mc_att_control: major cleanup and code reorganization

1 files changed, 377 insertions, 327 deletions

diff --git a/src/modules/mc_att_control/mc_att_control_main.cpp b/src/modules/mc_att_control/mc_att_control_main.cpp
index 44baccefc..e37fe18b8 100644
--- a/src/modules/mc_att_control/mc_att_control_main.cpp
+++ b/src/modules/mc_att_control/mc_att_control_main.cpp
@@ -113,28 +113,39 @@ private:
 	bool	_task_should_exit;		/**< if true, sensor task should exit */
 	int		_control_task;			/**< task handle for sensor task */
 
-	int		_att_sub;				/**< vehicle attitude subscription */
-	int		_att_sp_sub;			/**< vehicle attitude setpoint */
-	int		_control_mode_sub;		/**< vehicle control mode subscription */
-	int 	_params_sub;			/**< notification of parameter updates */
-	int 	_manual_sub;			/**< notification of manual control updates */
-	int		_arming_sub;			/**< arming status of outputs */
+	int		_v_att_sub;				/**< vehicle attitude subscription */
+	int		_v_att_sp_sub;			/**< vehicle attitude setpoint subscription */
+	int		_v_rates_sp_sub;		/**< vehicle rates setpoint subscription */
+	int		_v_control_mode_sub;	/**< vehicle control mode subscription */
+	int		_params_sub;			/**< parameter updates subscription */
+	int		_manual_control_sp_sub;	/**< manual control setpoint subscription */
+	int		_armed_sub;				/**< arming status subscription */
 
 	orb_advert_t	_att_sp_pub;			/**< attitude setpoint publication */
-	orb_advert_t	_rates_sp_pub;			/**< rate setpoint publication */
-	orb_advert_t	_actuators_0_pub;		/**< actuator control group 0 setpoint */
+	orb_advert_t	_v_rates_sp_pub;		/**< rate setpoint publication */
+	orb_advert_t	_actuators_0_pub;		/**< attitude actuator controls publication */
 
-	struct vehicle_attitude_s			_att;			/**< vehicle attitude */
-	struct vehicle_attitude_setpoint_s	_att_sp;		/**< vehicle attitude setpoint */
-	struct manual_control_setpoint_s	_manual;		/**< r/c channel data */
-	struct vehicle_control_mode_s		_control_mode;	/**< vehicle control mode */
-	struct actuator_controls_s			_actuators;		/**< actuator control inputs */
-	struct actuator_armed_s				_arming;		/**< actuator arming status */
-	struct vehicle_rates_setpoint_s		_rates_sp;		/**< vehicle rates setpoint */
+	struct vehicle_attitude_s			_v_att;				/**< vehicle attitude */
+	struct vehicle_attitude_setpoint_s	_v_att_sp;			/**< vehicle attitude setpoint */
+	struct vehicle_rates_setpoint_s		_v_rates_sp;		/**< vehicle rates setpoint */
+	struct manual_control_setpoint_s	_manual_control_sp;	/**< manual control setpoint */
+	struct vehicle_control_mode_s		_v_control_mode;	/**< vehicle control mode */
+	struct actuator_controls_s			_actuators;			/**< actuator controls */
+	struct actuator_armed_s				_armed;				/**< actuator arming status */
 
 	perf_counter_t	_loop_perf;			/**< loop performance counter */
 
-	math::Vector<3> _rates_prev;			/**< angular rates on previous step */
+	math::Matrix<3, 3>	_R_sp;			/**< attitude setpoint rotation matrix */
+	math::Matrix<3, 3>	_R;				/**< rotation matrix for current state */
+	math::Vector<3>		_rates_prev;	/**< angular rates on previous step */
+	math::Vector<3>		_rates_sp;		/**< angular rates setpoint */
+	math::Vector<3>		_rates_int;		/**< angular rates integral error */
+	float				_thrust_sp;		/**< thrust setpoint */
+	math::Vector<3>		_att_control;	/**< attitude control vector */
+
+	math::Matrix<3, 3>	I;				/**< identity matrix */
+
+	bool	_reset_yaw_sp;			/**< reset yaw setpoint flag */
 
 	struct {
 		param_t att_p;
@@ -160,9 +171,9 @@ private:
 	int			parameters_update();
 
 	/**
-	 * Update control outputs
+	 * Check for parameter update and handle it.
 	 */
-	void		control_update();
+	void		parameter_update_poll();
 
 	/**
 	 * Check for changes in vehicle control mode.
@@ -175,9 +186,14 @@ private:
 	void		vehicle_manual_poll();
 
 	/**
-	 * Check for set triplet updates.
+	 * Check for attitude setpoint updates.
+	 */
+	void		vehicle_attitude_setpoint_poll();
+
+	/**
+	 * Check for rates setpoint updates.
 	 */
-	void		vehicle_setpoint_poll();
+	void		vehicle_rates_setpoint_poll();
 
 	/**
 	 * Check for arming status updates.
@@ -185,6 +201,16 @@ private:
 	void		arming_status_poll();
 
