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px4-firmware/EKF/control.cpp

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/****************************************************************************
*
* Copyright (c) 2015 Estimation and Control Library (ECL). All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name ECL nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file control.cpp
* Control functions for ekf attitude and position estimator.
*
* @author Paul Riseborough <p_riseborough@live.com.au>
*
*/
#include "ekf.h"
void Ekf::controlFusionModes()
{
// Store the status to enable change detection
_control_status_prev.value = _control_status.value;
// Get the magnetic declination
calcMagDeclination();
// Once the angular uncertainty has reduced sufficiently, initialise the yaw and magnetic field states
float total_angle_variance = P[0][0] + P[1][1] + P[2][2] + P[3][3];
if (total_angle_variance < 0.002f && !_control_status.flags.tilt_align) {
_control_status.flags.tilt_align = true;
_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag);
}
// optical flow fusion mode selection logic
// to start using optical flow data we need angular alignment complete, and fresh optical flow and height above terrain data
if ((_params.fusion_mode & MASK_USE_OF) && !_control_status.flags.opt_flow && _control_status.flags.tilt_align
&& (_time_last_imu - _time_last_optflow) < 5e5 && (_time_last_imu - _time_last_hagl_fuse) < 5e5) {
// If the heading is not aligned, reset the yaw and magnetic field states
if (!_control_status.flags.yaw_align) {
_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag);
}
// If the heading is valid, start using optical flow aiding
if (_control_status.flags.yaw_align) {
// set the flag and reset the fusion timeout
_control_status.flags.opt_flow = true;
_time_last_of_fuse = _time_last_imu;
// if we are not using GPS then the velocity and position states and covariances need to be set
if (!_control_status.flags.gps) {
// constrain height above ground to be above minimum possible
float heightAboveGndEst = fmaxf((_terrain_vpos - _state.pos(2)), _params.rng_gnd_clearance);
// calculate absolute distance from focal point to centre of frame assuming a flat earth
float range = heightAboveGndEst / _R_to_earth(2, 2);
if ((range - _params.rng_gnd_clearance) > 0.3f && _flow_sample_delayed.dt > 0.05f) {
// we should ahve reliable OF measurements so
// calculate X and Y body relative velocities from OF measurements
Vector3f vel_optflow_body;
vel_optflow_body(0) = - range * _flow_sample_delayed.flowRadXYcomp(1) / _flow_sample_delayed.dt;
vel_optflow_body(1) = range * _flow_sample_delayed.flowRadXYcomp(0) / _flow_sample_delayed.dt;
vel_optflow_body(2) = 0.0f;
// rotate from body to earth frame
Vector3f vel_optflow_earth;
vel_optflow_earth = _R_to_earth * vel_optflow_body;
// take x and Y components
_state.vel(0) = vel_optflow_earth(0);
_state.vel(1) = vel_optflow_earth(1);
} else {
_state.vel(0) = 0.0f;
_state.vel(1) = 0.0f;
}
// reset the velocity covariance terms
zeroRows(P,4,5);
zeroCols(P,4,5);
// reset the horizontal velocity variance using the optical flow noise variance
P[5][5] = P[4][4] = sq(range) * calcOptFlowMeasVar();
if (!_control_status.flags.in_air) {
// we are likely starting OF for the first time so reset the horizontal position and vertical velocity states
_state.pos(0) = 0.0f;
_state.pos(1) = 0.0f;
// reset the coresponding covariances
// we are by definition at the origin at commencement so variances are also zeroed
zeroRows(P,7,8);
zeroCols(P,7,8);
// align the output observer to the EKF states
alignOutputFilter();
}
}
}
} else if (!(_params.fusion_mode & MASK_USE_OF)) {
_control_status.flags.opt_flow = false;
}
// GPS fusion mode selection logic
// To start use GPS we need angular alignment completed, the local NED origin set and fresh GPS data
