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Merge pull request #76 from PX4/pr-fixRngHgtMode

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EKF: Fix bugs preventing use of range finder as primary height source

Flight testing completed and I have checked that the other pending PR #75 rebases cleanly on it.
This commit is contained in:
Paul Riseborough 2016-03-14 09:46:58 +11:00
commit 4bd79c9e5d
7 changed files with 98 additions and 30 deletions
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23
EKF/control.cpp
View File

@ -125,6 +125,7 @@ void Ekf::controlFusionModes()
if (_control_status.flags.yaw_align) {
_control_status.flags.gps = true;
_time_last_gps = _time_last_imu;
// if we are not already aiding with optical flow, then we need to reset the position and velocity
if (!_control_status.flags.opt_flow) {
_control_status.flags.gps = resetPosition();
@ -159,8 +160,8 @@ void Ekf::controlFusionModes()
// Handle the case where we have rejected height measurements for an extended period
// This excessive vibration levels can cause this so a reset gives the filter a chance to recover
// After 10 seconds without aiding we reset to the height measurement provided the data is fresh
if ((_time_last_imu - _time_last_hgt_fuse > 10e6) && (_time_last_imu - _time_last_baro < 5e5)) {
// After 10 seconds without aiding we reset to the height measurement
if (_time_last_imu - _time_last_hgt_fuse > 10e6) {
// Reset vertical position and velocity states to the last measurement
resetHeight();
}
@ -247,10 +248,22 @@ void Ekf::controlFusionModes()
}
// Control the soure of height measurements for the main filter
_control_status.flags.baro_hgt = true;
_control_status.flags.rng_hgt = false;
_control_status.flags.gps_hgt = false;
if (_params.vdist_sensor_type == VDIST_SENSOR_BARO) {
_control_status.flags.baro_hgt = true;
_control_status.flags.rng_hgt = false;
_control_status.flags.gps_hgt = false;
} else if (_params.vdist_sensor_type == VDIST_SENSOR_RANGE) {
_control_status.flags.baro_hgt = false;
_control_status.flags.rng_hgt = true;
_control_status.flags.gps_hgt = false;
} else {
// TODO functionality to fuse GPS height
_control_status.flags.baro_hgt = false;
_control_status.flags.rng_hgt = false;
_control_status.flags.gps_hgt = false;
}
// Placeholder for control of wind velocity states estimation
// TODO add methods for true airspeed and/or sidelsip fusion or some type of drag force measurement