 	/**
+	 * Attitude controller.
+	 */
+	void		control_attitude(float dt);
+
+	/**
+	 * Attitude rates controller.
+	 */
+	void		control_attitude_rates(float dt);
+
+	/**
 	 * Shim for calling task_main from task_create.
 	 */
 	static void	task_main_trampoline(int argc, char *argv[]);
@@ -195,7 +221,7 @@ private:
 	void		task_main() __attribute__((noreturn));
 };
 
-namespace att_control
+namespace mc_att_control
 {
 
 /* oddly, ERROR is not defined for c++ */
@@ -213,34 +239,42 @@ MulticopterAttitudeControl::MulticopterAttitudeControl() :
 	_control_task(-1),
 
 /* subscriptions */
-	_att_sub(-1),
-	_att_sp_sub(-1),
-	_control_mode_sub(-1),
+	_v_att_sub(-1),
+	_v_att_sp_sub(-1),
+	_v_control_mode_sub(-1),
 	_params_sub(-1),
-	_manual_sub(-1),
-	_arming_sub(-1),
+	_manual_control_sp_sub(-1),
+	_armed_sub(-1),
 
 /* publications */
 	_att_sp_pub(-1),
-	_rates_sp_pub(-1),
+	_v_rates_sp_pub(-1),
 	_actuators_0_pub(-1),
 
 /* performance counters */
 	_loop_perf(perf_alloc(PC_ELAPSED, "fw att control"))
 
 {
-	memset(&_att, 0, sizeof(_att));
-	memset(&_att_sp, 0, sizeof(_att_sp));
-	memset(&_manual, 0, sizeof(_manual));
-	memset(&_control_mode, 0, sizeof(_control_mode));
-	memset(&_arming, 0, sizeof(_arming));
+	memset(&_v_att, 0, sizeof(_v_att));
+	memset(&_v_att_sp, 0, sizeof(_v_att_sp));
+	memset(&_manual_control_sp, 0, sizeof(_manual_control_sp));
+	memset(&_v_control_mode, 0, sizeof(_v_control_mode));
+	memset(&_armed, 0, sizeof(_armed));
 
 	_params.p.zero();
 	_params.rate_p.zero();
 	_params.rate_i.zero();
 	_params.rate_d.zero();
 
+	_R_sp.identity();
+	_R.identity();
 	_rates_prev.zero();
+	_rates_sp.zero();
+	_rates_int.zero();
+	_thrust_sp = 0.0f;
+	_att_control.zero();
+
+	I.identity();
 
 	_params_handles.att_p		= 	param_find("MC_ATT_P");
 	_params_handles.yaw_p		=	param_find("MC_YAW_P");
@@ -276,7 +310,7 @@ MulticopterAttitudeControl::~MulticopterAttitudeControl()
 		} while (_control_task != -1);
 	}
 
-	att_control::g_control = nullptr;
+	mc_att_control::g_control = nullptr;
 }
 
 int
@@ -312,393 +346,409 @@ MulticopterAttitudeControl::parameters_update()
 }
 
 void
-MulticopterAttitudeControl::vehicle_control_mode_poll()
+MulticopterAttitudeControl::parameter_update_poll()
 {
-	bool control_mode_updated;
+	bool updated;
 
 	/* Check HIL state if vehicle status has changed */
-	orb_check(_control_mode_sub, &control_mode_updated);
+	orb_check(_params_sub, &updated);
 
-	if (control_mode_updated) {
+	if (updated) {
+		struct parameter_update_s param_update;
+		orb_copy(ORB_ID(parameter_update), _params_sub, &param_update);
+		parameters_update();
+	}
+}
 
-		orb_copy(ORB_ID(vehicle_control_mode), _control_mode_sub, &_control_mode);
+void
+MulticopterAttitudeControl::vehicle_control_mode_poll()
+{
+	bool updated;
+
+	/* Check HIL state if vehicle status has changed */
+	orb_check(_v_control_mode_sub, &updated);
+
+	if (updated) {
+		orb_copy(ORB_ID(vehicle_control_mode), _v_control_mode_sub, &_v_control_mode);
 	}
 }
 
 void
 MulticopterAttitudeControl::vehicle_manual_poll()
 {
-	bool manual_updated;
+	bool updated;
 
 	/* get pilots inputs */
-	orb_check(_manual_sub, &manual_updated);
+	orb_check(_manual_control_sp_sub, &updated);
 
-	if (manual_updated) {
+	if (updated) {
 
-		orb_copy(ORB_ID(manual_control_setpoint), _manual_sub, &_manual);
+		orb_copy(ORB_ID(manual_control_setpoint), _manual_control_sp_sub, &_manual_control_sp);
 	}
 }
 
 void
-MulticopterAttitudeControl::vehicle_setpoint_poll()
+MulticopterAttitudeControl::vehicle_attitude_setpoint_poll()
 {
 	/* check if there is a new setpoint */
-	bool att_sp_updated;
-	orb_check(_att_sp_sub, &att_sp_updated);
+	bool updated;
+	orb_check(_v_att_sp_sub, &updated);
 
