reference_setpoint = _att_ref_sp_sub.get();
+
+		_last_update_timestamp = now;
+
+		_attitude_setpoint_output = _att_ref_sp_sub.get();
+		_attitude_setpoint_output.timestamp = now;
+
+		if (_param_ref_r_en.get()) {
+			_attitude_setpoint_output.roll_body = _roll_ref_model.getState();
+			_attitiude_rate_feedforward_output(0) = _roll_ref_model.getRate();
+			_attitiude_torque_feedforward_output(0) = _roll_ref_model.getAccel();
+		}
+
+		if (_param_ref_p_en.get()) {
+			_attitude_setpoint_output.pitch_body = _pitch_ref_model.getState();
+			_attitiude_rate_feedforward_output(1) = _pitch_ref_model.getRate();
+			_attitiude_torque_feedforward_output(1) = _pitch_ref_model.getAccel();
+
+		}
+
+		// Other fields in the attitude setpoints are passed through
+
+		// Publish attitude setpoint for logging
+		_att_sp_pub.publish(_attitude_setpoint_output);
+		_last_att_setpoint_timestamp = _attitude_setpoint_output.timestamp;
+
+	} else {
+		_attitude_setpoint_output = _att_sp_sub.get();
+		_roll_ref_model.reset(_att_sp_sub.get().roll_body);
+		_pitch_ref_model.reset(_att_sp_sub.get().pitch_body);
+		_is_initialized = true;
+		_last_update_timestamp = now;
+		_last_att_setpoint_timestamp = _att_sp_sub.get().timestamp;
+	}
+}
+
+void FixedwingAttitudeReferenceModel::reset()
+{
+	_is_initialized = false;
+
+	if (_mode == ModelMode::MODELMODE_FILTERING) {
+		_att_ref_sp_sub.update();
+		_attitude_setpoint_output = _att_ref_sp_sub.get();
+
+	} else {
+		_att_sp_sub.update();
+		_attitude_setpoint_output = _att_sp_sub.get();
+	}
+
+	_attitiude_rate_feedforward_output = matrix::Vector2f{};
+	_attitiude_torque_feedforward_output = matrix::Vector2f{};
+}
+
+void FixedwingAttitudeReferenceModel::parameters_update()
+{
+	if (_parameter_update_sub.updated()) {
+		parameter_update_s param_update;
+		_parameter_update_sub.copy(&param_update);
+
+		// If any parameter updated, call updateParams() to check if
+		// this class attributes need updating (and do so).
+		updateParams();
+
+		_roll_ref_model.setParameters(_param_ref_r_freq.get(), REFERENCE_MODEL_DAMPING, _param_ref_r_vel_limit.get(),
+					      _param_ref_r_acc_limit.get());
+		_pitch_ref_model.setParameters(_param_ref_p_freq.get(), REFERENCE_MODEL_DAMPING, _param_ref_p_vel_limit.get(),
+					       _param_ref_p_acc_limit.get());
+	}
+}

