/**************************************************************************** * * 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 * */ #include "../ecl.h" #include "ekf.h" #include "mathlib.h" 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); // send alignment status message to the console if (_control_status.flags.baro_hgt) { ECL_INFO("EKF aligned, (pressure height, IMU buf: %i, OBS buf: %i)",(int)_imu_buffer_length,(int)_obs_buffer_length); } else if (_control_status.flags.ev_hgt) { ECL_INFO("EKF aligned, (EV height, IMU buf: %i, OBS buf: %i)",(int)_imu_buffer_length,(int)_obs_buffer_length); } else if (_control_status.flags.gps_hgt) { ECL_INFO("EKF aligned, (GPS height, IMU buf: %i, OBS buf: %i)",(int)_imu_buffer_length,(int)_obs_buffer_length); } else if (_control_status.flags.rng_hgt) { ECL_INFO("EKF aligned, (range height, IMU buf: %i, OBS buf: %i)",(int)_imu_buffer_length,(int)_obs_buffer_length); } else { ECL_ERR("EKF aligned, (unknown height, IMU buf: %i, OBS buf: %i)",(int)_imu_buffer_length,(int)_obs_buffer_length); } } } // check faultiness (before pop_first_older_than) to see if we can change back to original height sensor baroSample baro_init = _baro_buffer.get_newest(); _baro_hgt_faulty = !((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL); gpsSample gps_init = _gps_buffer.get_newest(); _gps_hgt_faulty = !((_time_last_imu - gps_init.time_us) < 2 * GPS_MAX_INTERVAL); rangeSample rng_init = _range_buffer.get_newest(); _rng_hgt_faulty = !((_time_last_imu - rng_init.time_us) < 2 * RNG_MAX_INTERVAL); // 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); _delta_time_baro_us = _baro_sample_delayed.time_us; _baro_data_ready = _baro_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_baro_sample_delayed); // if we have a new baro sample save the delta time between this sample and the last sample which is // used below for baro offset calculations if (_baro_data_ready) { _delta_time_baro_us = _baro_sample_delayed.time_us - _delta_time_baro_us; } // calculate 2,2 element of rotation matrix from sensor frame to earth frame _R_rng_to_earth_2_2 = _R_to_earth(2, 0) * _sin_tilt_rng + _R_to_earth(2, 2) * _cos_tilt_rng; _range_data_ready = _range_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_range_sample_delayed) && (_R_rng_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(); controlAirDataFusion(); controlBetaFusion(); controlDragFusion(); controlHeightFusion(); // for efficiency, fusion of direct state observations for position and velocity is performed sequentially // in a single function using sensor data from multiple sources (GPS, external vision, baro, range finder, etc) controlVelPosFusion(); // report dead reckoning if we are no longer fusing measurements that constrain velocity drift _is_dead_reckoning = (_time_last_imu - _time_last_pos_fuse > _params.no_aid_timeout_max) && (_time_last_imu - _time_last_vel_fuse > _params.no_aid_timeout_max) && (_time_last_imu - _time_last_of_fuse > _params.no_aid_timeout_max); } void Ekf::controlExternalVisionFusion() { // Check for new exernal vision data if (_ev_data_ready) { // external vision position aiding selection logic if ((_params.fusion_mode & MASK_USE_EVPOS) && !_control_status.flags.ev_pos && _control_status.flags.tilt_align && _control_status.flags.yaw_align) { // check for a exernal vision measurement that has fallen behind the fusion time horizon if (_time_last_imu - _time_last_ext_vision < 2 * EV_MAX_INTERVAL) { // turn on use of external vision measurements for position and height setControlEVHeight(); ECL_INFO("EKF commencing external vision position fusion"); // reset the position, height and velocity resetPosition(); resetVelocity(); resetHeight(); _control_status.flags.ev_pos=true; } } // external vision yaw aiding selection logic if ((_params.fusion_mode & MASK_USE_EVYAW) && !