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   *
   *   Copyright (c) 2013, 2014 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
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   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   ****************************************************************************/
  
  /**
   * @file mc_att_control_main.cpp
   * Multicopter attitude controller.
   *
   * @author Tobias Naegeli <naegelit@student.ethz.ch>
   * @author Lorenz Meier <lm@inf.ethz.ch>
   * @author Anton Babushkin <anton.babushkin@me.com>
   *
   * The controller has two loops: P loop for angular error and PD loop for angular rate error.
   * Desired rotation calculated keeping in mind that yaw response is normally slower than roll/pitch.
   * For small deviations controller rotates copter to have shortest path of thrust vector and independently rotates around yaw,
   * so actual rotation axis is not constant. For large deviations controller rotates copter around fixed axis.
   * These two approaches fused seamlessly with weight depending on angular error.
   * When thrust vector directed near-horizontally (e.g. roll ~= PI/2) yaw setpoint ignored because of singularity.
   * Controller doesn't use Euler angles for work, they generated only for more human-friendly control and logging.
   * If rotation matrix setpoint is invalid it will be generated from Euler angles for compatibility with old position controllers.
   */
  
  #include <nuttx/config.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  #include <errno.h>
  #include <math.h>
  #include <poll.h>
  #include <drivers/drv_hrt.h>
  #include <arch/board/board.h>
  #include <uORB/uORB.h>
  #include <uORB/topics/vehicle_attitude_setpoint.h>
  #include <uORB/topics/manual_control_setpoint.h>
  #include <uORB/topics/actuator_controls.h>
  #include <uORB/topics/vehicle_rates_setpoint.h>
  #include <uORB/topics/vehicle_attitude.h>
  #include <uORB/topics/vehicle_control_mode.h>
  #include <uORB/topics/vehicle_status.h>
  #include <uORB/topics/actuator_armed.h>
  #include <uORB/topics/parameter_update.h>
  #include <systemlib/param/param.h>
  #include <systemlib/err.h>
  #include <systemlib/perf_counter.h>
  #include <systemlib/systemlib.h>
  #include <systemlib/circuit_breaker.h>
  #include <lib/mathlib/mathlib.h>
  #include <lib/geo/geo.h>
  
  /**
   * Multicopter attitude control app start / stop handling function
   *
   * @ingroup apps
   */
  extern "C" __EXPORT int mc_att_control_main(int argc, char *argv[]);
  
  #define YAW_DEADZONE	0.05f
  #define MIN_TAKEOFF_THRUST    0.2f
  #define RATES_I_LIMIT	0.3f
  
  class MulticopterAttitudeControl
  {
  public:
  	/**
  	 * Constructor
  	 */
  	MulticopterAttitudeControl();
  
  	/**
  	 * Destructor, also kills the main task
  	 */
  	~MulticopterAttitudeControl();
  
  	/**
  	 * Start the multicopter attitude control task.
  	 *
  	 * @return		OK on success.
  	 */
  	int		start();
  
  private:
  
  	bool	_task_should_exit;		/**< if true, task_main() should exit */
  	int		_control_task;			/**< task handle */
  
  	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 */
  	int		_vehicle_status_sub;	/**< vehicle status subscription */
  
  	orb_advert_t	_att_sp_pub;			/**< attitude setpoint publication */
  	orb_advert_t	_v_rates_sp_pub;		/**< rate setpoint publication */
  	orb_advert_t	_actuators_0_pub;		/**< attitude actuator controls publication */
  
  	orb_id_t _rates_sp_id;	/**< pointer to correct rates setpoint uORB metadata structure */
  	orb_id_t _actuators_id;	/**< pointer to correct actuator controls0 uORB metadata structure */
  
  	bool		_actuators_0_circuit_breaker_enabled;	/**< circuit breaker to suppress output */
  
