ardupilot/libraries/AP_TempCalibration/AP_TempCalibration.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
temperature calibration library
*/
#include "AP_TempCalibration.h"
#include <stdio.h>
#include <AP_Baro/AP_Baro.h>
extern const AP_HAL::HAL& hal;
#define TCAL_DEBUG 0
#if TCAL_DEBUG
# define debug(fmt, args ...) do {printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); } while(0)
#else
# define debug(fmt, args ...)
#endif
// table of user settable and learned parameters
const AP_Param::GroupInfo AP_TempCalibration::var_info[] = {
// @Param: _ENABLED
// @DisplayName: Temperature calibration enable
// @Description: Enable temperature calibration. Set to 0 to disable. Set to 1 to use learned values. Set to 2 to learn new values and use the values
// @Values: 0:Disabled,1:Enabled,2:EnableAndLearn
// @User: Advanced
AP_GROUPINFO_FLAGS("_ENABLED", 1, AP_TempCalibration, enabled, TC_DISABLED, AP_PARAM_FLAG_ENABLE),
// @Param: _TEMP_MIN
// @DisplayName: Temperature calibration min learned temperature
// @Description: Minimum learned temperature. This is automatically set by the learning process
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// @Units: degC
// @ReadOnly: True
// @Volatile: True
// @User: Advanced
AP_GROUPINFO("_TEMP_MIN", 2, AP_TempCalibration, temp_min, 0),
// 3 was used by a duplicated temp_min entry (do not use in the future!)
// @Param: _TEMP_MAX
// @DisplayName: Temperature calibration max learned temperature
// @Description: Maximum learned temperature. This is automatically set by the learning process
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// @Units: degC
// @ReadOnly: True
// @Volatile: True
// @User: Advanced
AP_GROUPINFO("_TEMP_MAX", 4, AP_TempCalibration, temp_max, 0),
// @Param: _BARO_EXP
// @DisplayName: Temperature Calibration barometer exponent
// @Description: Learned exponent for barometer temperature correction
// @ReadOnly: True
// @Volatile: True
// @User: Advanced
AP_GROUPINFO("_BARO_EXP", 5, AP_TempCalibration, baro_exponent, 0),
AP_GROUPEND
};
/*
calculate the correction given an exponent and a temperature
This one parameter correction is deliberately chosen to be very
robust for extrapolation. It fits the characteristics of the
ICM-20789 barometer nicely.
*/
float AP_TempCalibration::calculate_correction(float temp, float exponent) const
{
return powf(MAX(temp - Tzero, 0), exponent);
}
/*
setup for learning
*/
void AP_TempCalibration::setup_learning(void)
{
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learn_temp_start = AP::baro().get_temperature();
learn_temp_step = 0.25;
learn_count = 200;
learn_i = 0;
if (learn_values != nullptr) {
delete [] learn_values;
}
learn_values = new float[learn_count];
if (learn_values == nullptr) {
return;
}
}
/*
calculate the sum of squares range of pressure values we get with
the current data. This is the function we try to minimise in the
calibration
*/
float AP_TempCalibration::calculate_p_range(float baro_factor) const
{
float sum = 0;
float P0 = learn_values[0] + calculate_correction(learn_temp_start, baro_factor);
for (uint16_t i=0; i<learn_i; i++) {
if (is_zero(learn_values[i])) {
// gap in the data
continue;
}
float temp = learn_temp_start + learn_temp_step*i;
float correction = calculate_correction(temp, baro_factor);
float P = learn_values[i] + correction;
sum += sq(P - P0);
}
return sum / learn_i;
}
/*
calculate a calibration value
This fits a simple single value power function to the baro data to
find the calibration exponent.
*/
void AP_TempCalibration::calculate_calibration(void)
{
float current_err = calculate_p_range(baro_exponent);
float test_exponent = baro_exponent + learn_delta;
float test_err = calculate_p_range(test_exponent);
if (test_err >= current_err) {
test_exponent = baro_exponent - learn_delta;
test_err = calculate_p_range(test_exponent);
}
if (test_exponent <= exp_limit_max &&
test_exponent >= exp_limit_min &&
test_err < current_err) {
// move to new value
debug("CAL: %.2f\n", test_exponent);
if (!is_equal(test_exponent, baro_exponent.get())) {
baro_exponent.set_and_save(test_exponent);
}
temp_min.set_and_save_ifchanged(learn_temp_start);
temp_max.set_and_save_ifchanged(learn_temp_start + learn_i*learn_temp_step);
}
}
/*
update calibration learning
*/
void AP_TempCalibration::learn_calibration(void)
{
// just for first baro now
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const AP_Baro &baro = AP::baro();
if (!baro.healthy(0) ||
hal.util->get_soft_armed() ||
baro.get_temperature(0) < Tzero) {
return;
}
// if we have any movement then we reset learning
if (learn_values == nullptr ||
!AP::ins().is_still()) {
debug("learn reset\n");
setup_learning();
if (learn_values == nullptr) {
return;
}
}
float temp = baro.get_temperature(0);
float P = baro.get_pressure(0);
uint16_t idx = (temp - learn_temp_start) / learn_temp_step;
if (idx >= learn_count) {
// could change learn_temp_step here
return;
}
if (is_zero(learn_values[idx])) {
learn_values[idx] = P;
debug("learning %u %.2f at %.2f\n", idx, learn_values[idx], temp);
} else {
// filter in new value
learn_values[idx] = 0.9 * learn_values[idx] + 0.1 * P;
}
learn_i = MAX(learn_i, idx);
uint32_t now = AP_HAL::millis();
if (now - last_learn_ms > 100 &&
idx*learn_temp_step > min_learn_temp_range &&
temp - learn_temp_start > temp_max - temp_min) {
last_learn_ms = now;
// run estimation and update parameters
calculate_calibration();
}
}
/*
apply learned calibration for current temperature
*/
void AP_TempCalibration::apply_calibration(void)
{
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AP_Baro &baro = AP::baro();
// just for first baro now
if (!baro.healthy(0)) {
return;
}
float temp = baro.get_temperature(0);
float correction = calculate_correction(temp, baro_exponent);
baro.set_pressure_correction(0, correction);
}
/*
called at 10Hz from the main thread. This is called both when armed
and disarmed. It only does learning while disarmed, but needs to
supply the corrections to the sensor libraries at all times
*/
void AP_TempCalibration::update(void)
{
switch (enabled.get()) {
case TC_DISABLED:
break;
case TC_ENABLE_LEARN:
learn_calibration();
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FALLTHROUGH;
case TC_ENABLE_USE:
apply_calibration();
break;
}
}