_control_status.flags.ev_yaw && _control_status.flags.tilt_align) { // check for a exernal vision measurement that has fallen behind the fusion time horizon if (_time_last_imu - _time_last_ext_vision < 2 * EV_MAX_INTERVAL) { // reset the yaw angle to the value from the observaton quaternion // get the roll, pitch, yaw estimates from the quaternion states Quatf q_init(_state.quat_nominal); Eulerf euler_init(q_init); // get initial yaw from the observation quaternion extVisionSample ev_newest = _ext_vision_buffer.get_newest(); Quatf q_obs(ev_newest.quat); Eulerf euler_obs(q_obs); euler_init(2) = euler_obs(2); // save a copy of the quaternion state for later use in calculating the amount of reset change Quatf quat_before_reset = _state.quat_nominal; // calculate initial quaternion states for the ekf _state.quat_nominal = Quatf(euler_init); // calculate the amount that the quaternion has changed by _state_reset_status.quat_change = _state.quat_nominal * quat_before_reset.inversed(); // add the reset amount to the output observer buffered data outputSample output_states; unsigned output_length = _output_buffer.get_length(); for (unsigned i=0; i < output_length; i++) { output_states = _output_buffer.get_from_index(i); output_states.quat_nominal *= _state_reset_status.quat_change; _output_buffer.push_to_index(i,output_states); } // apply the change in attitude quaternion to our newest quaternion estimate // which was already taken out from the output buffer _output_new.quat_nominal *= _state_reset_status.quat_change; // capture the reset event _state_reset_status.quat_counter++; // flag the yaw as aligned _control_status.flags.yaw_align = true; // turn on fusion of external vision yaw measurements and disable all magnetoemter fusion _control_status.flags.ev_yaw = true; _control_status.flags.mag_hdg = false; _control_status.flags.mag_3D = false; _control_status.flags.mag_dec = false; ECL_INFO("EKF commencing external vision yaw fusion"); } } // determine if we should use the height observation if (_params.vdist_sensor_type == VDIST_SENSOR_EV) { setControlEVHeight(); _fuse_height = true; } // determine if we should use the horizontal position observations if (_control_status.flags.ev_pos) { _fuse_pos = true; // correct position and height for offset relative to IMU Vector3f pos_offset_body = _params.ev_pos_body - _params.imu_pos_body; Vector3f pos_offset_earth = _R_to_earth * pos_offset_body; _ev_sample_delayed.posNED(0) -= pos_offset_earth(0); _ev_sample_delayed.posNED(1) -= pos_offset_earth(1); _ev_sample_delayed.posNED(2) -= pos_offset_earth(2); } // determine if we should use the yaw observation if (_control_status.flags.ev_yaw) { fuseHeading(); } } // handle the case when we are relying on ev data and lose it if (_control_status.flags.ev_pos && !_control_status.flags.gps && !_control_status.flags.opt_flow) { // We are relying on ev aiding to constrain drift so after 5s without aiding we need to do something if ((_time_last_imu - _time_last_pos_fuse > 5e6)) { // Switch to the non-aiding mode, zero the velocity states // and set the synthetic position to the current estimate _control_status.flags.ev_pos = false; _last_known_posNE(0) = _state.pos(0); _last_known_posNE(1) = _state.pos(1); _state.vel.setZero(); } } } 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_rng_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; } else { // set to the last known position _state.pos(0) = _last_known_posNE(0); _state.pos(1) = _last_known_posNE(1); } // 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 && !_control_status.flags.ev_pos) { // 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::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) { // if we are not already aiding with optical flow, then we need to reset the position and velocity // otherwise we only need to reset the position _control_status.flags.gps = true; if (!_control_status.flags.opt_flow) { if (!resetPosition() || !resetVelocity()) { _control_status.flags.gps = false; } } else if (!resetPosition()) { _control_status.flags.gps = false; } if (_control_status.flags.gps) { ECL_INFO("EKF commencing GPS fusion"); _time_last_gps = _time_last_imu; } } } } else if (!(_params.fusion_mode & MASK_USE_GPS)) { _control_status.flags.gps = false; } // handle the case when we now have GPS, but have not been using it for an extended period if (_control_status.flags.gps && !