/**************************************************************************** * * Copyright (c) 2013 PX4 Development Team. 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 PX4 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 accelerometer_calibration.cpp * * Implementation of accelerometer calibration. * * Transform acceleration vector to true orientation, scale and offset * * ===== Model ===== * accel_corr = accel_T * (accel_raw - accel_offs) * * accel_corr[3] - fully corrected acceleration vector in body frame * accel_T[3][3] - accelerometers transform matrix, rotation and scaling transform * accel_raw[3] - raw acceleration vector * accel_offs[3] - acceleration offset vector * * ===== Calibration ===== * * Reference vectors * accel_corr_ref[6][3] = [ g 0 0 ] // nose up * | -g 0 0 | // nose down * | 0 g 0 | // left side down * | 0 -g 0 | // right side down * | 0 0 g | // on back * [ 0 0 -g ] // level * accel_raw_ref[6][3] * * accel_corr_ref[i] = accel_T * (accel_raw_ref[i] - accel_offs), i = 0...5 * * 6 reference vectors * 3 axes = 18 equations * 9 (accel_T) + 3 (accel_offs) = 12 unknown constants * * Find accel_offs * * accel_offs[i] = (accel_raw_ref[i*2][i] + accel_raw_ref[i*2+1][i]) / 2 * * Find accel_T * * 9 unknown constants * need 9 equations -> use 3 of 6 measurements -> 3 * 3 = 9 equations * * accel_corr_ref[i*2] = accel_T * (accel_raw_ref[i*2] - accel_offs), i = 0...2 * * Solve separate system for each row of accel_T: * * accel_corr_ref[j*2][i] = accel_T[i] * (accel_raw_ref[j*2] - accel_offs), j = 0...2 * * A * x = b * * x = [ accel_T[0][i] ] * | accel_T[1][i] | * [ accel_T[2][i] ] * * b = [ accel_corr_ref[0][i] ] // One measurement per axis is enough * | accel_corr_ref[2][i] | * [ accel_corr_ref[4][i] ] * * a[i][j] = accel_raw_ref[i][j] - accel_offs[j], i = 0;2;4, j = 0...2 * * Matrix A is common for all three systems: * A = [ a[0][0] a[0][1] a[0][2] ] * | a[2][0] a[2][1] a[2][2] | * [ a[4][0] a[4][1] a[4][2] ] * * x = A^-1 * b * * accel_T = A^-1 * g * g = 9.80665 * * ===== Rotation ===== * * Calibrating using model: * accel_corr = accel_T_r * (rot * accel_raw - accel_offs_r) * * Actual correction: * accel_corr = rot * accel_T * (accel_raw - accel_offs) * * Known: accel_T_r, accel_offs_r, rot * Unknown: accel_T, accel_offs * * Solution: * accel_T_r * (rot * accel_raw - accel_offs_r) = rot * accel_T * (accel_raw - accel_offs) * rot^-1 * accel_T_r * (rot * accel_raw - accel_offs_r) = accel_T * (accel_raw - accel_offs) * rot^-1 * accel_T_r * rot * accel_raw - rot^-1 * accel_T_r * accel_offs_r = accel_T * accel_raw - accel_T * accel_offs) * => accel_T = rot^-1 * accel_T_r * rot * => accel_offs = rot^-1 * accel_offs_r * * @author Anton Babushkin */ #include "accelerometer_calibration.h" #include "calibration_messages.h" #include "commander_helper.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* oddly, ERROR is not defined for c++ */ #ifdef ERROR # undef ERROR #endif static const int ERROR = -1; static const char *sensor_name = "accel"; int do_accel_calibration_measurements(int mavlink_fd, float accel_offs[3], float accel_T[3][3]); int detect_orientation(int mavlink_fd, int sub_sensor_combined); int read_accelerometer_avg(int sensor_combined_sub, float accel_avg[3], int samples_num); int mat_invert3(float src[3][3], float dst[3][3]); int calculate_calibration_values(float accel_ref[6][3], float accel_T[3][3], float accel_offs[3], float g); int do_accel_calibration(int mavlink_fd) { int fd; mavlink_log_info(mavlink_fd, CAL_STARTED_MSG, sensor_name); struct accel_scale