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ardupilot/libraries/AP_NavEKF2/AP_NavEKF2_AirDataFusion.cpp

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#include <AP_HAL/AP_HAL.h>
#include "AP_NavEKF2.h"
#include "AP_NavEKF2_core.h"
extern const AP_HAL::HAL& hal;
/********************************************************
* RESET FUNCTIONS *
********************************************************/
/********************************************************
* FUSE MEASURED_DATA *
********************************************************/
/*
* Fuse true airspeed measurements using explicit algebraic equations generated with Matlab symbolic toolbox.
* The script file used to generate these and other equations in this filter can be found here:
* https://github.com/priseborough/InertialNav/blob/master/derivations/RotationVectorAttitudeParameterisation/GenerateNavFilterEquations.m
*/
void NavEKF2_core::FuseAirspeed()
{
// declarations
ftype vn;
ftype ve;
ftype vd;
ftype vwn;
ftype vwe;
ftype EAS2TAS = dal.get_EAS2TAS();
const ftype R_TAS = sq(constrain_ftype(frontend->_easNoise, 0.5f, 5.0f) * constrain_ftype(EAS2TAS, 0.9f, 10.0f));
Vector3 SH_TAS;
ftype SK_TAS;
Vector24 H_TAS;
ftype VtasPred;
// copy required states to local variable names
vn = stateStruct.velocity.x;
ve = stateStruct.velocity.y;
vd = stateStruct.velocity.z;
vwn = stateStruct.wind_vel.x;
vwe = stateStruct.wind_vel.y;
// calculate the predicted airspeed
VtasPred = norm((ve - vwe) , (vn - vwn) , vd);
// perform fusion of True Airspeed measurement
if (VtasPred > 1.0f)
{
// calculate observation jacobians
SH_TAS[0] = 1.0f/(sqrtF(sq(ve - vwe) + sq(vn - vwn) + sq(vd)));
SH_TAS[1] = (SH_TAS[0]*(2*ve - 2*vwe))/2;
SH_TAS[2] = (SH_TAS[0]*(2*vn - 2*vwn))/2;
for (uint8_t i=0; i<=2; 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];
for (uint8_t i=6; i<=21; i++) H_TAS[i] = 0.0f;
// calculate Kalman gains
ftype 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 (temp >= R_TAS) {
SK_TAS = 1.0f / temp;
faultStatus.bad_airspeed = false;
} else {
// the calculation is badly conditioned, so we cannot perform fusion on this step
// we reset the covariance matrix and try again next measurement
CovarianceInit();
faultStatus.bad_airspeed = true;
return;
}
Kfusion[0] = SK_TAS*(P[0][3]*SH_TAS[2] - P[0][22]*SH_TAS[2] + P[0][4]*SH_TAS[1] - P[0][23]*SH_TAS[1] + P[0][5]*vd*SH_TAS[0]);
Kfusion[1] = SK_TAS*(P[1][3]*SH_TAS[2] - P[1][22]*SH_TAS[2] + P[1][4]*SH_TAS[1] - P[1][23]*SH_TAS[1] + P[1][5]*vd*SH_TAS[0]);
Kfusion[2] = SK_TAS*(P[2][3]*SH_TAS[2] - P[2][22]*SH_TAS[2] + P[2][4]*SH_TAS[1] - P[2][23]*SH_TAS[1] + P[2][5]*vd*SH_TAS[0]);
