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EKF: Enable fallback to baro alt when using range finder for height

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This commit is contained in:
Paul Riseborough
2016-03-13 21:17:51 +11:00
parent 370f643f42
commit c58ab3e256
5 changed files with 52 additions and 20 deletions
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EKF/ekf.cpp
+37 -16
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@@ -40,6 +40,7 @@
*/
#include "ekf.h"
#include "mathlib.h"
Ekf::Ekf():
_filter_initialised(false),
@@ -78,7 +79,8 @@ Ekf::Ekf():
_terrain_vpos(0.0f),
_hagl_innov(0.0f),
_hagl_innov_var(0.0f),
_time_last_hagl_fuse(0)
_time_last_hagl_fuse(0),
_baro_hgt_offset(0.0f)
{
_control_status = {};
_control_status_prev = {};
@@ -101,7 +103,7 @@ Ekf::Ekf():
_mag_sum = {};
_delVel_sum = {};
_flow_gyro_bias = {};
_imu_del_ang_of = {};
_imu_del_ang_of = {};
}
Ekf::~Ekf()
@@ -209,7 +211,7 @@ bool Ekf::update()
// determine if range finder data has fallen behind the fusin time horizon fuse it if we are
// not tilted too much to use it
if (_range_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_range_sample_delayed)
&& (_R_prev(2, 2) > 0.7071f)) {
&& (_R_prev(2, 2) > 0.7071f)) {
// if we have range data we always try to estimate terrain height
_fuse_hagl_data = true;
@@ -217,20 +219,34 @@ bool Ekf::update()
if (_control_status.flags.rng_hgt) {
_fuse_height = true;
}
}
// If we are supposed to be using range finder data as the primary height sensor and haven't received it for a while
// and are on the ground, then set the measurement to the expected on ground value
if ((_time_last_imu - _time_last_hgt_fuse) > 5e5 && _control_status.flags.rng_hgt && !_in_air) {
_range_sample_delayed.rng = _params.rng_gnd_clearance;
_range_sample_delayed.time_us = _imu_sample_delayed.time_us;
} else if ((_time_last_imu - _time_last_hgt_fuse) > 5e5 && _control_status.flags.rng_hgt) {
// If we are supposed to be using range finder data as the primary height sensor, have missed or rejected measurements
// and are on the ground, then synthesise a measurement at the expected on ground value
if (!_in_air) {
_range_sample_delayed.rng = _params.rng_gnd_clearance;
_range_sample_delayed.time_us = _imu_sample_delayed.time_us;
} else {
// if this happens in the air, fuse the baro measurement to constrain drift
// use the baro for this update only
_control_status.flags.baro_hgt = true;
_control_status.flags.rng_hgt = false;
}
_fuse_height = true;
}
// determine if baro data has fallen behind the fuson time horizon and fuse it in the main filter if enabled
if (_baro_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_baro_sample_delayed)
&& _control_status.flags.baro_hgt) {
_fuse_height = true;
if (_baro_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_baro_sample_delayed)) {
if (_control_status.flags.baro_hgt) {
_fuse_height = true;
} else {
// calculate a filtered offset between the baro origin and local NED origin if we are not using the baro as a height reference
_baro_hgt_offset += 0.02f * math::constrain((_baro_sample_delayed.hgt + _state.pos(2) - _baro_hgt_offset), -5.0f, 5.0f);
}
}
// If we are using GPS aiding and data has fallen behind the fusion time horizon then fuse it
@@ -242,15 +258,15 @@ bool Ekf::update()
// If we are using optical flow aiding and data has fallen behind the fusion time horizon, then fuse it
if (_flow_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_flow_sample_delayed)
&& _control_status.flags.opt_flow && (_time_last_imu - _time_last_optflow) < 2e5
&& (_R_prev(2, 2) > 0.7071f)) {
&& _control_status.flags.opt_flow && (_time_last_imu - _time_last_optflow) < 2e5
&& (_R_prev(2, 2) > 0.7071f)) {
_fuse_flow = true;
}
// if we aren't doing any aiding, fake GPS measurements at the last known position to constrain drift
// Coincide fake measurements with baro data for efficiency with a minimum fusion rate of 5Hz
if (!_control_status.flags.gps && !_control_status.flags.opt_flow
&& ((_time_last_imu - _time_last_fake_gps > 2e5) || _fuse_height)) {
&& ((_time_last_imu - _time_last_fake_gps > 2e5) || _fuse_height)) {
_fuse_pos = true;
_gps_sample_delayed.pos(0) = _last_known_posNE(0);
_gps_sample_delayed.pos(1) = _last_known_posNE(1);
@@ -375,9 +391,14 @@ bool Ekf::initialiseFilter(void)
// calculate the initial magnetic field and yaw alignment
resetMagHeading(mag_init);
// calculate the averaged height reading
// calculate the averaged height reading to calulate the height of the origin
_hgt_at_alignment = _hgt_sum / (float)_hgt_counter;
// if we are not using the baro height as the primary source, then calculate an offset relative to the origin
// so it can be used as a backup
baroSample baro_newest = _baro_buffer.get_newest();
_baro_hgt_offset = baro_newest.hgt;
// set the velocity to the GPS measurement (by definition, the initial position and height is at the origin)
resetVelocity();