-	if (att_sp_updated) {
-		orb_copy(ORB_ID(vehicle_attitude_setpoint), _att_sp_sub, &_att_sp);
+	if (updated) {
+		orb_copy(ORB_ID(vehicle_attitude_setpoint), _v_att_sp_sub, &_v_att_sp);
 	}
 }
 
 void
-MulticopterAttitudeControl::arming_status_poll()
+MulticopterAttitudeControl::vehicle_rates_setpoint_poll()
 {
 	/* check if there is a new setpoint */
-	bool arming_updated;
-	orb_check(_arming_sub, &arming_updated);
+	bool updated;
+	orb_check(_v_rates_sp_sub, &updated);
 
-	if (arming_updated) {
-		orb_copy(ORB_ID(actuator_armed), _arming_sub, &_arming);
+	if (updated) {
+		orb_copy(ORB_ID(vehicle_rates_setpoint), _v_rates_sp_sub, &_v_rates_sp);
 	}
 }
 
 void
-MulticopterAttitudeControl::task_main_trampoline(int argc, char *argv[])
+MulticopterAttitudeControl::arming_status_poll()
 {
-	att_control::g_control->task_main();
+	/* check if there is a new setpoint */
+	bool updated;
+	orb_check(_armed_sub, &updated);
+
+	if (updated) {
+		orb_copy(ORB_ID(actuator_armed), _armed_sub, &_armed);
+	}
 }
 
+/*
+ * Attitude controller.
+ * Input: 'manual_control_setpoint' and 'vehicle_attitude_setpoint' topics (depending on mode)
+ * Output: '_rates_sp' vector, '_thrust_sp', 'vehicle_attitude_setpoint' topic (for manual modes)
+ */
 void
-MulticopterAttitudeControl::task_main()
+MulticopterAttitudeControl::control_attitude(float dt)
 {
-	/* inform about start */
-	warnx("started");
-	fflush(stdout);
-
-	/*
-	 * do subscriptions
-	 */
-	_att_sp_sub = orb_subscribe(ORB_ID(vehicle_attitude_setpoint));
-	_att_sub = orb_subscribe(ORB_ID(vehicle_attitude));
-	_control_mode_sub = orb_subscribe(ORB_ID(vehicle_control_mode));
-	_params_sub = orb_subscribe(ORB_ID(parameter_update));
-	_manual_sub = orb_subscribe(ORB_ID(manual_control_setpoint));
-	_arming_sub = orb_subscribe(ORB_ID(actuator_armed));
+	float yaw_sp_move_rate = 0.0f;
+	bool publish_att_sp = false;
 
-	/* rate limit attitude updates to 100Hz */
-	orb_set_interval(_att_sub, 10);
+	if (_v_control_mode.flag_control_manual_enabled) {
+		/* manual input, set or modify attitude setpoint */
 
-	parameters_update();
-
-	/* initialize values of critical structs until first regular update */
-	_arming.armed = false;
+		if (_v_control_mode.flag_control_velocity_enabled || _v_control_mode.flag_control_climb_rate_enabled) {
+			/* in assisted modes poll 'vehicle_attitude_setpoint' topic and modify it */
+			vehicle_attitude_setpoint_poll();
+		}
 
-	/* get an initial update for all sensor and status data */
-	vehicle_setpoint_poll();
-	vehicle_control_mode_poll();
-	vehicle_manual_poll();
-	arming_status_poll();
+		if (!_v_control_mode.flag_control_climb_rate_enabled) {
+			/* pass throttle directly if not in altitude stabilized mode */
+			_v_att_sp.thrust = _manual_control_sp.throttle;
+			publish_att_sp = true;
+		}
 
-	/* setpoint rotation matrix */
-	math::Matrix<3, 3> R_sp;
-	R_sp.identity();
+		if (!_armed.armed) {
+			/* reset yaw setpoint when disarmed */
+			_reset_yaw_sp = true;
+		}
 
-	/* rotation matrix for current state */
-	math::Matrix<3, 3> R;
-	R.identity();
+		/* move yaw setpoint in all modes */
+		if (_v_att_sp.thrust < 0.1f) {
+			// TODO
+			//if (_status.condition_landed) {
+			/* reset yaw setpoint if on ground */
+			//	reset_yaw_sp = true;
+			//}
+		} else {
+			if (_manual_control_sp.yaw < -YAW_DEADZONE || YAW_DEADZONE < _manual_control_sp.yaw) {
+				/* move yaw setpoint */
+				yaw_sp_move_rate = _manual_control_sp.yaw;
+				_v_att_sp.yaw_body = _wrap_pi(_v_att_sp.yaw_body + yaw_sp_move_rate * dt);
+				_v_att_sp.R_valid = false;
+				publish_att_sp = true;
+			}
+		}
 
