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373 lines
16 KiB
373 lines
16 KiB
/**************************************************************************** |
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* |
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* Copyright (c) 2015 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 control.cpp |
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* Control functions for ekf attitude and position estimator. |
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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 "ekf.h" |
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void Ekf::controlFusionModes() |
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{ |
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// Determine the vehicle status |
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calculateVehicleStatus(); |
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// Get the magnetic declination |
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calcMagDeclination(); |
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// Check for tilt convergence during initial alignment |
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// filter the tilt error vector using a 1 sec time constant LPF |
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float filt_coef = 1.0f * _imu_sample_delayed.delta_ang_dt; |
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_tilt_err_length_filt = filt_coef * _tilt_err_vec.norm() + (1.0f - filt_coef) * _tilt_err_length_filt; |
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// Once the tilt error has reduced sufficiently, initialise the yaw and magnetic field states |
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if (_tilt_err_length_filt < 0.005f && !_control_status.flags.tilt_align) { |
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_control_status.flags.tilt_align = true; |
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_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); |
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} |
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// optical flow fusion mode selection logic |
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// to start using optical flow data we need angular alignment complete, and fresh optical flow and height above terrain data |
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if ((_params.fusion_mode & MASK_USE_OF) && !_control_status.flags.opt_flow && _control_status.flags.tilt_align |
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&& (_time_last_imu - _time_last_optflow) < 5e5 && (_time_last_imu - _time_last_hagl_fuse) < 5e5) { |
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// If the heading is not aligned, reset the yaw and magnetic field states |
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if (!_control_status.flags.yaw_align) { |
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_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); |
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} |
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// If the heading is valid, start using optical flow aiding |
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if (_control_status.flags.yaw_align) { |
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// set the flag and reset the fusion timeout |
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_control_status.flags.opt_flow = true; |
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_time_last_of_fuse = _time_last_imu; |
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// 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 |
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if (!_control_status.flags.gps) { |
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// calculate the rotation matrix from body to earth frame |
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matrix::Dcm<float> body_to_earth(_state.quat_nominal); |
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// constrain height above ground to be above minimum possible |
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float heightAboveGndEst = fmaxf((_terrain_vpos - _state.pos(2)), _params.rng_gnd_clearance); |
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// calculate absolute distance from focal point to centre of frame assuming a flat earth |
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float range = heightAboveGndEst / body_to_earth(2, 2); |
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if (_in_air && (range - _params.rng_gnd_clearance) > 0.3f && _flow_sample_delayed.dt > 0.05f) { |
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// calculate X and Y body relative velocities from OF measurements |
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Vector3f vel_optflow_body; |
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vel_optflow_body(0) = - range * _flow_sample_delayed.flowRadXYcomp(1) / _flow_sample_delayed.dt; |
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vel_optflow_body(1) = range * _flow_sample_delayed.flowRadXYcomp(0) / _flow_sample_delayed.dt; |
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vel_optflow_body(2) = 0.0f; |
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// rotate from body to earth frame |
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Vector3f vel_optflow_earth; |
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vel_optflow_earth = body_to_earth * vel_optflow_body; |
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// take x and Y components |
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_state.vel(0) = vel_optflow_earth(0); |
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_state.vel(1) = vel_optflow_earth(1); |
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} else { |
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_state.vel.setZero(); |
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} |
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} |
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} |
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} else if (!(_params.fusion_mode & MASK_USE_OF)) { |
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_control_status.flags.opt_flow = false; |
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} |
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// GPS fusion mode selection logic |
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// To start use GPS we need angular alignment completed, the local NED origin set and fresh GPS data |
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if ((_params.fusion_mode & MASK_USE_GPS) && !_control_status.flags.gps) { |
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if (_control_status.flags.tilt_align && (_time_last_imu - _time_last_gps) < 5e5 && _NED_origin_initialised |
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&& (_time_last_imu - _last_gps_fail_us > 5e6)) { |
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// If the heading is not aligned, reset the yaw and magnetic field states |
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if (!_control_status.flags.yaw_align) { |
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_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); |
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} |
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// If the heading is valid start using gps aiding |
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if (_control_status.flags.yaw_align) { |
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_control_status.flags.gps = true; |
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_time_last_gps = _time_last_imu; |
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// if we are not already aiding with optical flow, then we need to reset the position and velocity |
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if (!_control_status.flags.opt_flow) { |
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_control_status.flags.gps = resetPosition(); |
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_control_status.flags.gps = resetVelocity(); |
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} |
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} |
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} |
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} else if (!(_params.fusion_mode & MASK_USE_GPS)) { |
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_control_status.flags.gps = false; |
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} |
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// handle the case when we are relying on GPS fusion and lose it |
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if (_control_status.flags.gps && !_control_status.flags.opt_flow) { |
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// We are relying on GPS aiding to constrain attitude drift so after 10 seconds without aiding we need to do something |
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if ((_time_last_imu - _time_last_pos_fuse > 10e6) && (_time_last_imu - _time_last_vel_fuse > 10e6)) { |
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if (_time_last_imu - _time_last_gps > 5e5) { |
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// if we don't have gps then we need to switch to the non-aiding mode, zero the veloity states |
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// and set the synthetic GPS position to the current estimate |
