/**************************************************************************** * * 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 airspeed_fusion.cpp * airspeed fusion methods. * * @author Carl Olsson * @author Roman Bast * @author Paul Riseborough * */ #include "ekf.h" #include "mathlib.h" void Ekf::fuseAirspeed() { // Initialize variables float vn; // Velocity in north direction float ve; // Velocity in east direction float vd; // Velocity in downwards direction float vwn; // Wind speed in north direction float vwe; // Wind speed in east direction float v_tas_pred; // Predicted measurement float R_TAS = sq(math::constrain(_params.eas_noise, 0.5f, 5.0f) * math::constrain(_airspeed_sample_delayed.eas2tas, 0.9f, 10.0f)); // Variance for true airspeed measurement - (m/sec)^2 float SH_TAS[3] = {}; // Varialbe used to optimise calculations of measurement jacobian float H_TAS[24] = {}; // Observation Jacobian float SK_TAS[2] = {}; // Varialbe used to optimise calculations of the Kalman gain vector float Kfusion[24] = {}; // Kalman gain vector // Copy required states to local variable names vn = _state.vel(0); ve = _state.vel(1); vd = _state.vel(2); vwn = _state.wind_vel(0); vwe = _state.wind_vel(1); // Calculate the predicted airspeed v_tas_pred = sqrtf((ve - vwe) * (ve - vwe) + (vn - vwn) * (vn - vwn) + vd * vd); // Perform fusion of True Airspeed measurement if (v_tas_pred > 1.0f) { // Calculate the observation jacobian // intermediate variable from algebraic optimisation SH_TAS[0] = 1 / v_tas_pred; SH_TAS[1] = (SH_TAS[0] * (2 * ve - 2 * vwe)) / 2.0f; SH_TAS[2] = (SH_TAS[0] * (2 * vn - 2 * vwn)) / 2.0f; for (uint8_t i = 0; i < _k_num_states; i++) { H_TAS[i] = 0.0f; } H_TAS[3] = SH_TAS[2]; H_TAS[4] = SH_TAS[1]; H_TAS[5] = vd * SH_TAS[0]; H_TAS[22] = -SH_TAS[2]; H_TAS[23] = -SH_TAS[1]; // We don't want to update the innovation variance if the calculation is ill conditioned float _airspeed_innov_var_temp = (R_TAS + SH_TAS[2] * (P[3][3] * SH_TAS[2] + P[4][3] * SH_TAS[1] - P[22][3] * SH_TAS[2] - P[23][3] * SH_TAS[1] + P[5][3] * vd * SH_TAS[0]) + SH_TAS[1] * (P[3][4] * SH_TAS[2] + P[4][4] * SH_TAS[1] - P[22][4] * SH_TAS[2] - P[23][4] * SH_TAS[1] + P[5][4] * vd * SH_TAS[0]) - SH_TAS[2] * (P[3][22] * SH_TAS[2] + P[4][22] * SH_TAS[1] - P[22][22] * SH_TAS[2] - P[23][22] * SH_TAS[1] + P[5][22] * vd * SH_TAS[0]) - SH_TAS[1] * (P[3][23] * SH_TAS[2] + P[4][23] * SH_TAS[1] - P[22][23] * SH_TAS[2] - P[23][23] * SH_TAS[1] + P[5][23] * vd * SH_TAS[0]) + vd * SH_TAS[0] * (P[3][5] * SH_TAS[2] + P[4][5] * SH_TAS[1] - P[22][5] * SH_TAS[2] - P[23][5] * SH_TAS[1] + P[5][5] * vd * SH_TAS[0])); if (_airspeed_innov_var_temp >= R_TAS) { // Check for badly conditioned calculation SK_TAS[0] = 1.0f / _airspeed_innov_var_temp; } else { // Reset the estimator