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Quaternion: code cleanups and added comments

This commit is contained in:
Andrew Tridgell 2012-03-07 17:19:51 +11:00
parent f405477875
commit 982712d58f
1 changed files with 20 additions and 49 deletions
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69
libraries/AP_Quaternion/AP_Quaternion.cpp
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@ -307,7 +307,9 @@ void AP_Quaternion::update_MARG(float deltat, Vector3f &gyro, Vector3f &accel, V
}
// Function to compute one quaternion iteration including magnetometer
// Function to update our gyro_bias drift estimate using the accelerometer
// and magnetometer. This is a cut-down version of update_MARG(), but
// without the quaternion update.
void AP_Quaternion::update_drift(float deltat, Vector3f &gyro, Vector3f &accel, Vector3f &mag)
{
// local system variables
@ -458,11 +460,6 @@ void AP_Quaternion::update(void)
Vector3f gyro, accel;
float deltat;
#ifdef DESKTOP_BUILD
Quaternion q_saved = q;
Vector3f bias_saved = gyro_bias;
#endif
_imu->update();
deltat = _imu->get_delta_time();
@ -513,11 +510,21 @@ void AP_Quaternion::update(void)
accel.z += (gyro.y - gyro_bias.y) * veloc;
}
#if 1
_gyro_sum += gyro;
_accel_sum += accel;
_sum_count++;
/*
The full Madgwick quaternion 'MARG' system assumes you get
gyro, accel and magnetometer updates at the same rate. On
APM we get them at very different rates, and re-calculating
our drift due to the magnetometer in the fast loop is very
wasteful of CPU.
Instead, we only update the gyro_bias vector when we get a
new magnetometer point, and use the much simpler
update_IMU() as the main quaternion update function.
*/
if (_compass != NULL && _compass->use_for_yaw() &&
_compass->last_update != _compass_last_update &&
_sum_count != 0) {
@ -533,64 +540,28 @@ void AP_Quaternion::update(void)
_compass_last_update = _compass->last_update;
}
// step the quaternion solution
// step the quaternion solution using just gyros and accels
gyro -= gyro_bias;
update_IMU(deltat, gyro, accel);
#else
if (_compass != NULL && _compass->use_for_yaw()) {
// use new compass sample for drift correction
Vector3f mag = Vector3f(_compass->mag_x, _compass->mag_y, - _compass->mag_z);
update_MARG(deltat, gyro, accel, mag);
} else {
// step the quaternion without drift correction
gyro -= gyro_bias;
_gyro_sum += gyro;
_accel_sum += accel;
_sum_count++;
update_IMU(deltat, gyro, accel);
}
#endif
#ifdef DESKTOP_BUILD
if (q.is_nan()) {
SITL_debug("QUAT NAN: deltat=%f roll=%f pitch=%f yaw=%f q0=[%f %f %f %f] q=[%f %f %f %f] a=[%f %f %f] g=(%f %f %f)\n",
SITL_debug("QUAT NAN: deltat=%f roll=%f pitch=%f yaw=%f q=[%f %f %f %f] a=[%f %f %f] g=(%f %f %f)\n",
deltat, roll, pitch, yaw,
q_saved.q1, q_saved.q2, q_saved.q3, q_saved.q4,
q.q1, q.q2, q.q3, q.q4,
accel.x, accel.y, accel.z,
gyro.x, gyro.y, gyro.z);
q = q_saved;
gyro_bias = bias_saved;
update_IMU(deltat, gyro, accel);
}
#endif
// keep the corrected gyro for reporting
_gyro_corrected = gyro;
// compute the Eulers
float test = (SEq_1*SEq_3 - SEq_4*SEq_2);
const float singularity = 0.499; // 86.3 degrees?
if (test > singularity) {
// singularity at south pole
// this one is ok..
yaw = 2.0 * atan2(SEq_4, SEq_1);
pitch = ToRad(-90.0);
roll = 0.0;
} else if (test < -singularity) {
// singularity at north pole
// this one is invalid :( .. fix it.
yaw = -2.0 * atan2(SEq_4, SEq_1);
pitch = ToRad(90.0);
roll = 0.0;
} else {
roll = -(atan2(2.0*(SEq_1*SEq_2 + SEq_3*SEq_4),
1 - 2.0*(SEq_2*SEq_2 + SEq_3*SEq_3)));
pitch = -safe_asin(2.0*test);
yaw = atan2(2.0*(SEq_1*SEq_4 + SEq_2*SEq_3),
1 - 2.0*(SEq_3*SEq_3 + SEq_4*SEq_4));
}
// calculate our euler angles for high level control and navigation
euler_from_quaternion(q, &roll, &pitch, &yaw);
// the code above assumes zero magnetic declination, so offset
// the yaw here
if (_compass != NULL) {
yaw += _compass->get_declination();
}