src/modules/fw_att_control/att_ref_model.h

@@ -0,0 +1,178 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2023 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:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include <cstdint>
+#include <matrix/math.hpp>
+#include <mathlib/mathlib.h>
+
+#include <drivers/drv_hrt.h>
+
+#include <px4_platform_common/module_params.h>
+
+#include <lib/mathlib/math/filter/second_order_reference_model.hpp>
+#include <lib/slew_rate/SlewRateYaw.hpp>
+
+#include <uORB/Publication.hpp>
+#include <uORB/Subscription.hpp>
+#include <uORB/SubscriptionInterval.hpp>
+#include <uORB/topics/parameter_update.h>
+#include <uORB/topics/vehicle_attitude_setpoint.h>
+
+using namespace time_literals;
+
+class AttitudeReferenceModel : public math::SecondOrderReferenceModel<float>
+{
+public:
+	AttitudeReferenceModel()
+	{
+		setDiscretizationMethod(math::SecondOrderReferenceModel<float>::DiscretizationMethod::kForwardEuler);
+	};
+
+	/**
+	 * Set the system parameters
+	 *
+	 * Calculates the damping coefficient, spring constant, and maximum allowed
+	 * time step based on the natural frequency.
+	 *
+	 * @param[in] natural_freq The desired undamped natural frequency of the system [rad/s]
+	 * @param[in] damping_ratio The desired damping ratio of the system
+	 * @param[in] vel_limit the limit for the velocity [rad/s]
+	 * @param[in] acc_limit the limit for the acceleration [rad/s^2]
+	 * @param[in] jerk_limit set maximum jerk [rad/s^3]. Optional, only used in kForwardEuler mode
+	 * @return Whether or not the param set was successful
+	 */
+	bool setParameters(const float natural_freq, const float damping_ratio, float vel_limit = INFINITY,
+			   float acc_limit = INFINITY)
+	{
+		if (acc_limit < FLT_EPSILON) {
+			acc_limit_ = INFINITY;
+
+		} else {
+			acc_limit_ = acc_limit;
+		}
+
+		if (vel_limit < FLT_EPSILON) {
+			vel_limit_ = INFINITY;
+
+		} else {
+			vel_limit_ = vel_limit;
+		}
+
+		return math::SecondOrderReferenceModel<float>::setParameters(natural_freq, damping_ratio);
+	}
+
+private:
+	float vel_limit_; 	/** velocity limit [rad/s]*/
+	float acc_limit_; 	/** acceleration limit [rad/s^2]*/
+
+	/**
+	 * Take one integration step using Euler-forward integration
+	 *
+	 * @param[in] time_step Integration time [s]
+	 * @param[in] state_sample [rad]
+	 * @param[in] rate_sample [rad/s]
+	 */
+	void integrateStatesForwardEuler(const float time_step, const float &state_sample, const float &rate_sample) override
+	{
+		filter_accel_ = calculateInstantaneousAcceleration(state_sample, rate_sample);
+
+		if (filter_accel_ > 0.f) {
+			filter_accel_ = math::min(math::min(filter_accel_, (vel_limit_ - filter_rate_) / time_step), acc_limit_);
+
+		} else {
+			filter_accel_ = math::max(math::max(filter_accel_, (-vel_limit_ - filter_rate_) / time_step), -acc_limit_);
+		}
+
+		const float new_rate = filter_rate_ + filter_accel_ * time_step;
+		const float new_state = filter_state_ + filter_rate_ * time_step;
+
+		filter_state_ = new_state;
+		filter_rate_ = new_rate;
+	}
+};
+
+class FixedwingAttitudeReferenceModel : public ModuleParams
+{
+public:
+	FixedwingAttitudeReferenceModel();
+	~FixedwingAttitudeReferenceModel() = default;
+
+	void update();
+
+	void reset();
+
+	const vehicle_attitude_setpoint_s &getOutput() {return _attitude_setpoint_output;};
+
+	const matrix::Vector2f &getRateFeedforward() {return _attitiude_rate_feedforward_output;};
+	const matrix::Vector2f &getTorqueFeedforward() {return _attitiude_torque_feedforward_output;};
+
+private:
+
+	enum class ModelMode {
+		MODELMODE_THROUGHPUT,
+		MODELMODE_FILTERING
+	} _mode{ModelMode::MODELMODE_THROUGHPUT}; /*< Mode in which the attitude reference model works on */
+
+	/**
+	 * Check for parameter changes and update them if needed.
+	 */
+	void parameters_update();
+
+	AttitudeReferenceModel _roll_ref_model;  /*< Second order reference filter for the roll angle */
+	AttitudeReferenceModel _pitch_ref_model; /*< Second order reference filter for the pitch angle */
+	bool _is_initialized{false}; /*< Flag indicating if the reference model is already initialized */
+	uint64_t _last_att_setpoint_timestamp{UINT64_C(0)}; /*< Timestamp of the last own published vehicle attitude setpoint topic */
+	hrt_abstime _last_update_timestamp{0U}; 	/*< Timestamp of the last update*/
+	vehicle_attitude_setpoint_s _last_attitude_reference_setpoint; /*< Last attitude reference setpoint input */
+	vehicle_attitude_setpoint_s _attitude_setpoint_output; /*< Attitude setpoint to be set by output*/
+	matrix::Vector2f 	_attitiude_rate_feedforward_output; /*< Attitude rate feedforward output */
+	matrix::Vector2f 	_attitiude_torque_feedforward_output; /*< Attitude torque feedforward output */
+
+	uORB::SubscriptionInterval _parameter_update_sub{ORB_ID(parameter_update), 1_s}; /*< parameter update subscription */
+	uORB::SubscriptionData<vehicle_attitude_setpoint_s> _att_ref_sp_sub{ORB_ID(vehicle_attitude_reference_setpoint)};	/*< vehicle attitude reference setpoint */
+	uORB::SubscriptionData<vehicle_attitude_setpoint_s> _att_sp_sub{ORB_ID(vehicle_attitude_setpoint)};	/*< vehicle attitude setpoint */
+	uORB::Publication<vehicle_attitude_setpoint_s> _att_sp_pub{ORB_ID(vehicle_attitude_setpoint)}; /*< vehicle attitude setpoint publication when reference model is active for logging */
+
+	DEFINE_PARAMETERS(
+		(ParamFloat<px4::params::FW_REF_R_FREQ>) _param_ref_r_freq,
+		(ParamFloat<px4::params::FW_REF_R_V_LIM>) _param_ref_r_vel_limit,
+		(ParamFloat<px4::params::FW_REF_R_A_LIM>) _param_ref_r_acc_limit,
+		(ParamBool<px4::params::FW_REF_R_EN>) _param_ref_r_en,
+		(ParamFloat<px4::params::FW_REF_P_FREQ>) _param_ref_p_freq,
+		(ParamFloat<px4::params::FW_REF_P_V_LIM>) _param_ref_p_vel_limit,
+		(ParamFloat<px4::params::FW_REF_P_A_LIM>) _param_ref_p_acc_limit,
+		(ParamBool<px4::params::FW_REF_P_EN>) _param_ref_p_en
+	)
+};

