Repository Summary

Checkout URI
VCS Type git
VCS Version master
Last Updated 2019-11-01
CI status No Continuous Integration
Package Tags No category tags.


Name Version
lex_common_msgs 3.1.0
lex_node 3.1.0




The ROS lex_node node enables a robot to comprehend natural language commands by voice or textual input and respond through a set of actions, which an AWS Lex Bot maps to ROS messages. Out of the box this node provides a ROS interface to communicate with a specified Amazon Lex bot (configured via sample_configuration.yaml) and requires configuration of AWS credentials. The Amazon Lex bot needs to be defined with responses and slots for customer prompts. A set of default slots and mappings are demonstrated in the sample app and include actions as “Create ,” “Go to ” and “Stop.” Additional guides on configuring bots with are available at Getting Started with Amazon Lex.

Delivering a voice-enabled customer experience (e.g. “Robot, go to x”) will require dialog facilitation, wake word, and offline processing which are not yet provided by this integration. A wake word would trigger the dialog facilitation node to start recording and send the audio to Amazon Lex, then prompt the user for more information should Amazon Lex require it.

The ROS lex_node wraps the aws-sdk-c++ in a ROS service API.

Amazon Lex Summary: Amazon Lex is a service for building conversational interfaces into any application using voice and text. Amazon Lex provides the advanced deep learning functionality of automatic speech recognition (ASR) for converting speech to text, and natural language understanding (NLU) to recognize the intent of the text, to enable you to build applications with highly engaging user experiences and lifelike conversational interactions. With Amazon Lex, the same deep learning technologies that power Amazon Alexa are now available to any developer, enabling you to quickly and easily build sophisticated, natural language, conversational bots (“chatbots”).


The source code is released under an Apache 2.0.

Author: AWS RoboMaker
Affiliation: Amazon Web Services (AWS)
Maintainer: AWS RoboMaker,

Supported ROS Distributions

  • Dashing

Build status

  • Travis CI:
    • "master" branch Build Status
    • "release-latest" branch Build Status
    • ROS build farm:
    • ROS Dashing @ u18.04 Bionic Build Status


AWS Credentials

You will need to create an AWS Account and configure the credentials to be able to communicate with AWS services. You may find AWS Configuration and Credential Files helpful.

This node requires an IAM User with the following permission policy: - AmazonLexRunBotsOnly


On Ubuntu you can install the latest version of this package using the following command

    sudo apt-get update
    sudo apt-get install -y ros-$ROS_DISTRO-lex-node

Building from Source

To build from source you'll need to create a new workspace, clone and checkout the latest release branch of this repository, install all the dependencies, and compile. If you need the latest development features you can clone from the master branch instead of the latest release branch. While we guarantee the release branches are stable, the master should be considered to have an unstable build due to ongoing development.

  • Create a ROS workspace and a source directory

    mkdir -p ~/ros-workspace/src

  • Clone the package into the source directory .

    cd ~/ros-workspace/src
    git clone -b release-latest
  • Install dependencies

    cd ~/ros-workspace 
    sudo apt-get update && rosdep update
    rosdep install --from-paths src --ignore-src -r -y

Note: If building the master branch instead of a release branch you may need to also checkout and build the master branches of the packages this package depends on.

  • Build the packages

    cd ~/ros-workspace && colcon build
  • Configure ROS library Path

    source ~/ros-workspace/install/local_setup.bash
  • Build and run the unit tests

    colcon test --packages-select lex_node && colcon test-result --all

Launch Files

An example launch file called is provided.


Resource Setup

  1. Go to Amazon Lex
  2. Create sample bot: BookTrip
  3. Select publish, create a new alias
  4. Modify the configuration file in config/sample_configuration.yaml to reflect the new alias

Run the node

  • ros2 launch lex_node

Send a test voice message

`ros2 service call /lex_conversation lex_common_msgs/AudioTextConversation "{content_type: 'text/plain; charset=utf-8', accept_type: 'text/plain; charset=utf-8', text_request: 'make a reservation'}"`

Verify the test voice was received

  • Receive response from Amazon Lex and continue conversation

Configuration File and Parameters

An example configuration file called sample_configuration.yaml is provided.

Client Configuration

Name Type
region String
userAgent String
endpointOverride String
proxyHost String
proxyUserName String
proxyPassword String
caPath String
caFile String
requestTimeoutMs int
connectTimeoutMs int
maxConnections int
proxyPort int
useDualStack bool
enableClockSkewAdjustment bool
followRedirects bool

Amazon Lex Configuration

Key Type Description
user_id string e.g. “lex_node”
bot_name string e.g. “BookTrip” (corresponds to Amazon Lex bot)
bot_alias string e.g. “Demo”



Enables a robot to comprehend natural language commands by voice or textual input and respond through a set of actions.


Topic: /lex_conversation



Key Type Description
content_type string The input data type to request Amazon Lex
accept_type string The Amazon Lex output data type desired
text_request string Input text data for Lex
audio_request uint8[] Common audio msg format, input audio data for Lex


Key Type Description
text_response string Output text from Lex, if accept type was text
audio_response uint8[] Output audio data from Lex, if accept type was audio
slots KeyValuePair[] Slots returned from Lex
intent_name string The intent Amazon Lex is attempting to fulfill
message_format_type string Format of output data from Lex
dialog_state string Amazon Lex internal dialog_state

Subscribed Topics


Published Topics


Bugs & Feature Requests

Please contact the team directly if you would like to request a feature.

Please report bugs in Issue Tracker.