  	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 */
  	struct vehicle_status_s				_vehicle_status;	/**< vehicle status */
  
  	perf_counter_t	_loop_perf;			/**< loop performance counter */
  
  	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 roll_p;
  		param_t roll_rate_p;
  		param_t roll_rate_i;
  		param_t roll_rate_d;
  		param_t pitch_p;
  		param_t pitch_rate_p;
  		param_t pitch_rate_i;
  		param_t pitch_rate_d;
  		param_t yaw_p;
  		param_t yaw_rate_p;
  		param_t yaw_rate_i;
  		param_t yaw_rate_d;
  		param_t yaw_ff;
  		param_t yaw_rate_max;
  
  		param_t man_roll_max;
  		param_t man_pitch_max;
  		param_t man_yaw_max;
  		param_t acro_roll_max;
  		param_t acro_pitch_max;
  		param_t acro_yaw_max;
  
  	}		_params_handles;		/**< handles for interesting parameters */
  
  	struct {
  		math::Vector<3> att_p;					/**< P gain for angular error */
  		math::Vector<3> rate_p;				/**< P gain for angular rate error */
  		math::Vector<3> rate_i;				/**< I gain for angular rate error */
  		math::Vector<3> rate_d;				/**< D gain for angular rate error */
  		float yaw_ff;						/**< yaw control feed-forward */
  		float yaw_rate_max;					/**< max yaw rate */
  
  		float man_roll_max;
  		float man_pitch_max;
  		float man_yaw_max;
  		math::Vector<3> acro_rate_max;		/**< max attitude rates in acro mode */
  
  	}		_params;
  
  	/**
  	 * Update our local parameter cache.
  	 */
  	int			parameters_update();
  
  	/**
  	 * Check for parameter update and handle it.
  	 */
  	void		parameter_update_poll();
  
  	/**
  	 * Check for changes in vehicle control mode.
  	 */
  	void		vehicle_control_mode_poll();
  
  	/**
  	 * Check for changes in manual inputs.
  	 */
  	void		vehicle_manual_poll();
  
  	/**
  	 * Check for attitude setpoint updates.
  	 */
  	void		vehicle_attitude_setpoint_poll();
  
  	/**
  	 * Check for rates setpoint updates.
  	 */
  	void		vehicle_rates_setpoint_poll();
  
  	/**
  	 * Check for arming status updates.
  	 */
  	void		arming_status_poll();
  
  	/**
  	 * Attitude controller.
  	 */
  	void		control_attitude(float dt);
  
  	/**
  	 * Attitude rates controller.
  	 */
  	void		control_attitude_rates(float dt);
  
  	/**
  	 * Check for vehicle status updates.
  	 */
  	void		vehicle_status_poll();
  
  	/**
  	 * Shim for calling task_main from task_create.
  	 */
  	static void	task_main_trampoline(int argc, char *argv[]);
  
  	/**
  	 * Main attitude control task.
  	 */
  	void		task_main();
  };
  
  namespace mc_att_control
  {
  
  /* oddly, ERROR is not defined for c++ */
  #ifdef ERROR
  # undef ERROR
  #endif
  static const int ERROR = -1;
  
  MulticopterAttitudeControl	*g_control;
  }
  
  MulticopterAttitudeControl::MulticopterAttitudeControl() :
  
  	_task_should_exit(false),
  	_control_task(-1),
  
  /* subscriptions */
  	_v_att_sub(-1),
  	_v_att_sp_sub(-1),
  	_v_control_mode_sub(-1),
  	_params_sub(-1),
  	_manual_control_sp_sub(-1),
  	_armed_sub(-1),
  	_vehicle_status_sub(-1),
  
  /* publications */
  	_att_sp_pub(-1),
  	_v_rates_sp_pub(-1),
  	_actuators_0_pub(-1),
  	_rates_sp_id(0),
  	_actuators_id(0),
  
  	_actuators_0_circuit_breaker_enabled(false),
  
  /* performance counters */
  	_loop_perf(perf_alloc(PC_ELAPSED, "mc_att_control"))
  
