void ahrs_update_accel(void) {
// c2 = ltp z-axis in imu-frame
struct Int32Vect3 c2 = { RMAT_ELMT(ahrs.ltp_to_imu_rmat, 0,2),
RMAT_ELMT(ahrs.ltp_to_imu_rmat, 1,2),
RMAT_ELMT(ahrs.ltp_to_imu_rmat, 2,2)};
struct Int32Vect3 residual;
struct Int32Vect3 pseudo_gravity_measurement;
if (ahrs_impl.correct_gravity && ahrs_impl.ltp_vel_norm_valid) {
/*
* centrifugal acceleration in body frame
* a_c_body = omega x (omega x r)
* (omega x r) = tangential velocity in body frame
* a_c_body = omega x vel_tangential_body
* assumption: tangential velocity only along body x-axis
*/
// FIXME: check overflows !
const struct Int32Vect3 vel_tangential_body = {(ahrs_impl.ltp_vel_norm>>INT32_ACCEL_FRAC), 0.0, 0.0};
struct Int32Vect3 acc_c_body;
VECT3_RATES_CROSS_VECT3(acc_c_body, ahrs.body_rate, vel_tangential_body);
INT32_VECT3_RSHIFT(acc_c_body, acc_c_body, INT32_SPEED_FRAC+INT32_RATE_FRAC-INT32_ACCEL_FRAC-INT32_ACCEL_FRAC);
/* convert centrifucal acceleration from body to imu frame */
struct Int32Vect3 acc_c_imu;
INT32_RMAT_VMULT(acc_c_imu, imu.body_to_imu_rmat, acc_c_body);
/* and subtract it from imu measurement to get a corrected measurement of the gravitiy vector */
INT32_VECT3_DIFF(pseudo_gravity_measurement, imu.accel, acc_c_imu);
} else {
void ahrs_update_accel(void) {
/* last column of roation matrix = ltp z-axis in imu-frame */
struct FloatVect3 c2 = { RMAT_ELMT(ahrs_impl.ltp_to_imu_rmat, 0,2),
RMAT_ELMT(ahrs_impl.ltp_to_imu_rmat, 1,2),
RMAT_ELMT(ahrs_impl.ltp_to_imu_rmat, 2,2)
};
struct FloatVect3 imu_accel_float;
ACCELS_FLOAT_OF_BFP(imu_accel_float, imu.accel);
struct FloatVect3 residual;
if (ahrs_impl.correct_gravity && ahrs_impl.ltp_vel_norm_valid) {
/*
* centrifugal acceleration in body frame
* a_c_body = omega x (omega x r)
* (omega x r) = tangential velocity in body frame
* a_c_body = omega x vel_tangential_body
* assumption: tangential velocity only along body x-axis
*/
const struct FloatVect3 vel_tangential_body = {ahrs_impl.ltp_vel_norm, 0.0, 0.0};
struct FloatVect3 acc_c_body;
VECT3_RATES_CROSS_VECT3(acc_c_body, *stateGetBodyRates_f(), vel_tangential_body);
/* convert centrifugal acceleration from body to imu frame */
struct FloatVect3 acc_c_imu;
FLOAT_RMAT_VECT3_MUL(acc_c_imu, ahrs_impl.body_to_imu_rmat, acc_c_body);
/* and subtract it from imu measurement to get a corrected measurement of the gravitiy vector */
struct FloatVect3 corrected_gravity;
VECT3_DIFF(corrected_gravity, imu_accel_float, acc_c_imu);
/* compute the residual of gravity vector in imu frame */
FLOAT_VECT3_CROSS_PRODUCT(residual, corrected_gravity, c2);
} else {
FLOAT_VECT3_CROSS_PRODUCT(residual, imu_accel_float, c2);
}
