mirror of https://github.com/ArduPilot/ardupilot
AHRS: adapt the quaternion library to AHRS
This commit is contained in:
Andrew Tridgell
parent
2d12bdb412
commit
fe63e79416
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@ -1,5 +1,5 @@
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/*
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AP_Quaternion code, based on quaternion code from Jeb Madgwick
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AP_AHRS_Quaternion code, based on quaternion code from Jeb Madgwick
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See http://www.x-io.co.uk/res/doc/madgwick_internal_report.pdf
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@ -13,24 +13,7 @@
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version.
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*/
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#include <FastSerial.h>
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#include <AP_Quaternion.h>
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#define ToRad(x) (x*0.01745329252) // *pi/180
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#define ToDeg(x) (x*57.2957795131) // *180/pi
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// this is the speed in cm/s above which we first get a yaw lock with
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// the GPS
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#define GPS_SPEED_MIN 300
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// this is the speed in cm/s at which we stop using drift correction
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// from the GPS and wait for the ground speed to get above GPS_SPEED_MIN
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#define GPS_SPEED_RESET 100
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void
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AP_Quaternion::set_compass(Compass *compass)
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{
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_compass = compass;
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}
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#include <AP_AHRS.h>
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// to keep the code as close to the original as possible, we use these
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// macros for quaternion access
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@ -40,7 +23,7 @@ AP_Quaternion::set_compass(Compass *compass)
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#define SEq_4 q.q4
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// Function to compute one quaternion iteration without magnetometer
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void AP_Quaternion::update_IMU(float deltat, Vector3f &gyro, Vector3f &accel)
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void AP_AHRS_Quaternion::update_IMU(float deltat, Vector3f &gyro, Vector3f &accel)
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{
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// Local system variables
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float norm; // vector norm
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@ -134,7 +117,7 @@ void AP_Quaternion::update_IMU(float deltat, Vector3f &gyro, Vector3f &accel)
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// Function to compute one quaternion iteration including magnetometer
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void AP_Quaternion::update_MARG(float deltat, Vector3f &gyro, Vector3f &accel, Vector3f &mag)
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void AP_AHRS_Quaternion::update_MARG(float deltat, Vector3f &gyro, Vector3f &accel, Vector3f &mag)
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{
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// local system variables
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float norm; // vector norm
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@ -253,7 +236,7 @@ void AP_Quaternion::update_MARG(float deltat, Vector3f &gyro, Vector3f &accel, V
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// don't allow the drift rate to be exceeded. This prevents a
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// sudden drift change coming from a outage in the compass
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float max_change = gyroMeasDrift * deltat;
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float max_change = _gyro_drift_limit * deltat;
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drift_delta.x = constrain(drift_delta.x, -max_change, max_change);
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drift_delta.y = constrain(drift_delta.y, -max_change, max_change);
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drift_delta.z = constrain(drift_delta.z, -max_change, max_change);
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@ -308,161 +291,8 @@ void AP_Quaternion::update_MARG(float deltat, Vector3f &gyro, Vector3f &accel, V
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}
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// Function to update our gyro_bias drift estimate using the accelerometer
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// and magnetometer. This is a cut-down version of update_MARG(), but
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// without the quaternion update.
