Takeoff: address @RomanBapst's review comments

src/lib/FlightTasks/tasks/FlightTask/FlightTask.cpp

@@ -152,7 +152,7 @@ bool FlightTask::_checkTakeoff()
 	bool position_triggered_takeoff = false;
 
 	if (PX4_ISFINITE(_position_setpoint(2))) {
-		//minimal altitude either 20cm or what is necessary for correct estimation e.g. optical flow
+		// minimal altitude either 20cm or what is necessary for correct estimation e.g. optical flow
 		float min_altitude = 0.2f;
 		const float min_distance_to_ground = _sub_vehicle_local_position->get().hagl_min;
 

src/lib/FlightTasks/tasks/ManualAltitude/FlightTaskManualAltitude.cpp

@@ -347,7 +347,7 @@ void FlightTaskManualAltitude::_updateSetpoints()
 
 bool FlightTaskManualAltitude::_checkTakeoff()
 {
-	// stick is deflected above the middle 15% of the range
+	// stick is deflected above 65% throttle (_sticks(2) is in the range [-1,1])
 	return _sticks(2) < -0.3f;
 }
 

src/modules/mc_pos_control/Takeoff/Takeoff.cpp

@@ -38,7 +38,7 @@
 #include "Takeoff.hpp"
 #include <mathlib/mathlib.h>
 
-void Takeoff::generateInitialValue(const float hover_thrust, float velocity_p_gain)
+void Takeoff::generateInitialRampValue(const float hover_thrust, float velocity_p_gain)
 {
 	velocity_p_gain = math::max(velocity_p_gain, 0.01f);
 	_takeoff_ramp_vz_init = -hover_thrust / velocity_p_gain;

src/modules/mc_pos_control/Takeoff/Takeoff.hpp

@@ -61,7 +61,14 @@ class Takeoff
 	// initialize parameters
 	void setTakeoffRampTime(const float seconds) { _takeoff_ramp_time = seconds; }
 	void setSpoolupTime(const float seconds) { _spoolup_time_hysteresis.set_hysteresis_time_from(false, (hrt_abstime)(seconds * (float)1_s)); }
-	void generateInitialValue(const float hover_thrust, const float velocity_p_gain);
+
+	/**
+	 * Calculate a vertical velocity to initialize the takeoff ramp
+	 * that when passed to the velocity controller results in a zero throttle setpoint.
+	 * @param hover_thrust normalized thrsut value with which the vehicle hovers
+	 * @param velocity_p_gain proportional gain of the velocity controller to calculate the thrust
+	 */
+	void generateInitialRampValue(const float hover_thrust, const float velocity_p_gain);
 
 	/**
 	 * Update the state for the takeoff.
@@ -70,6 +77,15 @@ class Takeoff
 	 */
 	void updateTakeoffState(const bool armed, const bool landed, const bool want_takeoff,
 				const float takeoff_desired_vz, const bool skip_takeoff);
+
+	/**
+	 * Update and return the velocity constraint ramp value during takeoff.
+	 * By ramping up _takeoff_ramp_vz during the takeoff and using it to constain the maximum climb rate a smooth takeoff behavior is achieved.
+	 * Returns zero on the ground and takeoff_desired_vz in flight.
+	 * @param dt time in seconds since the last call/loop iteration
+	 * @param takeoff_desired_vz end value for the velocity ramp
+	 * @return true if setpoint has updated correctly
+	 */
 	float updateRamp(const float dt, const float takeoff_desired_vz);
 
 	TakeoffState getTakeoffState() { return _takeoff_state; }

src/modules/mc_pos_control/mc_pos_control_main.cpp

@@ -360,7 +360,7 @@ MulticopterPositionControl::parameters_update(bool force)
 		// set trigger time for takeoff delay
 		_takeoff.setSpoolupTime(_param_mpc_spoolup_time.get());
 		_takeoff.setTakeoffRampTime(_param_mpc_tko_ramp_t.get());
-		_takeoff.generateInitialValue(_param_mpc_thr_hover.get(), _param_mpc_z_vel_p.get());
+		_takeoff.generateInitialRampValue(_param_mpc_thr_hover.get(), _param_mpc_z_vel_p.get());
 
 		if (_wv_controller != nullptr) {
 			_wv_controller->update_parameters();