_control_status.flags.opt_flow) { // We are relying on GPS aiding to constrain attitude drift so after 7 seconds without aiding we need to do something bool do_reset = (_time_last_imu - _time_last_pos_fuse > _params.no_gps_timeout_max) && (_time_last_imu - _time_last_vel_fuse > _params.no_gps_timeout_max); // Our position measurments have been rejected for more than 14 seconds do_reset |= _time_last_imu - _time_last_pos_fuse > 2 * _params.no_gps_timeout_max; if (do_reset) { // Reset states to the last GPS measurement resetPosition(); resetVelocity(); ECL_WARN("EKF GPS fusion timeout - reset 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); } } else { // handle the case where we do not have GPS and have not been using it for an extended period, but are still relying on it if ((_time_last_imu - _time_last_gps > 10e6) && (_time_last_imu - _time_last_airspeed > 1e6) && (_time_last_imu - _time_last_optflow > 1e6) && _control_status.flags.gps) { // if we don't have a source of aiding to constrain attitude drift, // 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 measurement timeout - stopping navigation"); } } } void Ekf::controlHeightSensorTimeouts() { /* * 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 IMU accelerometer vibration induced clipping as evidenced by the vertical innovations being positive and not stale. // Clipping causes the average accel reading to move towards zero which makes the INS think it is falling and produces positive vertical innovations float var_product_lim = sq(_params.vert_innov_test_lim) * sq(_params.vert_innov_test_lim); bool bad_vert_accel = (_control_status.flags.baro_hgt && // we can only run this check if vertical position and velocity observations are indepedant (sq(_vel_pos_innov[5] * _vel_pos_innov[2]) > var_product_lim * (_vel_pos_innov_var[5] * _vel_pos_innov_var[2])) && // vertical position and velocity sensors are in agreement that we have a significant error (_vel_pos_innov[2] > 0.0f) && // positive innovation indicates that the inertial nav thinks it is falling ((_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 fresh // record time of last bad vert accel if (bad_vert_accel) { _time_bad_vert_accel = _time_last_imu; } else { _time_good_vert_accel = _time_last_imu; } // declare a bad vertical acceleration measurement and make the declaration persist // for a minimum of 10 seconds if (_bad_vert_accel_detected) { _bad_vert_accel_detected = (_time_last_imu - _time_bad_vert_accel < BADACC_PROBATION); } else { _bad_vert_accel_detected = bad_vert_accel; } // check if height is continuously failing becasue of accel errors bool continuous_bad_accel_hgt = ((_time_last_imu - _time_good_vert_accel) > (unsigned)_params.bad_acc_reset_delay_us); // check if height has been inertial deadreckoning for too long bool hgt_fusion_timeout = ((_time_last_imu - _time_last_hgt_fuse) > 5e6); // reset the vertical position and velocity states if ((P[9][9] > sq(_params.hgt_reset_lim)) && (hgt_fusion_timeout || continuous_bad_accel_hgt)) { // 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 < BADACC_PROBATION); // 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; // declare the GPS height healthy _gps_hgt_faulty = false; // reset the height mode setControlGPSHeight(); // request a reset reset_height = true; ECL_WARN("EKF baro hgt timeout - reset to GPS"); } else if (reset_to_baro){ // set height sensor health _baro_hgt_faulty = false; // reset the height mode setControlBaroHeight(); // request a reset reset_height = true; ECL_WARN("EKF baro hgt timeout - reset to baro"); } 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 setControlBaroHeight(); // request a reset reset_height = true; ECL_WARN("EKF gps hgt timeout - reset to baro"); } else if (reset_to_gps) { // set height sensor health _gps_hgt_faulty = false; // reset the height mode setControlGPSHeight(); // request a reset reset_height = true; ECL_WARN("EKF gps hgt timeout - reset to GPS"); } 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 setControlBaroHeight(); // request a reset reset_height = true; ECL_WARN("EKF rng hgt timeout - reset to baro"); } else if (reset_to_rng) { // set height sensor health _rng_hgt_faulty = false; // reset the height mode setControlRangeHeight(); // request a reset reset_height = true; ECL_WARN("EKF rng hgt timeout - reset to rng hgt"); } else { // we