-	/* current angular rates */
-	math::Vector<3> rates;
-	rates.zero();
+		/* reset yaw setpint to current position if needed */
+		if (_reset_yaw_sp) {
+			_reset_yaw_sp = false;
+			_v_att_sp.yaw_body = _v_att.yaw;
+			_v_att_sp.R_valid = false;
+			publish_att_sp = true;
+		}
 
-	/* angular rates integral error */
-	math::Vector<3> rates_int;
-	rates_int.zero();
+		if (!_v_control_mode.flag_control_velocity_enabled) {
+			/* update attitude setpoint if not in position control mode */
+			_v_att_sp.roll_body = _manual_control_sp.roll;
+			_v_att_sp.pitch_body = _manual_control_sp.pitch;
+			_v_att_sp.R_valid = false;
+			publish_att_sp = true;
+		}
 
-	/* identity matrix */
-	math::Matrix<3, 3> I;
-	I.identity();
+	} else {
+		/* in non-manual mode use 'vehicle_attitude_setpoint' topic */
+		vehicle_attitude_setpoint_poll();
 
-	math::Quaternion q;
+		/* reset yaw setpoint after non-manual control mode */
+		_reset_yaw_sp = true;
+	}
 
-	bool reset_yaw_sp = true;
+	_thrust_sp = _v_att_sp.thrust;
 
-	/* wakeup source(s) */
-	struct pollfd fds[2];
+	/* construct attitude setpoint rotation matrix */
+	if (_v_att_sp.R_valid) {
+		/* rotation matrix in _att_sp is valid, use it */
+		_R_sp.set(&_v_att_sp.R_body[0][0]);
 
-	/* Setup of loop */
-	fds[0].fd = _params_sub;
-	fds[0].events = POLLIN;
-	fds[1].fd = _att_sub;
-	fds[1].events = POLLIN;
+	} else {
+		/* rotation matrix in _att_sp is not valid, use euler angles instead */
+		_R_sp.from_euler(_v_att_sp.roll_body, _v_att_sp.pitch_body, _v_att_sp.yaw_body);
 
-	while (!_task_should_exit) {
+		/* copy rotation matrix back to setpoint struct */
+		memcpy(&_v_att_sp.R_body[0][0], &_R_sp.data[0][0], sizeof(_v_att_sp.R_body));
+		_v_att_sp.R_valid = true;
+	}
 
-		/* wait for up to 500ms for data */
-		int pret = poll(&fds[0], (sizeof(fds) / sizeof(fds[0])), 100);
+	/* publish the attitude setpoint if needed */
+	if (publish_att_sp) {
+		_v_att_sp.timestamp = hrt_absolute_time();
 
-		/* timed out - periodic check for _task_should_exit, etc. */
-		if (pret == 0)
-			continue;
+		if (_att_sp_pub > 0) {
+			orb_publish(ORB_ID(vehicle_attitude_setpoint), _att_sp_pub, &_v_att_sp);
 
-		/* this is undesirable but not much we can do - might want to flag unhappy status */
-		if (pret < 0) {
-			warn("poll error %d, %d", pret, errno);
-			continue;
+		} else {
+			_att_sp_pub = orb_advertise(ORB_ID(vehicle_attitude_setpoint), &_v_att_sp);
 		}
+	}
 
-		perf_begin(_loop_perf);
+	/* rotation matrix for current state */
+	_R.set(_v_att.R);
 
-		/* only update parameters if they changed */
-		if (fds[0].revents & POLLIN) {
-			/* copy the topic to clear updated flag */
-			struct parameter_update_s update;
-			orb_copy(ORB_ID(parameter_update), _params_sub, &update);
+	/* all input data is ready, run controller itself */
 
-			parameters_update();
-		}
+	/* try to move thrust vector shortest way, because yaw response is slower than roll/pitch */
+	math::Vector<3> R_z(_R(0, 2), _R(1, 2), _R(2, 2));
+	math::Vector<3> R_sp_z(_R_sp(0, 2), _R_sp(1, 2), _R_sp(2, 2));
 
-		/* only run controller if attitude changed */
-		if (fds[1].revents & POLLIN) {
-			static uint64_t last_run = 0;
-			float dt = (hrt_absolute_time() - last_run) / 1000000.0f;
-			last_run = hrt_absolute_time();
+	/* axis and sin(angle) of desired rotation */
+	math::Vector<3> e_R = _R.transposed() * (R_z % R_sp_z);
 
-			/* guard against too large dt's */
-			if (dt > 0.02f)
-				dt = 0.02f;
+	/* calculate angle error */
+	float e_R_z_sin = e_R.length();
+	float e_R_z_cos = R_z * R_sp_z;
 
-			/* copy attitude topic */
-			orb_copy(ORB_ID(vehicle_attitude), _att_sub, &_att);
+	/* calculate weight for yaw control */
+	float yaw_w = _R_sp(2, 2) * _R_sp(2, 2);
 
-			vehicle_setpoint_poll();
-			vehicle_control_mode_poll();
-			arming_status_poll();
-			vehicle_manual_poll();
+	/* calculate rotation matrix after roll/pitch only rotation */
+	math::Matrix<3, 3> R_rp;
 