  {
  	memset(&_v_att, 0, sizeof(_v_att));
  	memset(&_v_att_sp, 0, sizeof(_v_att_sp));
  	memset(&_v_rates_sp, 0, sizeof(_v_rates_sp));
  	memset(&_manual_control_sp, 0, sizeof(_manual_control_sp));
  	memset(&_v_control_mode, 0, sizeof(_v_control_mode));
  	memset(&_actuators, 0, sizeof(_actuators));
  	memset(&_armed, 0, sizeof(_armed));
  	memset(&_vehicle_status, 0, sizeof(_vehicle_status));
  	_vehicle_status.is_rotary_wing = true;
  
  	_params.att_p.zero();
  	_params.rate_p.zero();
  	_params.rate_i.zero();
  	_params.rate_d.zero();
  	_params.yaw_ff = 0.0f;
  	_params.yaw_rate_max = 0.0f;
  	_params.man_roll_max = 0.0f;
  	_params.man_pitch_max = 0.0f;
  	_params.man_yaw_max = 0.0f;
  	_params.acro_rate_max.zero();
  
  	_rates_prev.zero();
  	_rates_sp.zero();
  	_rates_int.zero();
  	_thrust_sp = 0.0f;
  	_att_control.zero();
  
  	_I.identity();
  
  	_params_handles.roll_p			= 	param_find("MC_ROLL_P");
  	_params_handles.roll_rate_p		= 	param_find("MC_ROLLRATE_P");
  	_params_handles.roll_rate_i		= 	param_find("MC_ROLLRATE_I");
  	_params_handles.roll_rate_d		= 	param_find("MC_ROLLRATE_D");
  	_params_handles.pitch_p			= 	param_find("MC_PITCH_P");
  	_params_handles.pitch_rate_p	= 	param_find("MC_PITCHRATE_P");
  	_params_handles.pitch_rate_i	= 	param_find("MC_PITCHRATE_I");
  	_params_handles.pitch_rate_d	= 	param_find("MC_PITCHRATE_D");
  	_params_handles.yaw_p			=	param_find("MC_YAW_P");
  	_params_handles.yaw_rate_p		= 	param_find("MC_YAWRATE_P");
  	_params_handles.yaw_rate_i		= 	param_find("MC_YAWRATE_I");
  	_params_handles.yaw_rate_d		= 	param_find("MC_YAWRATE_D");
  	_params_handles.yaw_ff			= 	param_find("MC_YAW_FF");
  	_params_handles.yaw_rate_max	= 	param_find("MC_YAWRATE_MAX");
  	_params_handles.man_roll_max	= 	param_find("MC_MAN_R_MAX");
  	_params_handles.man_pitch_max	= 	param_find("MC_MAN_P_MAX");
  	_params_handles.man_yaw_max		= 	param_find("MC_MAN_Y_MAX");
  	_params_handles.acro_roll_max	= 	param_find("MC_ACRO_R_MAX");
  	_params_handles.acro_pitch_max	= 	param_find("MC_ACRO_P_MAX");
  	_params_handles.acro_yaw_max		= 	param_find("MC_ACRO_Y_MAX");
  
  	/* fetch initial parameter values */
  	parameters_update();
  }
  
  MulticopterAttitudeControl::~MulticopterAttitudeControl()
  {
  	if (_control_task != -1) {
  		/* task wakes up every 100ms or so at the longest */
  		_task_should_exit = true;
  
  		/* wait for a second for the task to quit at our request */
  		unsigned i = 0;
  
  		do {
  			/* wait 20ms */
  			usleep(20000);
  
  			/* if we have given up, kill it */
  			if (++i > 50) {
  				task_delete(_control_task);
  				break;
  			}
  		} while (_control_task != -1);
  	}
  
  	mc_att_control::g_control = nullptr;
  }
  
  int
  MulticopterAttitudeControl::parameters_update()
  {
  	float v;
  