have nothing to reset to reset_height = false; } } // handle the case where we are using external vision data for height if (_control_status.flags.ev_hgt) { // check if vision data is available extVisionSample ev_init = _ext_vision_buffer.get_newest(); bool ev_data_available = ((_time_last_imu - ev_init.time_us) < 2 * EV_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 vision data and baro data is available bool reset_to_baro = !ev_data_available && baro_data_available; // reset to ev data if it is available bool reset_to_ev = ev_data_available; if (reset_to_baro) { // set height sensor health _baro_hgt_faulty = false; // reset the height mode setControlBaroHeight(); // request a reset reset_height = true; ECL_WARN("EKF ev hgt timeout - reset to baro"); } else if (reset_to_ev) { // reset the height mode setControlEVHeight(); // request a reset reset_height = true; ECL_WARN("EKF ev hgt timeout - reset to ev hgt"); } 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; } } } void Ekf::controlHeightFusion() { // set control flags for the desired primary height source if (_range_data_ready) { // correct the range data for position offset relative to the IMU Vector3f pos_offset_body = _params.rng_pos_body - _params.imu_pos_body; Vector3f pos_offset_earth = _R_to_earth * pos_offset_body; _range_sample_delayed.rng += pos_offset_earth(2) / _R_rng_to_earth_2_2; } if (_params.vdist_sensor_type == VDIST_SENSOR_BARO) { _in_range_aid_mode = rangeAidConditionsMet(_in_range_aid_mode); if (_in_range_aid_mode && _range_data_ready && !_rng_hgt_faulty) { setControlRangeHeight(); _fuse_height = true; // we have just switched to using range finder, calculate height sensor offset such that current // measurment matches our current height estimate if (_control_status_prev.flags.rng_hgt != _control_status.flags.rng_hgt) { if (_terrain_initialised) { _hgt_sensor_offset = _terrain_vpos; } else { _hgt_sensor_offset = _R_rng_to_earth_2_2 * _range_sample_delayed.rng + _state.pos(2); } } } else if (_baro_data_ready && !_baro_hgt_faulty && !(_in_range_aid_mode && !_range_data_ready && !_rng_hgt_faulty)) { setControlBaroHeight(); _fuse_height = true; _in_range_aid_mode = false; // we have just switched to using baro height, we don't need to set a height sensor offset // since we track a separate _baro_hgt_offset if (_control_status_prev.flags.baro_hgt != _control_status.flags.baro_hgt) { _hgt_sensor_offset = 0.0f; } } else if (_control_status.flags.gps_hgt && _gps_data_ready && !_gps_hgt_faulty) { // switch to gps if there was a reset to gps _fuse_height = true; _in_range_aid_mode = false; // we have just switched to using gps height, calculate height sensor offset such that current // measurment matches our current height estimate if (_control_status_prev.flags.gps_hgt != _control_status.flags.gps_hgt) { _hgt_sensor_offset = _gps_sample_delayed.hgt - _gps_alt_ref + _state.pos(2); } } } // set the height data source to range if requested if ((_params.vdist_sensor_type == VDIST_SENSOR_RANGE) && !_rng_hgt_faulty) { setControlRangeHeight(); _fuse_height = _range_data_ready; // we have just switched to using range finder, calculate height sensor offset such that current // measurment matches our current height estimate if (_control_status_prev.flags.rng_hgt != _control_status.flags.rng_hgt) { // use the parameter rng_gnd_clearance if on ground to avoid a noisy offset initialization (e.g. sonar) if (_control_status.flags.in_air && _terrain_initialised) { _hgt_sensor_offset = _terrain_vpos; } else if (_control_status.flags.in_air) { _hgt_sensor_offset = _R_rng_to_earth_2_2 * _range_sample_delayed.rng + _state.pos(2); } else { _hgt_sensor_offset = _params.rng_gnd_clearance; } } } else if ((_params.vdist_sensor_type == VDIST_SENSOR_RANGE) && _baro_data_ready && !_baro_hgt_faulty) { setControlBaroHeight(); _fuse_height = true; // we have just switched to using baro height, we don't need to set a height sensor offset // since we track a separate _baro_hgt_offset if (_control_status_prev.flags.baro_hgt != _control_status.flags.baro_hgt) { _hgt_sensor_offset = 0.0f; } } // Determine if GPS should be used as the height source if (_params.vdist_sensor_type == VDIST_SENSOR_GPS) { _in_range_aid_mode = rangeAidConditionsMet(_in_range_aid_mode); if (_in_range_aid_mode && _range_data_ready && !