PX4-Autopilot/src/lib/external_lgpl/tecs/tecs.h

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-

/// @file    tecs.h
/// @brief   Combined Total Energy Speed & Height Control.

/*
 *  Written by Paul Riseborough 2013 to provide:
 *  - Combined control of speed and height using throttle to control
 *    total energy and pitch angle to control exchange of energy between
 *    potential and kinetic.
 *    Selectable speed or height priority modes when calculating pitch angle
 *  - Fallback mode when no airspeed measurement is available that
 *    sets throttle based on height rate demand and switches pitch angle control to
 *    height priority
 *  - Underspeed protection that demands maximum throttle switches pitch angle control
 *    to speed priority mode
 *  - Relative ease of tuning through use of intuitive time constant, trim rate and damping parameters and the use
 *    of easy to measure aircraft performance data
 */

#ifndef TECS_H
#define TECS_H

#include <mathlib/mathlib.h>
#include <stdint.h>

class __EXPORT TECS
{
public:
	TECS() :

		_airspeed_enabled(false),
		_throttle_slewrate(0.0f),
		_climbOutDem(false),
		_hgt_dem_prev(0.0f),
		_hgt_dem_adj_last(0.0f),
		_hgt_dem_in_old(0.0f),
		_TAS_dem_last(0.0f),
		_TAS_dem_adj(0.0f),
		_TAS_dem(0.0f),
		_integ1_state(0.0f),
		_integ2_state(0.0f),
		_integ3_state(0.0f),
		_integ4_state(0.0f),
		_integ5_state(0.0f),
		_integ6_state(0.0f),
		_integ7_state(0.0f),
		_pitch_dem(0.0f),
		_last_pitch_dem(0.0f),
		_SPE_dem(0.0f),
		_SKE_dem(0.0f),
		_SPEdot_dem(0.0f),
		_SKEdot_dem(0.0f),
		_SPE_est(0.0f),
		_SKE_est(0.0f),
		_SPEdot(0.0f),
		_SKEdot(0.0f),
		_vel_dot(0.0f),
		_STEdotErrLast(0.0f) {

	}

	bool airspeed_sensor_enabled() {
		return _airspeed_enabled;
	}

	void enable_airspeed(bool enabled) {
		_airspeed_enabled = enabled;
	}

	// Update of the estimated height and height rate internal state
	// Update of the inertial speed rate internal state
	// Should be called at 50Hz or greater
	void update_50hz(float baro_altitude, float airspeed, const math::Dcm &rotMat, const math::Vector3 &accel_body, const math::Vector3 &accel_earth);

	// Update the control loop calculations
	void update_pitch_throttle(const math::Dcm &rotMat, float pitch, float baro_altitude, float hgt_dem, float EAS_dem, float indicated_airspeed, float EAS2TAS, bool climbOutDem, float ptchMinCO,
				   float throttle_min, float throttle_max, float throttle_cruise,
				   float pitch_limit_min, float pitch_limit_max);
	// demanded throttle in percentage
	// should return 0 to 100
	float get_throttle_demand(void) {
		return _throttle_dem;
	}
	int32_t get_throttle_demand_percent(void) {
		return get_throttle_demand();
	}


	float get_pitch_demand() { return _pitch_dem; }

	// demanded pitch angle in centi-degrees
	// should return between -9000 to +9000
	int32_t get_pitch_demand_cd() { return int32_t(get_pitch_demand() * 5729.5781f);}

	// Rate of change of velocity along X body axis in m/s^2
	float get_VXdot(void) { return _vel_dot; }


	float get_speed_weight() {
		return _spdWeight;
	}

	// log data on internal state of the controller. Called at 10Hz
	// void log_data(DataFlash_Class &dataflash, uint8_t msgid);

	// struct PACKED log_TECS_Tuning {
	// 	LOG_PACKET_HEADER;
	// 	float hgt;
	// 	float dhgt;
	// 	float hgt_dem;
	// 	float dhgt_dem;
	// 	float spd_dem;
	// 	float spd;
	// 	float dspd;
	// 	float ithr;
	// 	float iptch;
	// 	float thr;
	// 	float ptch;
	// 	float dspd_dem;
	// } log_tuning;

	void set_time_const(float time_const) {
		_timeConst = time_const;
	}

	void set_min_sink_rate(float rate) {
		_minSinkRate = rate;
	}

	void set_max_sink_rate(float sink_rate) {
		_maxSinkRate = sink_rate;
	}

	void set_max_climb_rate(float climb_rate) {
		_maxClimbRate = climb_rate;
	}

	void set_throttle_damp(float throttle_damp) {
		_thrDamp = throttle_damp;
	}

	void set_integrator_gain(float gain) {
		_integGain = gain;
	}

	void set_vertical_accel_limit(float limit) {
		_vertAccLim = limit;
	}

	void set_height_comp_filter_omega(float omega) {
		_hgtCompFiltOmega = omega;
	}

	void set_speed_comp_filter_omega(float omega) {
		_spdCompFiltOmega = omega;
	}

	void set_roll_throttle_compensation(float compensation) {
		_rollComp = compensation;
	}

	void set_speed_weight(float weight) {
		_spdWeight = weight;
	}

	void set_pitch_damping(float damping) {
		_ptchDamp = damping;
	}

	void set_throttle_slewrate(float slewrate) {
		_throttle_slewrate = slewrate;
	}

	void set_indicated_airspeed_min(float airspeed) {
		_indicated_airspeed_min = airspeed;
	}

	void set_indicated_airspeed_max(float airspeed) {
		_indicated_airspeed_max = airspeed;
	}

private:
	// Last time update_50Hz was called
	uint64_t _update_50hz_last_usec;