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_control_status.flags.gps = false; |
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_last_known_posNE(0) = _state.pos(0); |
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_last_known_posNE(1) = _state.pos(1); |
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_state.vel.setZero(); |
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} else { |
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// Reset states to the last GPS measurement |
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resetPosition(); |
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resetVelocity(); |
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} |
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} |
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} |
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/* |
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* Handle the case where we have not fused height measurements recently and |
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* uncertainty exceeds the max allowable. Reset using the best available height |
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* measurement source, continue using it after the reset and declare the current |
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* source failed if we have switched. |
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*/ |
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if ((P[8][8] > sq(_params.hgt_reset_lim)) && ((_time_last_imu - _time_last_hgt_fuse) > 5e6)) { |
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// handle the case where we are using baro for height |
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if (_control_status.flags.baro_hgt) { |
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// check if GPS height is available |
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gpsSample gps_init = _gps_buffer.get_newest(); |
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bool gps_hgt_available = ((_time_last_imu - gps_init.time_us) < 2 * GPS_MAX_INTERVAL); |
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bool gps_hgt_accurate = (gps_init.vacc < _params.req_vacc); |
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baroSample baro_init = _baro_buffer.get_newest(); |
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bool baro_hgt_available = ((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL); |
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// use the gps if it is accurate or there is no baro data available |
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if (gps_hgt_available && (gps_hgt_accurate || !baro_hgt_available)) { |
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// declare the baro as unhealthy |
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_baro_hgt_faulty = true; |
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// set the height mode to the GPS |
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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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// adjust the height offset so we can use the GPS |
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_hgt_sensor_offset = _state.pos(2) + gps_init.hgt - _gps_alt_ref; |
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printf("EKF baro hgt timeout - switching to gps\n"); |
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} |
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} |
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// handle the case we are using GPS for height |
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if (_control_status.flags.gps_hgt) { |
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// check if GPS height is available |
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gpsSample gps_init = _gps_buffer.get_newest(); |
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bool gps_hgt_available = ((_time_last_imu - gps_init.time_us) < 2 * GPS_MAX_INTERVAL); |
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bool gps_hgt_accurate = (gps_init.vacc < _params.req_vacc); |
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// check the baro height source for consistency and freshness |
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baroSample baro_init = _baro_buffer.get_newest(); |
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bool baro_data_fresh = ((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL); |
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float baro_innov = _state.pos(2) - (_hgt_sensor_offset - baro_init.hgt + _baro_hgt_offset); |
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bool baro_data_consistent = fabsf(baro_innov) < (sq(_params.baro_noise) + P[8][8]) * sq(_params.baro_innov_gate); |
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// if baro data is consistent and fresh or GPS height is unavailable or inaccurate, we switch to baro for height |
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if ((baro_data_consistent && baro_data_fresh) || !gps_hgt_available || !gps_hgt_accurate) { |
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// declare the GPS height unhealthy |
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_gps_hgt_faulty = true; |
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// set the height mode to the baro |
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_control_status.flags.baro_hgt = true; |
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_control_status.flags.gps_hgt = false; |
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_control_status.flags.rng_hgt = false; |
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printf("EKF gps hgt timeout - switching to baro\n"); |
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} |
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} |
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// handle the case we are using range finder for height |
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if (_control_status.flags.rng_hgt) { |
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// check if range finder data is available |
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rangeSample rng_init = _range_buffer.get_newest(); |
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bool rng_data_available = ((_time_last_imu - rng_init.time_us) < 2 * RNG_MAX_INTERVAL); |
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// check if baro data is available |
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baroSample baro_init = _baro_buffer.get_newest(); |
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bool baro_data_available = ((_time_last_imu - baro_init.time_us) < 2 * BARO_MAX_INTERVAL); |
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// check if baro data is consistent |
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float baro_innov = _state.pos(2) - (_hgt_sensor_offset - baro_init.hgt + _baro_hgt_offset); |
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bool baro_data_consistent = sq(baro_innov) < (sq(_params.baro_noise) + P[8][8]) * sq(_params.baro_innov_gate); |
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// switch to baro if necessary or preferable |
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bool switch_to_baro = (!rng_data_available && baro_data_available) || (baro_data_consistent && baro_data_available); |
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if (switch_to_baro) { |
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// declare the range finder height unhealthy |
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_rng_hgt_faulty = true; |
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// set the height mode to the baro |
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_control_status.flags.baro_hgt = true; |
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_control_status.flags.gps_hgt = false; |
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_control_status.flags.rng_hgt = false; |
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printf("EKF rng hgt timeout - switching to baro\n"); |
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} |
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} |
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// Reset vertical position and velocity states to the last measurement |
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resetHeight(); |
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} |
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// handle the case when we are relying on optical flow fusion and lose it |
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if (_control_status.flags.opt_flow && !_control_status.flags.gps) { |
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// We are relying on flow aiding to constrain attitude drift so after 5s without aiding we need to do something |
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if ((_time_last_imu - _time_last_of_fuse > 5e6)) { |
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// Switch to the non-aiding mode, zero the veloity states |
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// and set the synthetic position to the current estimate |
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_control_status.flags.opt_flow = false; |
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_last_known_posNE(0) = _state.pos(0); |
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_last_known_posNE(1) = _state.pos(1); |
