mirror of https://github.com/ArduPilot/ardupilot
DCM: separate out the omega_yaw_P from omega_P
this cleans up the separation of drift rates and proportional correction from yaw source and accelerometers, allow the yaw to run at a different rate to the accel correction
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@ -104,7 +104,7 @@ AP_DCM::matrix_update(float _G_Dt)
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_omega_integ_corr = _gyro_vector + _omega_I;
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// Equation 16, adding proportional and integral correction terms
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_omega = _omega_integ_corr + _omega_P;
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_omega = _omega_integ_corr + _omega_P + _omega_yaw_P;
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// this is an expansion of the DCM matrix multiply (equation
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// 17), with known zero elements removed and the matrix
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@ -165,13 +165,12 @@ AP_DCM::matrix_reset(bool recover_eulers)
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}
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// reset the integration terms
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_omega_I.x = 0.0f;
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_omega_I.y = 0.0f;
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_omega_I.z = 0.0f;
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_omega_P = _omega_I;
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_omega_integ_corr = _omega_I;
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_omega_smoothed = _omega_I;
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_omega = _omega_I;
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_omega_I.zero();
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_omega_P.zero();
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_omega_yaw_P.zero();
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_omega_integ_corr.zero();
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_omega_smoothed.zero();
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_omega.zero();
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// if the caller wants us to try to recover to the current
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// attitude then calculate the dcm matrix from the current
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@ -316,6 +315,9 @@ AP_DCM::normalize(void)
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// gyro error. The _omega_P value is what pulls our attitude solution
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// back towards the reference vector quickly. The _omega_I term is an
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// attempt to learn the long term drift rate of the gyros.
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//
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// This function also updates _omega_yaw_P with a yaw correction term
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// from our yaw reference vector
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void
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AP_DCM::drift_correction(float deltat)
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{
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@ -357,31 +359,39 @@ AP_DCM::drift_correction(float deltat)
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accel.z = -sqrt(zsquared);
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}
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// calculate the error, in m/2^2, between the attitude
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// implied by the accelerometers and the attitude
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// in the current DCM matrix
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error = _dcm_matrix.c % accel;
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// error is in m/s^2 units
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// Limit max error to limit max omega_P and omega_I
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// error from the above is in m/s^2 units.
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// Limit max error to limit the effect of noisy values
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// on the algorithm. This limits the error to about 11
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// degrees
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error_norm = error.length();
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if (error_norm > 2) {
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error *= (2 / error_norm);
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}
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// scale the error for the time over which we are
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// applying it
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error *= deltat;
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// calculate the new proportional offset
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// we now want to calculate _omega_P and _omega_I. The
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// _omega_P value is what drags us quickly to the
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// accelerometer reading.
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_omega_P = error * _kp_roll_pitch;
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// we limit the change in the integrator to the
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// maximum gyro drift rate on each axis
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float drift_limit = ToRad(_gyro_drift_rate) * deltat / _ki_roll_pitch;
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error.x = constrain(error.x, -drift_limit, drift_limit);
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error.y = constrain(error.y, -drift_limit, drift_limit);
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error.z = constrain(error.z, -drift_limit, drift_limit);
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// the _omega_I is the long term accumulated gyro
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// error. This determines how much gyro drift we can
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// handle.
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Vector3f omega_I_delta = error * (_ki_roll_pitch * deltat);
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// update gyro drift estimate
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_omega_I += error * _ki_roll_pitch;
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// limit the slope of omega_I on each axis to
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// the maximum drift rate
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float drift_limit = _gyro_drift_limit * deltat;
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omega_I_delta.x = constrain(omega_I_delta.x, -drift_limit, drift_limit);
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omega_I_delta.y = constrain(omega_I_delta.y, -drift_limit, drift_limit);
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omega_I_delta.z = constrain(omega_I_delta.z, -drift_limit, drift_limit);
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_omega_I += omega_I_delta;
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}
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// these sums support the reporting of the DCM state via MAVLink
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@ -394,21 +404,23 @@ AP_DCM::drift_correction(float deltat)
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// reference vector. In between times we rely on the gyros for
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// yaw. Avoiding this calculation on every call to
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// update_DCM() saves a lot of time
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if (_compass && _compass->use_for_yaw() &&
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_compass->last_update != _compass_last_update) {
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if (_have_initial_yaw) {
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if (_compass && _compass->use_for_yaw()) {
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if (_compass->last_update != _compass_last_update) {
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yaw_deltat = 1.0e-6*(_compass->last_update - _compass_last_update);
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if (_have_initial_yaw && yaw_deltat < 2.0) {
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// Equation 23, Calculating YAW error
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// We make the gyro YAW drift correction based
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// on compass magnetic heading
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error_course = (_dcm_matrix.a.x * _compass->heading_y) - (_dcm_matrix.b.x * _compass->heading_x);
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yaw_deltat = 1.0e-6*(_compass->last_update - _compass_last_update);
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_compass_last_update = _compass->last_update;
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} else {
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// this is our first estimate of the yaw,
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// or the compass has come back online after
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// no readings for 2 seconds.
