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more fixes for the airspeed readout

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This commit is contained in:
Thomas Gubler
2013-02-24 16:01:08 +01:00
parent 2c2c65d446
commit 2707d2c1dd
4 changed files with 77 additions and 61 deletions
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apps/systemlib/airspeed.c
+28 -12
View File
@@ -40,14 +40,25 @@
*
*/
#include "math.h"
#include <stdio.h>
#include <math.h>
#include "conversions.h"
#include "airspeed.h"
float calc_indicated_airspeed(float pressure_front, float pressure_ambient, float temperature)
/**
* Calculate indicated airspeed.
*
* Note that the indicated airspeed is not the true airspeed because it
* lacks the air density compensation. Use the calc_true_airspeed functions to get
* the true airspeed.
*
* @param differential_pressure total_ pressure - static pressure
* @return indicated airspeed in m/s
*/
float calc_indicated_airspeed(float differential_pressure)
{
return sqrtf((2.0f*(pressure_front - pressure_ambient)) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C);
return sqrtf((2.0f*differential_pressure) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C);
}
/**
@@ -55,14 +66,14 @@ float calc_indicated_airspeed(float pressure_front, float pressure_ambient, floa
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param speed current indicated airspeed
* @param speed_indicated current indicated airspeed
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @param temperature_celsius air temperature in degrees celcius
* @return true airspeed in m/s
*/
float calc_true_airspeed_from_indicated(float speed, float pressure_ambient, float temperature)
float calc_true_airspeed_from_indicated(float speed_indicated, float pressure_ambient, float temperature_celsius)
{
return speed * sqrtf(CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C / get_air_density(pressure_ambient, temperature));
return speed_indicated * sqrtf(CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C / get_air_density(pressure_ambient, temperature_celsius));
}
/**
@@ -70,12 +81,17 @@ float calc_true_airspeed_from_indicated(float speed, float pressure_ambient, flo
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param pressure_front pressure inside the pitot/prandl tube
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @param total_pressure pressure inside the pitot/prandl tube
* @param static_pressure pressure at the side of the tube/airplane
* @param temperature_celsius air temperature in degrees celcius
* @return true airspeed in m/s
*/
float calc_true_airspeed(float pressure_front, float pressure_ambient, float temperature)
float calc_true_airspeed(float total_pressure, float static_pressure, float temperature_celsius)
{
return sqrtf((2.0f*(pressure_front - pressure_ambient)) / get_air_density(pressure_ambient, temperature));
float density = get_air_density(static_pressure, temperature_celsius);
if (density < 0.0001f || isnan(density)) {
density = CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C;
printf("Invalid air density, using density at sea level\n");
}
return sqrtf((2.0f*(total_pressure - static_pressure)) / density);
}
apps/systemlib/airspeed.h
+34 -35
View File
@@ -48,43 +48,42 @@
__BEGIN_DECLS
/**
* Calculate indicated airspeed.
*
* Note that the indicated airspeed is not the true airspeed because it
* lacks the air density compensation. Use the calc_true_airspeed functions to get
* the true airspeed.
*
* @param pressure_front pressure inside the pitot/prandl tube
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @return indicated airspeed in m/s
*/
__EXPORT float calc_indicated_airspeed(float pressure_front, float pressure_ambient, float temperature);
/**
* Calculate indicated airspeed.
*
* Note that the indicated airspeed is not the true airspeed because it
* lacks the air density compensation. Use the calc_true_airspeed functions to get
* the true airspeed.
*
* @param total_pressure pressure inside the pitot/prandtl tube
* @param static_pressure pressure at the side of the tube/airplane
* @return indicated airspeed in m/s
*/
__EXPORT float calc_indicated_airspeed(float differential_pressure);
/**
* Calculate true airspeed from indicated airspeed.
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param speed current indicated airspeed
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @return true airspeed in m/s
*/
__EXPORT float calc_true_airspeed_from_indicated(float speed, float pressure_ambient, float temperature);
/**
* Calculate true airspeed from indicated airspeed.
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param speed_indicated current indicated airspeed
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature_celsius air temperature in degrees celcius
* @return true airspeed in m/s
*/
__EXPORT float calc_true_airspeed_from_indicated(float speed_indicated, float pressure_ambient, float temperature_celsius);
/**
* Directly calculate true airspeed
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param pressure_front pressure inside the pitot/prandl tube
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @return true airspeed in m/s
*/
__EXPORT float calc_true_airspeed(float pressure_front, float pressure_ambient, float temperature);
/**
* Directly calculate true airspeed
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param total_pressure pressure inside the pitot/prandl tube
* @param static_pressure pressure at the side of the tube/airplane
* @param temperature_celsius air temperature in degrees celcius
* @return true airspeed in m/s
*/
__EXPORT float calc_true_airspeed(float total_pressure, float static_pressure, float temperature_celsius);
__END_DECLS