if ((_params.fusion_mode & MASK_USE_GPS) && !_control_status.flags.gps) {
if (_control_status.flags.tilt_align && (_time_last_imu - _time_last_gps) < 5e5 && _NED_origin_initialised
&& (_time_last_imu - _last_gps_fail_us > 5e6)) {
// If the heading is not aligned, reset the yaw and magnetic field states
if (!_control_status.flags.yaw_align) {
_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag);
}
// If the heading is valid start using gps aiding
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();
_control_status.flags.gps = resetVelocity();
}
}
}
} else if (!(_params.fusion_mode & MASK_USE_GPS)) {
_control_status.flags.gps = false;
}
// handle the case when we are relying on GPS fusion and lose it
if (_control_status.flags.gps && !_control_status.flags.opt_flow) {
// We are relying on GPS aiding to constrain attitude drift so after 10 seconds without aiding we need to do something
if ((_time_last_imu - _time_last_pos_fuse > 10e6) && (_time_last_imu - _time_last_vel_fuse > 10e6)) {
if (_time_last_imu - _time_last_gps > 5e5) {
// if we don't have gps then we need to switch to the non-aiding mode, zero the veloity states
// and set the synthetic GPS position to the current estimate
_control_status.flags.gps = false;
_last_known_posNE(0) = _state.pos(0);
_last_known_posNE(1) = _state.pos(1);
_state.vel.setZero();
} else {
// Reset states to the last GPS measurement
resetPosition();
resetVelocity();
// Reset the timeout counters
_time_last_pos_fuse = _time_last_imu;
_time_last_vel_fuse = _time_last_imu;
}
}
}
/*
* Handle the case where we have not fused height measurements recently and
* uncertainty exceeds the max allowable. Reset using the best available height
* measurement source, continue using it after the reset and declare the current
* source failed if we have switched.
*/
// check for inertial sensing errors as evidenced by the vertical innovations having the same sign and not stale
bool bad_vert_accel = (_control_status.flags.baro_hgt && // we can only run this check if vertical position and velocity observations are indepedant
(_vel_pos_innov[5] * _vel_pos_innov[2] > 0.0f) && // vertical position and velocity sensors are in agreement
((_imu_sample_delayed.time_us - _baro_sample_delayed.time_us) < 2 * BARO_MAX_INTERVAL) && // vertical position data is fresh
((_imu_sample_delayed.time_us - _gps_sample_delayed.time_us) < 2 * GPS_MAX_INTERVAL) && // vertical velocity data is freshs
_vel_pos_test_ratio[2] > 1.0f && // vertical velocty innovations have failed innovation consistency checks
_vel_pos_test_ratio[5] > 1.0f); // vertical position innovations have failed innovation consistency checks
// record time of last bad vert accel
if (bad_vert_accel) {
_time_bad_vert_accel = _time_last_imu;
}
if ((P[8][8] > sq(_params.hgt_reset_lim)) && ((_time_last_imu - _time_last_hgt_fuse) > 5e6)) {
// boolean that indicates we will do a height reset
bool reset_height = false;
// handle the case where we are using baro for height
if (_control_status.flags.baro_hgt) {
// check if GPS height is available
gpsSample gps_init = _gps_buffer.get_newest();
bool gps_hgt_available = ((_time_last_imu - gps_init.time_us) < 2 * GPS_MAX_INTERVAL);
bool gps_hgt_accurate = (gps_init.vacc < _params.req_vacc);
baroSample baro_init = _baro_buffer.get_newest();
bool baro_hgt_available = ((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL);
// check for inertial sensing errors in the last 10 seconds
bool prev_bad_vert_accel = (_time_last_imu - _time_bad_vert_accel < 10E6);
// reset to GPS if adequate GPS data is available and the timeout cannot be blamed on IMU data
bool reset_to_gps = gps_hgt_available && gps_hgt_accurate && !_gps_hgt_faulty && !prev_bad_vert_accel;
// reset to GPS if GPS data is available and there is no Baro data
reset_to_gps = reset_to_gps || (gps_hgt_available && !baro_hgt_available);
// reset to Baro if we are not doing a GPS reset and baro data is available
