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use non-uniform 1st order IIR lowpass filters for baro_gps_offset estimation

This commit is contained in:
Mark Whitehorn 2014-12-22 13:47:20 -07:00
parent 78b603bb35
commit 3c98c7119e
3 changed files with 57 additions and 9 deletions
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2
src/drivers/ms5611/ms5611.cpp
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@ -90,7 +90,7 @@ static const int ERROR = -1;
/* internal conversion time: 9.17 ms, so should not be read at rates higher than 100 Hz */
#define MS5611_CONVERSION_INTERVAL 10000 /* microseconds */
#define MS5611_MEASUREMENT_RATIO 3 /* pressure measurements per temperature measurement */
#define MS5611_MEASUREMENT_RATIO 100 /* pressure measurements per temperature measurement */
#define MS5611_BARO_DEVICE_PATH_EXT "/dev/ms5611_ext"
#define MS5611_BARO_DEVICE_PATH_INT "/dev/ms5611_int"

5
src/lib/mathlib/math/filter/LowPassFilter2p.cpp
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@ -66,6 +66,7 @@ float LowPassFilter2p::apply(float sample)
// no filtering
return sample;
}
// do the filtering
float delay_element_0 = sample - _delay_element_1 * _a1 - _delay_element_2 * _a2;
if (isnan(delay_element_0) || isinf(delay_element_0)) {
@ -82,7 +83,9 @@ float LowPassFilter2p::apply(float sample)
}
float LowPassFilter2p::reset(float sample) {
_delay_element_1 = _delay_element_2 = sample;
float dval = sample / (_b0 + _b1 + _b2);
_delay_element_1 = dval;
_delay_element_2 = dval;
return apply(sample);
}

