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EKF: Use intuitive units for gyro and accel bias process noise

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This also makes the tuning less sensitive to changes in the EKF update rate.
This commit is contained in:
Paul Riseborough
2016-05-05 21:23:03 +10:00
parent 799865c934
commit 29a361d3a3
2 changed files with 11 additions and 7 deletions
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EKF/common.h
+4 -4
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@@ -170,8 +170,8 @@ struct parameters {
float accel_noise; // IMU acceleration noise use for covariance prediction (m/sec/sec)
// process noise
float gyro_bias_p_noise; // process noise for IMU delta angle bias prediction (rad/sec)
float accel_bias_p_noise; // process noise for IMU delta velocity bias prediction (m/sec/sec)
float gyro_bias_p_noise; // process noise for IMU rate gyro bias prediction (rad/sec**2)
float accel_bias_p_noise; // process noise for IMU accelerometer bias prediction (m/sec**3)
float mage_p_noise; // process noise for earth magnetic field prediction (Guass/sec)
float magb_p_noise; // process noise for body magnetic field prediction (Guass/sec)
float wind_vel_p_noise; // process noise for wind velocity prediction (m/sec/sec)
@@ -250,8 +250,8 @@ struct parameters {
accel_noise = 2.5e-1f;
// process noise
gyro_bias_p_noise = 5.0e-6f;
accel_bias_p_noise = 1.0e-7f;
gyro_bias_p_noise = 1.0e-3f;
accel_bias_p_noise = 1.0e-5f;
mage_p_noise = 1.0e-3f;
magb_p_noise = 1.0e-4f;
wind_vel_p_noise = 1.0e-1f;
EKF/covariance.cpp
+7 -3
View File
@@ -143,11 +143,14 @@ void Ekf::predictCovariance()
// compute noise variance for stationary processes
float process_noise[_k_num_states] = {};
float d_ang_bias_sig = dt * math::constrain(_params.gyro_bias_p_noise, 0.0f, 1.0f);
float d_vel_bias_sig = dt * math::constrain(_params.accel_bias_p_noise, 0.0f, 1.0f);
float mag_I_sig, mag_B_sig;
// convert rate of change of rate gyro bias (rad/s**2) as specified by the parameter to an expected change in delta angle (rad) since the last update
float d_ang_bias_sig = dt * dt * math::constrain(_params.gyro_bias_p_noise, 0.0f, 1.0f);
// convert rate of change of acceerometer bias (m/s**3) as specified by the parameter to an expected change in delta velocity (m/s) since the last update
float d_vel_bias_sig = dt * dt * math::constrain(_params.accel_bias_p_noise, 0.0f, 1.0f);
// Don't continue to grow the earth field variances if they are becoming too large or we are not doing 3-axis fusion as this can make the covariance matrix badly conditioned
float mag_I_sig;
if (_control_status.flags.mag_3D && (P[16][16] + P[17][17] + P[18][8]) < 0.1f) {
mag_I_sig = dt * math::constrain(_params.mage_p_noise, 0.0f, 1.0f);
@@ -156,6 +159,7 @@ void Ekf::predictCovariance()
}
// Don't continue to grow the body field variances if they is becoming too large or we are not doing 3-axis fusion as this can make the covariance matrix badly conditioned
float mag_B_sig;
if (_control_status.flags.mag_3D && (P[19][19] + P[20][20] + P[21][21]) < 0.1f) {
mag_B_sig = dt * math::constrain(_params.magb_p_noise, 0.0f, 1.0f);