bool reset_to_baro = !reset_to_gps && baro_hgt_available;
if (reset_to_gps) {
// set height sensor health
_baro_hgt_faulty = true;
_gps_hgt_faulty = false;
// declare the GPS height healthy
_gps_hgt_faulty = false;
// reset the height mode
_control_status.flags.baro_hgt = false;
_control_status.flags.gps_hgt = true;
_control_status.flags.rng_hgt = false;
// request a reset
reset_height = true;
printf("EKF baro hgt timeout - reset to GPS\n");
} else if (reset_to_baro){
// set height sensor health
_baro_hgt_faulty = false;
// reset the height mode
_control_status.flags.baro_hgt = true;
_control_status.flags.gps_hgt = false;
_control_status.flags.rng_hgt = false;
// request a reset
reset_height = true;
printf("EKF baro hgt timeout - reset to baro\n");
} else {
// we have nothing we can reset to
// deny a reset
reset_height = false;
}
}
// handle the case we are using GPS for height
if (_control_status.flags.gps_hgt) {
// check if GPS height is available
gpsSample gps_init = _gps_buffer.get_newest();
bool gps_hgt_available = ((_time_last_imu - gps_init.time_us) < 2 * GPS_MAX_INTERVAL);
bool gps_hgt_accurate = (gps_init.vacc < _params.req_vacc);
// check the baro height source for consistency and freshness
baroSample baro_init = _baro_buffer.get_newest();
bool baro_data_fresh = ((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL);
float baro_innov = _state.pos(2) - (_hgt_sensor_offset - baro_init.hgt + _baro_hgt_offset);
bool baro_data_consistent = fabsf(baro_innov) < (sq(_params.baro_noise) + P[8][8]) * sq(_params.baro_innov_gate);
// if baro data is acceptable and GPS data is inaccurate, reset height to baro
bool reset_to_baro = baro_data_consistent && baro_data_fresh && !_baro_hgt_faulty && !gps_hgt_accurate;
// if GPS height is unavailable and baro data is available, reset height to baro
reset_to_baro = reset_to_baro || (!gps_hgt_available && baro_data_fresh);
// if we cannot switch to baro and GPs data is available, reset height to GPS
bool reset_to_gps = !reset_to_baro && gps_hgt_available;
if (reset_to_baro) {
// set height sensor health
_gps_hgt_faulty = true;
_baro_hgt_faulty = false;
// reset the height mode
_control_status.flags.baro_hgt = true;
_control_status.flags.gps_hgt = false;
_control_status.flags.rng_hgt = false;
// request a reset
reset_height = true;
printf("EKF gps hgt timeout - reset to baro\n");
} else if (reset_to_gps) {
// set height sensor health
_gps_hgt_faulty = false;
// reset the height mode
_control_status.flags.baro_hgt = false;
_control_status.flags.gps_hgt = true;
_control_status.flags.rng_hgt = false;
// request a reset
reset_height = true;
printf("EKF gps hgt timeout - reset to GPS\n");
} else {
// we have nothing to reset to
reset_height = false;
}
}
// handle the case we are using range finder for height
if (_control_status.flags.rng_hgt) {
// check if range finder data is available
rangeSample rng_init = _range_buffer.get_newest();
bool rng_data_available = ((_time_last_imu - rng_init.time_us) < 2 * RNG_MAX_INTERVAL);
// check if baro data is available
baroSample baro_init = _baro_buffer.get_newest();
bool baro_data_available = ((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL);
// reset to baro if we have no range data and baro data is available
bool reset_to_baro = !rng_data_available && baro_data_available;
// reset to range data if it is available
bool reset_to_rng = rng_data_available;
if (reset_to_baro) {
// set height sensor health
_rng_hgt_faulty = true;
_baro_hgt_faulty = false;
// reset the height mode
_control_status.flags.baro_hgt = true;
_control_status.flags.gps_hgt = false;
_control_status.flags.rng_hgt = false;
// request a reset
reset_height = true;
printf("EKF rng hgt timeout - reset to baro\n");
} else if (reset_to_rng) {
// set height sensor health
_rng_hgt_faulty = false;
// reset the height mode
_control_status.flags.baro_hgt = false;