59
src/modules/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp
View File

@ -82,12 +82,11 @@
#include <systemlib/perf_counter.h>
#include <systemlib/systemlib.h>
#include <mathlib/mathlib.h>
#include <mathlib/math/filter/LowPassFilter2p.hpp>
#include <mavlink/mavlink_log.h>
#include "estimator_23states.h"
/**
* estimator app start / stop handling function
*
@ -101,7 +100,7 @@ __EXPORT uint64_t getMicros();
static uint64_t IMUmsec = 0;
static uint64_t IMUusec = 0;
static const uint64_t FILTER_INIT_DELAY = 1 * 1000 * 1000;
static const uint64_t FILTER_INIT_DELAY = 1 * 1000 * 1000; // units: microseconds
uint32_t millis()
{
@ -222,8 +221,10 @@ private:
float _baro_ref; /**< barometer reference altitude */
float _baro_ref_offset; /**< offset between initial baro reference and GPS init baro altitude */
float _baro_gps_offset; /**< offset between baro altitude (at GPS init time) and GPS altitude */
hrt_abstime _last_debug_print = 0;
perf_counter_t _loop_perf; ///< loop performance counter
perf_counter_t _loop_intvl; ///< loop rate counter
perf_counter_t _perf_gyro; ///<local performance counter for gyro updates
perf_counter_t _perf_mag; ///<local performance counter for mag updates
perf_counter_t _perf_gps; ///<local performance counter for gps updates
@ -399,6 +400,7 @@ FixedwingEstimator::FixedwingEstimator() :
/* performance counters */
_loop_perf(perf_alloc(PC_ELAPSED, "ekf_att_pos_estimator")),
_loop_intvl(perf_alloc(PC_INTERVAL, "ekf_att_pos_est_interval")),
_perf_gyro(perf_alloc(PC_INTERVAL, "ekf_att_pos_gyro_upd")),
_perf_mag(perf_alloc(PC_INTERVAL, "ekf_att_pos_mag_upd")),
_perf_gps(perf_alloc(PC_INTERVAL, "ekf_att_pos_gps_upd")),
@ -782,6 +784,12 @@ FixedwingEstimator::task_main()
_gps.vel_e_m_s = 0.0f;
_gps.vel_d_m_s = 0.0f;
// init lowpass filters for baro and gps altitude
float _gps_alt_filt = 0, _baro_alt_filt = 0;
float _gps_last = 0, _baro_last = 0;
float rc = (1.0f/10); // actually 1/RC time constant of 1st order LPF
hrt_abstime baro_last = 0;
_task_running = true;
while (!_task_should_exit) {
@ -800,6 +808,7 @@ FixedwingEstimator::task_main()
}
perf_begin(_loop_perf);
perf_count(_loop_intvl);
/* only update parameters if they changed */
if (fds[0].revents & POLLIN) {
@ -1055,6 +1064,12 @@ FixedwingEstimator::task_main()
_ekf->gpsLon = math::radians(_gps.lon / (double)1e7) - M_PI;
_ekf->gpsHgt = _gps.alt / 1e3f;
// update LPF
_gps_alt_filt += (1 - expf(-gps_elapsed * rc)) * (_gps_last - _gps_alt_filt);
_gps_last = _ekf->gpsHgt;
//warnx("gps alt: %6.1f, interval: %6.3f", (double)_ekf->gpsHgt, (double)gps_elapsed);
// if (_gps.s_variance_m_s > 0.25f && _gps.s_variance_m_s < 100.0f * 100.0f) {
// _ekf->vneSigma = sqrtf(_gps.s_variance_m_s);
// } else {
@ -1070,7 +1085,6 @@ FixedwingEstimator::task_main()
// warnx("vel: %8.4f pos: %8.4f", _gps.s_variance_m_s, _gps.p_variance_m);
newDataGps = true;
last_gps = _gps.timestamp_position;
}
@ -1082,15 +1096,16 @@ FixedwingEstimator::task_main()
if (baro_updated) {
hrt_abstime baro_last = _baro.timestamp;
orb_copy(ORB_ID(sensor_baro0), _baro_sub, &_baro);
float baro_elapsed = (_baro.timestamp - baro_last) / 1e6f;
baro_last = _baro.timestamp;
_ekf->updateDtHgtFilt(math::constrain(baro_elapsed, 0.001f, 0.1f));
_ekf->baroHgt = _baro.altitude;
_baro_alt_filt += (1 - expf(-baro_elapsed * rc)) * (_baro_last - _baro_alt_filt);
_baro_last = _baro.altitude;
if (!_baro_init) {
_baro_ref = _baro.altitude;
@ -1180,6 +1195,24 @@ FixedwingEstimator::task_main()
float initVelNED[3];
// maintain filtered baro and gps altitudes to calculate weather offset
// baro sample rate is ~70Hz and measurement bandwidth is high
// gps sample rate is 5Hz and altitude is assumed accurate when averaged over 30 seconds
// maintain heavily filtered values for both baro and gps altitude
// Assume the filtered output should be identical for both sensors
_baro_gps_offset = _baro_alt_filt - _gps_alt_filt;
if (hrt_elapsed_time(&_last_debug_print) >= 5e6) {
_last_debug_print = hrt_absolute_time();
perf_print_counter(_perf_baro);
perf_reset(_perf_baro);
warnx("gpsoff: %5.1f, baro_alt_filt: %6.1f, gps_alt_filt: %6.1f, gpos.alt: %5.1f, lpos.z: %6.1f",
(double)_baro_gps_offset,
(double)_baro_alt_filt,
(double)_gps_alt_filt,
(double)_global_pos.alt,
(double)_local_pos.z);
}
/* Initialize the filter first */
if (!_gps_initialized && _gps.fix_type > 2 && _gps.eph < _parameters.pos_stddev_threshold && _gps.epv < _parameters.pos_stddev_threshold) {
@ -1195,7 +1228,13 @@ FixedwingEstimator::task_main()
// Set up height correctly
orb_copy(ORB_ID(sensor_baro0), _baro_sub, &_baro);
_baro_ref_offset = _ekf->states[9]; // this should become zero in the local frame
_baro_gps_offset = _baro.altitude - gps_alt;
// init filtered gps and baro altitudes
_gps_alt_filt = gps_alt;
_gps_last = gps_alt;
_baro_alt_filt = _baro.altitude;
_baro_last = _baro.altitude;
_ekf->baroHgt = _baro.altitude;
_ekf->hgtMea = 1.0f * (_ekf->baroHgt - (_baro_ref));
@ -1502,6 +1541,12 @@ FixedwingEstimator::task_main()
_global_pos.timestamp = _local_pos.timestamp;
// FIXME: usurp terrain alt field for baro_gps_offset
_global_pos.terrain_alt = _baro_gps_offset;
_global_pos.terrain_alt_valid = true;
_global_pos.eph = _baro_alt_filt;
_global_pos.epv = _gps_alt_filt;
/* lazily publish the global position only once available */
if (_global_pos_pub > 0) {
/* publish the global position */