void Ekf::controlFusionModes() { // Store the status to enable change detection _control_status_prev.value = _control_status.value; // Get the magnetic declination calcMagDeclination(); // monitor the tilt alignment if (!_control_status.flags.tilt_align) { // whilst we are aligning the tilt, monitor the variances Vector3f angle_err_var_vec = calcRotVecVariances(); // Once the tilt variances have reduced to equivalent of 3deg uncertainty, re-set the yaw and magnetic field states // and declare the tilt alignment complete if ((angle_err_var_vec(0) + angle_err_var_vec(1)) < sq(0.05235f)) { _control_status.flags.tilt_align = true; _control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); } } // control use of various external sources for position and velocity aiding controlExternalVisionAiding(); controlOpticalFlowAiding(); controlGpsAiding(); controlHeightAiding(); controlMagAiding(); }
void Ekf::controlGpsAiding() { // 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 velocity 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; } } } }
void Ekf::controlFusionModes() { // Store the status to enable change detection _control_status_prev.value = _control_status.value; // Get the magnetic declination calcMagDeclination(); // monitor the tilt alignment if (!_control_status.flags.tilt_align) { // whilst we are aligning the tilt, monitor the variances Vector3f angle_err_var_vec = calcRotVecVariances(); // Once the tilt variances have reduced to equivalent of 3deg uncertainty, re-set the yaw and magnetic field states // and declare the tilt alignment complete if ((angle_err_var_vec(0) + angle_err_var_vec(1)) < sq(0.05235f)) { _control_status.flags.tilt_align = true; _control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); ECL_INFO("EKF alignment complete"); } } // check for arrival of new sensor data at the fusion time horizon _gps_data_ready = _gps_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_gps_sample_delayed); _mag_data_ready = _mag_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_mag_sample_delayed); _baro_data_ready = _baro_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_baro_sample_delayed); _range_data_ready = _range_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_range_sample_delayed) && (_R_to_earth(2, 2) > 0.7071f); _flow_data_ready = _flow_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_flow_sample_delayed) && (_R_to_earth(2, 2) > 0.7071f); _ev_data_ready = _ext_vision_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_ev_sample_delayed); _tas_data_ready = _airspeed_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_airspeed_sample_delayed); // check for height sensor timeouts and reset and change sensor if necessary controlHeightSensorTimeouts(); // control use of observations for aiding controlMagFusion(); controlExternalVisionFusion(); controlOpticalFlowFusion(); controlGpsFusion(); controlBaroFusion(); controlRangeFinderFusion(); controlAirDataFusion(); // for efficiency, fusion of direct state observations for position ad velocity is performed sequentially // in a single function using sensor data from multiple sources (GPS, external vision, baro, range finder, etc) controlVelPosFusion(); }
void Ekf::controlMagFusion() { // If we are using external vision data for heading then no magnetometer fusion is used if (_control_status.flags.ev_yaw) { return; } // If we are on ground, store the local position and time to use as a reference if (!_control_status.flags.in_air) { _last_on_ground_posD = _state.pos(2); } // checs for new magnetometer data tath has fallen beind the fusion time horizon if (_mag_data_ready) { // 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) { // start 3D fusion if in-flight and height has increased sufficiently // to be away from ground magnetic anomalies // don't switch back to heading fusion until we are back on the ground bool height_achieved = (_last_on_ground_posD - _state.pos(2)) > 1.5f; bool use_3D_fusion = _control_status.flags.in_air && (_control_status.flags.mag_3D || height_achieved); if (use_3D_fusion && _control_status.flags.tilt_align) { // 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; } // fuse magnetometer data using the selected methods if (_control_status.flags.mag_3D && _control_status.flags.yaw_align) { fuseMag(); if (_control_status.flags.mag_dec) { fuseDeclination(); } } else if (_control_status.flags.mag_hdg && _control_status.flags.yaw_align) { // fusion of an Euler yaw angle from either a 321 or 312 rotation sequence fuseHeading(); } else { // do no fusion at all } } }
void Ekf::controlGpsFusion() { // Check for new GPS data that has fallen behind the fusion time horizon if (_gps_data_ready) { // Determine if we should use GPS aiding for velocity and horizontal position // To start using GPS we need angular alignment completed, the local NED origin set and GPS data that has not failed checks recently if ((_params.fusion_mode & MASK_USE_GPS) && !