Kfusion[3] = SK_TAS*(P[3][3]*SH_TAS[2] - P[3][22]*SH_TAS[2] + P[3][4]*SH_TAS[1] - P[3][23]*SH_TAS[1] + P[3][5]*vd*SH_TAS[0]);
Kfusion[4] = SK_TAS*(P[4][3]*SH_TAS[2] - P[4][22]*SH_TAS[2] + P[4][4]*SH_TAS[1] - P[4][23]*SH_TAS[1] + P[4][5]*vd*SH_TAS[0]);
Kfusion[5] = SK_TAS*(P[5][3]*SH_TAS[2] - P[5][22]*SH_TAS[2] + P[5][4]*SH_TAS[1] - P[5][23]*SH_TAS[1] + P[5][5]*vd*SH_TAS[0]);
Kfusion[6] = SK_TAS*(P[6][3]*SH_TAS[2] - P[6][22]*SH_TAS[2] + P[6][4]*SH_TAS[1] - P[6][23]*SH_TAS[1] + P[6][5]*vd*SH_TAS[0]);
Kfusion[7] = SK_TAS*(P[7][3]*SH_TAS[2] - P[7][22]*SH_TAS[2] + P[7][4]*SH_TAS[1] - P[7][23]*SH_TAS[1] + P[7][5]*vd*SH_TAS[0]);
Kfusion[8] = SK_TAS*(P[8][3]*SH_TAS[2] - P[8][22]*SH_TAS[2] + P[8][4]*SH_TAS[1] - P[8][23]*SH_TAS[1] + P[8][5]*vd*SH_TAS[0]);
Kfusion[9] = SK_TAS*(P[9][3]*SH_TAS[2] - P[9][22]*SH_TAS[2] + P[9][4]*SH_TAS[1] - P[9][23]*SH_TAS[1] + P[9][5]*vd*SH_TAS[0]);
Kfusion[10] = SK_TAS*(P[10][3]*SH_TAS[2] - P[10][22]*SH_TAS[2] + P[10][4]*SH_TAS[1] - P[10][23]*SH_TAS[1] + P[10][5]*vd*SH_TAS[0]);
Kfusion[11] = SK_TAS*(P[11][3]*SH_TAS[2] - P[11][22]*SH_TAS[2] + P[11][4]*SH_TAS[1] - P[11][23]*SH_TAS[1] + P[11][5]*vd*SH_TAS[0]);
Kfusion[12] = SK_TAS*(P[12][3]*SH_TAS[2] - P[12][22]*SH_TAS[2] + P[12][4]*SH_TAS[1] - P[12][23]*SH_TAS[1] + P[12][5]*vd*SH_TAS[0]);
Kfusion[13] = SK_TAS*(P[13][3]*SH_TAS[2] - P[13][22]*SH_TAS[2] + P[13][4]*SH_TAS[1] - P[13][23]*SH_TAS[1] + P[13][5]*vd*SH_TAS[0]);
Kfusion[14] = SK_TAS*(P[14][3]*SH_TAS[2] - P[14][22]*SH_TAS[2] + P[14][4]*SH_TAS[1] - P[14][23]*SH_TAS[1] + P[14][5]*vd*SH_TAS[0]);
Kfusion[15] = SK_TAS*(P[15][3]*SH_TAS[2] - P[15][22]*SH_TAS[2] + P[15][4]*SH_TAS[1] - P[15][23]*SH_TAS[1] + P[15][5]*vd*SH_TAS[0]);
Kfusion[22] = SK_TAS*(P[22][3]*SH_TAS[2] - P[22][22]*SH_TAS[2] + P[22][4]*SH_TAS[1] - P[22][23]*SH_TAS[1] + P[22][5]*vd*SH_TAS[0]);
Kfusion[23] = SK_TAS*(P[23][3]*SH_TAS[2] - P[23][22]*SH_TAS[2] + P[23][4]*SH_TAS[1] - P[23][23]*SH_TAS[1] + P[23][5]*vd*SH_TAS[0]);
// zero Kalman gains to inhibit magnetic field state estimation
if (!inhibitMagStates) {
Kfusion[16] = SK_TAS*(P[16][3]*SH_TAS[2] - P[16][22]*SH_TAS[2] + P[16][4]*SH_TAS[1] - P[16][23]*SH_TAS[1] + P[16][5]*vd*SH_TAS[0]);
Kfusion[17] = SK_TAS*(P[17][3]*SH_TAS[2] - P[17][22]*SH_TAS[2] + P[17][4]*SH_TAS[1] - P[17][23]*SH_TAS[1] + P[17][5]*vd*SH_TAS[0]);
Kfusion[18] = SK_TAS*(P[18][3]*SH_TAS[2] - P[18][22]*SH_TAS[2] + P[18][4]*SH_TAS[1] - P[18][23]*SH_TAS[1] + P[18][5]*vd*SH_TAS[0]);
Kfusion[19] = SK_TAS*(P[19][3]*SH_TAS[2] - P[19][22]*SH_TAS[2] + P[19][4]*SH_TAS[1] - P[19][23]*SH_TAS[1] + P[19][5]*vd*SH_TAS[0]);