  	/* roll gains */
  	param_get(_params_handles.roll_p, &v);
  	_params.att_p(0) = v;
  	param_get(_params_handles.roll_rate_p, &v);
  	_params.rate_p(0) = v;
  	param_get(_params_handles.roll_rate_i, &v);
  	_params.rate_i(0) = v;
  	param_get(_params_handles.roll_rate_d, &v);
  	_params.rate_d(0) = v;
  
  	/* pitch gains */
  	param_get(_params_handles.pitch_p, &v);
  	_params.att_p(1) = v;
  	param_get(_params_handles.pitch_rate_p, &v);
  	_params.rate_p(1) = v;
  	param_get(_params_handles.pitch_rate_i, &v);
  	_params.rate_i(1) = v;
  	param_get(_params_handles.pitch_rate_d, &v);
  	_params.rate_d(1) = v;
  
  	/* yaw gains */
  	param_get(_params_handles.yaw_p, &v);
  	_params.att_p(2) = v;
  	param_get(_params_handles.yaw_rate_p, &v);
  	_params.rate_p(2) = v;
  	param_get(_params_handles.yaw_rate_i, &v);
  	_params.rate_i(2) = v;
  	param_get(_params_handles.yaw_rate_d, &v);
  	_params.rate_d(2) = v;
  
  	param_get(_params_handles.yaw_ff, &_params.yaw_ff);
  	param_get(_params_handles.yaw_rate_max, &_params.yaw_rate_max);
  	_params.yaw_rate_max = math::radians(_params.yaw_rate_max);
  
  	/* manual control scale */
  	param_get(_params_handles.man_roll_max, &_params.man_roll_max);
  	param_get(_params_handles.man_pitch_max, &_params.man_pitch_max);
  	param_get(_params_handles.man_yaw_max, &_params.man_yaw_max);
  	_params.man_roll_max = math::radians(_params.man_roll_max);
  	_params.man_pitch_max = math::radians(_params.man_pitch_max);
  	_params.man_yaw_max = math::radians(_params.man_yaw_max);
  
  	/* acro control scale */
  	param_get(_params_handles.acro_roll_max, &v);
  	_params.acro_rate_max(0) = math::radians(v);
  	param_get(_params_handles.acro_pitch_max, &v);
  	_params.acro_rate_max(1) = math::radians(v);
  	param_get(_params_handles.acro_yaw_max, &v);
  	_params.acro_rate_max(2) = math::radians(v);
  
  	_actuators_0_circuit_breaker_enabled = circuit_breaker_enabled("CBRK_RATE_CTRL", CBRK_RATE_CTRL_KEY);
  
  	return OK;
  }
  
  void
  MulticopterAttitudeControl::parameter_update_poll()
  {
  	bool updated;
  
  	/* Check if parameters have changed */
  	orb_check(_params_sub, &updated);
  
  	if (updated) {
  		struct parameter_update_s param_update;
  		orb_copy(ORB_ID(parameter_update), _params_sub, &param_update);
  		parameters_update();
  	}
  }
  
  void
  MulticopterAttitudeControl::vehicle_control_mode_poll()
  {
  	bool updated;
  
  	/* Check if vehicle control mode 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 updated;
  
  	/* get pilots inputs */
  	orb_check(_manual_control_sp_sub, &updated);
  
  	if (updated) {
  		orb_copy(ORB_ID(manual_control_setpoint), _manual_control_sp_sub, &_manual_control_sp);
  	}
  }
  
  void
  MulticopterAttitudeControl::vehicle_attitude_setpoint_poll()
  {
  	/* check if there is a new setpoint */
  	bool updated;
  	orb_check(_v_att_sp_sub, &updated);
  
  	if (updated) {
  		orb_copy(ORB_ID(vehicle_attitude_setpoint), _v_att_sp_sub, &_v_att_sp);
  	}
  }
  
