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Diffstat (limited to 'apps/systemlib/airspeed.c')
-rw-r--r-- | apps/systemlib/airspeed.c | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/apps/systemlib/airspeed.c b/apps/systemlib/airspeed.c new file mode 100644 index 000000000..e213b66c2 --- /dev/null +++ b/apps/systemlib/airspeed.c @@ -0,0 +1,79 @@ +/**************************************************************************** + * + * Copyright (C) 2012-2013 PX4 Development Team. All rights reserved. + * Author: Lorenz Meier <lm@inf.ethz.ch> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name PX4 nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/** + * @file airspeed.c + * Airspeed estimation + * + * @author Lorenz Meier <lm@inf.ethz.ch> + * + */ + +#include "math.h" + + +float calc_indicated_airspeed(float pressure_front, float pressure_ambient, float temperature) +{ + return sqrtf((2.0f*(pressure_front - pressure_ambient)) / air_density_sea_level); +} + +/** + * 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 + */ +float calc_true_airspeed_from_indicated(float speed, float pressure_ambient, float temperature) +{ + return speed * sqrtf(air_density_sea_level / get_air_density(pressure_ambient, temperature)); +} + +/** + * 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 + */ +float calc_true_airspeed(float pressure_front, float pressure_ambient, float temperature) +{ + return sqrtf((2.0f*(pressure_front - pressure_ambient)) / get_air_density(pressure_ambient, temperature)); +}
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