-			float yaw_sp_move_rate = 0.0f;
-			bool publish_att_sp = false;
+	if (e_R_z_sin > 0.0f) {
+		/* get axis-angle representation */
+		float e_R_z_angle = atan2f(e_R_z_sin, e_R_z_cos);
+		math::Vector<3> e_R_z_axis = e_R / e_R_z_sin;
 
-			/* define which input is the dominating control input */
-			if (_control_mode.flag_control_manual_enabled) {
-				/* manual input */
-				if (!_control_mode.flag_control_climb_rate_enabled) {
-					/* pass throttle directly if not in altitude control mode */
-					_att_sp.thrust = _manual.throttle;
-				}
+		e_R = e_R_z_axis * e_R_z_angle;
 
-				if (!_arming.armed) {
-					/* reset yaw setpoint when disarmed */
-					reset_yaw_sp = true;
-				}
+		/* cross product matrix for e_R_axis */
+		math::Matrix<3, 3> e_R_cp;
+		e_R_cp.zero();
+		e_R_cp(0, 1) = -e_R_z_axis(2);
+		e_R_cp(0, 2) = e_R_z_axis(1);
+		e_R_cp(1, 0) = e_R_z_axis(2);
+		e_R_cp(1, 2) = -e_R_z_axis(0);
+		e_R_cp(2, 0) = -e_R_z_axis(1);
+		e_R_cp(2, 1) = e_R_z_axis(0);
 
-				if (_control_mode.flag_control_attitude_enabled) {
-					/* control attitude, update attitude setpoint depending on mode */
-
-					if (_att_sp.thrust < 0.1f) {
-						// TODO
-						//if (_status.condition_landed) {
-						/* reset yaw setpoint if on ground */
-						//	reset_yaw_sp = true;
-						//}
-					} else {
-						if (_manual.yaw < -YAW_DEADZONE || YAW_DEADZONE < _manual.yaw) {
-							/* move yaw setpoint */
-							yaw_sp_move_rate = _manual.yaw;
-							_att_sp.yaw_body = _wrap_pi(_att_sp.yaw_body + yaw_sp_move_rate * dt);
-							_att_sp.R_valid = false;
-							publish_att_sp = true;
-						}
-					}
-
-					/* reset yaw setpint to current position if needed */
-					if (reset_yaw_sp) {
-						reset_yaw_sp = false;
-						_att_sp.yaw_body = _att.yaw;
-						_att_sp.R_valid = false;
-						publish_att_sp = true;
-					}
-
-					if (!_control_mode.flag_control_velocity_enabled) {
-						/* update attitude setpoint if not in position control mode */
-						_att_sp.roll_body = _manual.roll;
-						_att_sp.pitch_body = _manual.pitch;
-						_att_sp.R_valid = false;
-						publish_att_sp = true;
-					}
+		/* rotation matrix for roll/pitch only rotation */
+		R_rp = _R * (I + e_R_cp * e_R_z_sin + e_R_cp * e_R_cp * (1.0f - e_R_z_cos));
 
-				} else {
-					/* manual rate inputs (ACRO) */
-					// TODO
-					/* reset yaw setpoint after ACRO */
-					reset_yaw_sp = true;
-				}
+	} else {
+		/* zero roll/pitch rotation */
+		R_rp = _R;
+	}
 
-			} else {
-				/* reset yaw setpoint after non-manual control */
-				reset_yaw_sp = true;
-			}
+	/* R_rp and _R_sp has the same Z axis, calculate yaw error */
+	math::Vector<3> R_sp_x(_R_sp(0, 0), _R_sp(1, 0), _R_sp(2, 0));
+	math::Vector<3> R_rp_x(R_rp(0, 0), R_rp(1, 0), R_rp(2, 0));
+	e_R(2) = atan2f((R_rp_x % R_sp_x) * R_sp_z, R_rp_x * R_sp_x) * yaw_w;
+
+	if (e_R_z_cos < 0.0f) {
+		/* for large thrust vector rotations use another rotation method:
+		 * calculate angle and axis for R -> R_sp rotation directly */
+		math::Quaternion q;
+		q.from_dcm(_R.transposed() * _R_sp);
+		math::Vector<3> e_R_d = q.imag();
+		e_R_d.normalize();
+		e_R_d *= 2.0f * atan2f(e_R_d.length(), q(0));
+
+		/* use fusion of Z axis based rotation and direct rotation */
+		float direct_w = e_R_z_cos * e_R_z_cos * yaw_w;
+		e_R = e_R * (1.0f - direct_w) + e_R_d * direct_w;
+	}
 
-			if (_att_sp.R_valid) {
-				/* rotation matrix in _att_sp is valid, use it */
-				R_sp.set(&_att_sp.R_body[0][0]);
+	/* calculate angular rates setpoint */
+	_rates_sp = _params.p.emult(e_R);
 
