text: /****************************************************************************
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   *   Copyright (c) 2018 PX4 Development Team. All rights reserved.
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  /**
   * @file FlightManualAltitude.hpp
   *
   * Flight task for manual controlled altitude.
   */
  
  #pragma once
  
  #include "FlightTask.hpp"
  #include "Sticks.hpp"
  #include <lib/mathlib/math/filter/AlphaFilter.hpp>
  #include <uORB/Subscription.hpp>
  
  class FlightTaskManualAltitude : public FlightTask
  {
  public:
  	FlightTaskManualAltitude();
  	virtual ~FlightTaskManualAltitude() = default;
  	bool activate(const vehicle_local_position_setpoint_s &last_setpoint) override;
  	bool updateInitialize() override;
  	bool update() override;
  
  protected:
  	void _updateHeadingSetpoints(); /**< sets yaw or yaw speed */
  	void _ekfResetHandlerHeading(float delta_psi) override; /**< adjust heading setpoint in case of EKF reset event */
  	virtual void _updateSetpoints(); /**< updates all setpoints */
  	virtual void _scaleSticks(); /**< scales sticks to velocity in z */
  	bool _checkTakeoff() override;
  	void _updateConstraintsFromEstimator();
  
  	/**
  	 * rotates vector into local frame
  	 */
  	void _rotateIntoHeadingFrame(matrix::Vector2f &vec);
  
  	/**
  	 *  Check and sets for position lock.
  	 *  If sticks are at center position, the vehicle
  	 *  will exit velocity control and enter position control.
  	 */
  	void _updateAltitudeLock();
  
  	Sticks _sticks;
  	bool _sticks_data_required = true; ///< let inherited task-class define if it depends on stick data
  
  	DEFINE_PARAMETERS_CUSTOM_PARENT(FlightTask,
  					(ParamFloat<px4::params::MPC_HOLD_MAX_Z>) _param_mpc_hold_max_z,
  					(ParamInt<px4::params::MPC_ALT_MODE>) _param_mpc_alt_mode,
  					(ParamFloat<px4::params::MPC_HOLD_MAX_XY>) _param_mpc_hold_max_xy,
  					(ParamFloat<px4::params::MPC_Z_P>) _param_mpc_z_p, /**< position controller altitude propotional gain */
  					(ParamFloat<px4::params::MPC_MAN_Y_MAX>) _param_mpc_man_y_max, /**< scaling factor from stick to yaw rate */
  					(ParamFloat<px4::params::MPC_MAN_Y_TAU>) _param_mpc_man_y_tau,
  					(ParamFloat<px4::params::MPC_MAN_TILT_MAX>) _param_mpc_man_tilt_max, /**< maximum tilt allowed for manual flight */
  					(ParamFloat<px4::params::MPC_LAND_ALT1>) _param_mpc_land_alt1, /**< altitude at which to start downwards slowdown */
  					(ParamFloat<px4::params::MPC_LAND_ALT2>) _param_mpc_land_alt2, /**< altitude below wich to land with land speed */
  					(ParamFloat<px4::params::MPC_LAND_SPEED>)
  					_param_mpc_land_speed, /**< desired downwards speed when approaching the ground */
  					(ParamFloat<px4::params::MPC_TKO_SPEED>)
  					_param_mpc_tko_speed, /**< desired upwards speed when still close to the ground */
  					(ParamFloat<px4::params::MC_MAN_TILT_TAU>) _param_mc_man_tilt_tau
  				       )
  private:
  	bool _isYawInput();
  	void _unlockYaw();
  	void _lockYaw();
  
  	/**
  	 * Filter between stick input and yaw setpoint
  	 *
  	 * @param yawspeed_target yaw setpoint desired by the stick
  	 * @return filtered value from independent filter state
  	 */
  	float _applyYawspeedFilter(float yawspeed_target);
  
  	/**
  	 * Terrain following.
  	 * During terrain following, the position setpoint is adjusted
  	 * such that the distance to ground is kept constant.
  	 * @param apply_brake is true if user wants to break
  	 * @param stopped is true if vehicle has stopped moving in D-direction
  	 */
  	void _terrainFollowing(bool apply_brake, bool stopped);
  
  	/**
  	 * Minimum Altitude during range sensor operation.
  	 * If a range sensor is used for altitude estimates, for
  	 * best operation a minimum altitude is required. The minimum
  	 * altitude is only enforced during altitude lock.
  	 */
  	void _respectMinAltitude();
  
  	void _respectMaxAltitude();
  
  	/**
  	 * Sets downwards velocity constraint based on the distance to ground.
  	 * To ensure a slowdown to land speed before hitting the ground.
  	 */
  	void _respectGroundSlowdown();
  
  	void setGearAccordingToSwitch();
  
  	float _yawspeed_filter_state{}; /**< state of low-pass filter in rad/s */
  	uint8_t _reset_counter = 0; /**< counter for estimator resets in z-direction */
  	float _max_speed_up = 10.0f;
  	float _max_speed_down = 1.0f;
  	bool _terrain_follow{false}; /**< true when the vehicle is following the terrain height */
  	bool _terrain_hold{false}; /**< true when vehicle is controlling height above a static ground position */
  
  	float _min_distance_to_ground{(float)(-INFINITY)}; /**< min distance to ground constraint */
  	float _max_distance_to_ground{(float)INFINITY};  /**< max distance to ground constraint */
  
  	/**
  	 * Distance to ground during terrain following.
  	 * If user does not demand velocity change in D-direction and the vehcile
  	 * is in terrain-following mode, then height to ground will be locked to
  	 * _dist_to_ground_lock.
  	 */
  	float _dist_to_ground_lock = NAN;
  
  	AlphaFilter<matrix::Vector2f> _man_input_filter;
  };
  