src/modules/fw_att_control/fw_att_control_params.c

@@ -254,3 +254,87 @@ PARAM_DEFINE_FLOAT(FW_MAN_R_MAX, 45.0f);
  * @group FW Attitude Control
  */
 PARAM_DEFINE_FLOAT(FW_MAN_P_MAX, 30.0f);
+
+/**
+ * Natural frequency of the roll reference model
+ *
+ * Frequency of the critically damped second order roll reference model
+ *
+ * @min 0.0
+ * @decimal 3
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_REF_R_FREQ, 5.0f);
+
+/**
+ * Velocity limit of the roll reference model
+ *
+ * Limit of the critically damped second order roll reference model velocity. A negative value disables the limit.
+ *
+ * @min -1.0
+ * @decimal 3
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_REF_R_V_LIM, -1.0f);
+
+/**
+ * Acceleration limit of the roll reference model
+ *
+ * Limit of the critically damped second order roll reference model acceleration. A negative value disables the limit.
+ *
+ * @min -1.0
+ * @decimal 3
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_REF_R_A_LIM, -1.0f);
+
+/**
+ * Enable roll reference model
+ *
+ *
+ * @boolean
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_INT32(FW_REF_R_EN, 0);
+
+/**
+ * Natural frequency of the roll reference model
+ *
+ * Frequency of the critically damped second order pitch reference model
+ *
+ * @min 0.0
+ * @decimal 3
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_REF_P_FREQ, 5.0f);
+
+/**
+ * Velocity limit of the pitch reference model
+ *
+ * Limit of the critically damped second order pitch reference model velocity. A negative value disables the limit.
+ *
+ * @min -1.0
+ * @decimal 3
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_REF_P_V_LIM, -1.0f);
+
+/**
+ * Acceleration limit of the pitch reference model
+ *
+ * Limit of the critically damped second order pitch reference model acceleration. A negative value disables the limit.
+ *
+ * @min -1.0
+ * @decimal 3
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_FLOAT(FW_REF_P_A_LIM, -1.0f);
+
+/**
+ * Enable pitch reference model
+ *
+ *
+ * @boolean
+ * @group FW Attitude Control
+ */
+PARAM_DEFINE_INT32(FW_REF_P_EN, 0);