  void
  MulticopterAttitudeControl::vehicle_rates_setpoint_poll()
  {
  	/* check if there is a new setpoint */
  	bool updated;
  	orb_check(_v_rates_sp_sub, &updated);
  
  	if (updated) {
  		orb_copy(ORB_ID(vehicle_rates_setpoint), _v_rates_sp_sub, &_v_rates_sp);
  	}
  }
  
  void
  MulticopterAttitudeControl::arming_status_poll()
  {
  	/* 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);
  	}
  }
  
  void
  MulticopterAttitudeControl::vehicle_status_poll()
  {
  	/* check if there is new status information */
  	bool vehicle_status_updated;
  	orb_check(_vehicle_status_sub, &vehicle_status_updated);
  
  	if (vehicle_status_updated) {
  		orb_copy(ORB_ID(vehicle_status), _vehicle_status_sub, &_vehicle_status);
  		/* set correct uORB ID, depending on if vehicle is VTOL or not */
  		if (!_rates_sp_id) {
  			if (_vehicle_status.is_vtol) {
  				_rates_sp_id = ORB_ID(mc_virtual_rates_setpoint);
  				_actuators_id = ORB_ID(actuator_controls_virtual_mc);
  			} else {
  				_rates_sp_id = ORB_ID(vehicle_rates_setpoint);
  				_actuators_id = ORB_ID(actuator_controls_0);
  			}
  		}
  	}
  }
  
  /*
   * 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::control_attitude(float dt)
  {
  	float yaw_sp_move_rate = 0.0f;
  	bool publish_att_sp = false;
  
  	if (_v_control_mode.flag_control_manual_enabled) {
  		/* manual input, set or modify attitude setpoint */
  
  		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();
  		}
  
  		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.z;
  			publish_att_sp = true;
  		}
  
  		if (!_armed.armed) {
  			/* reset yaw setpoint when disarmed */
  			_reset_yaw_sp = true;
  		}
  
  		/* 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 {
  			/* move yaw setpoint */
  			yaw_sp_move_rate = _manual_control_sp.r * _params.man_yaw_max;
  			_v_att_sp.yaw_body = _wrap_pi(_v_att_sp.yaw_body + yaw_sp_move_rate * dt);
  			float yaw_offs_max = _params.man_yaw_max / _params.att_p(2);
  			float yaw_offs = _wrap_pi(_v_att_sp.yaw_body - _v_att.yaw);
  			if (yaw_offs < - yaw_offs_max) {
  				_v_att_sp.yaw_body = _wrap_pi(_v_att.yaw - yaw_offs_max);
  
  			} else if (yaw_offs > yaw_offs_max) {
  				_v_att_sp.yaw_body = _wrap_pi(_v_att.yaw + yaw_offs_max);
  			}
  			_v_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;
  			_v_att_sp.yaw_body = _v_att.yaw;
  			_v_att_sp.R_valid = false;
  			publish_att_sp = true;
  		}
  
  		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.y * _params.man_roll_max;
  			_v_att_sp.pitch_body = -_manual_control_sp.x * _params.man_pitch_max;
  			_v_att_sp.R_valid = false;
  			publish_att_sp = true;
  		}
  
  	} else {
  		/* in non-manual mode use 'vehicle_attitude_setpoint' topic */
  		vehicle_attitude_setpoint_poll();
  
  		/* reset yaw setpoint after non-manual control mode */
  		_reset_yaw_sp = true;
  	}
  
  	_thrust_sp = _v_att_sp.thrust;
  
  	/* construct attitude setpoint rotation matrix */
  	math::Matrix<3, 3> R_sp;
  
  	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]);
  
  	} 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);
  
  		/* 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;
  	}
  
  	/* publish the attitude setpoint if needed */
  	if (publish_att_sp && _vehicle_status.is_rotary_wing) {
  		_v_att_sp.timestamp = hrt_absolute_time();
  
  		if (_att_sp_pub > 0) {
  			orb_publish(ORB_ID(vehicle_attitude_setpoint), _att_sp_pub, &_v_att_sp);
  