Kfusion[20] = SK_TAS*(P[20][3]*SH_TAS[2] - P[20][22]*SH_TAS[2] + P[20][4]*SH_TAS[1] - P[20][23]*SH_TAS[1] + P[20][5]*vd*SH_TAS[0]);
Kfusion[21] = SK_TAS*(P[21][3]*SH_TAS[2] - P[21][22]*SH_TAS[2] + P[21][4]*SH_TAS[1] - P[21][23]*SH_TAS[1] + P[21][5]*vd*SH_TAS[0]);
} else {
for (uint8_t i=16; i<=21; i++) {
Kfusion[i] = 0.0f;
}
}
// calculate measurement innovation variance
varInnovVtas = 1.0f/SK_TAS;
// calculate measurement innovation
innovVtas = VtasPred - tasDataDelayed.tas;
// calculate the innovation consistency test ratio
tasTestRatio = sq(innovVtas) / (sq(MAX(0.01f * (ftype)frontend->_tasInnovGate, 1.0f)) * varInnovVtas);
// fail if the ratio is > 1, but don't fail if bad IMU data
bool tasHealth = ((tasTestRatio < 1.0f) || badIMUdata);
tasTimeout = (imuSampleTime_ms - lastTasPassTime_ms) > frontend->tasRetryTime_ms;
if (!tasHealth) {
lastTasFailTime_ms = imuSampleTime_ms;
} else {
lastTasFailTime_ms = 0;
}
// test the ratio before fusing data, forcing fusion if airspeed and position are timed out as we have no choice but to try and use airspeed to constrain error growth
if (tasHealth || (tasTimeout && posTimeout)) {
// restart the counter
lastTasPassTime_ms = imuSampleTime_ms;
// zero the attitude error state - by definition it is assumed to be zero before each observation fusion
stateStruct.angErr.zero();
// correct the state vector
for (uint8_t j= 0; j<=stateIndexLim; j++) {
statesArray[j] = statesArray[j] - Kfusion[j] * innovVtas;
}
// the first 3 states represent the angular misalignment vector.
// This is used to correct the estimated quaternion on the current time step
stateStruct.quat.rotate(stateStruct.angErr);
// correct the covariance P = (I - K*H)*P
// take advantage of the empty columns in KH to reduce the
// number of operations
for (unsigned i = 0; i<=stateIndexLim; i++) {
for (unsigned j = 0; j<=2; j++) {
KH[i][j] = 0.0f;
}
for (unsigned j = 3; j<=5; j++) {
KH[i][j] = Kfusion[i] * H_TAS[j];
}
for (unsigned j = 6; j<=21; j++) {
KH[i][j] = 0.0f;
}
for (unsigned j = 22; j<=23; j++) {
KH[i][j] = Kfusion[i] * H_TAS[j];
}
}
for (unsigned j = 0; j<=stateIndexLim; j++) {
for (unsigned i = 0; i<=stateIndexLim; i++) {
ftype res = 0;
res += KH[i][3] * P[3][j];
res += KH[i][4] * P[4][j];
res += KH[i][5] * P[5][j];
res += KH[i][22] * P[22][j];
res += KH[i][23] * P[23][j];
KHP[i][j] = res;
}
}
for (unsigned i = 0; i<=stateIndexLim; i++) {
for (unsigned j = 0; j<=stateIndexLim; j++) {
P[i][j] = P[i][j] - KHP[i][j];
}
}
}
}
// force the covariance matrix to be symmetrical and limit the variances to prevent ill-conditioning.
