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276 lines
12 KiB
276 lines
12 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 airspeed_fusion.cpp |
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* airspeed fusion methods. |
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* |
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* @author Carl Olsson <carlolsson.co@gmail.com> |
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* @author Roman Bast <bapstroman@gmail.com> |
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* @author Paul Riseborough <p_riseborough@live.com.au> |
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* |
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*/ |
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#include "../ecl.h" |
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#include "ekf.h" |
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#include <mathlib/mathlib.h> |
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void Ekf::fuseAirspeed() |
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{ |
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// Initialize variables |
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float vn; // Velocity in north direction |
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float ve; // Velocity in east direction |
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float vd; // Velocity in downwards direction |
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float vwn; // Wind speed in north direction |
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float vwe; // Wind speed in east direction |
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float v_tas_pred; // Predicted measurement |
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float R_TAS = sq(math::constrain(_params.eas_noise, 0.5f, 5.0f) * math::constrain(_airspeed_sample_delayed.eas2tas, 0.9f, |
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10.0f)); // Variance for true airspeed measurement - (m/sec)^2 |
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float SH_TAS[3] = {}; // Varialbe used to optimise calculations of measurement jacobian |
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float H_TAS[24] = {}; // Observation Jacobian |
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float SK_TAS[2] = {}; // Varialbe used to optimise calculations of the Kalman gain vector |
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float Kfusion[24] = {}; // Kalman gain vector |
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// Copy required states to local variable names |
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vn = _state.vel(0); |
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ve = _state.vel(1); |
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vd = _state.vel(2); |
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vwn = _state.wind_vel(0); |
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vwe = _state.wind_vel(1); |
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// Calculate the predicted airspeed |
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v_tas_pred = sqrtf((ve - vwe) * (ve - vwe) + (vn - vwn) * (vn - vwn) + vd * vd); |
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// Perform fusion of True Airspeed measurement |
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if (v_tas_pred > 1.0f) { |
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// determine if we need the sideslip fusion to correct states other than wind |
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bool update_wind_only = !_is_wind_dead_reckoning; |
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// Calculate the observation jacobian |
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// intermediate variable from algebraic optimisation |
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SH_TAS[0] = 1.0f/v_tas_pred; |
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SH_TAS[1] = (SH_TAS[0]*(2.0f*ve - 2.0f*vwe))*0.5f; |
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SH_TAS[2] = (SH_TAS[0]*(2.0f*vn - 2.0f*vwn))*0.5f; |
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for (uint8_t i = 0; i < _k_num_states; i++) { H_TAS[i] = 0.0f; } |
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H_TAS[4] = SH_TAS[2]; |
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H_TAS[5] = SH_TAS[1]; |
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H_TAS[6] = vd*SH_TAS[0]; |
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H_TAS[22] = -SH_TAS[2]; |
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H_TAS[23] = -SH_TAS[1]; |
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// We don't want to update the innovation variance if the calculation is ill conditioned |
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float _airspeed_innov_var_temp = (R_TAS + SH_TAS[2]*(P[4][4]*SH_TAS[2] + P[5][4]*SH_TAS[1] - P[22][4]*SH_TAS[2] - P[23][4]*SH_TAS[1] + P[6][4]*vd*SH_TAS[0]) + SH_TAS[1]*(P[4][5]*SH_TAS[2] + P[5][5]*SH_TAS[1] - P[22][5]*SH_TAS[2] - P[23][5]*SH_TAS[1] + P[6][5]*vd*SH_TAS[0]) - SH_TAS[2]*(P[4][22]*SH_TAS[2] + P[5][22]*SH_TAS[1] - P[22][22]*SH_TAS[2] - P[23][22]*SH_TAS[1] + P[6][22]*vd*SH_TAS[0]) - SH_TAS[1]*(P[4][23]*SH_TAS[2] + P[5][23]*SH_TAS[1] - P[22][23]*SH_TAS[2] - P[23][23]*SH_TAS[1] + P[6][23]*vd*SH_TAS[0]) + vd*SH_TAS[0]*(P[4][6]*SH_TAS[2] + P[5][6]*SH_TAS[1] - P[22][6]*SH_TAS[2] - P[23][6]*SH_TAS[1] + P[6][6]*vd*SH_TAS[0])); |