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void AP_Quaternion::update_drift(float deltat, Vector3f &mag)
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{
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// local system variables
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float norm; // vector norm
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float f_4, f_5, f_6; // objective function elements
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float J_11or24, J_12or23, J_13or22, J_14or21, J_32, J_33, // objective function Jacobian elements
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J_41, J_42, J_43, J_44, J_51, J_52, J_53, J_54, J_61, J_62, J_63, J_64; //
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float SEqHatDot_1, SEqHatDot_2, SEqHatDot_3, SEqHatDot_4; // estimated direction of the gyroscope error
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// computed flux in the earth frame
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Vector3f flux;
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// estimated direction of the gyroscope error (radians)
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Vector3f w_err;
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// normalise the magnetometer measurement
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mag.normalize();
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if (mag.is_inf()) {
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// discard this data point
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renorm_range_count++;
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return;
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}
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// auxiliary variables to avoid repeated calculations
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float twoSEq_1 = 2.0f * SEq_1;
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float twoSEq_2 = 2.0f * SEq_2;
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float twoSEq_3 = 2.0f * SEq_3;
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float twoSEq_4 = 2.0f * SEq_4;
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float twob_x = 2.0f * b_x;
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float twob_z = 2.0f * b_z;
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float twob_xSEq_1 = 2.0f * b_x * SEq_1;
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float twob_xSEq_2 = 2.0f * b_x * SEq_2;
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float twob_xSEq_3 = 2.0f * b_x * SEq_3;
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float twob_xSEq_4 = 2.0f * b_x * SEq_4;
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float twob_zSEq_1 = 2.0f * b_z * SEq_1;
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float twob_zSEq_2 = 2.0f * b_z * SEq_2;
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float twob_zSEq_3 = 2.0f * b_z * SEq_3;
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float twob_zSEq_4 = 2.0f * b_z * SEq_4;
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float SEq_1SEq_2;
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float SEq_1SEq_3 = SEq_1 * SEq_3;
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float SEq_1SEq_4;
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float SEq_2SEq_3;
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float SEq_2SEq_4 = SEq_2 * SEq_4;
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float SEq_3SEq_4;
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Vector3f twom = mag * 2.0;
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// compute the objective function and Jacobian
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f_4 = twob_x * (0.5f - SEq_3 * SEq_3 - SEq_4 * SEq_4) + twob_z * (SEq_2SEq_4 - SEq_1SEq_3) - mag.x;
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f_5 = twob_x * (SEq_2 * SEq_3 - SEq_1 * SEq_4) + twob_z * (SEq_1 * SEq_2 + SEq_3 * SEq_4) - mag.y;
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f_6 = twob_x * (SEq_1SEq_3 + SEq_2SEq_4) + twob_z * (0.5f - SEq_2 * SEq_2 - SEq_3 * SEq_3) - mag.z;
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J_11or24 = twoSEq_3; // J_11 negated in matrix multiplication
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J_12or23 = 2.0f * SEq_4;
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J_13or22 = twoSEq_1; // J_12 negated in matrix multiplication
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J_14or21 = twoSEq_2;
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J_32 = 2.0f * J_14or21; // negated in matrix multiplication
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J_33 = 2.0f * J_11or24; // negated in matrix multiplication
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J_41 = twob_zSEq_3; // negated in matrix multiplication
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J_42 = twob_zSEq_4;
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J_43 = 2.0f * twob_xSEq_3 + twob_zSEq_1; // negated in matrix multiplication
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J_44 = 2.0f * twob_xSEq_4 - twob_zSEq_2; // negated in matrix multiplication
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J_51 = twob_xSEq_4 - twob_zSEq_2; // negated in matrix multiplication
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J_52 = twob_xSEq_3 + twob_zSEq_1;
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J_53 = twob_xSEq_2 + twob_zSEq_4;
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J_54 = twob_xSEq_1 - twob_zSEq_3; // negated in matrix multiplication
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J_61 = twob_xSEq_3;
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J_62 = twob_xSEq_4 - 2.0f * twob_zSEq_2;
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J_63 = twob_xSEq_1 - 2.0f * twob_zSEq_3;
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J_64 = twob_xSEq_2;
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// compute the gradient (matrix multiplication)
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SEqHatDot_1 = - J_41 * f_4 - J_51 * f_5 + J_61 * f_6;
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SEqHatDot_2 = + J_42 * f_4 + J_52 * f_5 + J_62 * f_6;
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SEqHatDot_3 = - J_43 * f_4 + J_53 * f_5 + J_63 * f_6;
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SEqHatDot_4 = - J_44 * f_4 - J_54 * f_5 + J_64 * f_6;
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// normalise the gradient to estimate direction of the gyroscope error
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norm = 1.0 / safe_sqrt(SEqHatDot_1 * SEqHatDot_1 + SEqHatDot_2 * SEqHatDot_2 + SEqHatDot_3 * SEqHatDot_3 + SEqHatDot_4 * SEqHatDot_4);
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if (isinf(norm)) {
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// discard this data point
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renorm_range_count++;