_rng_hgt_faulty) { setControlRangeHeight(); _fuse_height = true; // we have just switched to using range finder, calculate height sensor offset such that current // measurment matches our current height estimate if (_control_status_prev.flags.rng_hgt != _control_status.flags.rng_hgt) { if (_terrain_initialised) { _hgt_sensor_offset = _terrain_vpos; } else { _hgt_sensor_offset = _R_rng_to_earth_2_2 * _range_sample_delayed.rng + _state.pos(2); } } } else if (_gps_data_ready && !_gps_hgt_faulty && !(_in_range_aid_mode && !_range_data_ready && !_rng_hgt_faulty)) { setControlGPSHeight(); _fuse_height = true; _in_range_aid_mode = false; // we have just switched to using gps height, calculate height sensor offset such that current // measurment matches our current height estimate if (_control_status_prev.flags.gps_hgt != _control_status.flags.gps_hgt) { _hgt_sensor_offset = _gps_sample_delayed.hgt - _gps_alt_ref + _state.pos(2); } } else if (_control_status.flags.baro_hgt && _baro_data_ready && !_baro_hgt_faulty) { // switch to baro if there was a reset to baro _fuse_height = true; _in_range_aid_mode = false; // we have just switched to using baro height, we don't need to set a height sensor offset // since we track a separate _baro_hgt_offset if (_control_status_prev.flags.baro_hgt != _control_status.flags.baro_hgt) { _hgt_sensor_offset = 0.0f; } } } // calculate a filtered offset between the baro origin and local NED origin if we are not using the baro as a height reference if (!_control_status.flags.baro_hgt && _baro_data_ready) { float local_time_step = 1e-6f * _delta_time_baro_us; local_time_step = math::constrain(local_time_step, 0.0f, 1.0f); // apply a 10 second first order low pass filter to baro offset float offset_rate_correction = 0.1f * (_baro_sample_delayed.hgt + _state.pos( 2) - _baro_hgt_offset); _baro_hgt_offset += local_time_step * math::constrain(offset_rate_correction, -0.1f, 0.1f); } if ((_time_last_imu - _time_last_hgt_fuse) > 2 * RNG_MAX_INTERVAL && _control_status.flags.rng_hgt && !_range_data_ready) { // 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 (!_control_status.flags.in_air) { _range_sample_delayed.rng = _params.rng_gnd_clearance; _range_sample_delayed.time_us = _imu_sample_delayed.time_us; } _fuse_height = true; } } bool Ekf::rangeAidConditionsMet(bool in_range_aid_mode) { // if the parameter for range aid is enabled we allow to switch from using the primary height source to using range finder as height source // under the following conditions // 1) we are not further than max_range_for_dual_fusion away from the ground // 2) our ground speed is not higher than max_vel_for_dual_fusion // 3) Our terrain estimate is stable (needs better checks) if (_params.range_aid) { // check if we should use range finder measurements to estimate height, use hysteresis to avoid rapid switching bool use_range_finder; if (in_range_aid_mode) { use_range_finder = (_terrain_vpos - _state.pos(2) < _params.max_hagl_for_range_aid) && _terrain_initialised; } else { // if we were not using range aid in the previous iteration then require the current height above terrain to be // smaller than 70 % of the maximum allowed ground distance for range aid use_range_finder = (_terrain_vpos - _state.pos(2) < 0.7f * _params.max_hagl_for_range_aid) && _terrain_initialised; } bool horz_vel_valid = (_control_status.flags.gps || _control_status.flags.ev_pos || _control_status.flags.opt_flow) && (_fault_status.value == 0); if (horz_vel_valid) { float ground_vel = sqrtf(_state.vel(0) * _state.vel(0) + _state.vel(1) * _state.vel(1)); if (in_range_aid_mode) { use_range_finder &= ground_vel < _params.max_vel_for_range_aid; } else { // if we were not using range aid in the previous iteration then require the ground velocity to be // smaller than 70 % of the maximum allowed ground velocity for range aid use_range_finder &= ground_vel < 0.7f * _params.max_vel_for_range_aid; } } else { use_range_finder = false; } use_range_finder &= ((_hagl_innov * _hagl_innov / (sq(_params.range_aid_innov_gate) * _hagl_innov_var)) < 1.0f); return use_range_finder; } else { return false; } } void Ekf::controlAirDataFusion() { // control activation and initialisation/reset of wind states required for airspeed fusion // If both airspeed and sideslip fusion have timed out and we are not using a drag observation model then we no longer have valid wind estimates bool airspeed_timed_out = _time_last_imu - _time_last_arsp_fuse > 10e6; bool sideslip_timed_out = _time_last_imu - _time_last_beta_fuse > 10e6; if (_control_status.flags.wind && airspeed_timed_out && sideslip_timed_out && !