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if (_airspeed_innov_var_temp >= R_TAS) { // Check for badly conditioned calculation |
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SK_TAS[0] = 1.0f / _airspeed_innov_var_temp; |
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_fault_status.flags.bad_airspeed = false; |
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} else { // Reset the estimator covarinace matrix |
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_fault_status.flags.bad_airspeed = true; |
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// if we are getting aiding from other sources, warn and reset the wind states and covariances only |
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if (update_wind_only) { |
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resetWindStates(); |
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resetWindCovariance(); |
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ECL_ERR("EKF airspeed fusion badly conditioned - wind covariance reset"); |
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} else { |
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initialiseCovariance(); |
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_state.wind_vel.setZero(); |
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ECL_ERR("EKF airspeed fusion badly conditioned - full covariance reset"); |
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} |
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return; |
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} |
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SK_TAS[1] = SH_TAS[1]; |
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if (update_wind_only) { |
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// If we are getting aiding from other sources, then don't allow the airspeed measurements to affect the non-windspeed states |
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for (unsigned row = 0; row <= 21; row++) { |
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Kfusion[row] = 0.0f; |
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} |
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} else { |
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// we have no other source of aiding, so use airspeed measurements to correct states |
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Kfusion[0] = SK_TAS[0]*(P[0][4]*SH_TAS[2] - P[0][22]*SH_TAS[2] + P[0][5]*SK_TAS[1] - P[0][23]*SK_TAS[1] + P[0][6]*vd*SH_TAS[0]); |
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Kfusion[1] = SK_TAS[0]*(P[1][4]*SH_TAS[2] - P[1][22]*SH_TAS[2] + P[1][5]*SK_TAS[1] - P[1][23]*SK_TAS[1] + P[1][6]*vd*SH_TAS[0]); |
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Kfusion[2] = SK_TAS[0]*(P[2][4]*SH_TAS[2] - P[2][22]*SH_TAS[2] + P[2][5]*SK_TAS[1] - P[2][23]*SK_TAS[1] + P[2][6]*vd*SH_TAS[0]); |
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Kfusion[3] = SK_TAS[0]*(P[3][4]*SH_TAS[2] - P[3][22]*SH_TAS[2] + P[3][5]*SK_TAS[1] - P[3][23]*SK_TAS[1] + P[3][6]*vd*SH_TAS[0]); |
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Kfusion[4] = SK_TAS[0]*(P[4][4]*SH_TAS[2] - P[4][22]*SH_TAS[2] + P[4][5]*SK_TAS[1] - P[4][23]*SK_TAS[1] + P[4][6]*vd*SH_TAS[0]); |
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Kfusion[5] = SK_TAS[0]*(P[5][4]*SH_TAS[2] - P[5][22]*SH_TAS[2] + P[5][5]*SK_TAS[1] - P[5][23]*SK_TAS[1] + P[5][6]*vd*SH_TAS[0]); |
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Kfusion[6] = SK_TAS[0]*(P[6][4]*SH_TAS[2] - P[6][22]*SH_TAS[2] + P[6][5]*SK_TAS[1] - P[6][23]*SK_TAS[1] + P[6][6]*vd*SH_TAS[0]); |
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Kfusion[7] = SK_TAS[0]*(P[7][4]*SH_TAS[2] - P[7][22]*SH_TAS[2] + P[7][5]*SK_TAS[1] - P[7][23]*SK_TAS[1] + P[7][6]*vd*SH_TAS[0]); |
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Kfusion[8] = SK_TAS[0]*(P[8][4]*SH_TAS[2] - P[8][22]*SH_TAS[2] + P[8][5]*SK_TAS[1] - P[8][23]*SK_TAS[1] + P[8][6]*vd*SH_TAS[0]); |
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Kfusion[9] = SK_TAS[0]*(P[9][4]*SH_TAS[2] - P[9][22]*SH_TAS[2] + P[9][5]*SK_TAS[1] - P[9][23]*SK_TAS[1] + P[9][6]*vd*SH_TAS[0]); |
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Kfusion[10] = SK_TAS[0]*(P[10][4]*SH_TAS[2] - P[10][22]*SH_TAS[2] + P[10][5]*SK_TAS[1] - P[10][23]*SK_TAS[1] + P[10][6]*vd*SH_TAS[0]); |
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Kfusion[11] = SK_TAS[0]*(P[11][4]*SH_TAS[2] - P[11][22]*SH_TAS[2] + P[11][5]*SK_TAS[1] - P[11][23]*SK_TAS[1] + P[11][6]*vd*SH_TAS[0]); |
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Kfusion[12] = SK_TAS[0]*(P[12][4]*SH_TAS[2] - P[12][22]*SH_TAS[2] + P[12][5]*SK_TAS[1] - P[12][23]*SK_TAS[1] + P[12][6]*vd*SH_TAS[0]); |
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Kfusion[13] = SK_TAS[0]*(P[13][4]*SH_TAS[2] - P[13][22]*SH_TAS[2] + P[13][5]*SK_TAS[1] - P[13][23]*SK_TAS[1] + P[13][6]*vd*SH_TAS[0]); |
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Kfusion[14] = SK_TAS[0]*(P[14][4]*SH_TAS[2] - P[14][22]*SH_TAS[2] + P[14][5]*SK_TAS[1] - P[14][23]*SK_TAS[1] + P[14][6]*vd*SH_TAS[0]); |
