Air Data interface. More...

#include "std.h"
#include "pprzlink/pprzlink_device.h"
#include "pprzlink/pprzlink_transport.h"

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Data Structures
struct	AirData
	Air Data strucute. More...

Functions
void	air_data_init (void)
	AirData initialization. More...

void	air_data_periodic (void)
	Check health. More...

void	air_data_parse_WIND_INFO (struct link_device dev, struct transport_tx trans, uint8_t *buf)
	Parse datalink wind info message. More...

float	air_data_get_amsl (void)
	Return AMSL (altitude AboveSeaLevel). More...

float	eas_from_dynamic_pressure (float q)
	Calculate equivalent airspeed from dynamic pressure. More...

float	get_tas_factor (float p, float t)
	Calculate true airspeed (TAS) factor. More...

float	tas_from_eas (float eas)
	Calculate true airspeed from equivalent airspeed. More...

float	eas_from_tas (float tas)
	Calculate equivalent airspeed from true airspeed. More...

float	tas_from_dynamic_pressure (float q)
	Calculate true airspeed from dynamic pressure. More...

Variables
struct AirData	air_data
	global AirData state More...

Detailed Description

Air Data interface.

pressures
airspeed
angle of attack and sideslip
wind

Definition in file air_data.h.

Data Structure Documentation

◆ AirData

struct AirData

Air Data strucute.

Definition at line 39 of file air_data.h.

Data Fields
float	airspeed	Equivalent Air Speed (equals to Calibrated Air Speed at low speed/altitude) (in m/s, -1 if unknown.
float	amsl_baro	altitude above sea level in m from pressure and QNH
bool	amsl_baro_valid	TRUE if amsl_baro is currently valid.
float	aoa	angle of attack (rad)
bool	calc_airspeed	if TRUE, calculate airspeed from differential pressure
bool	calc_amsl_baro	if TRUE, calculate amsl_baro
bool	calc_qnh_once	flag to calculate QNH with next pressure measurement
bool	calc_tas_factor	if TRUE, calculate tas_factor when getting a temp measurement
float	differential	Differential pressure (total - static pressure) (Pa)
float	pressure	Static atmospheric pressure (Pa), -1 if unknown.
float	qnh	Barometric pressure adjusted to sea level in hPa, -1 if unknown.
float	sideslip	sideslip angle (rad)
float	tas	True Air Speed (TAS) in m/s, -1 if unknown.
float	tas_factor	factor to convert equivalent airspeed (EAS) to true airspeed (TAS)
float	temperature	temperature in degrees Celcius, -1000 if unknown
float	wind_dir	wind direction (rad, 0 north, >0 clockwise)
float	wind_speed	wind speed (m/s)

Function Documentation

◆ air_data_get_amsl()

float air_data_get_amsl ( void )

Return AMSL (altitude AboveSeaLevel).

If AMSL from baro is valid, return that, otherwise from gps.

Definition at line 258 of file air_data.c.

References air_data, LlaCoor_f::alt, AirData::amsl_baro, AirData::amsl_baro_valid, and stateGetPositionLla_f().

Referenced by compute_tas_factor().

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◆ air_data_init()

void air_data_init ( void )

AirData initialization.

Called at startup.

Called at startup. Bind ABI messages

Definition at line 217 of file air_data.c.

References air_data, AIR_DATA_AIRSPEED_ID, AIR_DATA_BARO_ABS_ID, AIR_DATA_BARO_DIFF_ID, AIR_DATA_CALC_AIRSPEED, AIR_DATA_CALC_AMSL_BARO, AIR_DATA_CALC_TAS_FACTOR, AIR_DATA_INCIDENCE_ID, AIR_DATA_TAS_FACTOR, AIR_DATA_TEMPERATURE_ID, AirData::airspeed, airspeed_cb(), airspeed_ev, AirData::amsl_baro, AirData::amsl_baro_valid, AirData::aoa, baro_health_counter, AirData::calc_airspeed, AirData::calc_amsl_baro, AirData::calc_qnh_once, AirData::calc_tas_factor, DefaultPeriodic, AirData::differential, incidence_cb(), incidence_ev, AirData::pressure, pressure_abs_cb(), pressure_abs_ev, pressure_diff_cb(), pressure_diff_ev, AirData::qnh, register_periodic_telemetry(), send_air_data(), send_amsl(), send_baro_raw(), AirData::sideslip, AirData::tas, AirData::tas_factor, AirData::temperature, temperature_cb(), temperature_ev, AirData::wind_dir, and AirData::wind_speed.

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◆ air_data_parse_WIND_INFO()

void air_data_parse_WIND_INFO	(	struct link_device *	dev,
		struct transport_tx *	trans,
		uint8_t *	buf
	)

Parse datalink wind info message.

Definition at line 278 of file air_data.c.

References air_data, AirData::airspeed, dev, eas_from_tas(), float_vect2_norm(), stateGetAirspeed_f(), stateSetAirspeed_f(), stateSetHorizontalWindspeed_f(), stateSetVerticalWindspeed_f(), AirData::tas, AirData::wind_dir, AirData::wind_speed, FloatVect2::x, and FloatVect2::y.