71
EKF/ekf.cpp
View File

@ -40,6 +40,7 @@
*/
#include "ekf.h"
#include "mathlib.h"
Ekf::Ekf():
_filter_initialised(false),
@ -70,13 +71,16 @@ Ekf::Ekf():
_last_gps_origin_time_us(0),
_gps_alt_ref(0.0f),
_hgt_counter(0),
_time_last_hgt(0),
_hgt_sum(0.0f),
_mag_counter(0),
_time_last_mag(0),
_hgt_at_alignment(0.0f),
_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 = {};
@ -99,7 +103,7 @@ Ekf::Ekf():
_mag_sum = {};
_delVel_sum = {};
_flow_gyro_bias = {};
_imu_del_ang_of = {};
_imu_del_ang_of = {};
}
Ekf::~Ekf()
@ -156,8 +160,6 @@ bool Ekf::init(uint64_t timestamp)
bool Ekf::update()
{
// Only run the filter if IMU data in the buffer has been updated
if (_imu_updated) {
if (!_filter_initialised) {
_filter_initialised = initialiseFilter();
@ -166,6 +168,9 @@ bool Ekf::update()
}
}
// Only run the filter if IMU data in the buffer has been updated
if (_imu_updated) {
// perform state and covariance prediction for the main filter
predictState();
predictCovariance();
@ -207,21 +212,43 @@ 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;
// only use range finder as a height observation in the main filter if specifically enabled
if (_params.vdist_sensor_type == VDIST_SENSOR_RANGE) {
if (_control_status.flags.rng_hgt) {
_fuse_height = true;
}
} 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)
&& _params.vdist_sensor_type == VDIST_SENSOR_BARO) {
_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
float offset_error = _baro_sample_delayed.hgt + _state.pos(2) - _baro_hgt_offset;
_baro_hgt_offset += 0.02f * math::constrain(offset_error, -5.0f, 5.0f);
}
}
// If we are using GPS aiding and data has fallen behind the fusion time horizon then fuse it
@ -233,15 +260,15 @@ 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);
@ -303,22 +330,27 @@ bool Ekf::initialiseFilter(void)
if (_params.vdist_sensor_type == VDIST_SENSOR_RANGE) {
rangeSample range_init = _range_buffer.get_newest();
if (range_init.time_us != 0) {
if (range_init.time_us != _time_last_hgt) {
_hgt_counter ++;
_hgt_sum += range_init.rng;
_time_last_hgt = range_init.time_us;
}
} else {
} else if (_params.vdist_sensor_type == VDIST_SENSOR_BARO) {
// initialize vertical position with newest baro measurement
baroSample baro_init = _baro_buffer.get_newest();
if (baro_init.time_us != 0) {
if (baro_init.time_us != _time_last_hgt) {
_hgt_counter ++;
_hgt_sum += baro_init.hgt;
_time_last_hgt = baro_init.time_us;
}
} else {
return false;
}
// check to see if we have enough measruements and return false if not
// check to see if we have enough measurements and return false if not
if (_hgt_counter < 10 || _mag_counter < 10) {
return false;
@ -361,9 +393,14 @@ bool Ekf::initialiseFilter(void)
// calculate the initial magnetic field and yaw alignment
resetMagHeading(mag_init);
// calculate the averaged barometer 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();

8
EKF/ekf.h
View File

@ -197,9 +197,11 @@ private:
float _gps_alt_ref; // WGS-84 height (m)
// Variables used to initialise the filter states
uint8_t _hgt_counter; // number of baro samples averaged
float _hgt_sum; // summed baro measurement
uint8_t _hgt_counter; // number of height samples averaged
uint64_t _time_last_hgt; // measurement time of last height sample
float _hgt_sum; // summed height measurement
uint8_t _mag_counter; // number of magnetometer samples averaged
uint64_t _time_last_mag; // measurement time of last magnetomter sample
Vector3f _mag_sum; // summed magnetometer measurement
Vector3f _delVel_sum; // summed delta velocity
float _hgt_at_alignment; // baro offset relative to alignment position
@ -214,6 +216,8 @@ private:
uint64_t _time_last_hagl_fuse; // last system time in usec that the hagl measurement failed it's checks
bool _terrain_initialised; // true when the terrain estimator has been intialised
float _baro_hgt_offset; // number of metres the baro height origin is above the local NED origin (m)
// update the real time complementary filter states. This includes the prediction
// and the correction step
void calculateOutputStates();

15
EKF/ekf_helper.cpp
View File

@ -87,7 +87,7 @@ bool Ekf::resetPosition()
// Reset height state using the last height measurement
void Ekf::resetHeight()
{
if (_params.vdist_sensor_type == VDIST_SENSOR_RANGE) {
if (_control_status.flags.rng_hgt) {
rangeSample range_newest = _range_buffer.get_newest();
if (_time_last_imu - range_newest.time_us < 200000) {
@ -96,7 +96,12 @@ void Ekf::resetHeight()
} else {
// TODO: reset to last known range based estimate
}
} else {
// reset the baro offset which is subtracted from the baro reading if we need to use it as a backup
baroSample baro_newest = _baro_buffer.get_newest();
_baro_hgt_offset = baro_newest.hgt + _state.pos(2);
} else if (_control_status.flags.baro_hgt) {
// initialize vertical position with newest baro measurement
baroSample baro_newest = _baro_buffer.get_newest();
@ -106,6 +111,12 @@ void Ekf::resetHeight()
} else {
// TODO: reset to last known baro based estimate
}
// the baro height offset should be zero if baro is our primary height source
_baro_hgt_offset = 0.0f;
} else {
// TODO: reset to GPS height
}
}