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_state.vel.setZero(); |
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} |
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} |
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// Determine if we should use simple magnetic heading fusion which works better when there are large external disturbances |
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// or the more accurate 3-axis fusion |
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if (_params.mag_fusion_type == MAG_FUSE_TYPE_AUTO) { |
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if (!_control_status.flags.armed) { |
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// use heading fusion for initial startup |
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_control_status.flags.mag_hdg = true; |
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_control_status.flags.mag_2D = false; |
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_control_status.flags.mag_3D = false; |
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} else { |
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if (_control_status.flags.in_air) { |
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// if transitioning into 3-axis fusion mode, we need to initialise the yaw angle and field states |
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if (!_control_status.flags.mag_3D) { |
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_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); |
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} |
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// use 3D mag fusion when airborne |
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_control_status.flags.mag_hdg = false; |
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_control_status.flags.mag_2D = false; |
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_control_status.flags.mag_3D = true; |
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} else { |
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// use heading fusion when on the ground |
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_control_status.flags.mag_hdg = true; |
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_control_status.flags.mag_2D = false; |
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_control_status.flags.mag_3D = false; |
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} |
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} |
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} else if (_params.mag_fusion_type == MAG_FUSE_TYPE_HEADING) { |
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// always use heading fusion |
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_control_status.flags.mag_hdg = true; |
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_control_status.flags.mag_2D = false; |
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_control_status.flags.mag_3D = false; |
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} else if (_params.mag_fusion_type == MAG_FUSE_TYPE_2D) { |
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// always use 2D mag fusion |
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_control_status.flags.mag_hdg = false; |
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_control_status.flags.mag_2D = true; |
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_control_status.flags.mag_3D = false; |
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} else if (_params.mag_fusion_type == MAG_FUSE_TYPE_3D) { |
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// if transitioning into 3-axis fusion mode, we need to initialise the yaw angle and field states |
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if (!_control_status.flags.mag_3D) { |
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_control_status.flags.yaw_align = resetMagHeading(_mag_sample_delayed.mag); |
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} |
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// always use 3-axis mag fusion |
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_control_status.flags.mag_hdg = false; |
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_control_status.flags.mag_2D = false; |
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_control_status.flags.mag_3D = true; |
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} else { |
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// do no magnetometer fusion at all |
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_control_status.flags.mag_hdg = false; |
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_control_status.flags.mag_2D = false; |
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_control_status.flags.mag_3D = false; |
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} |
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// 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 |
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// fusing declination when gps aiding is available is optional, but recommneded to prevent problem if the vehicle is static for extended periods of time |
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if (_control_status.flags.mag_3D && (!_control_status.flags.gps || (_params.mag_declination_source & MASK_FUSE_DECL))) { |
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_control_status.flags.mag_dec = true; |
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} else { |
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_control_status.flags.mag_dec = false; |
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} |
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// Control the soure of height measurements for the main filter |
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if ((_params.vdist_sensor_type == VDIST_SENSOR_BARO && !_baro_hgt_faulty) || _control_status.flags.baro_hgt) { |
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_control_status.flags.baro_hgt = true; |
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_control_status.flags.gps_hgt = false; |
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_control_status.flags.rng_hgt = false; |
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} else if ((_params.vdist_sensor_type == VDIST_SENSOR_GPS && !_gps_hgt_faulty) || _control_status.flags.gps_hgt) { |
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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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} else if (_params.vdist_sensor_type == VDIST_SENSOR_RANGE && !_rng_hgt_faulty) { |
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_control_status.flags.baro_hgt = false; |
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_control_status.flags.gps_hgt = false; |
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_control_status.flags.rng_hgt = true; |
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} |
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// Placeholder for control of wind velocity states estimation |
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// TODO add methods for true airspeed and/or sidelsip fusion or some type of drag force measurement |
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if (false) { |
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_control_status.flags.wind = false; |
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} |
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// Store the status to enable change detection |
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_control_status_prev.value = _control_status.value; |
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} |
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void Ekf::calculateVehicleStatus() |
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{ |
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// determine if the vehicle is armed |
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_control_status.flags.armed = _vehicle_armed; |
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// record vertical position whilst disarmed to use as a height change reference |
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if (!_control_status.flags.armed) { |
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_last_disarmed_posD = _state.pos(2); |
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} |
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// Transition to in-air occurs when armed and when altitude has increased sufficiently from the altitude at arming |
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bool in_air = _control_status.flags.armed && (_state.pos(2) - _last_disarmed_posD) < -1.0f; |
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if (!_control_status.flags.in_air && in_air) { |
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_control_status.flags.in_air = true; |
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} |
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// Transition to on-ground occurs when disarmed or if the land detector indicated landed state |
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if (_control_status.flags.in_air && (!_control_status.flags.armed || !_in_air)) { |
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_control_status.flags.in_air = false; |
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} |
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}
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