ardupilot/libraries/AP_Baro/AP_Baro_HIL.cpp

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#include "AP_Baro_HIL.h"
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#include <AP_HAL/AP_HAL.h>
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extern const AP_HAL::HAL& hal;
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AP_Baro_HIL::AP_Baro_HIL(AP_Baro &baro) :
AP_Baro_Backend(baro)
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{
_instance = _frontend.register_sensor();
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}
// ==========================================================================
// based on tables.cpp from http://www.pdas.com/atmosdownload.html
/*
Compute the temperature, density, and pressure in the standard atmosphere
Correct to 20 km. Only approximate thereafter.
*/
void AP_Baro::SimpleAtmosphere(
const float alt, // geometric altitude, km.
float& sigma, // density/sea-level standard density
float& delta, // pressure/sea-level standard pressure
float& theta) // temperature/sea-level standard temperature
{
const float REARTH = 6369.0f; // radius of the Earth (km)
const float GMR = 34.163195f; // gas constant
float h=alt*REARTH/(alt+REARTH); // geometric to geopotential altitude
if (h < 11.0f) {
// Troposphere
theta = (SSL_AIR_TEMPERATURE - 6.5f * h) / SSL_AIR_TEMPERATURE;
delta = powf(theta, GMR / 6.5f);
} else {
// Stratosphere
theta = 216.65f / SSL_AIR_TEMPERATURE;
delta = 0.2233611f * expf(-GMR * (h - 11.0f) / 216.65f);
}
sigma = delta/theta;
}
void AP_Baro::SimpleUnderWaterAtmosphere(
float alt, // depth, km.
float& rho, // density/sea-level
float& delta, // pressure/sea-level standard pressure
float& theta) // temperature/sea-level standard temperature
{
// Values and equations based on:
// https://en.wikipedia.org/wiki/Standard_sea_level
const float seaDensity = 1.024f; // g/cm3
const float maxSeaDensity = 1.028f; // g/cm3
const float pAC = maxSeaDensity - seaDensity; // pycnocline angular coefficient
// From: https://www.windows2universe.org/earth/Water/density.html
rho = seaDensity;
if (alt < 1.0f) {
// inside pycnocline
rho += pAC*alt;
} else {
rho += pAC;
}
rho = rho/seaDensity;
// From: https://www.grc.nasa.gov/www/k-12/WindTunnel/Activities/fluid_pressure.html
// \f$P = \rho (kg) \cdot gravity (m/s2) \cdot depth (m)\f$
// \f$P_{atmosphere} = 101.325 kPa\f$
// \f$P_{total} = P_{atmosphere} + P_{fluid}\f$
delta = (SSL_AIR_PRESSURE + (seaDensity * 1e3) * GRAVITY_MSS * (alt * 1e3)) / SSL_AIR_PRESSURE;
// From: http://residualanalysis.blogspot.com.br/2010/02/temperature-of-ocean-water-at-given.html
// \f$T(D)\f$ Temperature underwater at given temperature
// \f$S\f$ Surface temperature at the surface
// \f$T(D)\approx\frac{S}{1.8 \cdot 10^{-4} \cdot S \cdot T + 1}\f$
const float seaTempSurface = 15.0f; // Celsius
const float S = seaTempSurface * 0.338f;
theta = 1.0f / ((1.8e-4) * S * (alt * 1e3) + 1.0f);
}
/*
convert an altitude in meters above sea level to a presssure and temperature
*/
void AP_Baro::setHIL(float altitude_msl)
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{
float sigma, delta, theta;
SimpleAtmosphere(altitude_msl*0.001f, sigma, delta, theta);
float p = SSL_AIR_PRESSURE * delta;
float T = 303.16f * theta - C_TO_KELVIN; // Assume 30 degrees at sea level - converted to degrees Kelvin
_hil.pressure = p;
_hil.temperature = T;
_hil.updated = true;
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}
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/*
set HIL pressure and temperature for an instance
*/
void AP_Baro::setHIL(uint8_t instance, float pressure, float temperature, float altitude, float climb_rate, uint32_t last_update_ms)
{
if (instance >= _num_sensors) {
// invalid
return;
}
_hil.pressure = pressure;
_hil.temperature = temperature;
_hil.altitude = altitude;
_hil.climb_rate = climb_rate;
_hil.updated = true;
_hil.have_alt = true;
if (last_update_ms != 0) {
_hil.last_update_ms = last_update_ms;
_hil.have_last_update = true;
}
}
// Read the sensor
void AP_Baro_HIL::update(void)
{
if (_frontend._hil.updated) {
_frontend._hil.updated = false;
_copy_to_frontend(0, _frontend._hil.pressure, _frontend._hil.temperature);
}
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}