ForceSymmetry();
ConstrainVariances();
}
// select fusion of true airspeed measurements
void NavEKF2_core::SelectTasFusion()
{
// Check if the magnetometer has been fused on that time step and the filter is running at faster than 200 Hz
// If so, don't fuse measurements on this time step to reduce frame over-runs
// Only allow one time slip to prevent high rate magnetometer data locking out fusion of other measurements
if (magFusePerformed && dtIMUavg < 0.005f && !airSpdFusionDelayed) {
airSpdFusionDelayed = true;
return;
} else {
airSpdFusionDelayed = false;
}
// get true airspeed measurement
readAirSpdData();
// If we haven't received airspeed data for a while, then declare the airspeed data as being timed out
if (imuSampleTime_ms - tasDataNew.time_ms > frontend->tasRetryTime_ms) {
tasTimeout = true;
}
// if the filter is initialised, wind states are not inhibited and we have data to fuse, then perform TAS fusion
if (tasDataToFuse && statesInitialised && !inhibitWindStates) {
FuseAirspeed();
prevTasStep_ms = imuSampleTime_ms;
}
}
// select fusion of synthetic sideslip measurements
// synthetic sidelip fusion only works for fixed wing aircraft and relies on the average sideslip being close to zero
// it requires a stable wind for best results and should not be used for aerobatic flight with manoeuvres that induce large sidslip angles (eg knife-edge, spins, etc)
void NavEKF2_core::SelectBetaFusion()
{
// Check if the magnetometer has been fused on that time step and the filter is running at faster than 200 Hz
// If so, don't fuse measurements on this time step to reduce frame over-runs
// Only allow one time slip to prevent high rate magnetometer data preventing fusion of other measurements
if (magFusePerformed && dtIMUavg < 0.005f && !sideSlipFusionDelayed) {
sideSlipFusionDelayed = true;
return;
} else {
sideSlipFusionDelayed = false;
}
// set true when the fusion time interval has triggered
bool f_timeTrigger = ((imuSampleTime_ms - prevBetaStep_ms) >= frontend->betaAvg_ms);
// set true when use of synthetic sideslip fusion is necessary because we have limited sensor data or are dead reckoning position
bool f_required = !(use_compass() && useAirspeed() && ((imuSampleTime_ms - lastPosPassTime_ms) < frontend->posRetryTimeNoVel_ms));
// set true when sideslip fusion is feasible (requires zero sideslip assumption to be valid and use of wind states)
bool f_feasible = (assume_zero_sideslip() && !inhibitWindStates);
// use synthetic sideslip fusion if feasible, required and enough time has lapsed since the last fusion
if (f_feasible && f_required && f_timeTrigger) {
FuseSideslip();
prevBetaStep_ms = imuSampleTime_ms;
}
}
/*
* Fuse synthetic sideslip measurement of zero using explicit algebraic equations generated with Matlab symbolic toolbox.
* The script file used to generate these and other equations in this filter can be found here:
* https://github.com/priseborough/InertialNav/blob/master/derivations/RotationVectorAttitudeParameterisation/GenerateNavFilterEquations.m
*/
void NavEKF2_core::FuseSideslip()
{
// declarations
ftype q0;
ftype q1;
ftype q2;
ftype q3;
ftype vn;
ftype ve;
ftype vd;
ftype vwn;
ftype vwe;
const ftype R_BETA = 0.03f; // assume a sideslip angle RMS of ~10 deg
Vector10 SH_BETA;
Vector5 SK_BETA;
Vector3F vel_rel_wind;
Vector24 H_BETA;
ftype innovBeta;
// copy required states to local variable names
q0 = stateStruct.quat[0];
q1 = stateStruct.quat[1];
q2 = stateStruct.quat[2];
q3 = stateStruct.quat[3];
vn = stateStruct.velocity.x;
ve = stateStruct.velocity.y;
