forked from Archive/PX4-Autopilot
248 lines
10 KiB
C++
248 lines
10 KiB
C++
/****************************************************************************
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*
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* Copyright (c) 2013 Estimation and Control Library (ECL). All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name ECL nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file gps_checks.cpp
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* Perform pre-flight and in-flight GPS quality checks
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*
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* @author Paul Riseborough <p_riseborough@live.com.au>
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*
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*/
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#include "../ecl.h"
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#include "ekf.h"
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#include "mathlib.h"
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#include "geo.h"
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// GPS pre-flight check bit locations
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#define MASK_GPS_NSATS (1<<0)
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#define MASK_GPS_GDOP (1<<1)
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#define MASK_GPS_HACC (1<<2)
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#define MASK_GPS_VACC (1<<3)
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#define MASK_GPS_SACC (1<<4)
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#define MASK_GPS_HDRIFT (1<<5)
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#define MASK_GPS_VDRIFT (1<<6)
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#define MASK_GPS_HSPD (1<<7)
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#define MASK_GPS_VSPD (1<<8)
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bool Ekf::collect_gps(uint64_t time_usec, struct gps_message *gps)
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{
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// 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
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if (!_NED_origin_initialised) {
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// we have good GPS data so can now set the origin's WGS-84 position
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if (gps_is_good(gps) && !_NED_origin_initialised) {
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ECL_INFO("EKF gps is good - setting origin");
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// Set the origin's WGS-84 position to the last gps fix
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double lat = gps->lat / 1.0e7;
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double lon = gps->lon / 1.0e7;
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map_projection_init_timestamped(&_pos_ref, lat, lon, _time_last_imu);
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// if we are already doing aiding, corect for the change in posiiton since the EKF started navigating
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if (_control_status.flags.opt_flow || _control_status.flags.gps) {
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double est_lat, est_lon;
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map_projection_reproject(&_pos_ref, -_state.pos(0), -_state.pos(1), &est_lat, &est_lon);
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map_projection_init_timestamped(&_pos_ref, est_lat, est_lon, _time_last_imu);
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}
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// Take the current GPS height and subtract the filter height above origin to estimate the GPS height of the origin
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_gps_alt_ref = 1e-3f * (float)gps->alt + _state.pos(2);
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_NED_origin_initialised = true;
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_last_gps_origin_time_us = _time_last_imu;
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// set the magnetic declination returned by the geo library using the current GPS position
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_mag_declination_gps = math::radians(get_mag_declination(lat, lon));
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// save the horizontal and vertical position uncertainty of the origin
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_gps_origin_eph = gps->eph;
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_gps_origin_epv = gps->epv;
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// if the user has selected GPS as the primary height source, switch across to using it
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if (_primary_hgt_source == VDIST_SENSOR_GPS) {
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ECL_INFO("EKF switching to GPS height");
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_control_status.flags.baro_hgt = false;
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_control_status.flags.gps_hgt = true;
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_control_status.flags.rng_hgt = false;
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// zero the sensor offset
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_hgt_sensor_offset = 0.0f;
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}
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}
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}
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// start collecting GPS if there is a 3D fix and the NED origin has been set
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if (_NED_origin_initialised && gps->fix_type >= 3) {
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return true;
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} else {
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return false;
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}
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return false;
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}
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/*
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* Return true if the GPS solution quality is adequate to set an origin for the EKF
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* and start GPS aiding.
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* All activated checks must pass for 10 seconds.
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* Checks are activated using the EKF2_GPS_CHECK bitmask parameter
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* Checks are adjusted using the EKF2_REQ_* parameters
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*/
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bool Ekf::gps_is_good(struct gps_message *gps)
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{
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// Check the fix type
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_gps_check_fail_status.flags.fix = (gps->fix_type < 3);
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// Check the number of satellites
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_gps_check_fail_status.flags.nsats = (gps->nsats < _params.req_nsats);
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// Check the geometric dilution of precision
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_gps_check_fail_status.flags.gdop = (gps->gdop > _params.req_gdop);
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// Check the reported horizontal position accuracy
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_gps_check_fail_status.flags.hacc = (gps->eph > _params.req_hacc);
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// Check the reported vertical position accuracy
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_gps_check_fail_status.flags.vacc = (gps->epv > _params.req_vacc);
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// Check the reported speed accuracy
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_gps_check_fail_status.flags.sacc = (gps->sacc > _params.req_sacc);
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// Calculate position movement since last measurement
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float delta_posN = 0.0f;
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float delta_PosE = 0.0f;
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double lat = gps->lat * 1.0e-7;
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double lon = gps->lon * 1.0e-7;
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if (_pos_ref.init_done) {
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map_projection_project(&_pos_ref, lat, lon, &delta_posN, &delta_PosE);