  		} else {
  			_att_sp_pub = orb_advertise(ORB_ID(vehicle_attitude_setpoint), &_v_att_sp);
  		}
  	}
  
  	/* rotation matrix for current state */
  	math::Matrix<3, 3> R;
  	R.set(_v_att.R);
  
  	/* all input data is ready, run controller itself */
  
  	/* 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));
  
  	/* axis and sin(angle) of desired rotation */
  	math::Vector<3> e_R = R.transposed() * (R_z % R_sp_z);
  
  	/* calculate angle error */
  	float e_R_z_sin = e_R.length();
  	float e_R_z_cos = R_z * R_sp_z;
  
  	/* calculate weight for yaw control */
  	float yaw_w = R_sp(2, 2) * R_sp(2, 2);
  
  	/* calculate rotation matrix after roll/pitch only rotation */
  	math::Matrix<3, 3> R_rp;
  
  	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;
  
  		e_R = e_R_z_axis * e_R_z_angle;
  
  		/* 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);
  
  		/* 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 {
  		/* zero roll/pitch rotation */
  		R_rp = R;
  	}
  
  	/* 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;
  	}
  
  	/* calculate angular rates setpoint */
  	_rates_sp = _params.att_p.emult(e_R);
  
  	/* limit yaw rate */
  	_rates_sp(2) = math::constrain(_rates_sp(2), -_params.yaw_rate_max, _params.yaw_rate_max);
  
  	/* feed forward yaw setpoint rate */
  	_rates_sp(2) += yaw_sp_move_rate * yaw_w * _params.yaw_ff;
  }
  
  /*
   * 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 || !_vehicle_status.is_rotary_wing) {
  		_rates_int.zero();
  	}
  
  	/* 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 > MIN_TAKEOFF_THRUST) {
  		for (int i = 0; i < 3; i++) {
  			if (fabsf(_att_control(i)) < _thrust_sp) {
  				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;
  				}
  			}
  		}
  	}
  }
  
  void
  MulticopterAttitudeControl::task_main_trampoline(int argc, char *argv[])
  {
  	mc_att_control::g_control->task_main();
  }
  
  void
  MulticopterAttitudeControl::task_main()
  {
  
  	/*
  	 * 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));
  	_vehicle_status_sub = orb_subscribe(ORB_ID(vehicle_status));
  
  	/* initialize parameters cache */
  	parameters_update();
  
  	/* wakeup source: vehicle attitude */
  	struct pollfd fds[1];
  
  	fds[0].fd = _v_att_sub;
  	fds[0].events = POLLIN;
  
  	while (!_task_should_exit) {
  
  		/* wait for up to 100ms for data */
  		int pret = poll(&fds[0], (sizeof(fds) / sizeof(fds[0])), 100);
  
  		/* timed out - periodic check for _task_should_exit */
  		if (pret == 0)
  			continue;
  
  		/* 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;
  		}
  
  		perf_begin(_loop_perf);
  
  		/* 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();
  
  			/* guard against too small (< 2ms) and too large (> 20ms) dt's */
  			if (dt < 0.002f) {
  				dt = 0.002f;
  
  			} else if (dt > 0.02f) {
  				dt = 0.02f;
  			}
  
  			/* copy attitude topic */
  			orb_copy(ORB_ID(vehicle_attitude), _v_att_sub, &_v_att);
  
  			/* check for updates in other topics */
  			parameter_update_poll();
  			vehicle_control_mode_poll();
  			arming_status_poll();
  			vehicle_manual_poll();
  			vehicle_status_poll();
  
  			if (_v_control_mode.flag_control_attitude_enabled) {
  				control_attitude(dt);
  
  				/* 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();
  
  				if (_v_rates_sp_pub > 0) {
  					orb_publish(_rates_sp_id, _v_rates_sp_pub, &_v_rates_sp);
  