accel_scale = { 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, }; int res = OK; /* reset all offsets to zero and all scales to one */ fd = open(ACCEL_DEVICE_PATH, 0); res = ioctl(fd, ACCELIOCSSCALE, (long unsigned int)&accel_scale); close(fd); if (res != OK) { mavlink_log_critical(mavlink_fd, CAL_FAILED_RESET_CAL_MSG); } float accel_offs[3]; float accel_T[3][3]; if (res == OK) { /* measure and calculate offsets & scales */ res = do_accel_calibration_measurements(mavlink_fd, accel_offs, accel_T); } if (res == OK) { /* measurements completed successfully, rotate calibration values */ param_t board_rotation_h = param_find("SENS_BOARD_ROT"); int32_t board_rotation_int; param_get(board_rotation_h, &(board_rotation_int)); enum Rotation board_rotation_id = (enum Rotation)board_rotation_int; math::Matrix<3, 3> board_rotation; get_rot_matrix(board_rotation_id, &board_rotation); math::Matrix<3, 3> board_rotation_t = board_rotation.transposed(); math::Vector<3> accel_offs_vec(&accel_offs[0]); math::Vector<3> accel_offs_rotated = board_rotation_t *accel_offs_vec; math::Matrix<3, 3> accel_T_mat(&accel_T[0][0]); math::Matrix<3, 3> accel_T_rotated = board_rotation_t *accel_T_mat * board_rotation; accel_scale.x_offset = accel_offs_rotated(0); accel_scale.x_scale = accel_T_rotated(0, 0); accel_scale.y_offset = accel_offs_rotated(1); accel_scale.y_scale = accel_T_rotated(1, 1); accel_scale.z_offset = accel_offs_rotated(2); accel_scale.z_scale = accel_T_rotated(2, 2); /* set parameters */ if (param_set(param_find("SENS_ACC_XOFF"), &(accel_scale.x_offset)) || param_set(param_find("SENS_ACC_YOFF"), &(accel_scale.y_offset)) || param_set(param_find("SENS_ACC_ZOFF"), &(accel_scale.z_offset)) || param_set(param_find("SENS_ACC_XSCALE"), &(accel_scale.x_scale)) || param_set(param_find("SENS_ACC_YSCALE"), &(accel_scale.y_scale)) || param_set(param_find("SENS_ACC_ZSCALE"), &(accel_scale.z_scale))) { mavlink_log_critical(mavlink_fd, CAL_FAILED_SET_PARAMS_MSG); res = ERROR; } } if (res == OK) { /* apply new scaling and offsets */ fd = open(ACCEL_DEVICE_PATH, 0); res = ioctl(fd, ACCELIOCSSCALE, (long unsigned int)&accel_scale); close(fd); if (res != OK) { mavlink_log_critical(mavlink_fd, CAL_FAILED_APPLY_CAL_MSG); } } if (res == OK) { /* auto-save to EEPROM */ res = param_save_default(); if (res != OK) { mavlink_log_critical(mavlink_fd, CAL_FAILED_SAVE_PARAMS_MSG); } } if (res == OK) { mavlink_log_info(mavlink_fd, CAL_DONE_MSG, sensor_name); } else { mavlink_log_info(mavlink_fd, CAL_FAILED_MSG, sensor_name); } return res; } int do_accel_calibration_measurements(int mavlink_fd, float accel_offs[3], float accel_T[3][3]) { const int samples_num = 2500; float accel_ref[6][3]; bool data_collected[6] = { false, false, false, false, false, false }; const char *orientation_strs[6] = { "x+", "x-", "y+", "y-", "z+", "z-" }; int sensor_combined_sub = orb_subscribe(ORB_ID(sensor_combined)); unsigned done_count = 0; int res = OK; while (true) { bool done = true; unsigned old_done_count = done_count; done_count = 0; for (int i = 0; i < 6; i++) { if (data_collected[i]) { done_count++; } else { done = false; } } if (old_done_count != done_count) { mavlink_log_info(mavlink_fd, CAL_PROGRESS_MSG, sensor_name, 17 * done_count); } if (done) { break; } mavlink_log_info(mavlink_fd, "directions left: %s%s%s%s%s%s", (!data_collected[0]) ? "x+ " : "", (!data_collected[1]) ? "x- " : "", (!data_collected[2]) ? "y+ " : "", (!data_collected[3]) ? "y- " : "", (!data_collected[4]) ? "z+ " : "", (!data_collected[5]) ? "z- " : ""); int