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]