Overview

The Extend Kalman Filter Localizer estimates robust and less noisy robot pose and twist by integrating the 2D vehicle dynamics model with input ego-pose and ego-twist messages. The algorithm is designed especially for fast-moving robots such as autonomous driving systems.

Flowchart

The overall flowchart of the autoware_ekf_localizer is described below.

Features

This package includes the following features:

• Time delay compensation for input messages, which enables proper integration of input information with varying time delays. This is important especially for high-speed moving robots, such as autonomous driving vehicles. (see the following figure).
• Automatic estimation of yaw bias prevents modeling errors caused by sensor mounting angle errors, which can improve estimation accuracy.
• Mahalanobis distance gate enables probabilistic outlier detection to determine which inputs should be used or ignored.
• Smooth update, the Kalman Filter measurement update is typically performed when a measurement is obtained, but it can cause large changes in the estimated value, especially for low-frequency measurements. Since the algorithm can consider the measurement time, the measurement data can be divided into multiple pieces and integrated smoothly while maintaining consistency (see the following figure).
• Calculation of vertical correction amount from pitch mitigates localization instability on slopes. For example, when going uphill, it behaves as if it is buried in the ground (see the left side of the “Calculate delta from pitch” figure) because EKF only considers 3DoF(x,y,yaw). Therefore, EKF corrects the z-coordinate according to the formula (see the right side of the “Calculate delta from pitch” figure).

Node

Subscribed Topics

Published Topics

Published TF

• base_link TF from map coordinate to estimated pose.

Functions

Predict

The current robot state is predicted from previously estimated data using a given prediction model. This calculation is called at a constant interval (predict_frequency [Hz]). The prediction equation is described at the end of this page.

Measurement Update

Before the update, the Mahalanobis distance is calculated between the measured input and the predicted state, the measurement update is not performed for inputs where the Mahalanobis distance exceeds the given threshold.

The predicted state is updated with the latest measured inputs, measured_pose, and measured_twist. The updates are performed with the same frequency as prediction, usually at a high frequency, in order to enable smooth state estimation.

Parameter description

The parameters are set in launch/ekf_localizer.launch .

For Node

{{ json_to_markdown(“localization/autoware_ekf_localizer/schema/sub/node.sub_schema.json”) }}

For pose measurement

{{ json_to_markdown(“localization/autoware_ekf_localizer/schema/sub/pose_measurement.sub_schema.json”) }}

For twist measurement

{{ json_to_markdown(“localization/autoware_ekf_localizer/schema/sub/twist_measurement.sub_schema.json”) }}

For process noise

{{ json_to_markdown(“localization/autoware_ekf_localizer/schema/sub/process_noise.sub_schema.json”) }}

note: process noise for positions x & y are calculated automatically from nonlinear dynamics.

Simple 1D Filter Parameters

{{ json_to_markdown(“localization/autoware_ekf_localizer/schema/sub/simple_1d_filter_parameters.sub_schema.json”) }}

File truncated at 100 lines see the full file

Changelog for package autoware_ekf_localizer

1.1.0 (2025-05-01)

1.3.0 (2025-06-23)

• fix: to be consistent version in all package.xml(s)

• feat: support ROS 2 Jazzy (#487)

  • fix ekf_localizer
  • fix lanelet2_map_loader_node
  • MUST REVERT
  • fix pybind
  • fix depend
  • add buildtool
  • remove
  • revert
  • find_package
  • wip
  • remove embed
  • find python_cmake_module
  • public
  • remove ament_cmake_python
  • fix autoware_trajectory
  • add .lcovrc
  • fix egm
  • use char*
  • use global
  • namespace
  • string view
  • clock
  • version
  • wait
  • fix egm2008-1
  • typo
  • fixing
  • fix egm2008-1
  • MUST REVERT
  • fix egm2008-1
  • fix twist_with_covariance

  * Revert "MUST REVERT" This reverts commit 93b7a57f99dccf571a01120132348460dbfa336e.

  • namespace
  • fix qos
  • revert some
  • comment

  * Revert "MUST REVERT" This reverts commit 7a680a796a875ba1dabc7e714eaea663d1e5c676.

  • fix dungling pointer
  • fix memory alignment
  • ignored

  * spellcheck ---------

• fix: tf2 uses hpp headers in rolling (and is backported) (#483)

  • tf2 uses hpp headers in rolling (and is backported)

  * fixup! tf2 uses hpp headers in rolling (and is backported) ---------

• fix(autoware_ekf_localizer): use constexpr and string_view (#435)

  • fix(autoware_ekf_localizer) use constexpr and string_view
  • add std::string_view header

  * add std::string header ---------

• chore: bump up version to 1.1.0 (#462) (#464)

• fix(autoware_ekf_localizer): modified log output section to use warning_message and throttle (#374)

  • fix(autoware_ekf_localizer): Modified log output section to use warning_message and throttle

  * use constexpr and string_view ---------

• fix(autoware_ekf_localizer): fix deprecated autoware_utils header (#412)

  • fix autoware_utils import

  * fix autoware_utils packages ---------

• Contributors: Masaki Baba, RyuYamamoto, Tim Clephas, Yutaka Kondo, github-actions

1.0.0 (2025-03-31)

File truncated at 100 lines see the full file