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EKF: Improve protection against bad magnetometer fusion

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This commit is contained in:
Paul Riseborough 2016-05-07 14:23:20 +10:00
parent 310bd97080
commit c8d95586e7
1 changed files with 106 additions and 25 deletions
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131
EKF/mag_fusion.cpp
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@ -296,9 +296,6 @@ void Ekf::fuseMag()
return;
}
// correct states
fuse(Kfusion, _mag_innov[index]);
// apply covariance correction via P_new = (I -K*H)*P
// first calculate expression for KHP
// then calculate P - KHP
@ -329,14 +326,49 @@ void Ekf::fuseMag()
}
}
for (unsigned row = 0; row < _k_num_states; row++) {
for (unsigned column = 0; column < _k_num_states; column++) {
P[row][column] -= KHP[row][column];
// if the covariance correction will result in a negative variance, then
// the covariance marix is unhealthy and must be corrected
bool healthy = true;
_fault_status.bad_mag_x = false;
_fault_status.bad_mag_y = false;
_fault_status.bad_mag_z = false;
for (int i = 0; i < _k_num_states; i++) {
if (P[i][i] < KHP[i][i]) {
// zero rows and columns
zeroRows(P,i,i);
zeroCols(P,i,i);
//flag as unhealthy
healthy = false;
// update individual measurement health status
if (index == 0) {
_fault_status.bad_mag_x = true;
} else if (index == 1) {
_fault_status.bad_mag_y = true;
} else if (index == 2) {
_fault_status.bad_mag_z = true;
}
}
}
makeSymmetrical();
limitCov();
// only apply covariance and state corrrections if healthy
if (healthy) {
// apply the covariance corrections
for (unsigned row = 0; row < _k_num_states; row++) {
for (unsigned column = 0; column < _k_num_states; column++) {
P[row][column] = P[row][column] - KHP[row][column];
}
}
// correct the covariance marix for gross errors
makeSymmetrical();
limitCov();
// apply the state corrections
fuse(Kfusion, _mag_innov[index]);
}
}
}
@ -557,9 +589,6 @@ void Ekf::fuseHeading()
_mag_healthy = true;
}
// update the states
fuse(Kfusion, _heading_innov);
// apply covariance correction via P_new = (I -K*H)*P
// first calculate expression for KHP
// then calculate P - KHP
@ -579,14 +608,42 @@ void Ekf::fuseHeading()
}
}
for (unsigned row = 0; row < _k_num_states; row++) {
for (unsigned column = 0; column < _k_num_states; column++) {
P[row][column] -= KHP[row][column];
// if the covariance correction will result in a negative variance, then
// the covariance marix is unhealthy and must be corrected
bool healthy = true;
_fault_status.bad_mag_hdg = false;
for (int i = 0; i < _k_num_states; i++) {
if (P[i][i] < KHP[i][i]) {
// zero rows and columns
zeroRows(P,i,i);
zeroCols(P,i,i);
//flag as unhealthy
healthy = false;
// update individual measurement health status
_fault_status.bad_mag_hdg = true;
}
}
makeSymmetrical();
limitCov();
// only apply covariance and state corrrections if healthy
if (healthy) {
// apply the covariance corrections
for (unsigned row = 0; row < _k_num_states; row++) {
for (unsigned column = 0; column < _k_num_states; column++) {
P[row][column] = P[row][column] - KHP[row][column];
}
}
// correct the covariance marix for gross errors
makeSymmetrical();
limitCov();
// apply the state corrections
fuse(Kfusion, _heading_innov);
}
}
void Ekf::fuseDeclination()
@ -668,9 +725,6 @@ void Ekf::fuseDeclination()
float innovation = atan2f(magE , magN) - _mag_declination;
innovation = math::constrain(innovation, -0.5f, 0.5f);
// perform the state correction
fuse(Kfusion, innovation);
// apply covariance correction via P_new = (I -K*H)*P
// first calculate expression for KHP
// then calculate P - KHP
@ -689,13 +743,40 @@ void Ekf::fuseDeclination()
}
}
for (unsigned row = 0; row < _k_num_states; row++) {
for (unsigned column = 0; column < _k_num_states; column++) {
P[row][column] -= KHP[row][column];
// if the covariance correction will result in a negative variance, then
// the covariance marix is unhealthy and must be corrected
bool healthy = true;
_fault_status.bad_mag_decl = false;
for (int i = 0; i < _k_num_states; i++) {
if (P[i][i] < KHP[i][i]) {
// zero rows and columns
zeroRows(P,i,i);
zeroCols(P,i,i);
//flag as unhealthy
healthy = false;
// update individual measurement health status
_fault_status.bad_mag_decl = true;
}
}
// force the covariance matrix to be symmetrical and don't allow the variances to be negative.
makeSymmetrical();
limitCov();
// only apply covariance and state corrrections if healthy
if (healthy) {
// apply the covariance corrections
for (unsigned row = 0; row < _k_num_states; row++) {
for (unsigned column = 0; column < _k_num_states; column++) {
P[row][column] = P[row][column] - KHP[row][column];
}
}
// correct the covariance marix for gross errors
makeSymmetrical();
limitCov();
// apply the state corrections
fuse(Kfusion, innovation);
}
}