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return;
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}
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SEqHatDot_1 *= norm;
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SEqHatDot_2 *= norm;
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SEqHatDot_3 *= norm;
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SEqHatDot_4 *= norm;
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// compute angular estimated direction of the gyroscope error
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w_err.x = twoSEq_1 * SEqHatDot_2 - twoSEq_2 * SEqHatDot_1 - twoSEq_3 * SEqHatDot_4 + twoSEq_4 * SEqHatDot_3;
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w_err.y = twoSEq_1 * SEqHatDot_3 + twoSEq_2 * SEqHatDot_4 - twoSEq_3 * SEqHatDot_1 - twoSEq_4 * SEqHatDot_2;
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w_err.z = twoSEq_1 * SEqHatDot_4 - twoSEq_2 * SEqHatDot_3 + twoSEq_3 * SEqHatDot_2 - twoSEq_4 * SEqHatDot_1;
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// keep track of the error rates
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_error_rp_sum += 0.5*(fabs(w_err.x) + fabs(w_err.y));
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_error_yaw_sum += fabs(w_err.z);
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_error_rp_count++;
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_error_yaw_count++;
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// compute the gyroscope bias delta
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Vector3f drift_delta = w_err * (deltat * zeta);
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// don't allow the drift rate to be exceeded. This prevents a
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// sudden drift change coming from a outage in the compass
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float max_change = gyroMeasDrift * deltat;
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drift_delta.x = constrain(drift_delta.x, -max_change, max_change);
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drift_delta.y = constrain(drift_delta.y, -max_change, max_change);
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drift_delta.z = constrain(drift_delta.z, -max_change, max_change);
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gyro_bias += drift_delta;
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// compute then integrate the estimated quaternion rate
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SEq_1 -= (beta * SEqHatDot_1) * deltat;
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SEq_2 -= (beta * SEqHatDot_2) * deltat;
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SEq_3 -= (beta * SEqHatDot_3) * deltat;
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SEq_4 -= (beta * SEqHatDot_4) * deltat;
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// normalise quaternion
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norm = 1.0/safe_sqrt(SEq_1 * SEq_1 + SEq_2 * SEq_2 + SEq_3 * SEq_3 + SEq_4 * SEq_4);
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if (isinf(norm)) {
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// our quaternion is bad! Reset based on roll/pitch/yaw
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// and hope for the best ...
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renorm_blowup_count++;
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_compass->null_offsets_disable();
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q.from_euler(roll, pitch, yaw);
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_compass->null_offsets_disable();
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return;
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}
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SEq_1 *= norm;
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SEq_2 *= norm;
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SEq_3 *= norm;
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SEq_4 *= norm;
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// compute flux in the earth frame
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// recompute axulirary variables
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SEq_1SEq_2 = SEq_1 * SEq_2;
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SEq_1SEq_3 = SEq_1 * SEq_3;
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SEq_1SEq_4 = SEq_1 * SEq_4;
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SEq_3SEq_4 = SEq_3 * SEq_4;
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SEq_2SEq_3 = SEq_2 * SEq_3;
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SEq_2SEq_4 = SEq_2 * SEq_4;
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flux.x = twom.x * (0.5f - SEq_3 * SEq_3 - SEq_4 * SEq_4) + twom.y * (SEq_2SEq_3 - SEq_1SEq_4) + twom.z * (SEq_2SEq_4 + SEq_1SEq_3);
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flux.y = twom.x * (SEq_2SEq_3 + SEq_1SEq_4) + twom.y * (0.5f - SEq_2 * SEq_2 - SEq_4 * SEq_4) + twom.z * (SEq_3SEq_4 - SEq_1SEq_2);
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flux.z = twom.x * (SEq_2SEq_4 - SEq_1SEq_3) + twom.y * (SEq_3SEq_4 + SEq_1SEq_2) + twom.z * (0.5f - SEq_2 * SEq_2 - SEq_3 * SEq_3);
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// normalise the flux vector to have only components in the x and z
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b_x = sqrt((flux.x * flux.x) + (flux.y * flux.y));
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b_z = flux.z;
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}
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// Function to compute one quaternion iteration
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void AP_Quaternion::update(void)
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void AP_AHRS_Quaternion::update(void)
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{
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Vector3f gyro, accel;
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float deltat;
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@ -518,41 +348,14 @@ void AP_Quaternion::update(void)
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accel.z += (gyro.y - gyro_bias.y) * veloc;
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}
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#define SEPARATE_DRIFT 0
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#if SEPARATE_DRIFT
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/*
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The full Madgwick quaternion 'MARG' system assumes you get
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gyro, accel and magnetometer updates at the same rate. On
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APM we get them at very different rates, and re-calculating
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our drift due to the magnetometer in the fast loop is very
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wasteful of CPU.
