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autoware_imu_corrector#

imu_corrector#

imu_corrector_node is a node that correct imu data.

  1. Correct yaw rate offset \(b\) by reading the parameter.
  2. Correct yaw rate standard deviation \(\sigma\) by reading the parameter.

Mathematically, we assume the following equation:

\[ \tilde{\omega}(t) = \omega(t) + b(t) + n(t) \]

where \(\tilde{\omega}\) denotes observed angular velocity, \(\omega\) denotes true angular velocity, \(b\) denotes an offset, and \(n\) denotes a gaussian noise. We also assume that \(n\sim\mathcal{N}(0, \sigma^2)\).

Input#

Name Type Description
~input sensor_msgs::msg::Imu raw imu data

Output#

Name Type Description
~output sensor_msgs::msg::Imu corrected imu data

Parameters#

Name Type Description
angular_velocity_offset_x double roll rate offset in imu_link [rad/s]
angular_velocity_offset_y double pitch rate offset imu_link [rad/s]
angular_velocity_offset_z double yaw rate offset imu_link [rad/s]
angular_velocity_stddev_xx double roll rate standard deviation imu_link [rad/s]
angular_velocity_stddev_yy double pitch rate standard deviation imu_link [rad/s]
angular_velocity_stddev_zz double yaw rate standard deviation imu_link [rad/s]
acceleration_stddev double acceleration standard deviation imu_link [m/s^2]

gyro_bias_estimator#

gyro_bias_validator is a node that validates the bias of the gyroscope. It subscribes to the sensor_msgs::msg::Imu topic and validate if the bias of the gyroscope is within the specified range.

Note that the node calculates bias from the gyroscope data by averaging the data only when the vehicle is stopped.

Input#

Name Type Description
~/input/imu_raw sensor_msgs::msg::Imu raw imu data
~/input/pose geometry_msgs::msg::PoseWithCovarianceStamped ndt pose

Note that the input pose is assumed to be accurate enough. For example when using NDT, we assume that the NDT is appropriately converged.

Currently, it is possible to use methods other than NDT as a pose_source for Autoware, but less accurate methods are not suitable for IMU bias estimation.

In the future, with careful implementation for pose errors, the IMU bias estimated by NDT could potentially be used not only for validation but also for online calibration.

Output#

Name Type Description
~/output/gyro_bias geometry_msgs::msg::Vector3Stamped bias of the gyroscope [rad/s]

Parameters#

Note that this node also uses angular_velocity_offset_x, angular_velocity_offset_y, angular_velocity_offset_z parameters from imu_corrector.param.yaml.

Name Type Description
gyro_bias_threshold double threshold of the bias of the gyroscope [rad/s]
timer_callback_interval_sec double seconds about the timer callback function [sec]
diagnostics_updater_interval_sec double period of the diagnostics updater [sec]
straight_motion_ang_vel_upper_limit double upper limit of yaw angular velocity, beyond which motion is not considered straight [rad/s]