4
EKF/gps_checks.cpp
View File

@ -56,7 +56,7 @@
bool Ekf::collect_gps(uint64_t time_usec, struct gps_message *gps)
{
// If we have defined the WGS-84 position of the NED origin, run gps quality checks until they pass, then define the origins WGS-84 position using the last GPS fix
if (!_NED_origin_initialised ) {
if (!_NED_origin_initialised) {
// we have good GPS data so can now set the origin's WGS-84 position
if (gps_is_good(gps) && !_NED_origin_initialised) {
printf("gps is good - setting EKF origin\n");
@ -64,12 +64,14 @@ bool Ekf::collect_gps(uint64_t time_usec, struct gps_message *gps)
double lat = gps->lat / 1.0e7;
double lon = gps->lon / 1.0e7;
map_projection_init_timestamped(&_pos_ref, lat, lon, _time_last_imu);
// if we are already doing aiding, corect for the change in posiiton since the EKF started navigating
if (_control_status.flags.opt_flow || _control_status.flags.gps) {
double est_lat, est_lon;
map_projection_reproject(&_pos_ref, -_state.pos(0), -_state.pos(1), &est_lat, &est_lon);
map_projection_init_timestamped(&_pos_ref, est_lat, est_lon, _time_last_imu);
}
// Take the current GPS height and subtract the filter height above origin to estimate the GPS height of the origin
_gps_alt_ref = 1e-3f * (float)gps->alt + _state.pos(2);
_NED_origin_initialised = true;

3
EKF/terrain_estimator.cpp
View File

@ -78,7 +78,8 @@ void Ekf::predictHagl()
_terrain_var += sq(_imu_sample_delayed.delta_vel_dt * _params.terrain_p_noise);
// process noise due to terrain gradient
_terrain_var += sq(_imu_sample_delayed.delta_vel_dt * _params.terrain_gradient) * (sq(_state.vel(0)) + sq(_state.vel(1)));
_terrain_var += sq(_imu_sample_delayed.delta_vel_dt * _params.terrain_gradient) * (sq(_state.vel(0)) + sq(_state.vel(
1)));
// limit the variance to prevent it becoming badly conditioned
_terrain_var = math::constrain(_terrain_var, 0.0f, 1e4f);

4
EKF/vel_pos_fusion.cpp
View File

@ -110,7 +110,7 @@ void Ekf::fuseVelPosHeight()
if (_control_status.flags.baro_hgt) {
fuse_map[5] = true;
// vertical position innovation - baro measurement has opposite sign to earth z axis
_vel_pos_innov[5] = _state.pos(2) - (_hgt_at_alignment - _baro_sample_delayed.hgt);
_vel_pos_innov[5] = _state.pos(2) - (_hgt_at_alignment - _baro_sample_delayed.hgt + _baro_hgt_offset);
// observation variance - user parameter defined
R[5] = fmaxf(_params.baro_noise, 0.01f);
R[5] = R[5] * R[5];
@ -120,7 +120,7 @@ void Ekf::fuseVelPosHeight()
} else if (_control_status.flags.rng_hgt && (_R_prev(2, 2) > 0.7071f)) {
fuse_map[5] = true;
// use range finder with tilt correction
_vel_pos_innov[5] = _state.pos(2) - (-math::max(_range_sample_delayed.rng *_R_prev(2, 2),
_vel_pos_innov[5] = _state.pos(2) - (-math::max(_range_sample_delayed.rng * _R_prev(2, 2),
_params.rng_gnd_clearance));
// observation variance - user parameter defined
R[5] = fmaxf(_params.range_noise, 0.01f);