#ifdef AHRS_GRAVITY_UPDATE_NORM_HEURISTIC
/* heuristic on acceleration norm */
const float acc_norm = FLOAT_VECT3_NORM(imu_accel_float);
const float weight = Chop(1.-6*fabs((9.81-acc_norm)/9.81), 0., 1.);
#else
const float weight = 1.;
#endif
/* compute correction */
const float gravity_rate_update_gain = -5e-2; // -5e-2
FLOAT_RATES_ADD_SCALED_VECT(ahrs_impl.rate_correction, residual, weight*gravity_rate_update_gain);
const float gravity_bias_update_gain = 1e-5; // -5e-6
FLOAT_RATES_ADD_SCALED_VECT(ahrs_impl.gyro_bias, residual, weight*gravity_bias_update_gain);
/* FIXME: saturate bias */
}
void ahrs_icq_update_accel(struct Int32Vect3 *accel, float dt)
{
// check if we had at least one propagation since last update
if (ahrs_icq.accel_cnt == 0) {
return;
}
// c2 = ltp z-axis in imu-frame
struct Int32RMat ltp_to_imu_rmat;
int32_rmat_of_quat(<p_to_imu_rmat, &ahrs_icq.ltp_to_imu_quat);
struct Int32Vect3 c2 = { RMAT_ELMT(ltp_to_imu_rmat, 0, 2),
RMAT_ELMT(ltp_to_imu_rmat, 1, 2),
RMAT_ELMT(ltp_to_imu_rmat, 2, 2)
};
struct Int32Vect3 residual;
struct Int32Vect3 pseudo_gravity_measurement;
if (ahrs_icq.correct_gravity && ahrs_icq.ltp_vel_norm_valid) {
/*
* centrifugal acceleration in body frame
* a_c_body = omega x (omega x r)
* (omega x r) = tangential velocity in body frame
* a_c_body = omega x vel_tangential_body
* assumption: tangential velocity only along body x-axis
*/
// FIXME: check overflows !
#define COMPUTATION_FRAC 16
#define ACC_FROM_CROSS_FRAC INT32_RATE_FRAC + INT32_SPEED_FRAC - INT32_ACCEL_FRAC - COMPUTATION_FRAC
const struct Int32Vect3 vel_tangential_body =
{ahrs_icq.ltp_vel_norm >> COMPUTATION_FRAC, 0, 0};
struct Int32RMat *body_to_imu_rmat = orientationGetRMat_i(&ahrs_icq.body_to_imu);
struct Int32Rates body_rate;
int32_rmat_transp_ratemult(&body_rate, body_to_imu_rmat, &ahrs_icq.imu_rate);
struct Int32Vect3 acc_c_body;
VECT3_RATES_CROSS_VECT3(acc_c_body, body_rate, vel_tangential_body);
INT32_VECT3_RSHIFT(acc_c_body, acc_c_body, ACC_FROM_CROSS_FRAC);
/* convert centrifucal acceleration from body to imu frame */
struct Int32Vect3 acc_c_imu;
int32_rmat_vmult(&acc_c_imu, body_to_imu_rmat, &acc_c_body);
/* and subtract it from imu measurement to get a corrected measurement
* of the gravity vector */
VECT3_DIFF(pseudo_gravity_measurement, *accel, acc_c_imu);
} else {
void ahrs_fc_update_accel(struct Int32Vect3 *accel, float dt)
{
// check if we had at least one propagation since last update
if (ahrs_fc.accel_cnt == 0) {
return;
}
/* last column of roation matrix = ltp z-axis in imu-frame */
struct FloatVect3 c2 = { RMAT_ELMT(ahrs_fc.ltp_to_imu_rmat, 0, 2),
RMAT_ELMT(ahrs_fc.ltp_to_imu_rmat, 1, 2),