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} else {
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map_projection_init_timestamped(&_pos_ref, lat, lon, _time_last_imu);
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_gps_alt_ref = 1e-3f * (float)gps->alt;
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}
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// Calculate time lapsed since last update, limit to prevent numerical errors and calculate the lowpass filter coefficient
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const float filt_time_const = 10.0f;
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float dt = fminf(fmaxf(float(_time_last_imu - _last_gps_origin_time_us) * 1e-6f, 0.001f), filt_time_const);
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float filter_coef = dt / filt_time_const;
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// Calculate the horizontal drift velocity components and limit to 10x the threshold
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float vel_limit = 10.0f * _params.req_hdrift;
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float velN = fminf(fmaxf(delta_posN / dt, -vel_limit), vel_limit);
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float velE = fminf(fmaxf(delta_PosE / dt, -vel_limit), vel_limit);
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// Apply a low pass filter
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_gpsDriftVelN = velN * filter_coef + _gpsDriftVelN * (1.0f - filter_coef);
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_gpsDriftVelE = velE * filter_coef + _gpsDriftVelE * (1.0f - filter_coef);
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// Calculate the horizontal drift speed and fail if too high
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// This check can only be used if the vehicle is stationary during alignment
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if (!_control_status.flags.in_air) {
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float drift_speed = sqrtf(_gpsDriftVelN * _gpsDriftVelN + _gpsDriftVelE * _gpsDriftVelE);
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_gps_check_fail_status.flags.hdrift = (drift_speed > _params.req_hdrift);
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} else {
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_gps_check_fail_status.flags.hdrift = false;
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}
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// Save current position as the reference for next time
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map_projection_init_timestamped(&_pos_ref, lat, lon, _time_last_imu);
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_last_gps_origin_time_us = _time_last_imu;
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// Calculate the vertical drift velocity and limit to 10x the threshold
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vel_limit = 10.0f * _params.req_vdrift;
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float velD = fminf(fmaxf((_gps_alt_ref - 1e-3f * (float)gps->alt) / dt, -vel_limit), vel_limit);
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// Save the current height as the reference for next time
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_gps_alt_ref = 1e-3f * (float)gps->alt;
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// Apply a low pass filter to the vertical velocity
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_gps_drift_velD = velD * filter_coef + _gps_drift_velD * (1.0f - filter_coef);
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// Fail if the vertical drift speed is too high
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// This check can only be used if the vehicle is stationary during alignment
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if (!_control_status.flags.in_air) {
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_gps_check_fail_status.flags.vdrift = (fabsf(_gps_drift_velD) > _params.req_vdrift);
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} else {
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_gps_check_fail_status.flags.vdrift = false;
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}
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// Check the magnitude of the filtered horizontal GPS velocity
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// This check can only be used if the vehicle is stationary during alignment
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if (!_control_status.flags.in_air) {
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vel_limit = 10.0f * _params.req_hdrift;
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float gps_velN = fminf(fmaxf(gps->vel_ned[0], -vel_limit), vel_limit);
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float gps_velE = fminf(fmaxf(gps->vel_ned[1], -vel_limit), vel_limit);
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_gps_velN_filt = gps_velN * filter_coef + _gps_velN_filt * (1.0f - filter_coef);
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_gps_velE_filt = gps_velE * filter_coef + _gps_velE_filt * (1.0f - filter_coef);
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float horiz_speed = sqrtf(_gps_velN_filt * _gps_velN_filt + _gps_velE_filt * _gps_velE_filt);
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_gps_check_fail_status.flags.hspeed = (horiz_speed > _params.req_hdrift);
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} else {
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_gps_check_fail_status.flags.hspeed = false;
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}
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// Check the filtered difference between GPS and EKF vertical velocity
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vel_limit = 10.0f * _params.req_vdrift;
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float vertVel = fminf(fmaxf((gps->vel_ned[2] - _state.vel(2)), -vel_limit), vel_limit);
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_gps_velD_diff_filt = vertVel * filter_coef + _gps_velD_diff_filt * (1.0f - filter_coef);
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_gps_check_fail_status.flags.vspeed = (fabsf(_gps_velD_diff_filt) > _params.req_vdrift);
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// assume failed first time through
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if (_last_gps_fail_us == 0) {
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_last_gps_fail_us = _time_last_imu;
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}
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// if any user selected checks have failed, record the fail time
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if (
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_gps_check_fail_status.flags.fix ||
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(_gps_check_fail_status.flags.nsats && (_params.gps_check_mask & MASK_GPS_NSATS)) ||
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(_gps_check_fail_status.flags.gdop && (_params.gps_check_mask & MASK_GPS_GDOP)) ||
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(_gps_check_fail_status.flags.hacc && (_params.gps_check_mask & MASK_GPS_HACC)) ||
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(_gps_check_fail_status.flags.vacc && (_params.gps_check_mask & MASK_GPS_VACC)) ||
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(_gps_check_fail_status.flags.sacc && (_params.gps_check_mask & MASK_GPS_SACC)) ||
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(_gps_check_fail_status.flags.hdrift && (_params.gps_check_mask & MASK_GPS_HDRIFT)) ||
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(_gps_check_fail_status.flags.vdrift && (_params.gps_check_mask & MASK_GPS_VDRIFT)) ||
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(_gps_check_fail_status.flags.hspeed && (_params.gps_check_mask & MASK_GPS_HSPD)) ||
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(_gps_check_fail_status.flags.vspeed && (_params.gps_check_mask & MASK_GPS_VSPD))
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) {
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_last_gps_fail_us = _time_last_imu;
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}
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// continuous period without fail of 10 seconds required to return a healthy status
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if (_time_last_imu - _last_gps_fail_us > 1e7) {
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return true;
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}
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return false;
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}
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