	// Last time update_speed was called
	uint64_t _update_speed_last_usec;

	// Last time update_pitch_throttle was called
	uint64_t _update_pitch_throttle_last_usec;

	// TECS tuning parameters
	float _hgtCompFiltOmega;
	float _spdCompFiltOmega;
	float _maxClimbRate;
	float _minSinkRate;
	float _maxSinkRate;
	float _timeConst;
	float _ptchDamp;
	float _thrDamp;
	float _integGain;
	float _vertAccLim;
	float _rollComp;
	float _spdWeight;

	// throttle demand in the range from 0.0 to 1.0
	float _throttle_dem;

	// pitch angle demand in radians
	float _pitch_dem;

	// Integrator state 1 - height filter second derivative
	float _integ1_state;

	// Integrator state 2 - height rate
	float _integ2_state;

	// Integrator state 3 - height
	float _integ3_state;

	// Integrator state 4 - airspeed filter first derivative
	float _integ4_state;

	// Integrator state 5 - true airspeed
	float _integ5_state;

	// Integrator state 6 - throttle integrator
	float _integ6_state;

	// Integrator state 6 - pitch integrator
	float _integ7_state;

	// throttle demand rate limiter state
	float _last_throttle_dem;

	// pitch demand rate limiter state
	float _last_pitch_dem;

	// Rate of change of speed along X axis
	float _vel_dot;

	// Equivalent airspeed
	float _EAS;

	// True airspeed limits
	float _TASmax;
	float _TASmin;

	// Current and last true airspeed demand
	float _TAS_dem;
	float _TAS_dem_last;

	// Equivalent airspeed demand
	float _EAS_dem;

	// height demands
	float _hgt_dem;
	float _hgt_dem_in_old;
	float _hgt_dem_adj;
	float _hgt_dem_adj_last;
	float _hgt_rate_dem;
	float _hgt_dem_prev;

	// Speed demand after application of rate limiting
	// This is the demand tracked by the TECS control loops
	float _TAS_dem_adj;

	// Speed rate demand after application of rate limiting
	// This is the demand tracked by the TECS control loops
	float _TAS_rate_dem;

	// Total energy rate filter state
	float _STEdotErrLast;

	// Underspeed condition
	bool _underspeed;

	// Bad descent condition caused by unachievable airspeed demand
	bool _badDescent;

	// climbout mode
	bool _climbOutDem;

	// throttle demand before limiting
	float _throttle_dem_unc;

	// pitch demand before limiting
	float _pitch_dem_unc;

	// Maximum and minimum specific total energy rate limits
	float _STEdot_max;
	float _STEdot_min;

	// Maximum and minimum floating point throttle limits
	float _THRmaxf;
	float _THRminf;

	// Maximum and minimum floating point pitch limits
	float _PITCHmaxf;
	float _PITCHminf;

	// Specific energy quantities
	float _SPE_dem;
	float _SKE_dem;
	float _SPEdot_dem;
	float _SKEdot_dem;
	float _SPE_est;
	float _SKE_est;
	float _SPEdot;
	float _SKEdot;

	// Specific energy error quantities
	float _STE_error;

	// Time since last update of main TECS loop (seconds)
	float _DT;

	bool _airspeed_enabled;
	float _throttle_slewrate;
	float _indicated_airspeed_min;
	float _indicated_airspeed_max;

	// Update the airspeed internal state using a second order complementary filter
	void _update_speed(float airspeed_demand, float indicated_airspeed,
			   float indicated_airspeed_min, float indicated_airspeed_max, float EAS2TAS);

	// Update the demanded airspeed
	void _update_speed_demand(void);

	// Update the demanded height
	void _update_height_demand(float demand);

	// Detect an underspeed condition
	void _detect_underspeed(void);

	// Update Specific Energy Quantities
	void _update_energies(void);

	// Update Demanded Throttle
	void _update_throttle(float throttle_cruise, const math::Dcm &rotMat);

	// Detect Bad Descent
	void _detect_bad_descent(void);

	// Update Demanded Pitch Angle
	void _update_pitch(void);

	// Initialise states and variables
	void _initialise_states(float pitch, float throttle_cruise, float baro_altitude, float ptchMinCO_rad);

	// Calculate specific total energy rate limits
	void _update_STE_rate_lim(void);

};

#endif //TECS_H