orient = detect_orientation(mavlink_fd, sensor_combined_sub); if (orient < 0) { res = ERROR; break; } if (data_collected[orient]) { mavlink_log_info(mavlink_fd, "%s done, rotate to a different axis", orientation_strs[orient]); continue; } mavlink_log_info(mavlink_fd, "accel measurement started: %s axis", orientation_strs[orient]); read_accelerometer_avg(sensor_combined_sub, &(accel_ref[orient][0]), samples_num); mavlink_log_info(mavlink_fd, "result for %s axis: [ %.2f %.2f %.2f ]", orientation_strs[orient], (double)accel_ref[orient][0], (double)accel_ref[orient][1], (double)accel_ref[orient][2]); data_collected[orient] = true; tune_neutral(true); } close(sensor_combined_sub); if (res == OK) { /* calculate offsets and transform matrix */ res = calculate_calibration_values(accel_ref, accel_T, accel_offs, CONSTANTS_ONE_G); if (res != OK) { mavlink_log_info(mavlink_fd, "ERROR: calibration values calculation error"); } } return res; } /* * Wait for vehicle become still and detect it's orientation. * * @return 0..5 according to orientation when vehicle is still and ready for measurements, * ERROR if vehicle is not still after 30s or orientation error is more than 5m/s^2 */ int detect_orientation(int mavlink_fd, int sub_sensor_combined) { struct sensor_combined_s sensor; /* exponential moving average of accel */ float accel_ema[3] = { 0.0f, 0.0f, 0.0f }; /* max-hold dispersion of accel */ float accel_disp[3] = { 0.0f, 0.0f, 0.0f }; /* EMA time constant in seconds*/ float ema_len = 0.5f; /* set "still" threshold to 0.25 m/s^2 */ float still_thr2 = pow(0.25f, 2); /* set accel error threshold to 5m/s^2 */ float accel_err_thr = 5.0f; /* still time required in us */ hrt_abstime still_time = 2000000; struct pollfd fds[1]; fds[0].fd = sub_sensor_combined; fds[0].events = POLLIN; hrt_abstime t_start = hrt_absolute_time(); /* set timeout to 30s */ hrt_abstime timeout = 30000000; hrt_abstime t_timeout = t_start + timeout; hrt_abstime t = t_start; hrt_abstime t_prev = t_start; hrt_abstime t_still = 0; unsigned poll_errcount = 0; while (true) { /* wait blocking for new data */ int poll_ret = poll(fds, 1, 1000); if (poll_ret) { orb_copy(ORB_ID(sensor_combined), sub_sensor_combined, &sensor); t = hrt_absolute_time(); float dt = (t - t_prev) / 1000000.0f; t_prev = t; float w = dt / ema_len; for (int i = 0; i < 3; i++) { float d = sensor.accelerometer_m_s2[i] - accel_ema[i]; accel_ema[i] += d * w; d = d * d; accel_disp[i] = accel_disp[i] * (1.0f - w); if (d > still_thr2 * 8.0f) { d = still_thr2 * 8.0f; } if (d > accel_disp[i]) { accel_disp[i] = d; } } /* still detector with hysteresis */ if (accel_disp[0] < still_thr2 && accel_disp[1] < still_thr2 && accel_disp[2] < still_thr2) { /* is still now */ if (t_still == 0) { /* first time */ mavlink_log_info(mavlink_fd, "detected rest position, waiting..."); t_still = t; t_timeout = t + timeout; } else { /* still since t_still */ if (t > t_still + still_time) { /* vehicle is still, exit from the loop to detection of its orientation */ break; } } } else if (accel_disp[0] > still_thr2 * 4.0f || accel_disp[1] > still_thr2 * 4.0f || accel_disp[2] > still_thr2 * 4.0f) { /* not still, reset still start time */ if (t_still != 0) { mavlink_log_info(mavlink_fd, "detected motion, hold still..."); t_still = 0; } } } else if (poll_ret == 0) { poll_errcount++; } if (t > t_timeout) { poll_errcount++; } if (poll_errcount > 1000) { mavlink_log_critical(mavlink_fd, CAL_FAILED_SENSOR_MSG); return ERROR; } } if (fabsf(accel_ema[0] - CONSTANTS_ONE_G) < accel_err_thr && fabsf(accel_ema[1]) < accel_err_thr && fabsf(accel_ema[2]) < accel_err_thr) { return 0; // [ g, 0, 0 ] } if (fabsf(accel_ema[0] + CONSTANTS_ONE_G) < accel_err_thr && fabsf(accel_ema[1]) < accel_err_thr && fabsf(accel_ema[2]) < accel_err_thr) { return 1; // [ -g, 0, 0 ] } if (fabsf(accel_ema[0]) < accel_err_thr && fabsf(accel_ema[1] - CONSTANTS_ONE_G) < accel_err_thr && fabsf(accel_ema[2]) < accel_err_thr) { return 2; // [ 0, g, 0 ] } if (fabsf(accel_ema[0]) < accel_err_thr && fabsf(accel_ema[1] + CONSTANTS_ONE_G) < accel_err_thr && fabsf(accel_ema[2]) < accel_err_thr) { return 3; // [ 0, -g, 0 ] } if (fabsf(accel_ema[0]) < accel_err_thr && fabsf(accel_ema[1]) < accel_err_thr && fabsf(accel_ema[2] - CONSTANTS_ONE_G) < accel_err_thr) { return 4; // [ 0, 0, g ] } if (fabsf(accel_ema[0]) < accel_err_thr && fabsf(accel_ema[1]) < accel_err_thr && fabsf(accel_ema[2] + CONSTANTS_ONE_G) < accel_err_thr) { return 5; // [ 0, 0, -g ] } mavlink_log_critical(mavlink_fd, "ERROR: invalid orientation"); return ERROR; // Can't detect orientation } /* * Read specified number of accelerometer samples, calculate average and dispersion. */ int read_accelerometer_avg(int sensor_combined_sub, float accel_avg[3], int samples_num) { struct pollfd fds[1]; fds[0].fd = sensor_combined_sub; fds[0].events = POLLIN; int count = 0; float accel_sum[3] = { 0.0f, 0.0f, 0.0f }; int errcount = 0; while (count < samples_num) { int poll_ret = poll(fds, 1, 1000); if (poll_ret == 1) { struct sensor_combined_s sensor; orb_copy(ORB_ID(sensor_combined), sensor_combined_sub, &sensor); for (int i = 0; i < 3; i++) { accel_sum[i] += sensor.accelerometer_m_s2[i]; } count++; } else { errcount++; continue; } if (errcount > samples_num / 10) { return ERROR; } } for (int i = 0; i < 3; i++) { accel_avg[i] = accel_sum[i] / count; } return OK; } int mat_invert3(float src[3][3], float dst[3][3]) { float det = src[0][0] * (src[1][1] * src[2][2] - src[1][2] * src[2][1]) - src[0][1] * (src[1][0] * src[2][2] - src[1][2] * src[2][0]) + src[0][2] * (src[1][0] * src[2][1] - src[1][1] * src[2][0]); if (fabsf(det) < FLT_EPSILON) { return ERROR; // Singular matrix } dst[0][0] = (src[1][1] * src[2][2] - src[1][2] * src[2][1]) / det; dst[1][0] = (src[1][2] * src[2][0] - src[1][0] * src[2][2]) / det; dst[2][0] = (src[1][0] * src[2][1] - src[1][1] * src[2][0]) / det; dst[0][1] = (src[0][2] * src[2][1] - src[0][1] * src[2][2]) / det; dst[1][1] = (src[0][0] * src[2][2] - src[0][2] * src[2][0]) / det; dst[2][1] = (src[0][1] * src[2][0] - src[0][0] * src[2][1]) / det; dst[0][2] = (src[0][1] * src[1][2] - src[0][2] * src[1][1]) / det; dst[1][2] = (src[0][2] * src[1][0] - src[0][0] * src[1][2]) / det; dst[2][2] = (src[0][0] * src[1][1] - src[0][1] * src[1][0]) / det; return OK; } int calculate_calibration_values(float accel_ref[6][3], float accel_T[3][3], float accel_offs[3], float g) { /* calculate offsets */ for (int i = 0; i < 3; i++) { accel_offs[i] = (accel_ref[i * 2][i] + accel_ref[i * 2 + 1][i]) / 2; } /* fill matrix A for linear equations system*/ float mat_A[3][3]; memset(mat_A, 0, sizeof(mat_A)); for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { float a = accel_ref[i * 2][j] - accel_offs[j]; mat_A[i][j] = a; } } /* calculate inverse matrix for A */ float mat_A_inv[3][3]; if (mat_invert3(mat_A, mat_A_inv) != OK) { return ERROR; } /* copy results to accel_T */ for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { /* simplify matrices mult because b has only one non-zero element == g at index i */ accel_T[j][i] = mat_A_inv[j][i] * g; } } return OK; }