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EKF: Add function enabling yaw variance to be increased

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This commit is contained in:
Paul Riseborough
2019-01-31 09:53:57 -05:00
committed by Daniel Agar
parent bf1f3a224e
commit bce1b96d17
3 changed files with 44 additions and 8 deletions
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EKF/ekf_helper.cpp
+32
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@@ -1647,3 +1647,35 @@ void Ekf::get_ekf2ev_quaternion(float *quat)
quat[i] = quat_ekf2ev(i);
}
}
// Increase the yaw error variance of the quaternions
// Argument is additional yaw variance in rad**2
void Ekf::increaseQuatYawErrVariance(float yaw_variance)
{
// See DeriveYawResetEquations.m for derivation
// Intermediate variables
float SG[3];
SG[0] = sq(_state.quat_nominal(0)) - sq(_state.quat_nominal(1)) - sq(_state.quat_nominal(2)) + sq(_state.quat_nominal(3));
SG[1] = 2*_state.quat_nominal(0)*_state.quat_nominal(2) - 2*_state.quat_nominal(1)*_state.quat_nominal(3);
SG[2] = 2*_state.quat_nominal(0)*_state.quat_nominal(1) + 2*_state.quat_nominal(2)*_state.quat_nominal(3);
float SQ[4];
SQ[0] = 0.5f * ((_state.quat_nominal(1)*SG[0]) - (_state.quat_nominal(0)*SG[2]) + (_state.quat_nominal(3)*SG[1]));
SQ[1] = 0.5f * ((_state.quat_nominal(0)*SG[1]) - (_state.quat_nominal(2)*SG[0]) + (_state.quat_nominal(3)*SG[2]));
SQ[2] = 0.5f * ((_state.quat_nominal(3)*SG[0]) - (_state.quat_nominal(1)*SG[1]) + (_state.quat_nominal(2)*SG[2]));
SQ[3] = 0.5f * ((_state.quat_nominal(0)*SG[0]) + (_state.quat_nominal(1)*SG[2]) + (_state.quat_nominal(2)*SG[1]));
// Add covariances for additonal yaw uncertainty to existing covariances.
// This assumes that the additional yaw error is uncorrrelated to existing errors
P[0][0] += yaw_variance*sq(SQ[2]);
P[0][1] += yaw_variance*SQ[1]*SQ[2];
P[1][1] += yaw_variance*sq(SQ[1]);
P[0][2] += yaw_variance*SQ[0]*SQ[2];
P[1][2] += yaw_variance*SQ[0]*SQ[1];
P[2][2] += yaw_variance*sq(SQ[0]);
P[0][3] += yaw_variance*SQ[2]*SQ[3];
P[1][3] += yaw_variance*SQ[1]*SQ[3];
P[2][3] += yaw_variance*SQ[0]*SQ[3];
P[3][3] += yaw_variance*sq(SQ[3]);
}