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sensors: sanity check differential pressure temperature (#15845)

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- if valid temperature unavailable then use ICAO Standard Atmosphere 15 degrees celcius
This commit is contained in:
Daniel Agar
2020-09-29 09:35:34 -04:00
committed by GitHub
parent da4d0e650a
commit c9c20666a2
2 changed files with 28 additions and 7 deletions
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17
src/lib/airspeed/airspeed.cpp
View File

@@ -58,6 +58,9 @@
float calc_IAS_corrected(enum AIRSPEED_COMPENSATION_MODEL pmodel, enum AIRSPEED_SENSOR_MODEL smodel,
float tube_len, float tube_dia_mm, float differential_pressure, float pressure_ambient, float temperature_celsius)
{
if (!PX4_ISFINITE(temperature_celsius)) {
temperature_celsius = 15.f; // ICAO Standard Atmosphere 15 degrees celcius
}
// air density in kg/m3
const float rho_air = get_air_density(pressure_ambient, temperature_celsius);
@@ -182,7 +185,6 @@ float calc_IAS_corrected(enum AIRSPEED_COMPENSATION_MODEL pmodel, enum AIRSPEED_
return (differential_pressure > 0.0f) ? airspeed_corrected : -airspeed_corrected;
}
/**
* Calculate indicated airspeed (IAS).
*
@@ -194,8 +196,6 @@ float calc_IAS_corrected(enum AIRSPEED_COMPENSATION_MODEL pmodel, enum AIRSPEED_
*/
float calc_IAS(float differential_pressure)
{
if (differential_pressure > 0.0f) {
return sqrtf((2.0f * differential_pressure) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C);
@@ -217,6 +217,10 @@ float calc_IAS(float differential_pressure)
*/
float calc_TAS_from_EAS(float speed_equivalent, float pressure_ambient, float temperature_celsius)
{
if (!PX4_ISFINITE(temperature_celsius)) {
temperature_celsius = 15.f; // ICAO Standard Atmosphere 15 degrees celcius
}
return speed_equivalent * sqrtf(CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C / get_air_density(pressure_ambient,
temperature_celsius));
}
@@ -266,6 +270,10 @@ float calc_TAS(float total_pressure, float static_pressure, float temperature_ce
float get_air_density(float static_pressure, float temperature_celsius)
{
if (!PX4_ISFINITE(temperature_celsius)) {
temperature_celsius = 15.f; // ICAO Standard Atmosphere 15 degrees celcius
}
return static_pressure / (CONSTANTS_AIR_GAS_CONST * (temperature_celsius - CONSTANTS_ABSOLUTE_NULL_CELSIUS));
}
@@ -281,6 +289,5 @@ float get_air_density(float static_pressure, float temperature_celsius)
*/
float calc_EAS_from_TAS(float speed_true, float pressure_ambient, float temperature_celsius)
{
return speed_true * sqrtf(get_air_density(pressure_ambient,
temperature_celsius) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C);
return speed_true * sqrtf(get_air_density(pressure_ambient, temperature_celsius) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C);
}

18
src/modules/sensors/sensors.cpp
View File

@@ -335,8 +335,22 @@ void Sensors::diff_pres_poll()
vehicle_air_data_s air_data{};
_vehicle_air_data_sub.copy(&air_data);
float air_temperature_celsius = (diff_pres.temperature > -300.0f) ? diff_pres.temperature :
(air_data.baro_temp_celcius - PCB_TEMP_ESTIMATE_DEG);
float air_temperature_celsius = NAN;
// assume anything outside of a (generous) operating range of -40C to 125C is invalid
if (PX4_ISFINITE(diff_pres.temperature) && (diff_pres.temperature >= -40.f) && (diff_pres.temperature <= 125.f)) {
air_temperature_celsius = diff_pres.temperature;
} else {
// differential pressure temperature invalid, check barometer
if ((air_data.timestamp != 0) && PX4_ISFINITE(air_data.baro_temp_celcius)
&& (air_data.baro_temp_celcius >= -40.f) && (air_data.baro_temp_celcius <= 125.f)) {
// TODO: review PCB_TEMP_ESTIMATE_DEG, ignore for external baro
air_temperature_celsius = air_data.baro_temp_celcius - PCB_TEMP_ESTIMATE_DEG;
}
}
airspeed_s airspeed{};
airspeed.timestamp = diff_pres.timestamp;