initialiseCovariance(); return; } SK_TAS[1] = SH_TAS[1]; Kfusion[0] = SK_TAS[0] * (P[0][3] * SH_TAS[2] - P[0][22] * SH_TAS[2] + P[0][4] * SK_TAS[1] - P[0][23] * SK_TAS[1] + P[0][5] * vd * SH_TAS[0]); Kfusion[1] = SK_TAS[0] * (P[1][3] * SH_TAS[2] - P[1][22] * SH_TAS[2] + P[1][4] * SK_TAS[1] - P[1][23] * SK_TAS[1] + P[1][5] * vd * SH_TAS[0]); Kfusion[2] = SK_TAS[0] * (P[2][3] * SH_TAS[2] - P[2][22] * SH_TAS[2] + P[2][4] * SK_TAS[1] - P[2][23] * SK_TAS[1] + P[2][5] * vd * SH_TAS[0]); Kfusion[3] = SK_TAS[0] * (P[3][3] * SH_TAS[2] - P[3][22] * SH_TAS[2] + P[3][4] * SK_TAS[1] - P[3][23] * SK_TAS[1] + P[3][5] * vd * SH_TAS[0]); Kfusion[4] = SK_TAS[0] * (P[4][3] * SH_TAS[2] - P[4][22] * SH_TAS[2] + P[4][4] * SK_TAS[1] - P[4][23] * SK_TAS[1] + P[4][5] * vd * SH_TAS[0]); Kfusion[5] = SK_TAS[0] * (P[5][3] * SH_TAS[2] - P[5][22] * SH_TAS[2] + P[5][4] * SK_TAS[1] - P[5][23] * SK_TAS[1] + P[5][5] * vd * SH_TAS[0]); Kfusion[6] = SK_TAS[0] * (P[6][3] * SH_TAS[2] - P[6][22] * SH_TAS[2] + P[6][4] * SK_TAS[1] - P[6][23] * SK_TAS[1] + P[6][5] * vd * SH_TAS[0]); Kfusion[7] = SK_TAS[0] * (P[7][3] * SH_TAS[2] - P[7][22] * SH_TAS[2] + P[7][4] * SK_TAS[1] - P[7][23] * SK_TAS[1] + P[7][5] * vd * SH_TAS[0]); Kfusion[8] = SK_TAS[0] * (P[8][3] * SH_TAS[2] - P[8][22] * SH_TAS[2] + P[8][4] * SK_TAS[1] - P[8][23] * SK_TAS[1] + P[8][5] * vd * SH_TAS[0]); Kfusion[9] = SK_TAS[0] * (P[9][3] * SH_TAS[2] - P[9][22] * SH_TAS[2] + P[9][4] * SK_TAS[1] - P[9][23] * SK_TAS[1] + P[9][5] * vd * SH_TAS[0]); Kfusion[10] = SK_TAS[0] * (P[10][3] * SH_TAS[2] - P[10][22] * SH_TAS[2] + P[10][4] * SK_TAS[1] - P[10][23] * SK_TAS[1] + P[10][5] * vd * SH_TAS[0]); Kfusion[11] = SK_TAS[0] * (P[11][3] * SH_TAS[2] - P[11][22] * SH_TAS[2] + P[11][4] * SK_TAS[1] - P[11][23] * SK_TAS[1] + P[11][5] * vd * SH_TAS[0]); Kfusion[12] = SK_TAS[0] * (P[12][3] * SH_TAS[2] - P[12][22] * SH_TAS[2] + P[12][4] * SK_TAS[1] - P[12][23] * SK_TAS[1] + P[12][5] * vd * SH_TAS[0]); Kfusion[13] = SK_TAS[0] * (P[13][3] * SH_TAS[2] - P[13][22] * SH_TAS[2] + P[13][4] * SK_TAS[1] - P[13][23] * SK_TAS[1] + P[13][5] * vd * SH_TAS[0]); Kfusion[14] = SK_TAS[0] * (P[14][3] * SH_TAS[2] - P[14][22] * SH_TAS[2] + P[14][4] * SK_TAS[1] - P[14][23] * SK_TAS[1] + P[14][5] * vd * SH_TAS[0]); Kfusion[15] = SK_TAS[0] * (P[15][3] * SH_TAS[2] - P[15][22] * SH_TAS[2] + P[15][4] * SK_TAS[1] - P[15][23] * SK_TAS[1] + P[15][5] * vd * SH_TAS[0]); Kfusion[22] = SK_TAS[0] * (P[22][3] * SH_TAS[2] - P[22][22] * SH_TAS[2] + P[22][4] * SK_TAS[1] - P[22][23] * SK_TAS[1] + P[22][5] * vd * SH_TAS[0]); Kfusion[23] = SK_TAS[0] * (P[23][3] * SH_TAS[2] - P[23][22] * SH_TAS[2] + P[23][4] * SK_TAS[1] - P[23][23] * SK_TAS[1] + P[23][5] * vd * SH_TAS[0]); // Only update the magnetometer states if we are airborne and using 3D mag fusion if (_control_status.flags.mag_3D && _control_status.flags.in_air) { Kfusion[16] = SK_TAS[0] * (P[16][3] * SH_TAS[2] - P[16][22] * SH_TAS[2] + P[16][4] * SK_TAS[1] - P[16][23] * SK_TAS[1] + P[16][5] * vd * SH_TAS[0]); Kfusion[17] = SK_TAS[0] * (P[17][3] * SH_TAS[2] - P[17][22] * SH_TAS[2] + P[17][4] * SK_TAS[1] - P[17][23] * SK_TAS[1] + P[17][5] * vd * SH_TAS[0]); Kfusion[18] = SK_TAS[0] * (P[18][3] * SH_TAS[2] - P[18][22] * SH_TAS[2] + P[18][4] * SK_TAS[1] - P[18][23] * SK_TAS[1] + P[18][5] * vd * SH_TAS[0]); Kfusion[19] = SK_TAS[0] * (P[19][3] * SH_TAS[2] - P[19][22] * SH_TAS[2] + P[19][4] * SK_TAS[1] - P[19][23] * SK_TAS[1] + P[19][5] * vd * SH_TAS[0]); Kfusion[20] = SK_TAS[0] * (P[20][3] * SH_TAS[2] - P[20][22] * SH_TAS[2] + P[20][4] * SK_TAS[1] - P[20][23] * SK_TAS[1] + P[20][5] * vd * SH_TAS[0]); Kfusion[21] = SK_TAS[0] * (P[21][3] * SH_TAS[2] - P[21][22] * SH_TAS[2] + P[21][4] * SK_TAS[1] - P[21][23] * SK_TAS[1] + P[21][5] * vd * SH_TAS[0]); } else { for (int i = 16; i <= 21; i++) { Kfusion[i] = 0.0f; } } // calculate measurement innovation _airspeed_innov = v_tas_pred - _airspeed_sample_delayed.true_airspeed; // This is TAS, maybe we should indicate that in some way // Calculate the innovation variance _airspeed_innov_var = 1.0f / SK_TAS[0]; // Compute the ratio of innovation to gate size _tas_test_ratio = sq(_airspeed_innov) / (sq(fmaxf(_params.tas_innov_gate, 1.0f)) * _airspeed_innov_var); // if the innocation consistency check fails then don't fuse the sample and indicate bad airspeed health if (_tas_test_ratio > 1.0f) { _airspeed_healthy = false; return; } // airspeed measurement sample has passed check so record it _time_last_arsp_fuse = _time_last_imu; // by definition the angle error state is zero at the fusion time _state.ang_error.setZero(); // Fuse airspeed measurement fuse(Kfusion, _airspeed_innov); //Why calculate angle error when it is always zero? // correct the nominal quaternion Quaternion dq; dq.from_axis_angle(_state.ang_error); _state.quat_nominal = dq * _state.quat_nominal; _state.quat_nominal.normalize(); // update covariance matrix via Pnew = (I - KH)P = P - KHP float KH[_k_num_states][_k_num_states] = {}; float KHP[_k_num_states][_k_num_states] = {}; for (unsigned row = 0; row < _k_num_states; row++) { for (unsigned column = 0; column < _k_num_states; column++) { // Here it will be a lot of zeros, should optimize that... KH[row][column] = Kfusion[row] * H_TAS[column]; } } for (unsigned row = 0; row < _k_num_states; row++) { for (unsigned column = 0; column < _k_num_states; column++) { for (unsigned i = 0; i < _k_num_states; i++) { // Check if this is correct matrix multiplication! KHP[row][column] += KH[row][i] * P[i][column]; } } } for (unsigned row = 0; row < _k_num_states; row++) { for (unsigned column = 0; column < _k_num_states; column++) { P[row][column] = P[row][column] - KHP[row][column]; } } makeSymmetrical(); limitCov(); } }