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◆ air_data_periodic()

void air_data_periodic ( void )

Check health.

Needs to be called periodically.

Definition at line 268 of file air_data.c.

References air_data, AirData::amsl_baro_valid, and baro_health_counter.

◆ eas_from_dynamic_pressure()

float eas_from_dynamic_pressure ( float q )

Calculate equivalent airspeed from dynamic pressure.

Dynamic pressure (also called impact pressure) is the difference between total(pitot) and static pressure.

Parameters

q	dynamic pressure in Pa

Returns: equivalent airspeed in m/s

Dynamic pressure (also called impact pressure) is the difference between total(pitot) and static pressure.

Airspeed from dynamic pressure:

$v = \frac12 \sqrt{\frac{2q}{\rho}}$

with $\rho$ as air density. Using standard sea level air density $\rho_0$ gives you equivalent airspeed (EAS).

Parameters

q	dynamic pressure in Pa

Returns: equivalent airspeed in m/s

Definition at line 321 of file air_data.c.

References PPRZ_ISA_AIR_DENSITY, and sign().

Referenced by pressure_diff_cb(), and tas_from_dynamic_pressure().

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◆ eas_from_tas()

float eas_from_tas ( float tas )

Calculate equivalent airspeed from true airspeed.

Parameters

tas	true airspeed (TAS) in m/s

Returns: equivalent airspeed in m/s

EAS from True airspeed (TAS): EAS = TAS / air_data.tas_factor

Parameters

tas	true airspeed (TAS) in m/s

Returns: equivalent airspeed in m/s

Definition at line 409 of file air_data.c.

References air_data, compute_tas_factor(), and AirData::tas_factor.

Referenced by air_data_parse_WIND_INFO(), and wind_estimation_quadrotor_periodic().

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◆ get_tas_factor()

float get_tas_factor	(	float	p,
		float	t
	)

Calculate true airspeed (TAS) factor.

TAS = tas_factor * EAS

Parameters

p	current air pressure in Pa
t	current air temperature in degrees Celcius

Returns: tas factor

TAS = tas_factor * EAS

True airspeed (TAS) from equivalent airspeed (EAS):

$\mbox{TAS} = \mbox{EAS} \sqrt{\frac{\rho_0}{\rho}}$

and $\frac{\rho_0}{\rho} = \frac{p_0T}{pT_0}$ where

is the air pressure at the flight condition
is the air pressure at sea level = 101325 Pa
is the air temperature at the flight condition
is the air temperature at sea level = 288.15 K

Parameters

p	current air pressure in Pa
t	current air temperature in degrees Celcius

Returns: tas factor

Definition at line 354 of file air_data.c.

References KelvinOfCelsius, p, PPRZ_ISA_SEA_LEVEL_PRESSURE, and PPRZ_ISA_SEA_LEVEL_TEMP.

Referenced by compute_tas_factor(), and temperature_cb().

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◆ tas_from_dynamic_pressure()

float tas_from_dynamic_pressure ( float q )

Calculate true airspeed from dynamic pressure.

Dynamic pressure (also called impact pressure) is the difference between total(pitot) and static pressure.

Parameters

q	dynamic pressure in Pa

Returns: true airspeed in m/s

Definition at line 423 of file air_data.c.

References eas_from_dynamic_pressure(), and tas_from_eas().

Referenced by pressure_diff_cb().

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◆ tas_from_eas()

float tas_from_eas ( float eas )

Calculate true airspeed from equivalent airspeed.

Parameters

eas	equivalent airspeed (EAS) in m/s

Returns: true airspeed in m/s

True airspeed (TAS) from EAS: TAS = air_data.tas_factor * EAS

Parameters

eas	equivalent airspeed (EAS) in m/s

Returns: true airspeed in m/s

Definition at line 394 of file air_data.c.

References air_data, compute_tas_factor(), and AirData::tas_factor.

Referenced by airspeed_cb(), pressure_diff_cb(), and tas_from_dynamic_pressure().

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Variable Documentation

◆ air_data

struct AirData air_data

extern

global AirData state

Definition at line 1 of file air_data.c.

Referenced by air_data_get_amsl(), air_data_init(), air_data_parse_WIND_INFO(), air_data_periodic(), airspeed_cb(), compute_tas_factor(), eas_from_tas(), incidence_cb(), pressure_abs_cb(), pressure_diff_cb(), send_air_data(), send_amsl(), send_baro_raw(), send_windtunnel_meas(), tas_from_eas(), and temperature_cb().

Data Structures

Functions

Variables

Detailed Description

Data Structure Documentation

◆ AirData

Function Documentation

◆ air_data_get_amsl()

◆ air_data_init()

◆ air_data_parse_WIND_INFO()

◆ air_data_periodic()

◆ eas_from_dynamic_pressure()

◆ eas_from_tas()

◆ get_tas_factor()

◆ tas_from_dynamic_pressure()

◆ tas_from_eas()

Variable Documentation

◆ air_data