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//
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// construct a DCM matrix based on the current
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// roll/pitch and the compass heading, but
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// first ensure the compass heading has been
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// roll/pitch and the compass heading.
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// First ensure the compass heading has been
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// calculated
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_compass->calculate(_dcm_matrix);
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@ -418,17 +430,19 @@ AP_DCM::drift_correction(float deltat)
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_compass->null_offsets_enable();
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_have_initial_yaw = true;
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_compass_last_update = _compass->last_update;
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error_course = 0;
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}
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} else if (_gps && _gps->status() == GPS::GPS_OK &&
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_gps->last_fix_time != _gps_last_update) {
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}
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} else if (_gps && _gps->status() == GPS::GPS_OK) {
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if (_gps->last_fix_time != _gps_last_update) {
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// Use GPS Ground course to correct yaw gyro drift
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if (_gps->ground_speed >= GPS_SPEED_MIN) {
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if (_have_initial_yaw) {
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yaw_deltat = 1.0e-3*(_gps->last_fix_time - _gps_last_update);
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if (_have_initial_yaw && yaw_deltat < 2.0) {
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float course_over_ground_x = cos(ToRad(_gps->ground_course/100.0));
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float course_over_ground_y = sin(ToRad(_gps->ground_course/100.0));
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// Equation 23, Calculating YAW error
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error_course = (_dcm_matrix.a.x * course_over_ground_y) - (_dcm_matrix.b.x * course_over_ground_x);
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yaw_deltat = 1.0e-3*(_gps->last_fix_time - _gps_last_update);
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_gps_last_update = _gps->last_fix_time;
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} else {
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// when we first start moving, set the
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@ -461,28 +475,37 @@ AP_DCM::drift_correction(float deltat)
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_have_initial_yaw = false;
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}
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}
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}
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// see if there is any error in our heading relative to the
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// yaw reference. This will be zero most of the time, as we
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// only calculate it when we get new data from the yaw
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// reference source
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if (yaw_deltat == 0 || error_course == 0) {
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// nothing to do
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// we don't have a new reference heading. Slowly
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// decay the _omega_yaw_P to ensure that if we have
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// lost the yaw reference sensor completely we don't
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// keep using a stale offset
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_omega_yaw_P *= 0.97;
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return;
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}
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// ensure the course error is scaled from -PI to PI
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if (error_course > PI) {
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error_course -= 2*PI;
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} else if (error_course < -PI) {
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error_course += 2*PI;
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}
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// Equation 24, Applys the yaw correction to the XYZ rotation of the aircraft
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// this gives us an error in radians
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error = _dcm_matrix.c * error_course;
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// Adding yaw correction to proportional correction vector. We
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// allow the yaw reference source to affect all 3 components
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// of _omega_P as we need to be able to correctly hold a
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// of _omega_yaw_P as we need to be able to correctly hold a
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// heading when roll and pitch are non-zero
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_omega_P += error * _kp_yaw;
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// limit maximum gyro drift from yaw reference
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float drift_limit = ToRad(_gyro_drift_rate) * yaw_deltat / _ki_yaw;
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error.z = constrain(error.z, -drift_limit, drift_limit);
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_omega_yaw_P = error * _kp_yaw;
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// add yaw correction to integrator correction vector, but
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// only for the z gyro. We rely on the accelerometers for x
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@ -490,7 +513,13 @@ AP_DCM::drift_correction(float deltat)
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// x/y drift correction is too inaccurate, and can lead to
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// incorrect builups in the x/y drift. We rely on the
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// accelerometers to get the x/y components right
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_omega_I.z += error.z * _ki_yaw;
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float omega_Iz_delta = error.z * (_ki_yaw * yaw_deltat);
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// limit the slope of omega_I.z to the maximum gyro drift rate
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float drift_limit = _gyro_drift_limit * yaw_deltat;
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omega_Iz_delta = constrain(omega_Iz_delta, -drift_limit, drift_limit);
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_omega_I.z += omega_Iz_delta;
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// we keep the sum of yaw error for reporting via MAVLink.