(_params.fusion_mode & MASK_USE_DRAG)) { _control_status.flags.wind = false; } // Always try to fuse airspeed data if available and we are in flight and the filter is operating in a normal aiding mode bool is_aiding = _control_status.flags.gps || _control_status.flags.opt_flow || _control_status.flags.ev_pos; if (_tas_data_ready && _control_status.flags.in_air && is_aiding) { // If starting wind state estimation, reset the wind states and covariances before fusing any data if (!_control_status.flags.wind) { // activate the wind states _control_status.flags.wind = true; // reset the timout timer to prevent repeated resets _time_last_arsp_fuse = _time_last_imu; _time_last_beta_fuse = _time_last_imu; // reset the wind speed states and corresponding covariances resetWindStates(); resetWindCovariance(); } fuseAirspeed(); } } void Ekf::controlBetaFusion() { // control activation and initialisation/reset of wind states required for synthetic sideslip fusion fusion // If both airspeed and sideslip fusion have timed out and we are not using a drag observation model then we no longer have valid wind estimates bool sideslip_timed_out = _time_last_imu - _time_last_beta_fuse > 10e6; bool airspeed_timed_out = _time_last_imu - _time_last_arsp_fuse > 10e6; if(_control_status.flags.wind && airspeed_timed_out && sideslip_timed_out && !(_params.fusion_mode & MASK_USE_DRAG)) { _control_status.flags.wind = false; } // Perform synthetic sideslip fusion when in-air and sideslip fuson had been enabled externally in addition to the following criteria: // Suffient time has lapsed sice the last fusion bool beta_fusion_time_triggered = _time_last_imu - _time_last_beta_fuse > _params.beta_avg_ft_us; // The filter is operating in a mode where velocity states can be used bool vel_states_active = _control_status.flags.gps || _control_status.flags.opt_flow || _control_status.flags.ev_pos; if(beta_fusion_time_triggered && _control_status.flags.fuse_beta && _control_status.flags.in_air && vel_states_active) { // If starting wind state estimation, reset the wind states and covariances before fusing any data if (!_control_status.flags.wind) { // activate the wind states _control_status.flags.wind = true; // reset the timeout timers to prevent repeated resets _time_last_beta_fuse = _time_last_imu; _time_last_arsp_fuse = _time_last_imu; // reset the wind speed states and corresponding covariances resetWindStates(); resetWindCovariance(); } fuseSideslip(); } } void Ekf::controlDragFusion() { if (_params.fusion_mode & MASK_USE_DRAG ) { if (_control_status.flags.in_air) { if (!_control_status.flags.wind) { // reset the wind states and covariances when starting drag accel fusion _control_status.flags.wind = true; resetWindStates(); resetWindCovariance(); } else if (_drag_buffer.pop_first_older_than(_imu_sample_delayed.time_us, &_drag_sample_delayed)) { fuseDrag(); } } else { _control_status.flags.wind = false; } } } 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 // Also reset the flight alignment flag so that the mag fields will be re-initialised next time we achieve flight altitude if (!_control_status.flags.in_air) { _last_on_ground_posD = _state.pos(2); _flt_mag_align_complete = false; } // check for new magnetometer data that has fallen behind 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) { // Check if height has increased sufficiently to be away from ground magnetic anomalies bool height_achieved = (_last_on_ground_posD - _state.pos(2)) > 1.5f; // Check if there has been enough change in horizontal velocity to make yaw observable // Apply hysteresis to check to avoid rapid toggling if (_yaw_angle_observable) { _yaw_angle_observable = _accel_lpf_NE.norm() > _params.mag_acc_gate; } else { _yaw_angle_observable = _accel_lpf_NE.norm() > 2.0f * _params.mag_acc_gate; } _yaw_angle_observable = _yaw_angle_observable && (_control_status.flags.gps || _control_status.flags.ev_pos); // check if there is enough yaw rotation to make the mag bias states observable if (!