src/modules/fw_pos_control/FixedwingPositionControl.cpp

@@ -52,6 +52,8 @@ FixedwingPositionControl::FixedwingPositionControl(bool vtol) :
 	ModuleParams(nullptr),
 	WorkItem(MODULE_NAME, px4::wq_configurations::nav_and_controllers),
 	_attitude_sp_pub(vtol ? ORB_ID(fw_virtual_attitude_setpoint) : ORB_ID(vehicle_attitude_setpoint)),
+	_attitude_ref_sp_pub(vtol ? ORB_ID(fw_virtual_vehicle_attitude_reference_setpoint) : ORB_ID(
+				     vehicle_attitude_reference_setpoint)),
 	_loop_perf(perf_alloc(PC_ELAPSED, MODULE_NAME": cycle")),
 	_launchDetector(this),
 	_runway_takeoff(this)
@@ -2435,7 +2437,14 @@ FixedwingPositionControl::Run()
 				q.copyTo(_att_sp.q_d);
 
 				_att_sp.timestamp = hrt_absolute_time();
-				_attitude_sp_pub.publish(_att_sp);
+
+				// Enable reference model use for auto modes except when transitioning.
+				if (_control_mode_current == FW_POSCTRL_MODE_AUTO && !_vehicle_status.in_transition_mode) {
+					_attitude_ref_sp_pub.publish(_att_sp);
+
+				} else {
+					_attitude_sp_pub.publish(_att_sp);
+				}
 
 				// only publish status in full FW mode
 				if (_vehicle_status.vehicle_type == vehicle_status_s::VEHICLE_TYPE_FIXED_WING

src/modules/fw_pos_control/FixedwingPositionControl.hpp

@@ -204,6 +204,7 @@ private:
 	uORB::Subscription _vehicle_status_sub{ORB_ID(vehicle_status)};
 
 	uORB::Publication<vehicle_attitude_setpoint_s> _attitude_sp_pub;
+	uORB::Publication<vehicle_attitude_setpoint_s> _attitude_ref_sp_pub;
 	uORB::Publication<vehicle_local_position_setpoint_s> _local_pos_sp_pub{ORB_ID(vehicle_local_position_setpoint)};
 	uORB::Publication<npfg_status_s> _npfg_status_pub{ORB_ID(npfg_status)};
 	uORB::Publication<position_controller_status_s>	_pos_ctrl_status_pub{ORB_ID(position_controller_status)};

src/modules/fw_rate_control/FixedwingRateControl.cpp

@@ -360,8 +360,10 @@ void FixedwingRateControl::Run()
 				const Vector3f angular_acceleration_setpoint = _rate_control.update(rates, body_rates_setpoint, angular_accel, dt,
 						_landed);
 
-				const float roll_feedforward = _param_fw_rr_ff.get() * _airspeed_scaling * body_rates_setpoint(0);
-				const float pitch_feedforward = _param_fw_pr_ff.get() * _airspeed_scaling * body_rates_setpoint(1);
+				const float roll_feedforward = _param_fw_rr_ff.get() * _airspeed_scaling * body_rates_setpoint(
+								       0) + _param_fw_ra_ff.get() * _rates_sp.accel_feedforward[0];
+				const float pitch_feedforward = _param_fw_pr_ff.get() * _airspeed_scaling * body_rates_setpoint(
+									1) + _param_fw_pa_ff.get() * _rates_sp.accel_feedforward[1];
 				const float yaw_feedforward = _param_fw_yr_ff.get() * _airspeed_scaling * body_rates_setpoint(2);
 
 				const float roll_u = angular_acceleration_setpoint(0) * _airspeed_scaling * _airspeed_scaling + roll_feedforward;

src/modules/fw_rate_control/FixedwingRateControl.hpp

@@ -182,6 +182,7 @@ private:
 		(ParamFloat<px4::params::FW_MAN_Y_SC>) _param_fw_man_y_sc,
 