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Instead, we only update the gyro_bias vector when we get a
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new magnetometer point, and use the much simpler
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update_IMU() as the main quaternion update function.
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*/
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_gyro_sum += gyro;
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_accel_sum += accel;
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_sum_count++;
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if (_compass != NULL && _compass->use_for_yaw() &&
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_compass->last_update != _compass_last_update &&
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_sum_count != 0) {
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// use new compass sample for drift correction
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float mag_deltat = 1.0e-6*(_compass->last_update - _compass_last_update);
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if (_compass != NULL && _compass->use_for_yaw()) {
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Vector3f mag = Vector3f(_compass->mag_x, _compass->mag_y, - _compass->mag_z);
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_sum_count = 0;
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update_drift(mag_deltat, mag);
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_compass_last_update = _compass->last_update;
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}
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update_MARG(deltat, gyro, accel, mag);
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} else {
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// step the quaternion solution using just gyros and accels
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gyro -= gyro_bias;
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update_IMU(deltat, gyro, accel);
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#else
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Vector3f mag = Vector3f(_compass->mag_x, _compass->mag_y, - _compass->mag_z);
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update_MARG(deltat, gyro, accel, mag);
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#endif
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}
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#ifdef DESKTOP_BUILD
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if (q.is_nan()) {
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@ -587,7 +390,7 @@ void AP_Quaternion::update(void)
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}
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// average error in roll/pitch since last call
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float AP_Quaternion::get_error_rp(void)
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float AP_AHRS_Quaternion::get_error_rp(void)
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{
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float ret;
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if (_error_rp_count == 0) {
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@ -600,7 +403,7 @@ float AP_Quaternion::get_error_rp(void)
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}
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// average error in yaw since last call
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float AP_Quaternion::get_error_yaw(void)
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float AP_AHRS_Quaternion::get_error_yaw(void)
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{
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float ret;
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if (_error_yaw_count == 0) {
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@ -611,3 +414,18 @@ float AP_Quaternion::get_error_yaw(void)
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_error_yaw_count = 0;
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return ret;
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}
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// reset attitude system
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void AP_AHRS_Quaternion::reset(bool recover_eulers)
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{
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if (recover_eulers) {
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q.from_euler(roll, pitch, yaw);
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} else {
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q(1, 0, 0, 0);
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}
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gyro_bias.zero();
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// reference direction of flux in earth frame
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b_x = 0;
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b_z = -1;
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}
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@ -13,66 +13,41 @@
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#include "WProgram.h"
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#endif
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class AP_Quaternion
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class AP_AHRS_Quaternion : public AP_AHRS
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{
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public:
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// Constructor
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AP_Quaternion(IMU *imu, GPS *&gps) :
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_imu(imu),
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_gps(gps)
