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AP_Baro: improved the accuracy of the barometer model

This commit is contained in:
Andrew Tridgell 2013-07-20 14:37:47 +10:00
parent c5028c04da
commit 0c6725f289
1 changed files with 12 additions and 9 deletions
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21
libraries/AP_Baro/AP_Baro_HIL.cpp
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@ -33,18 +33,21 @@ uint8_t AP_Baro_HIL::read()
void AP_Baro_HIL::setHIL(float altitude_msl)
{
// approximate a barometer. This uses the typical base pressure in
// Canberra, Australia
const float temperature = 312;
// approximate a barometer
// see http://en.wikipedia.org/wiki/Atmospheric_pressure
const float p0 = 101325;
const float L = 0.0065;
const float T0 = 288.15;
const float M = 0.0289644;
const float R = 8.31447;
float y = (altitude_msl - 584.0) / 29.271267;
y /= (temperature / 10.0) + 273.15;
y = 1.0/exp(y);
y *= 95446.0;
float p = p0 * pow(1.0 - (L*altitude_msl)/T0, (GRAVITY_MSS*M)/(R*L));
float T = 31.2 - altitude_msl * L;
_count++;
_pressure_sum += y;
_temperature_sum += temperature;
_pressure_sum += p;
_temperature_sum += T;
if (_count == 128) {
// we have summed 128 values. This only happens
// when we stop reading the barometer for a long time