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AP_NAvEKF: Prevent failure due to magnetometer fusion numerical errors 

If a badly conditioned covariance matrix causes negative innovation variances, then the filter will diverge. The previous approach of increasing process noise was not effective in some cases, so a hard reset of the covariance matrix has been adopted to guarantee recovery.
This fixes a numerical error observed using the replay on flight log which had significant periods of compass rejection.
This commit is contained in:
Paul Riseborough 2015-07-02 18:07:22 +10:00
parent bd27fed241
commit 4fb7beba4b
1 changed files with 6 additions and 6 deletions
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12
libraries/AP_NavEKF/AP_NavEKF.cpp
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@ -2402,8 +2402,8 @@ void NavEKF::FuseMagnetometer()
faultStatus.bad_xmag = false;
} else {
// the calculation is badly conditioned, so we cannot perform fusion on this step
// we increase the state variances and try again next time
P[19][19] += 0.1f*R_MAG;
// we reset the covariance matrix and try again next measurement
CovarianceInit();
obsIndex = 1;
faultStatus.bad_xmag = true;
return;
@ -2481,8 +2481,8 @@ void NavEKF::FuseMagnetometer()
faultStatus.bad_ymag = false;
} else {
// the calculation is badly conditioned, so we cannot perform fusion on this step
// we increase the state variances and try again next time
P[20][20] += 0.1f*R_MAG;
// we reset the covariance matrix and try again next measurement
CovarianceInit();
obsIndex = 2;
faultStatus.bad_ymag = true;
return;
@ -2556,8 +2556,8 @@ void NavEKF::FuseMagnetometer()
faultStatus.bad_zmag = false;
} else {
// the calculation is badly conditioned, so we cannot perform fusion on this step
// we increase the state variances and try again next time
P[21][21] += 0.1f*R_MAG;
// we reset the covariance matrix and try again next measurement
CovarianceInit();
obsIndex = 3;
faultStatus.bad_zmag = true;
return;