_control_status.flags.gps) { if (_control_status.flags.tilt_align && _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) { if (resetPosition() && resetVelocity()) { _control_status.flags.gps = true; } else { _control_status.flags.gps = false; } } if (_control_status.flags.gps) { ECL_INFO("EKF commencing GPS aiding"); } } } } 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 velocity 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(); ECL_WARN("EKF GPS fusion timout - stopping GPS aiding"); } else { // Reset states to the last GPS measurement resetPosition(); resetVelocity(); ECL_WARN("EKF GPS fusion timout - resetting to GPS"); // Reset the timeout counters _time_last_pos_fuse = _time_last_imu; _time_last_vel_fuse = _time_last_imu; } } } // Only use GPS data for position and velocity aiding if enabled if (_control_status.flags.gps) { _fuse_pos = true; _fuse_vert_vel = true; _fuse_hor_vel = true; // correct velocity for offset relative to IMU Vector3f ang_rate = _imu_sample_delayed.delta_ang * (1.0f/_imu_sample_delayed.delta_ang_dt); Vector3f pos_offset_body = _params.gps_pos_body - _params.imu_pos_body; Vector3f vel_offset_body = cross_product(ang_rate,pos_offset_body); Vector3f vel_offset_earth = _R_to_earth * vel_offset_body; _gps_sample_delayed.vel -= vel_offset_earth; // correct position and height for offset relative to IMU Vector3f pos_offset_earth = _R_to_earth * pos_offset_body; _gps_sample_delayed.pos(0) -= pos_offset_earth(0); _gps_sample_delayed.pos(1) -= pos_offset_earth(1); _gps_sample_delayed.hgt += pos_offset_earth(2); } // Determine if GPS should be used as the height source if (((_params.vdist_sensor_type == VDIST_SENSOR_GPS)) && !_gps_hgt_faulty) { _control_status.flags.baro_hgt = false; _control_status.flags.gps_hgt = true; _control_status.flags.rng_hgt = false; _control_status.flags.ev_hgt = false; _fuse_height = true; } } }
void Ekf::controlOpticalFlowFusion() { // Check for new optical flow data that has fallen behind the fusion time horizon if (_flow_data_ready) { // optical flow fusion mode selection logic if ((_params.fusion_mode & MASK_USE_OF) // optical flow has been selected by the user && !_control_status.flags.opt_flow // we are not yet using flow data && _control_status.flags.tilt_align // we know our tilt attitude && (_time_last_imu - _time_last_hagl_fuse) < 5e5) // we have a valid distance to ground estimate { // 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 have 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 corresponding 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; } // 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 velocity 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(); } } // fuse the data if (_control_status.flags.opt_flow) { // Update optical flow bias estimates calcOptFlowBias(); // Fuse optical flow LOS rate observations into the main filter fuseOptFlow(); _last_known_posNE(0) = _state.pos(0); _last_known_posNE(1) = _state.pos(1); } } }
void Ekf::controlMagAiding() { // If we are using external vision data for heading then no magnetometer fusion is used if (_control_status.flags.ev_yaw) { return; } // 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 && _control_status.flags.tilt_align) { // 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; } // 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; } }
bool Ekf::initialiseFilter(void) { // Keep accumulating measurements until we have a minimum of 10 samples for the baro and magnetoemter // Sum the IMU delta angle measurements imuSample imu_init = _imu_buffer.get_newest(); _delVel_sum += imu_init.delta_vel; // Sum the magnetometer measurements if (_mag_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_mag_sample_delayed)) { if (_mag_counter == 0) { _mag_filt_state = _mag_sample_delayed.mag; } _mag_counter ++; _mag_filt_state = _mag_filt_state * 0.9f + _mag_sample_delayed.mag * 0.1f; } // set the default height source from the adjustable parameter if (_hgt_counter == 0) { _primary_hgt_source = _params.vdist_sensor_type; } if (_primary_hgt_source == VDIST_SENSOR_RANGE) { if (_range_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_range_sample_delayed)) { if (_hgt_counter == 0) { _control_status.flags.baro_hgt = false; _control_status.flags.gps_hgt = false; _control_status.flags.rng_hgt = true; _hgt_filt_state = _range_sample_delayed.rng; } _hgt_counter ++; _hgt_filt_state = 0.9f * _hgt_filt_state + 0.1f * _range_sample_delayed.rng; } } else if (_primary_hgt_source == VDIST_SENSOR_BARO || _primary_hgt_source == VDIST_SENSOR_GPS) { if (_baro_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_baro_sample_delayed)) { if (_hgt_counter == 0) { _control_status.flags.baro_hgt = true; _control_status.flags.gps_hgt = false; _control_status.flags.rng_hgt = false; _hgt_filt_state = _baro_sample_delayed.hgt; } _hgt_counter ++; _hgt_filt_state = 0.9f * _hgt_filt_state + 0.1f * _baro_sample_delayed.hgt; } } else { return false; } // check to see if we have enough measurements and return false if not if (_hgt_counter <= 10 || _mag_counter <= 10) { return false; } else { // reset variables that are shared with post alignment GPS checks _gps_drift_velD = 0.0f; _gps_alt_ref = 0.0f; // Zero all of the states _state.ang_error.setZero(); _state.vel.setZero(); _state.pos.setZero(); _state.gyro_bias.setZero(); _state.gyro_scale(0) = _state.gyro_scale(1) = _state.gyro_scale(2) = 1.0f; _state.accel_z_bias = 0.0f; _state.mag_I.setZero(); _state.mag_B.setZero(); _state.wind_vel.setZero(); // get initial roll and pitch estimate from delta velocity vector, assuming vehicle is static float pitch = 0.0f; float roll = 0.0f; if (_delVel_sum.norm() > 0.001f) { _delVel_sum.normalize(); pitch = asinf(_delVel_sum(0)); roll = atan2f(-_delVel_sum(1), -_delVel_sum(2)); } else { return false; } // calculate initial tilt alignment matrix::Euler<float> euler_init(roll, pitch, 0.0f); _state.quat_nominal = Quaternion(euler_init); _output_new.quat_nominal = _state.quat_nominal; // initialise the filtered alignment error estimate to a larger starting value _tilt_err_length_filt = 1.0f; // calculate the averaged magnetometer reading Vector3f mag_init = _mag_filt_state; // calculate the initial magnetic field and yaw alignment resetMagHeading(mag_init); // calculate the averaged height reading to calulate the height of the origin _hgt_sensor_offset = _hgt_filt_state; // 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 if (!