-			} else {
-				/* rotation matrix in _att_sp is not valid, use euler angles instead */
-				R_sp.from_euler(_att_sp.roll_body, _att_sp.pitch_body, _att_sp.yaw_body);
+	/* feed forward yaw setpoint rate */
+	_rates_sp(2) += yaw_sp_move_rate * yaw_w;
+}
 
-				/* copy rotation matrix back to setpoint struct */
-				memcpy(&_att_sp.R_body[0][0], &R_sp.data[0][0], sizeof(_att_sp.R_body));
-				_att_sp.R_valid = true;
-			}
+/*
+ * Attitude rates controller.
+ * Input: '_rates_sp' vector, '_thrust_sp'
+ * Output: '_att_control' vector
+ */
+void
+MulticopterAttitudeControl::control_attitude_rates(float dt)
+{
+	/* reset integral if disarmed */
+	if (!_armed.armed) {
+		_rates_int.zero();
+	}
 
-			if (publish_att_sp) {
-				/* publish the attitude setpoint */
-				_att_sp.timestamp = hrt_absolute_time();
+	/* current body angular rates */
+	math::Vector<3> rates;
+	rates(0) = _v_att.rollspeed;
+	rates(1) = _v_att.pitchspeed;
+	rates(2) = _v_att.yawspeed;
+
+	/* angular rates error */
+	math::Vector<3> rates_err = _rates_sp - rates;
+	_att_control = _params.rate_p.emult(rates_err) + _params.rate_d.emult(_rates_prev - rates) / dt + _rates_int;
+	_rates_prev = rates;
+
+	/* update integral only if not saturated on low limit */
+	if (_thrust_sp > 0.1f && _att_control.length() < _thrust_sp) {
+		for (int i = 0; i < 3; i++) {
+			float rate_i = _rates_int(i) + _params.rate_i(i) * rates_err(i) * dt;
+
+			if (isfinite(rate_i) && rate_i > -RATES_I_LIMIT && rate_i < RATES_I_LIMIT &&
+			    _att_control(i) > -RATES_I_LIMIT && _att_control(i) < RATES_I_LIMIT) {
+				_rates_int(i) = rate_i;
+			}
+		}
+	}
+}
 
-				if (_att_sp_pub > 0) {
-					orb_publish(ORB_ID(vehicle_attitude_setpoint), _att_sp_pub, &_att_sp);
+void
+MulticopterAttitudeControl::task_main_trampoline(int argc, char *argv[])
+{
+	mc_att_control::g_control->task_main();
+}
 
-				} else {
-					_att_sp_pub = orb_advertise(ORB_ID(vehicle_attitude_setpoint), &_att_sp);
-				}
-			}
+void
+MulticopterAttitudeControl::task_main()
+{
+	warnx("started");
+	fflush(stdout);
 
-			/* rotation matrix for current state */
-			R.set(_att.R);
+	/*
+	 * do subscriptions
+	 */
+	_v_att_sp_sub = orb_subscribe(ORB_ID(vehicle_attitude_setpoint));
+	_v_rates_sp_sub = orb_subscribe(ORB_ID(vehicle_rates_setpoint));
+	_v_att_sub = orb_subscribe(ORB_ID(vehicle_attitude));
+	_v_control_mode_sub = orb_subscribe(ORB_ID(vehicle_control_mode));
+	_params_sub = orb_subscribe(ORB_ID(parameter_update));
+	_manual_control_sp_sub = orb_subscribe(ORB_ID(manual_control_setpoint));
+	_armed_sub = orb_subscribe(ORB_ID(actuator_armed));
 
-			/* current body angular rates */
-			rates(0) = _att.rollspeed;
-			rates(1) = _att.pitchspeed;
-			rates(2) = _att.yawspeed;
+	/* rate limit attitude updates to 200Hz, failsafe against spam, normally runs at the same rate as attitude estimator */
+	orb_set_interval(_v_att_sub, 5);
 
-			/* try to move thrust vector shortest way, because yaw response is slower than roll/pitch */
-			math::Vector<3> R_z(R(0, 2), R(1, 2), R(2, 2));
-			math::Vector<3> R_sp_z(R_sp(0, 2), R_sp(1, 2), R_sp(2, 2));
+	/* initialize parameters cache */
+	parameters_update();
 
-			/* axis and sin(angle) of desired rotation */
-			math::Vector<3> e_R = R.transposed() * (R_z % R_sp_z);
+	/* wakeup source: vehicle attitude */
+	struct pollfd fds[1];
 
-			/* calculate angle error */
-			float e_R_z_sin = e_R.length();
-			float e_R_z_cos = R_z * R_sp_z;
+	fds[0].fd = _v_att_sub;
+	fds[0].events = POLLIN;
 
-			/* calculate weight for yaw control */
-			float yaw_w = R_sp(2, 2) * R_sp(2, 2);
+	while (!_task_should_exit) {
 
-			/* calculate rotation matrix after roll/pitch only rotation */
-			math::Matrix<3, 3> R_rp;
+		/* wait for up to 100ms for data */
+		int pret = poll(&fds[0], (sizeof(fds) / sizeof(fds[0])), 100);
 