 		(ParamFloat<px4::params::FW_PR_FF>) _param_fw_pr_ff,
+		(ParamFloat<px4::params::FW_PA_FF>) _param_fw_pa_ff,
 		(ParamFloat<px4::params::FW_PR_I>) _param_fw_pr_i,
 		(ParamFloat<px4::params::FW_PR_IMAX>) _param_fw_pr_imax,
 		(ParamFloat<px4::params::FW_PR_P>) _param_fw_pr_p,
@@ -189,6 +190,7 @@ private:
 
 		(ParamFloat<px4::params::FW_RLL_TO_YAW_FF>) _param_fw_rll_to_yaw_ff,
 		(ParamFloat<px4::params::FW_RR_FF>) _param_fw_rr_ff,
+		(ParamFloat<px4::params::FW_RA_FF>) _param_fw_ra_ff,
 		(ParamFloat<px4::params::FW_RR_I>) _param_fw_rr_i,
 		(ParamFloat<px4::params::FW_RR_IMAX>) _param_fw_rr_imax,
 		(ParamFloat<px4::params::FW_RR_P>) _param_fw_rr_p,

src/modules/fw_rate_control/fw_rate_control_params.c

@@ -209,6 +209,18 @@ PARAM_DEFINE_FLOAT(FW_YR_IMAX, 0.2f);
  */
 PARAM_DEFINE_FLOAT(FW_RR_FF, 0.5f);
 
+/**
+ * roll acceleration feedforward gain
+ *
+ * feedforward gain for acceleration to scale rad/s^2 to percentage output
+ *
+ * @min 0.0
+ * @max 10.0
+ * @decimal 2
+ * @group FW Rate Control
+ */
+PARAM_DEFINE_FLOAT(FW_RA_FF, 0.0f);
+
 /**
  * Pitch rate feed forward
  *
@@ -223,6 +235,19 @@ PARAM_DEFINE_FLOAT(FW_RR_FF, 0.5f);
  */
 PARAM_DEFINE_FLOAT(FW_PR_FF, 0.5f);
 
+/**
+ * pitch acceleration feedforward gain
+ *
+ * feedforward gain for acceleration to scale rad/s^2 to unitless output
+ *
+ * @unit %/rad/s
+ * @min 0.0
+ * @max 10.0
+ * @decimal 2
+ * @group FW Rate Control
+ */
+PARAM_DEFINE_FLOAT(FW_PA_FF, 0.0f);
+
 /**
  * Yaw rate feed forward
  *

src/modules/logger/logged_topics.cpp

@@ -116,6 +116,7 @@ void LoggedTopics::add_default_topics()
 	add_topic("vehicle_angular_velocity", 20);
 	add_topic("vehicle_attitude", 50);
 	add_topic("vehicle_attitude_setpoint", 50);
+	add_topic("vehicle_attitude_reference_setpoint", 50);
 	add_topic("vehicle_command");
 	add_topic("vehicle_command_ack");
 	add_topic("vehicle_constraints", 1000);

src/modules/vtol_att_control/vtol_att_control_main.cpp

@@ -378,6 +378,18 @@ VtolAttitudeControl::Run()
 		// check if mc and fw sp were updated
 		const bool mc_att_sp_updated = _mc_virtual_att_sp_sub.update(&_mc_virtual_att_sp);
 		const bool fw_att_sp_updated = _fw_virtual_att_sp_sub.update(&_fw_virtual_att_sp);
+		const bool fw_att_ref_sp_updated = _fw_virtual_att_ref_sp_sub.update(&_fw_virtual_att_ref_sp);
+
+		if (fw_att_sp_updated) {
+			_is_in_att_ref_mode = false;
+
+		} else if (fw_att_ref_sp_updated) {
+			_is_in_att_ref_mode = true;
+		}
+
+		if (_is_in_att_ref_mode) {
+			_fw_virtual_att_sp = _fw_virtual_att_ref_sp;
+		}
 