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Kfusion[15] = SK_TAS[0]*(P[15][4]*SH_TAS[2] - P[15][22]*SH_TAS[2] + P[15][5]*SK_TAS[1] - P[15][23]*SK_TAS[1] + P[15][6]*vd*SH_TAS[0]); |
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Kfusion[16] = SK_TAS[0]*(P[16][4]*SH_TAS[2] - P[16][22]*SH_TAS[2] + P[16][5]*SK_TAS[1] - P[16][23]*SK_TAS[1] + P[16][6]*vd*SH_TAS[0]); |
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Kfusion[17] = SK_TAS[0]*(P[17][4]*SH_TAS[2] - P[17][22]*SH_TAS[2] + P[17][5]*SK_TAS[1] - P[17][23]*SK_TAS[1] + P[17][6]*vd*SH_TAS[0]); |
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Kfusion[18] = SK_TAS[0]*(P[18][4]*SH_TAS[2] - P[18][22]*SH_TAS[2] + P[18][5]*SK_TAS[1] - P[18][23]*SK_TAS[1] + P[18][6]*vd*SH_TAS[0]); |
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Kfusion[19] = SK_TAS[0]*(P[19][4]*SH_TAS[2] - P[19][22]*SH_TAS[2] + P[19][5]*SK_TAS[1] - P[19][23]*SK_TAS[1] + P[19][6]*vd*SH_TAS[0]); |
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Kfusion[20] = SK_TAS[0]*(P[20][4]*SH_TAS[2] - P[20][22]*SH_TAS[2] + P[20][5]*SK_TAS[1] - P[20][23]*SK_TAS[1] + P[20][6]*vd*SH_TAS[0]); |
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Kfusion[21] = SK_TAS[0]*(P[21][4]*SH_TAS[2] - P[21][22]*SH_TAS[2] + P[21][5]*SK_TAS[1] - P[21][23]*SK_TAS[1] + P[21][6]*vd*SH_TAS[0]); |
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} |
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Kfusion[22] = SK_TAS[0]*(P[22][4]*SH_TAS[2] - P[22][22]*SH_TAS[2] + P[22][5]*SK_TAS[1] - P[22][23]*SK_TAS[1] + P[22][6]*vd*SH_TAS[0]); |
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Kfusion[23] = SK_TAS[0]*(P[23][4]*SH_TAS[2] - P[23][22]*SH_TAS[2] + P[23][5]*SK_TAS[1] - P[23][23]*SK_TAS[1] + P[23][6]*vd*SH_TAS[0]); |
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// Calculate measurement innovation |
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_airspeed_innov = v_tas_pred - |
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_airspeed_sample_delayed.true_airspeed; |
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// Calculate the innovation variance |
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_airspeed_innov_var = 1.0f / SK_TAS[0]; |
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// Compute the ratio of innovation to gate size |
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_tas_test_ratio = sq(_airspeed_innov) / (sq(fmaxf(_params.tas_innov_gate, 1.0f)) * _airspeed_innov_var); |
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// If the innovation consistency check fails then don't fuse the sample and indicate bad airspeed health |
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if (_tas_test_ratio > 1.0f) { |
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_innov_check_fail_status.flags.reject_airspeed = true; |
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return; |
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} else { |
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_innov_check_fail_status.flags.reject_airspeed = false; |
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} |
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// Airspeed measurement sample has passed check so record it |
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_time_last_arsp_fuse = _time_last_imu; |
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// apply covariance correction via P_new = (I -K*H)*P |
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// first calculate expression for KHP |
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// then calculate P - KHP |
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float KHP[_k_num_states][_k_num_states]; |
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float KH[5]; |
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for (unsigned row = 0; row < _k_num_states; row++) { |
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KH[0] = Kfusion[row] * H_TAS[4]; |
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KH[1] = Kfusion[row] * H_TAS[5]; |
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KH[2] = Kfusion[row] * H_TAS[6]; |
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KH[3] = Kfusion[row] * H_TAS[22]; |
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KH[4] = Kfusion[row] * H_TAS[23]; |
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for (unsigned column = 0; column < _k_num_states; column++) { |
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float tmp = KH[0] * P[4][column]; |
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tmp += KH[1] * P[5][column]; |
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tmp += KH[2] * P[6][column]; |
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tmp += KH[3] * P[22][column]; |
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tmp += KH[4] * P[23][column]; |
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KHP[row][column] = tmp; |
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} |
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} |
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// if the covariance correction will result in a negative variance, then |
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// the covariance marix is unhealthy and must be corrected |