-			if (e_R_z_sin > 0.0f) {
-				/* get axis-angle representation */
-				float e_R_z_angle = atan2f(e_R_z_sin, e_R_z_cos);
-				math::Vector<3> e_R_z_axis = e_R / e_R_z_sin;
+		/* timed out - periodic check for _task_should_exit */
+		if (pret == 0)
+			continue;
 
-				e_R = e_R_z_axis * e_R_z_angle;
+		/* this is undesirable but not much we can do - might want to flag unhappy status */
+		if (pret < 0) {
+			warn("poll error %d, %d", pret, errno);
+			/* sleep a bit before next try */
+			usleep(100000);
+			continue;
+		}
 
-				/* cross product matrix for e_R_axis */
-				math::Matrix<3, 3> e_R_cp;
-				e_R_cp.zero();
-				e_R_cp(0, 1) = -e_R_z_axis(2);
-				e_R_cp(0, 2) = e_R_z_axis(1);
-				e_R_cp(1, 0) = e_R_z_axis(2);
-				e_R_cp(1, 2) = -e_R_z_axis(0);
-				e_R_cp(2, 0) = -e_R_z_axis(1);
-				e_R_cp(2, 1) = e_R_z_axis(0);
+		perf_begin(_loop_perf);
 
-				/* rotation matrix for roll/pitch only rotation */
-				R_rp = R * (I + e_R_cp * e_R_z_sin + e_R_cp * e_R_cp * (1.0f - e_R_z_cos));
+		/* run controller on attitude changes */
+		if (fds[0].revents & POLLIN) {
+			static uint64_t last_run = 0;
+			float dt = (hrt_absolute_time() - last_run) / 1000000.0f;
+			last_run = hrt_absolute_time();
 
-			} else {
-				/* zero roll/pitch rotation */
-				R_rp = R;
-			}
+			/* guard against too small (< 2ms) and too large (> 20ms) dt's */
+			if (dt < 0.002f) {
+				dt = 0.002f;
 
-			/* R_rp and R_sp has the same Z axis, calculate yaw error */
-			math::Vector<3> R_sp_x(R_sp(0, 0), R_sp(1, 0), R_sp(2, 0));
-			math::Vector<3> R_rp_x(R_rp(0, 0), R_rp(1, 0), R_rp(2, 0));
-			e_R(2) = atan2f((R_rp_x % R_sp_x) * R_sp_z, R_rp_x * R_sp_x) * yaw_w;
-
-			if (e_R_z_cos < 0.0f) {
-				/* for large thrust vector rotations use another rotation method:
-				 * calculate angle and axis for R -> R_sp rotation directly */
-				q.from_dcm(R.transposed() * R_sp);
-				math::Vector<3> e_R_d = q.imag();
-				e_R_d.normalize();
-				e_R_d *= 2.0f * atan2f(e_R_d.length(), q(0));
-
-				/* use fusion of Z axis based rotation and direct rotation */
-				float direct_w = e_R_z_cos * e_R_z_cos * yaw_w;
-				e_R = e_R * (1.0f - direct_w) + e_R_d * direct_w;
+			} else if (dt > 0.02f) {
+				dt = 0.02f;
 			}
 
-			/* angular rates setpoint*/
-			math::Vector<3> rates_sp = _params.p.emult(e_R);
+			/* copy attitude topic */
+			orb_copy(ORB_ID(vehicle_attitude), _v_att_sub, &_v_att);
 
-			/* feed forward yaw setpoint rate */
-			rates_sp(2) += yaw_sp_move_rate * yaw_w;
+			/* check for updates in other topics */
+			parameter_update_poll();
+			vehicle_control_mode_poll();
+			arming_status_poll();
+			vehicle_manual_poll();
 
-			/* reset integral if disarmed */
-			// TODO add LANDED flag here
-			if (!_arming.armed) {
-				rates_int.zero();
-			}
+			if (_v_control_mode.flag_control_attitude_enabled) {
+				control_attitude(dt);
 
-			/* rate controller */
-			math::Vector<3> rates_err = rates_sp - rates;
-			math::Vector<3> control = _params.rate_p.emult(rates_err) + _params.rate_d.emult(_rates_prev - rates) / fmaxf(dt, 0.003f) + rates_int;
-			_rates_prev = rates;
+				/* publish attitude rates setpoint */
+				_v_rates_sp.roll = _rates_sp(0);
+				_v_rates_sp.pitch = _rates_sp(1);
+				_v_rates_sp.yaw = _rates_sp(2);
+				_v_rates_sp.thrust = _thrust_sp;
+				_v_rates_sp.timestamp = hrt_absolute_time();
 
-			/* update integral */
-			for (int i = 0; i < 3; i++) {
-				float rate_i = rates_int(i) + _params.rate_i(i) * rates_err(i) * dt;
+				if (_v_rates_sp_pub > 0) {
+					orb_publish(ORB_ID(vehicle_rates_setpoint), _v_rates_sp_pub, &_v_rates_sp);
 
