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”) }}

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Changelog for package autoware_ekf_localizer

1.1.0 (2025-05-01)

1.8.0 (2026-05-01)

• Merge remote-tracking branch 'origin/main' into tmp/bot/bump_version_base

• fix(ekf_localizer): initialize diagnostics information before publishing them (#680)

  * fix: initialize diagnostics information before publishing them

  • chore: add comments and remove unnecessary code
  • test: reset measurement diag fields on timer early return
  • style(pre-commit): autofix

  * test(ekf_localizer): stabilize diagnostics period gtest timing ---------Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Junya Sasaki <<j2sasaki1990@gmail.com>>

• fix(ekf_localizer): ekf localizer diagnostics name (#1028)

  • test: add diagnostics topic test and log message names
  • fix: diagnostic task names and timer-driven publish
  • feat: mirror diagnostics on diagnostics_manual alongside updater
  • refactor: drop diagnostic_updater; publish /diagnostics manually

  * style(pre-commit): autofix ---------Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

• refactor(autoware_core): add USE_SCOPED_HEADER_INSTALL_DIR to localization packages (#984) Co-authored-by: github-actions <<github-actions@github.com>> Co-authored-by: Junya Sasaki <<j2sasaki1990@gmail.com>>

• fix(ekf_localizer): change diagnostic severity (#829)

  • change(ekf_localizer): change diagnostic severity for initialpose reception
  • feat(autoware_ekf_localizer): update README

  * chore(autoware_ekf_localizer): updated test code ---------Co-authored-by: Junya Sasaki <<j2sasaki1990@gmail.com>>

• feat(ekf_localizer): add adjustable publishing ekf_localizaer diagnostics (#826)

  • feat: adjustable publishing of diagnostics
  • test: add test for should_publish_diagnostics function
  • style(pre-commit): autofix
  • fix: cpp lint error
  • docs: update schema.json
  • test: fix parameter undefined
  • feat: latch ekf diagnostics info when error or warn occurs
  • test: latch ekf diagnostics info when error or warn occurs
  • style(pre-commit): autofix

  * feat: use diagnostic_updater publish on relative periodic timer

  • refactor: Add the corresponding diagnostics immediately after each process
  • refactor: remove unused includes
  • feat: publish callback_pose/callback_twist by period
  • When diagnostics_publish_period <= 0 (default): keep original behavior.

  - Timer_callback calls force_update() every tick so the latched ekf_localizer diagnostic is published at EKF rate.

  - Pose/twist callbacks publish callback_pose and callback_twist via publish_callback_return_diagnostics() and pub_diag_.

  • Updater internal timer is disabled (setPeriod(1e9)).
  • When diagnostics_publish_period > 0: use updater for all diagnostics.
  • Latched diagnostic is published at the configured period.

  - callback_pose and callback_twist are updated in callbacks (last_pose_callback_time_ / last_twist_callback_time_) and published at the same period via diagnose_callback_pose and diagnose_callback_twist; per-callback publish is not used.

  * test: add diagnostics publish tests for period and callbacks Add tests that verify /diagnostics publish behavior by diagnostics_publish_period:

  - diagnostics_published_at_specified_period: when period > 0, at least one message is published within 250 ms at the configured rate.

  - callback_pose_and_twist_published_at_period_when_period_positive:

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