  				} else if (_rates_sp_id) {
  					_v_rates_sp_pub = orb_advertise(_rates_sp_id, &_v_rates_sp);
  				}
  
  			} else {
  				/* attitude controller disabled, poll rates setpoint topic */
  				if (_v_control_mode.flag_control_manual_enabled) {
  					/* manual rates control - ACRO mode */
  					_rates_sp = math::Vector<3>(_manual_control_sp.y, -_manual_control_sp.x, _manual_control_sp.r).emult(_params.acro_rate_max);
  					_thrust_sp = _manual_control_sp.z;
  
  					/* reset yaw setpoint after ACRO */
  					_reset_yaw_sp = true;
  
  					/* 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();
  
  					if (_v_rates_sp_pub > 0) {
  						orb_publish(_rates_sp_id, _v_rates_sp_pub, &_v_rates_sp);
  
  					} else if (_rates_sp_id) {
  						_v_rates_sp_pub = orb_advertise(_rates_sp_id, &_v_rates_sp);
  					}
  
  				} else {
  					/* attitude controller disabled, poll rates setpoint topic */
  					vehicle_rates_setpoint_poll();
  					_rates_sp(0) = _v_rates_sp.roll;
  					_rates_sp(1) = _v_rates_sp.pitch;
  					_rates_sp(2) = _v_rates_sp.yaw;
  					_thrust_sp = _v_rates_sp.thrust;
  				}
  			}
  
  			if (_v_control_mode.flag_control_rates_enabled) {
  				control_attitude_rates(dt);
  
  				/* 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_circuit_breaker_enabled) {
  					if (_actuators_0_pub > 0) {
  						orb_publish(_actuators_id, _actuators_0_pub, &_actuators);
  
  					} else if (_actuators_id) {
  						_actuators_0_pub = orb_advertise(_actuators_id, &_actuators);
  					}
  
  				}
  			}
  		}
  
  		perf_end(_loop_perf);
  	}
  
  	warnx("exit");
  
  	_control_task = -1;
  	_exit(0);
  }
  
  int
  MulticopterAttitudeControl::start()
  {
  	ASSERT(_control_task == -1);
  
  	/* start the task */
  	_control_task = task_spawn_cmd("mc_att_control",
  				       SCHED_DEFAULT,
  				       SCHED_PRIORITY_MAX - 5,
  				       2000,
  				       (main_t)&MulticopterAttitudeControl::task_main_trampoline,
  				       nullptr);
  
  	if (_control_task < 0) {
  		warn("task start failed");
  		return -errno;
  	}
  
  	return OK;
  }
  
  int mc_att_control_main(int argc, char *argv[])
  {
  	if (argc < 1)
  		errx(1, "usage: mc_att_control {start|stop|status}");
  
  	if (!strcmp(argv[1], "start")) {
  
  		if (mc_att_control::g_control != nullptr)
  			errx(1, "already running");
  
  		mc_att_control::g_control = new MulticopterAttitudeControl;
  
  		if (mc_att_control::g_control == nullptr)
  			errx(1, "alloc failed");
  
  		if (OK != mc_att_control::g_control->start()) {
  			delete mc_att_control::g_control;
  			mc_att_control::g_control = nullptr;
  			err(1, "start failed");
  		}
  
  		exit(0);
  	}
  
  	if (!strcmp(argv[1], "stop")) {
  		if (mc_att_control::g_control == nullptr)
  			errx(1, "not running");
  
  		delete mc_att_control::g_control;
  		mc_att_control::g_control = nullptr;
  		exit(0);
  	}
  
  	if (!strcmp(argv[1], "status")) {
  		if (mc_att_control::g_control) {
  			errx(0, "running");
  
  		} else {
  			errx(1, "not running");
  		}
  	}
  
  	warnx("unrecognized command");
  	return 1;
  }
  