RMAT_ELMT(ahrs_fc.ltp_to_imu_rmat, 2, 2)
};
struct FloatVect3 imu_accel_float;
ACCELS_FLOAT_OF_BFP(imu_accel_float, *accel);
struct FloatVect3 residual;
struct FloatVect3 pseudo_gravity_measurement;
if (ahrs_fc.correct_gravity && ahrs_fc.ltp_vel_norm_valid) {
/*
* centrifugal acceleration in body frame
* a_c_body = omega x (omega x r)
* (omega x r) = tangential velocity in body frame
* a_c_body = omega x vel_tangential_body
* assumption: tangential velocity only along body x-axis
*/
const struct FloatVect3 vel_tangential_body = {ahrs_fc.ltp_vel_norm, 0.0, 0.0};
struct FloatRMat *body_to_imu_rmat = orientationGetRMat_f(&ahrs_fc.body_to_imu);
struct FloatRates body_rate;
float_rmat_transp_ratemult(&body_rate, body_to_imu_rmat, &ahrs_fc.imu_rate);
struct FloatVect3 acc_c_body;
VECT3_RATES_CROSS_VECT3(acc_c_body, body_rate, vel_tangential_body);
/* convert centrifugal acceleration from body to imu frame */
struct FloatVect3 acc_c_imu;
float_rmat_vmult(&acc_c_imu, body_to_imu_rmat, &acc_c_body);
/* and subtract it from imu measurement to get a corrected measurement of the gravity vector */
VECT3_DIFF(pseudo_gravity_measurement, imu_accel_float, acc_c_imu);
} else {
VECT3_COPY(pseudo_gravity_measurement, imu_accel_float);
}
VECT3_CROSS_PRODUCT(residual, pseudo_gravity_measurement, c2);
/* FIR filtered pseudo_gravity_measurement */
#define FIR_FILTER_SIZE 8
static struct FloatVect3 filtered_gravity_measurement = {0., 0., 0.};
VECT3_SMUL(filtered_gravity_measurement, filtered_gravity_measurement, FIR_FILTER_SIZE - 1);
VECT3_ADD(filtered_gravity_measurement, pseudo_gravity_measurement);
VECT3_SDIV(filtered_gravity_measurement, filtered_gravity_measurement, FIR_FILTER_SIZE);
if (ahrs_fc.gravity_heuristic_factor) {
/* heuristic on acceleration (gravity estimate) norm */
/* Factor how strongly to change the weight.
* e.g. for gravity_heuristic_factor 30:
* <0.66G = 0, 1G = 1.0, >1.33G = 0
*/
const float g_meas_norm = float_vect3_norm(&filtered_gravity_measurement) / 9.81;
ahrs_fc.weight = 1.0 - ahrs_fc.gravity_heuristic_factor * fabs(1.0 - g_meas_norm) / 10.0;
Bound(ahrs_fc.weight, 0.15, 1.0);
} else {
ahrs_fc.weight = 1.0;
}
/* Complementary filter proportional gain.
* Kp = 2 * zeta * omega * weight * ahrs_fc.accel_cnt
* with ahrs_fc.accel_cnt beeing the number of propagations since last update
*/
const float gravity_rate_update_gain = -2 * ahrs_fc.accel_zeta * ahrs_fc.accel_omega *
ahrs_fc.weight * ahrs_fc.accel_cnt / 9.81;
RATES_ADD_SCALED_VECT(ahrs_fc.rate_correction, residual, gravity_rate_update_gain);
// reset accel propagation counter
ahrs_fc.accel_cnt = 0;
/* Complementary filter integral gain
* Correct the gyro bias.