_mag_bias_observable && (fabsf(_yaw_rate_lpf_ef) > _params.mag_yaw_rate_gate)) { // initial yaw motion is detected _mag_bias_observable = true; _yaw_delta_ef = 0.0f; _time_yaw_started = _imu_sample_delayed.time_us; } else if (_mag_bias_observable) { // monitor yaw rotation in 45 deg sections. // a rotation of 45 deg is sufficient to make the mag bias observable if (fabsf(_yaw_delta_ef) > 0.7854f) { _time_yaw_started = _imu_sample_delayed.time_us; _yaw_delta_ef = 0.0f; } // require sustained yaw motion of 50% the initial yaw rate threshold float min_yaw_change_req = 0.5f * _params.mag_yaw_rate_gate * (1e-6f * (float)(_imu_sample_delayed.time_us - _time_yaw_started)); _mag_bias_observable = fabsf(_yaw_delta_ef) > min_yaw_change_req; } else { _mag_bias_observable = false; } // record the last time that movement was suitable for use of 3-axis magnetometer fusion if (_mag_bias_observable || _yaw_angle_observable) { _time_last_movement = _imu_sample_delayed.time_us; } // decide whether 3-axis magnetomer fusion can be used bool use_3D_fusion = _control_status.flags.tilt_align && // Use of 3D fusion requires valid tilt estimates _control_status.flags.in_air && // don't use when on the ground becasue of magnetic anomalies (_flt_mag_align_complete || height_achieved) && // once in-flight field alignment has been performed, ignore relative height ((_imu_sample_delayed.time_us - _time_last_movement) < 2 * 1000 * 1000); // Using 3-axis fusion for a minimum period after to allow for false negatives // perform switch-over if (use_3D_fusion) { if (!_control_status.flags.mag_3D) { if (!_flt_mag_align_complete) { // If we are flying a vehicle that flies forward, eg plane, then we can use the GPS course to check and correct the heading if (_control_status.flags.fixed_wing && _control_status.flags.in_air) { _control_status.flags.yaw_align = realignYawGPS(); _flt_mag_align_complete = _control_status.flags.yaw_align; } else { _control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); _flt_mag_align_complete = _control_status.flags.yaw_align; } } else { // reset the mag field covariances zeroRows(P, 16, 21); zeroCols(P, 16, 21); // re-instate the last used variances for (uint8_t index = 0; index <= 5; index ++) { P[index+16][index+16] = _saved_mag_variance[index]; } } } // only use one type of mag fusion at the same time _control_status.flags.mag_3D = _flt_mag_align_complete; _control_status.flags.mag_hdg = !_control_status.flags.mag_3D; } else { // save magnetic field state variances for next time if (_control_status.flags.mag_3D) { for (uint8_t index = 0; index <= 5; index ++) { _saved_mag_variance[index] = P[index+16][index+16]; } _control_status.flags.mag_3D = false; } _control_status.flags.mag_hdg = true; } // perform switch-over from only updating the mag states to updating all states if (!_control_status.flags.update_mag_states_only && _control_status_prev.flags.update_mag_states_only) { // When re-commencing use of magnetometer to correct vehicle states // set the field state variance to the observation variance and zero // the covariance terms to allow the field states re-learn rapidly zeroRows(P, 16, 21); zeroCols(P, 16, 21); for (uint8_t index = 0; index <= 5; index ++) { P[index+16][index+16] = sq(_params.mag_noise); } } } 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 recommended 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::controlVelPosFusion() { // 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 && !_control_status.flags.ev_pos && ((_time_last_imu - _time_last_fake_gps > 2e5) || _fuse_height)) { _fuse_pos = true; _time_last_fake_gps = _time_last_imu; } // Fuse available NED velocity and position data into the main filter if (_fuse_height || _fuse_pos || _fuse_hor_vel || _fuse_vert_vel) { fuseVelPosHeight(); _fuse_hor_vel = _fuse_vert_vel = _fuse_pos = _fuse_height = false; } }