Airmode - Add airmode parameter for multicopter mixer

src/lib/mixer/mixer.h

@@ -218,6 +218,13 @@ public:
 	 */
 	virtual void 			set_thrust_factor(float val) {}
 
+	/**
+	 * @brief Set airmode. Airmode allows the mixer to increase the total thrust in order to unsaturate the motors.
+	 *
+	 * @param[in]  airmode   Dis/-activate airmode by setting it to false/true
+	 */
+	virtual void set_airmode(bool airmode) {};
+
 protected:
 	/** client-supplied callback used when fetching control values */
 	ControlCallback			_control_cb;
@@ -403,6 +410,8 @@ public:
 	 */
 	virtual void	set_thrust_factor(float val);
 
+	virtual void 	set_airmode(bool airmode);
+
 private:
 	Mixer				*_first;	/**< linked list of mixers */
 
@@ -650,6 +659,8 @@ public:
 	 */
 	virtual void			set_thrust_factor(float val) {_thrust_factor = val;}
 
+	virtual void 			set_airmode(bool airmode);
+
 	union saturation_status {
 		struct {
 			uint16_t valid		: 1; // 0 - true when the saturation status is used
@@ -675,6 +686,8 @@ private:
 	float 				_delta_out_max;
 	float 				_thrust_factor;
 
+	bool                		_airmode;
+
 	void update_saturation_status(unsigned index, bool clipping_high, bool clipping_low);
 	saturation_status _saturation_status;
 

src/lib/mixer/mixer_group.cpp

@@ -185,7 +185,17 @@ MixerGroup::set_thrust_factor(float val)
 		mixer->set_thrust_factor(val);
 		mixer = mixer->_next;
 	}
+}
 
+void
+MixerGroup::set_airmode(bool airmode)
+{
+	Mixer	*mixer = _first;
+
+	while (mixer != nullptr) {
+		mixer->set_airmode(airmode);
+		mixer = mixer->_next;
+	}
 }
 
 uint16_t

src/lib/mixer/mixer_multirotor.cpp

@@ -84,6 +84,7 @@ MultirotorMixer::MultirotorMixer(ControlCallback control_cb,
 	_idle_speed(-1.0f + idle_speed * 2.0f),	/* shift to output range here to avoid runtime calculation */
 	_delta_out_max(0.0f),
 	_thrust_factor(0.0f),
+	_airmode(false),
 	_rotor_count(_config_rotor_count[(MultirotorGeometryUnderlyingType)geometry]),
 	_rotors(_config_index[(MultirotorGeometryUnderlyingType)geometry]),
 	_outputs_prev(new float[_rotor_count])
@@ -224,6 +225,9 @@ MultirotorMixer::mix(float *outputs, unsigned space)
 		boost = 1.0f - ((max_out - thrust) * roll_pitch_scale + thrust);
 	}
 
+	if (!_airmode) {
+		boost = math::min(boost, 0.0f); // Disable positive boosting if not in air-mode
+	}
 
 	// capture saturation
 	if (min_out < 0.0f) {
@@ -425,6 +429,12 @@ MultirotorMixer::update_saturation_status(unsigned index, bool clipping_high, bo
 	_saturation_status.flags.valid = true;
 }
 
+void
+MultirotorMixer::set_airmode(bool airmode)
+{
+	_airmode = airmode;
+}
+
 void
 MultirotorMixer::groups_required(uint32_t &groups)
 {