* Ki = (omega*weight)^2 * dt
*/
const float gravity_bias_update_gain = ahrs_fc.accel_omega * ahrs_fc.accel_omega *
ahrs_fc.weight * ahrs_fc.weight * dt / 9.81;
RATES_ADD_SCALED_VECT(ahrs_fc.gyro_bias, residual, gravity_bias_update_gain);
/* FIXME: saturate bias */
}
void ahrs_update_accel(void) {
/* last column of roation matrix = ltp z-axis in imu-frame */
struct FloatVect3 c2 = { RMAT_ELMT(ahrs_impl.ltp_to_imu_rmat, 0,2),
RMAT_ELMT(ahrs_impl.ltp_to_imu_rmat, 1,2),
RMAT_ELMT(ahrs_impl.ltp_to_imu_rmat, 2,2)};
struct FloatVect3 imu_accel_float;
ACCELS_FLOAT_OF_BFP(imu_accel_float, imu.accel);
struct FloatVect3 residual;
struct FloatVect3 pseudo_gravity_measurement;
if (ahrs_impl.correct_gravity && ahrs_impl.ltp_vel_norm_valid) {
/*
* centrifugal acceleration in body frame
* a_c_body = omega x (omega x r)
* (omega x r) = tangential velocity in body frame
* a_c_body = omega x vel_tangential_body
* assumption: tangential velocity only along body x-axis
*/
const struct FloatVect3 vel_tangential_body = {ahrs_impl.ltp_vel_norm, 0.0, 0.0};
struct FloatVect3 acc_c_body;
VECT3_RATES_CROSS_VECT3(acc_c_body, *stateGetBodyRates_f(), vel_tangential_body);
/* convert centrifugal acceleration from body to imu frame */
struct FloatVect3 acc_c_imu;
FLOAT_RMAT_VECT3_MUL(acc_c_imu, ahrs_impl.body_to_imu_rmat, acc_c_body);
/* and subtract it from imu measurement to get a corrected measurement of the gravity vector */
VECT3_DIFF(pseudo_gravity_measurement, imu_accel_float, acc_c_imu);
} else {
VECT3_COPY(pseudo_gravity_measurement, imu_accel_float);
}
FLOAT_VECT3_CROSS_PRODUCT(residual, pseudo_gravity_measurement, c2);
/* FIR filtered pseudo_gravity_measurement */
#define FIR_FILTER_SIZE 8
static struct FloatVect3 filtered_gravity_measurement = {0., 0., 0.};
VECT3_SMUL(filtered_gravity_measurement, filtered_gravity_measurement, FIR_FILTER_SIZE-1);
VECT3_ADD(filtered_gravity_measurement, pseudo_gravity_measurement);
VECT3_SDIV(filtered_gravity_measurement, filtered_gravity_measurement, FIR_FILTER_SIZE);
if (ahrs_impl.gravity_heuristic_factor) {
/* heuristic on acceleration (gravity estimate) norm */
/* Factor how strongly to change the weight.
* e.g. for gravity_heuristic_factor 30:
* <0.66G = 0, 1G = 1.0, >1.33G = 0
*/
const float g_meas_norm = FLOAT_VECT3_NORM(filtered_gravity_measurement) / 9.81;
ahrs_impl.weight = 1.0 - ahrs_impl.gravity_heuristic_factor * fabs(1.0 - g_meas_norm) / 10.0;
Bound(ahrs_impl.weight, 0.15, 1.0);
}
else {
ahrs_impl.weight = 1.0;
}
/* Complementary filter proportional gain.
* Kp = 2 * zeta * omega * weight * AHRS_PROPAGATE_FREQUENCY / AHRS_CORRECT_FREQUENCY
*/
const float gravity_rate_update_gain = -2 * ahrs_impl.accel_zeta * ahrs_impl.accel_omega *
ahrs_impl.weight * AHRS_PROPAGATE_FREQUENCY / (AHRS_CORRECT_FREQUENCY * 9.81);
FLOAT_RATES_ADD_SCALED_VECT(ahrs_impl.rate_correction, residual, gravity_rate_update_gain);
/* Complementary filter integral gain
* Correct the gyro bias.
* Ki = (omega*weight)^2/AHRS_CORRECT_FREQUENCY
*/
const float gravity_bias_update_gain = ahrs_impl.accel_omega * ahrs_impl.accel_omega *
ahrs_impl.weight * ahrs_impl.weight / (AHRS_CORRECT_FREQUENCY * 9.81);
FLOAT_RATES_ADD_SCALED_VECT(ahrs_impl.gyro_bias, residual, gravity_bias_update_gain);
/* FIXME: saturate bias */
}