vd = stateStruct.velocity.z;
vwn = stateStruct.wind_vel.x;
vwe = stateStruct.wind_vel.y;
// calculate predicted wind relative velocity in NED
vel_rel_wind.x = vn - vwn;
vel_rel_wind.y = ve - vwe;
vel_rel_wind.z = vd;
// rotate into body axes
vel_rel_wind = prevTnb * vel_rel_wind;
// perform fusion of assumed sideslip = 0
if (vel_rel_wind.x > 5.0f)
{
// Calculate observation jacobians
SH_BETA[0] = (vn - vwn)*(sq(q0) + sq(q1) - sq(q2) - sq(q3)) - vd*(2*q0*q2 - 2*q1*q3) + (ve - vwe)*(2*q0*q3 + 2*q1*q2);
if (fabsF(SH_BETA[0]) <= 1e-9f) {
faultStatus.bad_sideslip = true;
return;
} else {
faultStatus.bad_sideslip = false;
}
SH_BETA[0] = (vn - vwn)*(sq(q0) + sq(q1) - sq(q2) - sq(q3)) - vd*(2*q0*q2 - 2*q1*q3) + (ve - vwe)*(2*q0*q3 + 2*q1*q2);
SH_BETA[1] = (ve - vwe)*(sq(q0) - sq(q1) + sq(q2) - sq(q3)) + vd*(2*q0*q1 + 2*q2*q3) - (vn - vwn)*(2*q0*q3 - 2*q1*q2);
SH_BETA[2] = vd*(sq(q0) - sq(q1) - sq(q2) + sq(q3)) - (ve - vwe)*(2*q0*q1 - 2*q2*q3) + (vn - vwn)*(2*q0*q2 + 2*q1*q3);
SH_BETA[3] = 1/sq(SH_BETA[0]);
SH_BETA[4] = (sq(q0) - sq(q1) + sq(q2) - sq(q3))/SH_BETA[0];
SH_BETA[5] = sq(q0) + sq(q1) - sq(q2) - sq(q3);
SH_BETA[6] = 1/SH_BETA[0];
SH_BETA[7] = 2*q0*q3;
SH_BETA[8] = SH_BETA[7] + 2*q1*q2;
SH_BETA[9] = SH_BETA[7] - 2*q1*q2;
H_BETA[0] = SH_BETA[2]*SH_BETA[6];
H_BETA[1] = SH_BETA[1]*SH_BETA[2]*SH_BETA[3];
H_BETA[2] = - sq(SH_BETA[1])*SH_BETA[3] - 1;
H_BETA[3] = - SH_BETA[6]*SH_BETA[9] - SH_BETA[1]*SH_BETA[3]*SH_BETA[5];
H_BETA[4] = SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8];
H_BETA[5] = SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3);
for (uint8_t i=6; i<=21; i++) {
H_BETA[i] = 0.0f;
}
H_BETA[22] = SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5];
H_BETA[23] = SH_BETA[1]*SH_BETA[3]*SH_BETA[8] - SH_BETA[4];
// Calculate Kalman gains
ftype temp = (R_BETA + (SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8])*(P[22][4]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][4]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][4]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][4]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][4]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][4]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][4]*SH_BETA[2]*SH_BETA[6] + P[1][4]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) - (SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8])*(P[22][23]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][23]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][23]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][23]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][23]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][23]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][23]*SH_BETA[2]*SH_BETA[6] + P[1][23]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) - (SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5])*(P[22][3]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][3]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][3]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][3]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][3]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][3]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][3]*SH_BETA[2]*SH_BETA[6] + P[1][3]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) + (SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5])*(P[22][22]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][22]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][22]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][22]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][22]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][22]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][22]*SH_BETA[2]*SH_BETA[6] + P[1][22]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) - (sq(SH_BETA[1])*SH_BETA[3] + 