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bool healthy = true; |
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_fault_status.flags.bad_airspeed = false; |
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for (int i = 0; i < _k_num_states; i++) { |
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if (P[i][i] < KHP[i][i]) { |
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// zero rows and columns |
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zeroRows(P, i, i); |
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zeroCols(P, i, i); |
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//flag as unhealthy |
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healthy = false; |
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// update individual measurement health status |
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_fault_status.flags.bad_airspeed = true; |
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} |
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} |
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// only apply covariance and state corrrections if healthy |
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if (healthy) { |
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// apply the covariance corrections |
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for (unsigned row = 0; row < _k_num_states; row++) { |
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for (unsigned column = 0; column < _k_num_states; column++) { |
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P[row][column] = P[row][column] - KHP[row][column]; |
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} |
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} |
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// correct the covariance marix for gross errors |
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fixCovarianceErrors(); |
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// apply the state corrections |
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fuse(Kfusion, _airspeed_innov); |
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} |
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} |
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} |
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void Ekf::get_wind_velocity(float *wind) |
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{ |
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wind[0] = _state.wind_vel(0); |
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wind[1] = _state.wind_vel(1); |
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} |
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void Ekf::get_wind_velocity_var(float *wind_var) |
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{ |
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wind_var[0] = P[22][22]; |
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wind_var[1] = P[23][23]; |
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} |
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void Ekf::get_true_airspeed(float *tas) |
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{ |
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float tempvar = sqrtf(sq(_state.vel(0) - _state.wind_vel(0)) + sq(_state.vel(1) - _state.wind_vel(1)) + sq(_state.vel(2))); |
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memcpy(tas, &tempvar, sizeof(float)); |
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} |
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/* |
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* Reset the wind states using the current airspeed measurement, ground relative nav velocity, yaw angle and assumption of zero sideslip |
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*/ |
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void Ekf::resetWindStates() |
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{ |
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// get euler yaw angle |
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Eulerf euler321(_state.quat_nominal); |
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float euler_yaw = euler321(2); |
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if (_tas_data_ready && (_imu_sample_delayed.time_us - _airspeed_sample_delayed.time_us < (uint64_t)5e5)) { |
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// estimate wind using zero sideslip assumption and airspeed measurement if airspeed available |
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_state.wind_vel(0) = _state.vel(0) - _airspeed_sample_delayed.true_airspeed * cosf(euler_yaw); |
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_state.wind_vel(1) = _state.vel(1) - _airspeed_sample_delayed.true_airspeed * sinf(euler_yaw); |
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} else { |
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// If we don't have an airspeed measurement, then assume the wind is zero |
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_state.wind_vel(0) = 0.0f; |
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_state.wind_vel(1) = 0.0f; |
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} |
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}
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