fly316/PX4-Autopilot
7
0
Fork 0
mirror of https://gitee.com/mirrors_PX4/PX4-Autopilot.git synced 2026-05-17 18:47:34 +08:00
Code Issues Packages Projects Releases Wiki Activity

EKF: Improve yaw alignment

Browse Source 
Uses best conditioned of 321 or 312 Euler sequence to calculate initial yaw angle.
Allows alignment of yaw angle using external vision data
This commit is contained in:
Paul Riseborough
2016-05-18 10:34:23 +10:00
parent 57b2a256f7
commit e4b2e9c93d
1 changed files with 104 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
EKF/ekf_helper.cpp
+104 -20
View File
@@ -302,35 +302,119 @@ void Ekf::alignOutputFilter()
// Reset heading and magnetic field states
bool Ekf::resetMagHeading(Vector3f &mag_init)
{
// If we don't a tilt estimate then we cannot initialise the yaw
if (!_control_status.flags.tilt_align) {
return false;
// update transformation matrix from body to world frame using the current estimate
_R_to_earth = quat_to_invrotmat(_state.quat_nominal);
// calculate the initial quaternion
// determine if a 321 or 312 Euler sequence is best
if (fabsf(_R_to_earth(2, 0)) < fabsf(_R_to_earth(2, 1))) {
// use a 321 sequence
// rotate the magnetometer measurement into earth frame
matrix::Euler<float> euler321(_state.quat_nominal);
// Set the yaw angle to zero and calculate the rotation matrix from body to earth frame
euler321(2) = 0.0f;
matrix::Dcm<float> R_to_earth(euler321);
// calculate the observed yaw angle
if (_params.fusion_mode & MASK_USE_EVYAW) {
// convert the observed quaternion to a rotation matrix
matrix::Dcm<float> R_to_earth_ev(_ev_sample_delayed.quat); // transformation matrix from body to world frame
// calculate the yaw angle for a 312 sequence
euler321(2) = atan2f(R_to_earth_ev(1, 0) , R_to_earth_ev(0, 0));
} else if (_params.mag_fusion_type <= MAG_FUSE_TYPE_3D) {
// rotate the magnetometer measurements into earth frame using a zero yaw angle
Vector3f mag_earth_pred = R_to_earth * _mag_sample_delayed.mag;
// the angle of the projection onto the horizontal gives the yaw angle
euler321(2) = -atan2f(mag_earth_pred(1), mag_earth_pred(0)) + _mag_declination;
} else {
// there is no yaw observation
return false;
}
// calculate initial quaternion states for the ekf
// we don't change the output attitude to avoid jumps
_state.quat_nominal = Quaternion(euler321);
} else {
// use a 312 sequence
// Calculate the 312 sequence euler angles that rotate from earth to body frame
// See http://www.atacolorado.com/eulersequences.doc
Vector3f euler312;
euler312(0) = atan2f(-_R_to_earth(0, 1) , _R_to_earth(1, 1)); // first rotation (yaw)
euler312(1) = asinf(_R_to_earth(2, 1)); // second rotation (roll)
euler312(2) = atan2f(-_R_to_earth(2, 0) , _R_to_earth(2, 2)); // third rotation (pitch)
// Set the first rotation (yaw) to zero and calculate the rotation matrix from body to earth frame
euler312(0) = 0.0f;
// Calculate the body to earth frame rotation matrix from the euler angles using a 312 rotation sequence
float c2 = cosf(euler312(2));
float s2 = sinf(euler312(2));
float s1 = sinf(euler312(1));
float c1 = cosf(euler312(1));
float s0 = sinf(euler312(0));
float c0 = cosf(euler312(0));
matrix::Dcm<float> R_to_earth;
R_to_earth(0, 0) = c0 * c2 - s0 * s1 * s2;
R_to_earth(1, 1) = c0 * c1;
R_to_earth(2, 2) = c2 * c1;
R_to_earth(0, 1) = -c1 * s0;
R_to_earth(0, 2) = s2 * c0 + c2 * s1 * s0;
R_to_earth(1, 0) = c2 * s0 + s2 * s1 * c0;
R_to_earth(1, 2) = s0 * s2 - s1 * c0 * c2;
R_to_earth(2, 0) = -s2 * c1;
R_to_earth(2, 1) = s1;
// calculate the observed yaw angle
if (_params.fusion_mode & MASK_USE_EVYAW) {
// convert the observed quaternion to a rotation matrix
matrix::Dcm<float> R_to_earth_ev(_ev_sample_delayed.quat); // transformation matrix from body to world frame
// calculate the yaw angle for a 312 sequence
euler312(0) = atan2f(-R_to_earth_ev(0, 1) , R_to_earth_ev(1, 1));
} else if (_params.mag_fusion_type <= MAG_FUSE_TYPE_3D) {
// rotate the magnetometer measurements into earth frame using a zero yaw angle
Vector3f mag_earth_pred = R_to_earth * _mag_sample_delayed.mag;
// the angle of the projection onto the horizontal gives the yaw angle
euler312(0) = -atan2f(mag_earth_pred(1), mag_earth_pred(0)) + _mag_declination;
} else {
// there is no yaw observation
return false;
}
// re-calculate the rotation matrix using the updated yaw angle
s0 = sinf(euler312(0));
c0 = cosf(euler312(0));
R_to_earth(0, 0) = c0 * c2 - s0 * s1 * s2;
R_to_earth(1, 1) = c0 * c1;
R_to_earth(2, 2) = c2 * c1;
R_to_earth(0, 1) = -c1 * s0;
R_to_earth(0, 2) = s2 * c0 + c2 * s1 * s0;
R_to_earth(1, 0) = c2 * s0 + s2 * s1 * c0;
R_to_earth(1, 2) = s0 * s2 - s1 * c0 * c2;
R_to_earth(2, 0) = -s2 * c1;
R_to_earth(2, 1) = s1;
// calculate initial quaternion states for the ekf
// we don't change the output attitude to avoid jumps
_state.quat_nominal = Quaternion(R_to_earth);
}
// get the roll, pitch, yaw estimates and set the yaw to zero
matrix::Quaternion<float> q(_state.quat_nominal(0), _state.quat_nominal(1), _state.quat_nominal(2),
_state.quat_nominal(3));
matrix::Euler<float> euler_init(q);
euler_init(2) = 0.0f;
// rotate the magnetometer measurements into earth axes
matrix::Dcm<float> R_to_earth_zeroyaw(euler_init);
Vector3f mag_ef_zeroyaw = R_to_earth_zeroyaw * mag_init;
euler_init(2) = _mag_declination - atan2f(mag_ef_zeroyaw(1), mag_ef_zeroyaw(0));
// calculate initial quaternion states for the ekf
// we don't change the output attitude to avoid jumps
_state.quat_nominal = Quaternion(euler_init);
// reset the quaternion variances because the yaw angle could have changed by a significant amount
// by setting them to zero we avoid 'kicks' in angle when 3-D fusion starts and the imu process noise
// will grow them again.
zeroRows(P, 0, 3);
zeroCols(P, 0, 3);
// update transformation matrix from body to world frame using the current estimate
_R_to_earth = quat_to_invrotmat(_state.quat_nominal);
// calculate initial earth magnetic field states
matrix::Dcm<float> R_to_earth(euler_init);
_state.mag_I = R_to_earth * mag_init;
_state.mag_I = _R_to_earth * mag_init;
// reset the corresponding rows and columns in the covariance matrix and set the variances on the magnetic field states to the measurement variance
zeroRows(P, 16, 21);