 		// update the vtol state machine which decides which mode we are in
 		_vtol_type->update_vtol_state();
@@ -424,6 +436,10 @@ VtolAttitudeControl::Run()
 			if (fw_att_sp_updated) {
 				_vtol_type->update_fw_state();
 				_vehicle_attitude_sp_pub.publish(_vehicle_attitude_sp);
+
+			} else if (fw_att_ref_sp_updated) {
+				_vtol_type->update_fw_state();
+				_vehicle_attitude_ref_sp_pub.publish(_vehicle_attitude_sp);
 			}
 
 			break;

src/modules/vtol_att_control/vtol_att_control_main.h

@@ -159,6 +159,7 @@ private:
 	uORB::Subscription _action_request_sub{ORB_ID(action_request)};
 	uORB::Subscription _airspeed_validated_sub{ORB_ID(airspeed_validated)};
 	uORB::Subscription _fw_virtual_att_sp_sub{ORB_ID(fw_virtual_attitude_setpoint)};
+	uORB::Subscription _fw_virtual_att_ref_sp_sub{ORB_ID(fw_virtual_vehicle_attitude_reference_setpoint)};
 	uORB::Subscription _home_position_sub{ORB_ID(home_position)};
 	uORB::Subscription _land_detected_sub{ORB_ID(vehicle_land_detected)};
 	uORB::Subscription _local_pos_sp_sub{ORB_ID(vehicle_local_position_setpoint)};
@@ -175,6 +176,7 @@ private:
 	uORB::Publication<normalized_unsigned_setpoint_s>	_flaps_setpoint_pub{ORB_ID(flaps_setpoint)};
 	uORB::Publication<normalized_unsigned_setpoint_s>	_spoilers_setpoint_pub{ORB_ID(spoilers_setpoint)};
 	uORB::Publication<vehicle_attitude_setpoint_s>		_vehicle_attitude_sp_pub{ORB_ID(vehicle_attitude_setpoint)};
+	uORB::Publication<vehicle_attitude_setpoint_s>		_vehicle_attitude_ref_sp_pub{ORB_ID(vehicle_attitude_reference_setpoint)};
 	uORB::PublicationMulti<vehicle_thrust_setpoint_s>	_vehicle_thrust_setpoint0_pub{ORB_ID(vehicle_thrust_setpoint)};
 	uORB::PublicationMulti<vehicle_thrust_setpoint_s>	_vehicle_thrust_setpoint1_pub{ORB_ID(vehicle_thrust_setpoint)};
 	uORB::PublicationMulti<vehicle_torque_setpoint_s>	_vehicle_torque_setpoint0_pub{ORB_ID(vehicle_torque_setpoint)};
@@ -185,6 +187,7 @@ private:
 
 	vehicle_attitude_setpoint_s		_vehicle_attitude_sp{};	// vehicle attitude setpoint
 	vehicle_attitude_setpoint_s 		_fw_virtual_att_sp{};	// virtual fw attitude setpoint
+	vehicle_attitude_setpoint_s 		_fw_virtual_att_ref_sp{};	// virtual fw attitude setpoint
 	vehicle_attitude_setpoint_s 		_mc_virtual_att_sp{};	// virtual mc attitude setpoint
 
 	vehicle_torque_setpoint_s		_vehicle_torque_setpoint_virtual_mc{};
@@ -211,6 +214,8 @@ private:
 
 	float _air_density{atmosphere::kAirDensitySeaLevelStandardAtmos};	// [kg/m^3]
 
+	bool _is_in_att_ref_mode{false};
+
 	hrt_abstime _last_run_timestamp{0};
 
 	/* For multicopters it is usual to have a non-zero idle speed of the engines