1)*(P[22][2]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][2]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][2]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][2]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][2]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][2]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][2]*SH_BETA[2]*SH_BETA[6] + P[1][2]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) + (SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3))*(P[22][5]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][5]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][5]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][5]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][5]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][5]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][5]*SH_BETA[2]*SH_BETA[6] + P[1][5]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) + SH_BETA[2]*SH_BETA[6]*(P[22][0]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][0]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][0]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][0]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][0]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][0]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][0]*SH_BETA[2]*SH_BETA[6] + P[1][0]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]) + SH_BETA[1]*SH_BETA[2]*SH_BETA[3]*(P[22][1]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[3][1]*(SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5]) - P[2][1]*(sq(SH_BETA[1])*SH_BETA[3] + 1) + P[5][1]*(SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3)) + P[4][1]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) - P[23][1]*(SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8]) + P[0][1]*SH_BETA[2]*SH_BETA[6] + P[1][1]*SH_BETA[1]*SH_BETA[2]*SH_BETA[3]));
if (temp >= R_BETA) {
SK_BETA[0] = 1.0f / temp;
faultStatus.bad_sideslip = false;
} else {
// the calculation is badly conditioned, so we cannot perform fusion on this step
// we reset the covariance matrix and try again next measurement
CovarianceInit();
faultStatus.bad_sideslip = true;
return;
}
SK_BETA[1] = SH_BETA[6]*(2*q0*q1 + 2*q2*q3) + SH_BETA[1]*SH_BETA[3]*(2*q0*q2 - 2*q1*q3);
SK_BETA[2] = SH_BETA[6]*SH_BETA[9] + SH_BETA[1]*SH_BETA[3]*SH_BETA[5];
SK_BETA[3] = SH_BETA[4] - SH_BETA[1]*SH_BETA[3]*SH_BETA[8];
SK_BETA[4] = sq(SH_BETA[1])*SH_BETA[3] + 1;
Kfusion[0] = SK_BETA[0]*(P[0][5]*SK_BETA[1] - P[0][2]*SK_BETA[4] - P[0][3]*SK_BETA[2] + P[0][4]*SK_BETA[3] + P[0][22]*SK_BETA[2] - P[0][23]*SK_BETA[3] + P[0][0]*SH_BETA[6]*SH_BETA[2] + P[0][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[1] = SK_BETA[0]*(P[1][5]*SK_BETA[1] - P[1][2]*SK_BETA[4] - P[1][3]*SK_BETA[2] + P[1][4]*SK_BETA[3] + P[1][22]*SK_BETA[2] - P[1][23]*SK_BETA[3] + P[1][0]*SH_BETA[6]*SH_BETA[2] + P[1][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[2] = SK_BETA[0]*(P[2][5]*SK_BETA[1] - P[2][2]*SK_BETA[4] - P[2][3]*SK_BETA[2] + P[2][4]*SK_BETA[3] + P[2][22]*SK_BETA[2] - P[2][23]*SK_BETA[3] + P[2][0]*SH_BETA[6]*SH_BETA[2] + P[2][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[3] = SK_BETA[0]*(P[3][5]*SK_BETA[1] - P[3][2]*SK_BETA[4] - P[3][3]*SK_BETA[2] + P[3][4]*SK_BETA[3] + P[3][22]*SK_BETA[2] - P[3][23]*SK_BETA[3] + P[3][0]*SH_BETA[6]*SH_BETA[2] + P[3][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[4] = SK_BETA[0]*(P[4][5]*SK_BETA[1] - P[4][2]*SK_BETA[4] - P[4][3]*SK_BETA[2] + P[4][4]*SK_BETA[3] + P[4][22]*SK_BETA[2] - P[4][23]*SK_BETA[3] + P[4][0]*SH_BETA[6]*SH_BETA[2] + P[4][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[5] = SK_BETA[0]*(P[5][5]*SK_BETA[1] - P[5][2]*SK_BETA[4] - P[5][3]*SK_BETA[2] + P[5][4]*SK_BETA[3] + P[5][22]*SK_BETA[2] - P[5][23]*SK_BETA[3] + P[5][0]*SH_BETA[6]*SH_BETA[2] + P[5][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[6] = SK_BETA[0]*(P[6][5]*SK_BETA[1] - P[6][2]*SK_BETA[4] - P[6][3]*SK_BETA[2] + P[6][4]*SK_BETA[3] + P[6][22]*SK_BETA[2] - P[6][23]*SK_BETA[3] + P[6][0]*SH_BETA[6]*SH_BETA[2] + P[6][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[7] = SK_BETA[0]*(P[7][5]*SK_BETA[1] - P[7][2]*SK_BETA[4] - P[7][3]*SK_BETA[2] + P[7][4]*SK_BETA[3] + P[7][22]*SK_BETA[2] - P[7][23]*SK_BETA[3] + P[7][0]*SH_BETA[6]*SH_BETA[2] + P[7][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[8] = SK_BETA[0]*(P[8][5]*SK_BETA[1] - P[8][2]*SK_BETA[4] - P[8][3]*SK_BETA[2] + P[8][4]*SK_BETA[3] + P[8][22]*SK_BETA[2] - P[8][23]*SK_BETA[3] + P[8][0]*SH_BETA[6]*SH_BETA[2] + P[8][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[9] = SK_BETA[0]*(P[9][5]*SK_BETA[1] - P[9][2]*SK_BETA[4] - P[9][3]*SK_BETA[2] + P[9][4]*SK_BETA[3] + P[9][22]*SK_BETA[2] - P[9][23]*SK_BETA[3] + P[9][0]*SH_BETA[6]*SH_BETA[2] + P[9][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[10] = SK_BETA[0]*(P[10][5]*SK_BETA[1] - P[10][2]*SK_BETA[4] - P[10][3]*SK_BETA[2] + P[10][4]*SK_BETA[3] + P[10][22]*SK_BETA[2] - P[10][23]*SK_BETA[3] + P[10][0]*SH_BETA[6]*SH_BETA[2] + P[10][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[11] = SK_BETA[0]*(P[11][5]*SK_BETA[1] - P[11][2]*SK_BETA[4] - P[11][3]*SK_BETA[2] + P[11][4]*SK_BETA[3] + P[11][22]*SK_BETA[2] - P[11][23]*SK_BETA[3] + P[11][0]*SH_BETA[6]*SH_BETA[2] + P[11][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[12] = SK_BETA[0]*(P[12][5]*SK_BETA[1] - P[12][2]*SK_BETA[4] - P[12][3]*SK_BETA[2] + P[12][4]*SK_BETA[3] + P[12][22]*SK_BETA[2] - P[12][23]*SK_BETA[3] + P[12][0]*SH_BETA[6]*SH_BETA[2] + P[12][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[13] = SK_BETA[0]*(P[13][5]*SK_BETA[1] - P[13][2]*SK_BETA[4] - P[13][3]*SK_BETA[2] + P[13][4]*SK_BETA[3] + P[13][22]*SK_BETA[2] - P[13][23]*SK_BETA[3] + P[13][0]*SH_BETA[6]*SH_BETA[2] + P[13][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[14] = SK_BETA[0]*(P[14][5]*SK_BETA[1] - P[14][2]*SK_BETA[4] - P[14][3]*SK_BETA[2] + P[14][4]*SK_BETA[3] + P[14][22]*SK_BETA[2] - P[14][23]*SK_BETA[3] + P[14][0]*SH_BETA[6]*SH_BETA[2] + P[14][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[15] = SK_BETA[0]*(P[15][5]*SK_BETA[1] - P[15][2]*SK_BETA[4] - P[15][3]*SK_BETA[2] + P[15][4]*SK_BETA[3] + P[15][22]*SK_BETA[2] - P[15][23]*SK_BETA[3] + P[15][0]*SH_BETA[6]*SH_BETA[2] + P[15][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[22] = SK_BETA[0]*(P[22][5]*SK_BETA[1] - P[22][2]*SK_BETA[4] - P[22][3]*SK_BETA[2] + P[22][4]*SK_BETA[3] + P[22][22]*SK_BETA[2] - P[22][23]*SK_BETA[3] + P[22][0]*SH_BETA[6]*SH_BETA[2] + P[22][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[23] = SK_BETA[0]*(P[23][5]*SK_BETA[1] - P[23][2]*SK_BETA[4] - P[23][3]*SK_BETA[2] + P[23][4]*SK_BETA[3] + P[23][22]*SK_BETA[2] - P[23][23]*SK_BETA[3] + P[23][0]*SH_BETA[6]*SH_BETA[2] + P[23][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
