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AP_NavEKF3: Improve protection for badly conditioned dVel bias covariances 

If variance falls below desired minimum, set state noise to a larger value.
If variance drops below safe value, set to desired minimum and reset off-diagonals to zero.
This commit is contained in:
priseborough 2017-05-26 17:05:38 +10:00 committed by Francisco Ferreira
parent bf963f8b65
commit e58ba8044d
1 changed files with 36 additions and 4 deletions
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40
libraries/AP_NavEKF3/AP_NavEKF3_core.cpp
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@ -864,9 +864,14 @@ void NavEKF3_core::CovariancePrediction()
if (!inhibitDelVelBiasStates) {
float dVelBiasVar = sq(sq(dt) * constrain_float(frontend->_accelBiasProcessNoise, 0.0f, 1.0f));
for (uint8_t i=3; i<=4; i++) processNoiseVariance[i] = dVelBiasVar;
if (!expectGndEffectTakeoff) {
processNoiseVariance[5] = dVelBiasVar;
for (uint8_t i=3; i<=5; i++) {
uint8_t stateIndex = i + 10;
if (P[stateIndex][stateIndex] > 1E-8f) {
processNoiseVariance[i] = dVelBiasVar;
} else {
// increase the process noise variance up to a maximum of 100 x the nominal value if the variance is below the target minimum
processNoiseVariance[i] = 10.0f * dVelBiasVar * (1e-8f / fmaxf(P[stateIndex][stateIndex],1e-9f));
}
}
}
@ -1416,7 +1421,34 @@ void NavEKF3_core::ConstrainVariances()
}
if (!inhibitDelVelBiasStates) {
for (uint8_t i=13; i<=15; i++) P[i][i] = constrain_float(P[i][i],1e-9f,sq(10.0f * dtEkfAvg));
// limit delta velocity bias state variance levels and request a reset if below the safe minimum
bool resetRequired = false;
for (uint8_t i=13; i<=15; i++) {
if (P[i][i] > 1E-9f) {
// variance is above the safe minimum
P[i][i] = fminf(P[i][i], sq(10.0f * dtEkfAvg));
} else {
// Set the variance to the target minimum and request a covariance reset
P[i][i] = 1E-8f;
resetRequired = true;
}
}
// If any one axis is below the safe minimum, all delta velocity covariance terms must be reset to zero
if (resetRequired) {
float delVelBiasVar[3];
// store all delta velocity bias variances
for (uint8_t i=0; i<=2; i++) {
delVelBiasVar[i] = P[i+13][i+13];
}
// reset all delta velocity bias covariances
zeroCols(P,13,15);
// restore all delta velocity bias variances
for (uint8_t i=0; i<=2; i++) {
P[i+13][i+13] = delVelBiasVar[i];
}
}
} else {
zeroCols(P,13,15);
zeroRows(P,13,15);