From c0a852dab48e55aa12c995adc6dc0c32aa9a7ac3 Mon Sep 17 00:00:00 2001 From: Thomas Gubler Date: Sun, 24 Feb 2013 21:57:38 +0100 Subject: airspeed (pitot) offset calibration --- apps/systemlib/airspeed.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) (limited to 'apps/systemlib') diff --git a/apps/systemlib/airspeed.c b/apps/systemlib/airspeed.c index 32943b2f5..382df2ee4 100644 --- a/apps/systemlib/airspeed.c +++ b/apps/systemlib/airspeed.c @@ -58,7 +58,13 @@ */ float calc_indicated_airspeed(float differential_pressure) { - return sqrtf((2.0f*differential_pressure) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C); + + if (differential_pressure > 0) { + return sqrtf((2.0f*differential_pressure) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C); + } else { + return -sqrtf((2.0f*fabs(differential_pressure)) / CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C); + } + } /** @@ -89,9 +95,17 @@ float calc_true_airspeed_from_indicated(float speed_indicated, float pressure_am float calc_true_airspeed(float total_pressure, float static_pressure, float temperature_celsius) { float density = get_air_density(static_pressure, temperature_celsius); - if (density < 0.0001f || isnan(density)) { + if (density < 0.0001f || !isfinite(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); + + float pressure_difference = total_pressure - static_pressure; + + if(pressure_difference > 0) { + return sqrtf((2.0f*(pressure_difference)) / density); + } else + { + return -sqrtf((2.0f*fabs(pressure_difference)) / density); + } } -- cgit v1.2.3