-				if (isfinite(rate_i)) {
-					if (rate_i > -RATES_I_LIMIT && rate_i < RATES_I_LIMIT && control(i) > -RATES_I_LIMIT && control(i) < RATES_I_LIMIT) {
-						rates_int(i) = rate_i;
-					}
+				} else {
+					_v_rates_sp_pub = orb_advertise(ORB_ID(vehicle_rates_setpoint), &_v_rates_sp);
 				}
-			}
-
-			/* publish the attitude rates setpoint */
-			_rates_sp.roll = rates_sp(0);
-			_rates_sp.pitch = rates_sp(1);
-			_rates_sp.yaw = rates_sp(2);
-			_rates_sp.thrust = _att_sp.thrust;
-			_rates_sp.timestamp = hrt_absolute_time();
-
-			if (_rates_sp_pub > 0) {
-				orb_publish(ORB_ID(vehicle_rates_setpoint), _rates_sp_pub, &_rates_sp);
 
 			} else {
-				_rates_sp_pub = orb_advertise(ORB_ID(vehicle_rates_setpoint), &_rates_sp);
+				/* attitude controller disabled */
+				// TODO poll 'attitude_rates_setpoint' topic
+				_rates_sp.zero();
+				_thrust_sp = 0.0f;
 			}
 
-			/* publish the attitude controls */
-			if (_control_mode.flag_control_rates_enabled) {
-				_actuators.control[0] = (isfinite(control(0))) ? control(0) : 0.0f;
-				_actuators.control[1] = (isfinite(control(1))) ? control(1) : 0.0f;
-				_actuators.control[2] = (isfinite(control(2))) ? control(2) : 0.0f;
-				_actuators.control[3] = (isfinite(_rates_sp.thrust)) ? _rates_sp.thrust : 0.0f;
-				_actuators.timestamp = hrt_absolute_time();
+			if (_v_control_mode.flag_control_rates_enabled) {
+				control_attitude_rates(dt);
 
-			} else {
-				/* controller disabled, publish zero attitude controls */
-				_actuators.control[0] = 0.0f;
-				_actuators.control[1] = 0.0f;
-				_actuators.control[2] = 0.0f;
-				_actuators.control[3] = 0.0f;
+				/* publish actuator controls */
+				_actuators.control[0] = (isfinite(_att_control(0))) ? _att_control(0) : 0.0f;
+				_actuators.control[1] = (isfinite(_att_control(1))) ? _att_control(1) : 0.0f;
+				_actuators.control[2] = (isfinite(_att_control(2))) ? _att_control(2) : 0.0f;
+				_actuators.control[3] = (isfinite(_thrust_sp)) ? _thrust_sp : 0.0f;
 				_actuators.timestamp = hrt_absolute_time();
-			}
 
-			if (_actuators_0_pub > 0) {
-				/* publish the attitude setpoint */
-				orb_publish(ORB_ID(actuator_controls_0), _actuators_0_pub, &_actuators);
+				if (_actuators_0_pub > 0) {
+					orb_publish(ORB_ID(actuator_controls_0), _actuators_0_pub, &_actuators);
 
-			} else {
-				/* advertise and publish */
-				_actuators_0_pub = orb_advertise(ORB_ID(actuator_controls_0), &_actuators);
+				} else {
+					_actuators_0_pub = orb_advertise(ORB_ID(actuator_controls_0), &_actuators);
+				}
 			}
 		}
 
@@ -739,17 +789,17 @@ int mc_att_control_main(int argc, char *argv[])
 
 	if (!strcmp(argv[1], "start")) {
 
-		if (att_control::g_control != nullptr)
+		if (mc_att_control::g_control != nullptr)
 			errx(1, "already running");
 
-		att_control::g_control = new MulticopterAttitudeControl;
+		mc_att_control::g_control = new MulticopterAttitudeControl;
 
-		if (att_control::g_control == nullptr)
+		if (mc_att_control::g_control == nullptr)
 			errx(1, "alloc failed");
 
-		if (OK != att_control::g_control->start()) {
-			delete att_control::g_control;
-			att_control::g_control = nullptr;
+		if (OK != mc_att_control::g_control->start()) {
+			delete mc_att_control::g_control;
+			mc_att_control::g_control = nullptr;
 			err(1, "start failed");
 		}
 
@@ -757,16 +807,16 @@ int mc_att_control_main(int argc, char *argv[])
 	}
 
 	if (!strcmp(argv[1], "stop")) {
-		if (att_control::g_control == nullptr)
+		if (mc_att_control::g_control == nullptr)
 			errx(1, "not running");
 
-		delete att_control::g_control;
-		att_control::g_control = nullptr;
+		delete mc_att_control::g_control;
+		mc_att_control::g_control = nullptr;
 		exit(0);
 	}
 
 	if (!strcmp(argv[1], "status")) {
-		if (att_control::g_control) {
+		if (mc_att_control::g_control) {
 			errx(0, "running");
 
 		} else {