AltitudeSmoothVel - Create new altitude flight task that uses the

velocity smoothing library to create a jerk-limited trajectory along the
Z axis. This FlightTask is used when MPC_POS_MODE = 3.

src/lib/FlightTasks/tasks/ManualAltitudeSmoothVel/FlightTaskManualAltitudeSmoothVel.cpp

@@ -0,0 +1,167 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2019 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.
+ *
+ ****************************************************************************/
+
+/**
+ * @file FlightManualAltitude.cpp
+ */
+
+#include "FlightTaskManualAltitudeSmoothVel.hpp"
+
+#include <float.h>
+
+using namespace matrix;
+
+bool FlightTaskManualAltitudeSmoothVel::activate()
+{
+	bool ret = FlightTaskManualAltitude::activate();
+
+	_reset();
+
+	return ret;
+}
+
+void FlightTaskManualAltitudeSmoothVel::reActivate()
+{
+	// The task is reacivated while the vehicle is on the ground. To detect takeoff in mc_pos_control_main properly
+	// using the generated jerk, reset the z derivatives to zero
+	_reset(true);
+}
+
+void FlightTaskManualAltitudeSmoothVel::_reset(bool force_vz_zero)
+{
+	// Set the z derivatives to zero
+	if (force_vz_zero) {
+		_smoothing.reset(0.f, 0.f, _position(2));
+
+	} else {
+		// TODO: get current accel
+		_smoothing.reset(0.f, _velocity(2), _position(2));
+	}
+
+	// Always start unlocked
+	_position_lock_z_active = false;
+	_position_setpoint_z_locked = NAN;
+}
+
+void FlightTaskManualAltitudeSmoothVel::_checkEkfResetCounters()
+{
+	if (_sub_vehicle_local_position->get().z_reset_counter != _reset_counters.z) {
+		_smoothing.setCurrentPosition(_position(2));
+		_reset_counters.z = _sub_vehicle_local_position->get().z_reset_counter;
+	}
+
+	if (_sub_vehicle_local_position->get().vz_reset_counter != _reset_counters.vz) {
+		_smoothing.setCurrentVelocity(_velocity(2));
+		_reset_counters.vz = _sub_vehicle_local_position->get().vz_reset_counter;
+	}
+}
+
+void FlightTaskManualAltitudeSmoothVel::_updateSetpoints()
+{
+	/* Get yaw setpont, un-smoothed position setpoints.*/
+	FlightTaskManualAltitude::_updateSetpoints();
+
+	/* Update constraints */
+	if (_velocity_setpoint(2) < 0.f) { // up
+		_smoothing.setMaxAccel(_param_mpc_acc_up_max.get());
+		_smoothing.setMaxVel(_constraints.speed_up);
+
+	} else { // down
+		_smoothing.setMaxAccel(_param_mpc_acc_down_max.get());
+		_smoothing.setMaxVel(_constraints.speed_down);
+	}
+
+	float jerk = _param_mpc_jerk_max.get();
+
+	_checkEkfResetCounters();
+
+	/* Check for position unlock
+	 * During a position lock -> position unlock transition, we have to make sure that the velocity setpoint
+	 * is continuous. We know that the output of the position loop (part of the velocity setpoint) will suddenly become null
+	 * and only the feedforward (generated by this flight task) will remain. This is why the previous input of the velocity controller
+	 * is used to set current velocity of the trajectory.
+	 */
+
+	if (fabsf(_sticks_expo(2)) > FLT_EPSILON) {
+		if (_position_lock_z_active) {
+			_smoothing.setCurrentVelocity(_velocity_setpoint_feedback(
+							      2)); // Start the trajectory at the current velocity setpoint
+			_position_setpoint_z_locked = NAN;
+		}
+
+		_position_lock_z_active = false;
+	}
+
+	// During position lock, lower jerk to help the optimizer
+	// to converge to 0 acceleration and velocity
+	jerk = _position_lock_z_active ? 1.f : _param_mpc_jerk_max.get();
+
+	_smoothing.setMaxJerk(jerk);
+	_smoothing.updateDurations(_deltatime, _velocity_setpoint(2));
+
+	if (!_position_lock_z_active) {
+		_smoothing.setCurrentPosition(_position(2));
+	}
+
+	float pos_sp_smooth;
+
+	_smoothing.integrate(_acceleration_setpoint(2), _vel_sp_smooth, pos_sp_smooth);
+	_velocity_setpoint(2) = _vel_sp_smooth; // Feedforward
+	_jerk_setpoint(2) = _smoothing.getCurrentJerk();
+
+	if (fabsf(_vel_sp_smooth) < 0.1f &&
+	    fabsf(_acceleration_setpoint(2)) < .2f &&
+	    fabsf(_sticks_expo(2)) <= FLT_EPSILON) {
+		_position_lock_z_active = true;
+	}
+
+	// Set valid position setpoint while in position lock.
+	// When the position lock condition above is false, it does not
+	// mean that the unlock condition is true. This is why
+	// we are checking the lock flag here.
+	if (_position_lock_z_active) {
+		_position_setpoint_z_locked = pos_sp_smooth;
+
+		// If the velocity setpoint is smaller than 1mm/s and that the acceleration is 0, force the setpoints
+		// to zero. This is required because the generated velocity is never exactly zero and if the drone hovers
+		// for a long period of time, thr drift of the position setpoint will be noticeable.
+		if (fabsf(_velocity_setpoint(2)) < 1e-3f && fabsf(_acceleration_setpoint(2)) < FLT_EPSILON) {
+			_velocity_setpoint(2) = 0.f;
+			_acceleration_setpoint(2) = 0.f;
+			_smoothing.setCurrentVelocity(0.f);
+			_smoothing.setCurrentAcceleration(0.f);
+		}
+	}
+
+	_position_setpoint(2) = _position_setpoint_z_locked;
+}