// zero Kalman gains to inhibit magnetic field state estimation
if (!inhibitMagStates) {
Kfusion[16] = SK_BETA[0]*(P[16][5]*SK_BETA[1] - P[16][2]*SK_BETA[4] - P[16][3]*SK_BETA[2] + P[16][4]*SK_BETA[3] + P[16][22]*SK_BETA[2] - P[16][23]*SK_BETA[3] + P[16][0]*SH_BETA[6]*SH_BETA[2] + P[16][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[17] = SK_BETA[0]*(P[17][5]*SK_BETA[1] - P[17][2]*SK_BETA[4] - P[17][3]*SK_BETA[2] + P[17][4]*SK_BETA[3] + P[17][22]*SK_BETA[2] - P[17][23]*SK_BETA[3] + P[17][0]*SH_BETA[6]*SH_BETA[2] + P[17][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[18] = SK_BETA[0]*(P[18][5]*SK_BETA[1] - P[18][2]*SK_BETA[4] - P[18][3]*SK_BETA[2] + P[18][4]*SK_BETA[3] + P[18][22]*SK_BETA[2] - P[18][23]*SK_BETA[3] + P[18][0]*SH_BETA[6]*SH_BETA[2] + P[18][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[19] = SK_BETA[0]*(P[19][5]*SK_BETA[1] - P[19][2]*SK_BETA[4] - P[19][3]*SK_BETA[2] + P[19][4]*SK_BETA[3] + P[19][22]*SK_BETA[2] - P[19][23]*SK_BETA[3] + P[19][0]*SH_BETA[6]*SH_BETA[2] + P[19][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[20] = SK_BETA[0]*(P[20][5]*SK_BETA[1] - P[20][2]*SK_BETA[4] - P[20][3]*SK_BETA[2] + P[20][4]*SK_BETA[3] + P[20][22]*SK_BETA[2] - P[20][23]*SK_BETA[3] + P[20][0]*SH_BETA[6]*SH_BETA[2] + P[20][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
Kfusion[21] = SK_BETA[0]*(P[21][5]*SK_BETA[1] - P[21][2]*SK_BETA[4] - P[21][3]*SK_BETA[2] + P[21][4]*SK_BETA[3] + P[21][22]*SK_BETA[2] - P[21][23]*SK_BETA[3] + P[21][0]*SH_BETA[6]*SH_BETA[2] + P[21][1]*SH_BETA[1]*SH_BETA[3]*SH_BETA[2]);
} else {
for (uint8_t i=16; i<=21; i++) {
Kfusion[i] = 0.0f;
}
}
// calculate predicted sideslip angle and innovation using small angle approximation
innovBeta = vel_rel_wind.y / vel_rel_wind.x;
// reject measurement if greater than 3-sigma inconsistency
if (innovBeta > 0.5f) {
return;
}
// zero the attitude error state - by definition it is assumed to be zero before each observation fusion
stateStruct.angErr.zero();
// correct the state vector
for (uint8_t j= 0; j<=stateIndexLim; j++) {
statesArray[j] = statesArray[j] - Kfusion[j] * innovBeta;
}
// the first 3 states represent the angular misalignment vector.
// This is used to correct the estimated quaternion on the current time step
stateStruct.quat.rotate(stateStruct.angErr);
// correct the covariance P = (I - K*H)*P
// take advantage of the empty columns in KH to reduce the
// number of operations
for (unsigned i = 0; i<=stateIndexLim; i++) {
for (unsigned j = 0; j<=5; j++) {
KH[i][j] = Kfusion[i] * H_BETA[j];
}
for (unsigned j = 6; j<=21; j++) {
KH[i][j] = 0.0f;
}
for (unsigned j = 22; j<=23; j++) {
KH[i][j] = Kfusion[i] * H_BETA[j];
}
}
for (unsigned j = 0; j<=stateIndexLim; j++) {
for (unsigned i = 0; i<=stateIndexLim; i++) {
ftype res = 0;
res += KH[i][0] * P[0][j];
res += KH[i][1] * P[1][j];
res += KH[i][2] * P[2][j];
res += KH[i][3] * P[3][j];
res += KH[i][4] * P[4][j];
res += KH[i][5] * P[5][j];
res += KH[i][22] * P[22][j];
res += KH[i][23] * P[23][j];
KHP[i][j] = res;
}
}
for (unsigned i = 0; i<=stateIndexLim; i++) {
for (unsigned j = 0; j<=stateIndexLim; j++) {
P[i][j] = P[i][j] - KHP[i][j];
}
}
}
// force the covariance matrix to be symmetrical and limit the variances to prevent ill-conditioning.
ForceSymmetry();
ConstrainVariances();
}
/********************************************************
* MISC FUNCTIONS *
********************************************************/
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