air_data.h File Reference

Air Data interface. More...

#include "std.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...
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	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.

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Data Structure Documentation

struct AirData

Air Data strucute.

Definition at line 37 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

float air_data_get_amsl

(

void

)

Return AMSL (altitude AboveSeaLevel).

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

Definition at line 235 of file air_data.c.

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

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void air_data_init

(

void

)

AirData initialization.

Called at startup.

Called at startup. Bind ABI messages

Definition at line 195 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_TAS_FACTOR, AIR_DATA_TEMPERATURE_ID, AirData::airspeed, airspeed_cb(), AirData::amsl_baro, AirData::amsl_baro_valid, AirData::aoa, AirData::calc_airspeed, AirData::calc_amsl_baro, AirData::calc_qnh_once, AirData::calc_tas_factor, DefaultPeriodic, AirData::differential, AirData::pressure, pressure_abs_cb(), pressure_diff_cb(), AirData::qnh, register_periodic_telemetry(), send_air_data(), send_amsl(), send_baro_raw(), AirData::sideslip, AirData::tas, AirData::tas_factor, AirData::temperature, temperature_cb(), AirData::wind_dir, and AirData::wind_speed.

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void air_data_periodic

(

void

)

Check health.

Needs to be called periodically.

Definition at line 245 of file air_data.c.

References air_data, and AirData::amsl_baro_valid.

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:

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

Parameters

q	dynamic pressure in Pa

Returns

equivalent airspeed in m/s

Definition at line 269 of file air_data.c.

References Max, and PPRZ_ISA_AIR_DENSITY.

Referenced by pressure_diff_cb(), and tas_from_dynamic_pressure().

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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):

and 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 297 of file air_data.c.

References PPRZ_ISA_SEA_LEVEL_PRESSURE, and PPRZ_ISA_SEA_LEVEL_TEMP.

Referenced by temperature_cb().

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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 329 of file air_data.c.

References eas_from_dynamic_pressure(), and tas_from_eas().

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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 316 of file air_data.c.

References air_data, and AirData::tas_factor.

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

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Variable Documentation

struct AirData air_data

global AirData state

Definition at line 39 of file air_data.c.

Referenced by air_data_get_amsl(), air_data_init(), air_data_periodic(), airspeed_cb(), pressure_abs_cb(), pressure_diff_cb(), send_air_data(), send_amsl(), send_baro_raw(), tas_from_eas(), and temperature_cb().