_control_status.flags.baro_hgt) { baroSample baro_newest = _baro_buffer.get_newest(); _baro_hgt_offset = baro_newest.hgt - _hgt_sensor_offset; } else { _baro_hgt_offset = 0.0f; } // initialise the state covariance matrix initialiseCovariance(); // initialise the terrain estimator initHagl(); return true; } }
void Ekf::controlFusionModes() { // Determine the vehicle status calculateVehicleStatus(); // Get the magnetic declination calcMagDeclination(); // Check for tilt convergence during initial alignment // filter the tilt error vector using a 1 sec time constant LPF float filt_coef = 1.0f * _imu_sample_delayed.delta_ang_dt; _tilt_err_length_filt = filt_coef * _tilt_err_vec.norm() + (1.0f - filt_coef) * _tilt_err_length_filt; // Once the tilt error has reduced sufficiently, initialise the yaw and magnetic field states if (_tilt_err_length_filt < 0.005f && !_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 and are in air, then we need to reset the velocity to be consistent with the optical flow reading if (!_control_status.flags.gps) { // calculate the rotation matrix from body to earth frame matrix::Dcm<float> body_to_earth(_state.quat_nominal); // 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 / body_to_earth(2, 2); if (_in_air && (range - _params.rng_gnd_clearance) > 0.3f && _flow_sample_delayed.dt > 0.05f) { // 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 = body_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.setZero(); } } } } 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(); } } } /* * 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. */ if ((P[8][8] > sq(_params.hgt_reset_lim)) && ((_time_last_imu - _time_last_hgt_fuse) > 5e6)) { // 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); // use the gps if it is accurate or there is no baro data available if (gps_hgt_available && (gps_hgt_accurate || !baro_hgt_available)) { // declare the baro as unhealthy _baro_hgt_faulty = true; // set the height mode to the GPS _control_status.flags.baro_hgt = false; _control_status.flags.gps_hgt = true; _control_status.flags.rng_hgt = false; // adjust the height offset so we can use the GPS _hgt_sensor_offset = _state.pos(2) + gps_init.hgt - _gps_alt_ref; if (!baro_hgt_available) { printf("EKF baro hgt timeout - switching to gps\n"); } } } // 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 consistent and fresh or GPS height is unavailable or inaccurate, we switch to baro for height if ((baro_data_consistent && baro_data_fresh) || !gps_hgt_available || !gps_hgt_accurate) { // declare the GPS height unhealthy _gps_hgt_faulty = true; // set the height mode to the baro _control_status.flags.baro_hgt = true; _control_status.flags.gps_hgt = false; _control_status.flags.rng_hgt = false; printf("EKF gps hgt timeout - switching to baro\n"); } } // 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); // check if baro data is consistent float baro_innov = _state.pos(2) - (_hgt_sensor_offset - baro_init.hgt + _baro_hgt_offset); bool baro_data_consistent = sq(baro_innov) < (sq(_params.baro_noise) + P[8][8]) * sq(_params.baro_innov_gate); // switch to baro if necessary or preferable bool switch_to_baro = (!rng_data_available && baro_data_available) || (baro_data_consistent && baro_data_available); if (switch_to_baro) { // declare the range finder height unhealthy _rng_hgt_faulty = true; // set the height mode to the baro _control_status.flags.baro_hgt = true; _control_status.flags.gps_hgt = false; _control_status.flags.rng_hgt = false; printf("EKF rng hgt timeout - switching to baro\n"); } } // Reset vertical position and velocity states to the last measurement resetHeight(); } // 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.armed) { // use heading fusion for initial startup _control_status.flags.mag_hdg = true; _control_status.flags.mag_2D = false; _control_status.flags.mag_3D = false; } else { 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_2D = 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_2D = false; _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_2D = false; _control_status.flags.mag_3D = false; } else if (_params.mag_fusion_type == MAG_FUSE_TYPE_2D) { // always use 2D mag fusion _control_status.flags.mag_hdg = false; _control_status.flags.mag_2D = 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_2D = false; _control_status.flags.mag_3D = true; } else { // do no magnetometer fusion at all _control_status.flags.mag_hdg = false; _control_status.flags.mag_2D = 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; } // 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 if (false) { _control_status.flags.wind = false; } // Store the status to enable change detection _control_status_prev.value = _control_status.value; }