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_error_yaw_sum += error_course;
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@ -25,10 +25,8 @@ class AP_DCM
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public:
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// Constructors
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AP_DCM(IMU *imu, GPS *&gps) :
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_kp_roll_pitch(18.0),
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_ki_roll_pitch(0.0006),
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_kp_yaw(9.0),
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_ki_yaw(0.003),
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_kp_roll_pitch(0.13),
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_kp_yaw(0.8),
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_gps(gps),
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_imu(imu),
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_dcm_matrix(1, 0, 0,
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@ -36,7 +34,16 @@ public:
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0, 0, 1),
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_health(1.),
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_toggle(0)
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{}
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{
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// base the ki values by the sensors maximum drift
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// rate. The APM2 has gyros which are much less drift
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// prone than the APM1, so we should have a lower ki,
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// which will make us less prone to increasing omegaI
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// incorrectly due to sensor noise
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_gyro_drift_limit = imu->get_gyro_drift_rate();
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_ki_roll_pitch = _gyro_drift_limit * 3;
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_ki_yaw = _gyro_drift_limit * 4;
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}
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// Accessors
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@ -46,7 +53,7 @@ public:
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Matrix3f get_dcm_transposed(void) {Matrix3f temp = _dcm_matrix; return temp.transpose();}
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// return the current drift correction integrator value
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Vector3f get_integrator(void) {return _omega_I; }
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Vector3f get_gyro_drift(void) {return _omega_I; }
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float get_health(void) {return _health;}
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void set_centripetal(bool b) {_centripetal = b;}
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@ -55,7 +62,7 @@ public:
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// Methods
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void update_DCM(uint8_t drift_correction_frequency=1);
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void update_DCM_fast(void);
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void update(void) { update_DCM(); }
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void matrix_reset(bool recover_eulers = false);
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long roll_sensor; // Degrees * 100
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@ -70,18 +77,6 @@ public:
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uint8_t renorm_range_count;
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uint8_t renorm_blowup_count;
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float kp_roll_pitch() { return _kp_roll_pitch; }
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void kp_roll_pitch(float v) { _kp_roll_pitch = v; }
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float ki_roll_pitch() { return _ki_roll_pitch; }
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void ki_roll_pitch(float v) { _ki_roll_pitch = v; }
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float kp_yaw() { return _kp_yaw; }
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void kp_yaw(float v) { _kp_yaw = v; }
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float ki_yaw() { return _ki_yaw; }
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void ki_yaw(float v) { _ki_yaw = v; }
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// status reporting
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float get_accel_weight(void);
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float get_renorm_val(void);
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@ -93,6 +88,7 @@ private:
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float _ki_roll_pitch;
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float _kp_yaw;
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float _ki_yaw;
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float _gyro_drift_limit; // radians/s/s
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bool _have_initial_yaw;
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// Methods
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@ -106,9 +102,6 @@ private:
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void drift_correction(float deltat);
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void euler_angles(void);
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// max rate of gyro drift in degrees/s/s
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static const float _gyro_drift_rate = 0.04;
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// members
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Compass * _compass;
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@ -127,7 +120,8 @@ private:
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Vector3f _accel_sum;
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Vector3f _gyro_vector; // Store the gyros turn rate in a vector
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Vector3f _omega_P; // Omega Proportional correction
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Vector3f _omega_P; // accel Omega Proportional correction
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Vector3f _omega_yaw_P; // yaw Omega Proportional correction
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Vector3f _omega_I; // Omega Integrator correction
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Vector3f _omega_integ_corr; // Partially corrected Gyro_Vector data - used for centrepetal correction
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Vector3f _omega; // Corrected Gyro_Vector data
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