_control_status.flags.gps_hgt = false;
_control_status.flags.rng_hgt = true;
// request a reset
reset_height = true;
printf("EKF rng hgt timeout - reset to rng hgt\n");
} else {
// we have nothing to reset to
reset_height = false;
}
}
// Reset vertical position and velocity states to the last measurement
if (reset_height) {
resetHeight();
// Reset the timout timer
_time_last_hgt_fuse = _time_last_imu;
}
}
// handle the case when we are relying on optical flow fusion and lose it
if (_control_status.flags.opt_flow && !_control_status.flags.gps) {
// We are relying on flow aiding to constrain attitude drift so after 5s without aiding we need to do something
if ((_time_last_imu - _time_last_of_fuse > 5e6)) {
// Switch to the non-aiding mode, zero the veloity states
// and set the synthetic position to the current estimate
_control_status.flags.opt_flow = false;
_last_known_posNE(0) = _state.pos(0);
_last_known_posNE(1) = _state.pos(1);
_state.vel.setZero();
}
}
// Determine if we should use simple magnetic heading fusion which works better when there are large external disturbances
// or the more accurate 3-axis fusion
if (_params.mag_fusion_type == MAG_FUSE_TYPE_AUTO) {
if (_control_status.flags.in_air) {
// if transitioning into 3-axis fusion mode, we need to initialise the yaw angle and field states
if (!_control_status.flags.mag_3D) {
_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag);
}
// use 3D mag fusion when airborne
_control_status.flags.mag_hdg = false;
_control_status.flags.mag_3D = true;
} else {
// use heading fusion when on the ground
_control_status.flags.mag_hdg = true;
_control_status.flags.mag_3D = false;
}
} else if (_params.mag_fusion_type == MAG_FUSE_TYPE_HEADING) {
// always use heading fusion
_control_status.flags.mag_hdg = true;
_control_status.flags.mag_3D = false;
} else if (_params.mag_fusion_type == MAG_FUSE_TYPE_3D) {
// if transitioning into 3-axis fusion mode, we need to initialise the yaw angle and field states
if (!_control_status.flags.mag_3D) {
_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag);
}
// always use 3-axis mag fusion
_control_status.flags.mag_hdg = false;
_control_status.flags.mag_3D = true;
} else {
// do no magnetometer fusion at all
_control_status.flags.mag_hdg = false;
_control_status.flags.mag_3D = false;
}
// if we are using 3-axis magnetometer fusion, but without external aiding, then the declination must be fused as an observation to prevent long term heading drift
// fusing declination when gps aiding is available is optional, but recommneded to prevent problem if the vehicle is static for extended periods of time
if (_control_status.flags.mag_3D && (!_control_status.flags.gps || (_params.mag_declination_source & MASK_FUSE_DECL))) {
_control_status.flags.mag_dec = true;
} else {
_control_status.flags.mag_dec = false;
}
// Control the soure of height measurements for the main filter
if ((_params.vdist_sensor_type == VDIST_SENSOR_BARO && !_baro_hgt_faulty) || _control_status.flags.baro_hgt) {
_control_status.flags.baro_hgt = true;
_control_status.flags.gps_hgt = false;
_control_status.flags.rng_hgt = false;
} else if ((_params.vdist_sensor_type == VDIST_SENSOR_GPS && !_gps_hgt_faulty) || _control_status.flags.gps_hgt) {
_control_status.flags.baro_hgt = false;
_control_status.flags.gps_hgt = true;
_control_status.flags.rng_hgt = false;
} else if (_params.vdist_sensor_type == VDIST_SENSOR_RANGE && !_rng_hgt_faulty) {
_control_status.flags.baro_hgt = false;
_control_status.flags.gps_hgt = false;
_control_status.flags.rng_hgt = true;
}
// if the airspeed measurements have timed out for 10 seconds we declare the wind estimate to be invalid
if (_time_last_imu - _time_last_arsp_fuse > 10e6 || _time_last_arsp_fuse == 0) {
_control_status.flags.wind = false;
} else {
_control_status.flags.wind = true;
}
}
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