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Description

The sections below describe the API of this package for 2D (x,y,phi) EKF-based SLAM. This method takes input measurements to landmarks in the form of range-bearing observations.

Further documentation

The ROS node mrpt_ekf_slam_2d is a wrapper for the C++ classmrpt::slam::CRangeBearingKFSLAM2D , part of MRPT. Thus, check out the documentation of that class for further details.

For the convention on coordinate frames see ROS REP 105: "Coordinate Frames for Mobile Platforms".

Usage

In order to use mrpt_ekf_slam_2d package it is necessary to install the last MRPT build and themrpt_navigation (see also the tutorial) .

Example

The following video represents the EKF 2D SLAM in Rviz and MRPT GUI:

The example of usage EKF 2D SLAM in online regime:

roslaunch mrpt_ekf_slam_2d ekf_slam_2d.launch

The example of usage EKF 2D SLAM from .rawlog file:

roslaunch mrpt_ekf_slam_2d ekf_slam_2d_rawlog.launch

Nodes

mrpt_ekf_slam_2d

The mrpt_ekf_slam_2d node takes in mrpt_msgs/ObservationRangeBearing messages and builds a map with landmarks and robot pose. The map can be retrieved via a ROS topic.

Subscribed Topics

tf (tf/tfMessage)

• Transforms necessary to relate frames for laser, base, and odometry (see below)

landmark (mrpt_msgs/ObservationRangeBearing)

• Landmarks to create the map

Published Topics

state_viz (visualization_msgs/MarkerArray)

• Visualization of the current state of the EKF

data_association_viz (visualization_msgs/MarkerArray)

• Visualization of the currently observed landmarks by robot

Parameters

~global_frame_id (string, default: "map")

• the frame attached to the map

~base_frame_id (string, default: "base_link")

• The frame attached to the mobile base

~odom_frame_id (string, default: "odom")

• The frame attached to the odometry system

~sensor_source (string, default: "scan")

• The name of topics with 2d laser scans or beacons (the name of topic should contain word "scan" or "beacon")

~ini_filename (string, default: None)

• The path to the ini file with MRPT settings for SLAM (see tutorial folder)

~rawlog_filename (string, default: None)

• The path to rawlog file(if the rawlog file is not exists the SLAM starts in online regime)

~rawlog_play_delay (float, default: 0.1)

• Delay for replay SLAM from rawlog file.

~ellipse_scale (float, default: 1)

• The parameter for rescaling covariance ellipses visualization.

Required tf Transforms

<the frame attached to incoming scans> → base_link

• The relative pose of the laser sensor w.r.t. the robot. Usually a fixed value, broadcast periodically by a robot_state_publisher, or a tf static_transform_publisher.

base_link → odom

• The robot odometry, provided by the odometry system (e.g., the driver for the mobile base)

Provided tf Transforms

map → odom

• The current estimate of the robot's pose within the map frame