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AP_AHRS_Quaternion(IMU *imu, GPS *&gps) : AP_AHRS(imu, gps)
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{
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// reference direction of flux in earth frame
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b_x = 0;
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b_z = -1;
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// limit the drift to the drift rate reported by the
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// sensor driver
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gyroMeasDrift = imu->get_gyro_drift_rate();
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// scaled gyro drift limits
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beta = sqrt(3.0f / 4.0f) * gyroMeasError;
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zeta = sqrt(3.0f / 4.0f) * gyroMeasDrift;
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}
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zeta = sqrt(3.0f / 4.0f) * _gyro_drift_limit;
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// Accessors
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void set_centripetal(bool b) {_centripetal = b;}
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bool get_centripetal(void) {return _centripetal;}
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void set_compass(Compass *compass);
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// reset attitude
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reset();
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}
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// Methods
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void update(void);
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void reset(bool recover_eulers=false);
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// Euler angles (radians)
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float roll;
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float pitch;
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float yaw;
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// integer Euler angles (Degrees * 100)
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int32_t roll_sensor;
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int32_t pitch_sensor;
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int32_t yaw_sensor;
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// compatibility methods with DCM
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void update_DCM(void) { update(); }
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void update_DCM_fast(void) { update(); }
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// get corrected gyro vector
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Vector3f get_gyro(void) {
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// notice the sign reversals here
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return Vector3f(-_gyro_corrected.x, -_gyro_corrected.y, _gyro_corrected.z);
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}
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Vector3f get_gyro_drift(void) {
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// notice the sign reversals here
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return Vector3f(-gyro_bias.x, -gyro_bias.y, gyro_bias.z);
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// notice the sign reversals here. The quaternion
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// system uses a -ve gyro bias, DCM uses a +ve
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return Vector3f(gyro_bias.x, gyro_bias.y, -gyro_bias.z);
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}
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float get_accel_weight(void) { return 0; }
|
||||
float get_renorm_val(void) { return 0; }
|
||||
float get_health(void) { return 0; }
|
||||
void matrix_reset(void) { }
|
||||
uint8_t gyro_sat_count;
|
||||
uint8_t renorm_range_count;
|
||||
uint8_t renorm_blowup_count;
|
||||
|
||||
float get_error_rp(void);
|
||||
float get_error_yaw(void);
|
||||
|
||||
// convert quaternion to a DCM matrix, used by compass
|
||||
// null offsets code
|
||||
Matrix3f get_dcm_matrix(void) {
|
||||
Matrix3f ret;
|
||||
q.rotation_matrix(ret);
|
||||
|
|
@ -82,31 +57,16 @@ public:
|
|||
private:
|
||||
void update_IMU(float deltat, Vector3f &gyro, Vector3f &accel);
|
||||
void update_MARG(float deltat, Vector3f &gyro, Vector3f &accel, Vector3f &mag);
|
||||
void update_drift(float deltat, Vector3f &mag);
|
||||
|
||||
bool _have_initial_yaw;
|
||||
|
||||
// Methods
|
||||
void accel_adjust(void);
|
||||
|
||||
// members
|
||||
Compass * _compass;
|
||||
// time in microseconds of last compass update
|
||||
uint32_t _compass_last_update;
|
||||
|
||||
// note: we use ref-to-pointer here so that our caller can change the GPS without our noticing
|
||||
// IMU under us without our noticing.
|
||||
GPS *&_gps;
|
||||
IMU *_imu;
|
||||
|
||||
// true if we are doing centripetal acceleration correction
|
||||
bool _centripetal;
|
||||
|
||||
// maximum gyroscope measurement error in rad/s (set to 7 degrees/second)
|
||||
static const float gyroMeasError = 20.0 * (M_PI/180.0);
|
||||
|
||||
float gyroMeasDrift;
|
||||
|
||||
// scaled tuning constants
|
||||
float beta;
|
||||
float zeta;
|
||||
|
||||
|
|
@ -124,11 +84,6 @@ private:
|
|||
// the current corrected gyro vector
|
||||
Vector3f _gyro_corrected;
|
||||
|
||||
// accel and gyro accumulators for drift correction
|
||||
Vector3f _gyro_sum;
|
||||
Vector3f _accel_sum;
|
||||
uint32_t _sum_count;
|
||||
|
||||
// estimate of error
|
||||
float _error_rp_sum;
|
||||
uint16_t _error_rp_count;
|
||||
|
|
|
|||
Loading…
Reference in New Issue