Getting started

The current version of 3Laws Supervisor supports ground-based mobile platforms (wheeled or legged) with the following movement modalities:

Differential-drive

Omni-directional

Front-wheel steering - experimental

For perception, 3Laws Supervisor currently supports:

Raw 2D laserscan data

Pre-processed map of obstacles with their locations and shapes

The 3Laws Supervisor software is a ROS node available on x86_64 and ARM-64 processor architectures for multiple OS/ROS combinations:

Ubuntu Distribution	ROS1 version	ROS2 version
22.04	N/A	Humble/Iron
20.04	Noetic	Galactic/Foxy

1. Install Supervisor 

To install Supervisor on the system, open a terminal (on the target device) and run the following command:

bash <(curl https://raw.githubusercontent.com/3LawsRobotics/3laws/master/install.sh)

This will run a script to auto-detect the system architecture, install any missing dependencies, download the right binary, and guide you through any necessary configuration steps.

Important

sudo permission may be required in order to run APT during software installation.

Note

The ROS packages are installed into the global ROS installation directory. You will need to source the ROS setup script to make the new components available in the current terminal: source /opt/ros/<DISTRO>/setup.sh.

As with most ROS setups, adding a line to the startup file (ex. .bashrc) that sources the ROS environment is recommended.

2. Start the Control Panel 

Before the Supervisor can be started, it must be configured. In order to configure it, a web-based Control Panel is provided. The Control Panel creates if needed and modifies the file ~/.3laws/config/supervisor.yaml.

An existing (or backup) version of this file can be used if it is placed in the proper location; however, older versions might no be compatible with new software. If this file is copied from another device, please update the license.

To enable the Control Panel backend service, open a terminal and run the following command:

3laws control-panel autostart enable

Note

See CLI reference for more options to start the control panel.

3. Configure Supervisor 

Now that the Control Panel backend is running, access the control panel from any machine on the same network as the robot by opening a web browser and navigating to the following URL: http://<IP_ADDRESS_OF_THE_ROBOT>:8000/.

The initial view of the Control Panel is the “Configuration” page, which consists of sections (tabs) listed as:

Warning

The entire configuration process needs to be completed before starting the Supervisor software. If a part of the configuration is missing, the associated tab will be orange in color. Once the configuration is complete all tabs should be white.

Note

See Control Panel reference for more details on the configuration options.

Note

The Supervisor does not have to run during the configuration step. It loads the configuration file at start-up, so it needs to be started after the configuration is created/updated. However, if the rest of the robot is running while the Supervisor is being configured, the Control Panel will pre-filled the configuration with available information.

4. Interface with your stack 

In order to perform collision avoidance maneuvers, the Supervisor must be able to send commands to your robot actuators. These commands will be published on the /lll/ram/filtered_input topic.

Your low-level controller therefore needs to subscribe to this topic and apply the commands to your robot:

Signal routes for a typical robot (simplified).

Remapping 

ROS provides the ability to remap signals that are subscribed-to or published by nodes. The remapping can be specified during the start of the node either through a command line or through a launch file.

Using ROS remap when configuring and launching Supervisor.

The following can be added to the launch instructions for the “robot” portion so that it subscribes to /lll/ram/filtered_input instead of /cmd (or as appropriate.

<remap from="/cmd" to="/lll/ram/filtered_input"/>

Using ROS2 remap when configuring and launching Supervisor.

The following (step 2 above) remaps the output of the autonomy stack so that it produces a new signal that will not conflict with the Robot’s subscription.

remappings=[('/cmd', '/cmd_plan'),],

The Supervisor’s default launch file for ROS is installed /opt/ros/<DISTRO>/shared/lll_supervisor/launch/supervisor.launch.py for ROS2. A remapping as described in step 3 in the image above can be accomplished by adding the following inside the node specification:

remappings=[('/lll/ram/filtered_input', '/cmd'),],

The /cmd value needs to be set appropriately for the application system.

5. Launch 

To launch the Supervisor directly, use the following command:

roslaunch lll_supervisor supervisor.launch

ros2 launch lll_supervisor supervisor.launch.py

To include the Supervisor as part of your launch file, use the following code snippets:

<include file="$(find lll_supervisor)/launch/supervisor.launch">
  <arg name="log_level" value="info"/>
</include>"

from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch.substitutions import PathJoinSubstitution

# launchDesc = LaunchDescription()

launchDesc.add_action(
    IncludeLaunchDescription(
        PythonLaunchDescriptionSource(
            PathJoinSubstitution(
                [
                    get_package_share_directory("lll_supervisor"),
                    "launch",
                    "supervisor.launch.py",
                ]
            )
        ),
        launch_arguments={
            "log_level": "info",
        }.items(),
    )
)

If ROS is unable to find the lll_supervisor, re-run the source command for the ROS paths.

6. Monitor your system (optional)

The Control Panel provides an Operation page that can be used to monitor the status of the Supervisor working with your stack.

The Operation page requires that both the Supervisor and the Control Panel backend are running. Additionally, a rosbridge websocket must be running on the same network as the Supervisor.

To install the rosbridge suite, run the following command:

sudo apt-get install ros-<DISTRO>-rosbridge-suite

To start the rosbridge websocket, run the following command:

roslaunch rosbridge_server rosbridge_websocket.launch

ros2 launch rosbridge_server rosbridge_websocket_launch.xml

Important

Make sure to specify the rosbridge websocket IP address and port in the Control Panel if using something other than the defaults:

Operations page showing a configured robot that does not yet have sensor or planning data.

Note

See Control Panel reference for more details on the operation page.

7. Update (optional)

You can check for updates to the Supervisor by running the following command:

3laws check-update

To update the Supervisor, use the same command as for the installation:

bash <(curl https://raw.githubusercontent.com/3LawsRobotics/3laws/master/install.sh)

Note

The supervisor will be updated to the latest version available for the system’s distribution. The existing configurations will not be modified, but if new variables need to be configured, advisories will be given during the installation.

8. What’s next?

Continue with User Guide to discover everything the Supervisor can do.