Using the real Limo Robot

This is the getting started guide to help you start using the real Limo robot.

Get to know your Limo

Read Sections 1.1-1.6 of the manual whilst inspecting the real robot and its components.

When you are using the Limo robot you should make sure that you have read, understand and are following the risk assessment (intranet link). The high level overview of this is that you should check out the Limo before you use it, and take care not to drive it recklessly. You should not leave batteries charging unattended, and if you notice that the battery has been damaged, report this to a member of staff.

You should also take a point of noticing the LEDs at the front. They indicate what state the wheels are in. You should have them in the orange mode. This is for differential drive mode.

You may also want to stop the wheels, you do this by pressing the power button briefly. This will set the LEDs to red.

Setting up your robot

Get your robot and check it out

• Take the box and scan the QR code on it, or visit lncn.ac/LimoUse.
• Fill out the online form to check out the robot for your use.
• When you have finished using the robot, you will need to use the same form again to let us know you've finished using it!

Antennas

• Lift up the tracks from the carrying case and find the two antennas.
• Screw these into the top of the LIMO robot. Do not overtighten these.

Battery

• Make sure the leads coming from the battery are facing towards yourself, and on the left.
• Make sure the ribbon is laying underneath the battery (you should use this to lightly slide out the battery rather than the lead)

• You should then connect the two yellow connectors together.

• Then close the flap.

⚠️ When you have finished with the Limo, the battery should be placed back into the top of the case like you found it.

Power up

• Press and hold the power button for about 5 seconds (until it beeps) to turn the robot on. The light flashes before it beeps, wait until it beeps!

Power down

• Press the shutdown button on the back of the display
• Wait until the screen is completely off, then...
• Press and hold the power button for about 5 seconds (until it beeps) to turn the robot off again.
• Disconnect the battery and remove it from the robot
• Put everything away

Connecting the robot's ROS to your own DevContainer

The robot uses Docker under the hood to run a ROS2 environment. Don't worry — you don't need to know everything about it. You just need to know that all software on the robot runs on ROS2, just like your DevContainer.

This container is called the 'Zenoh Container' as it makes use of a Zenoh ROS2 Bridge which we use to connect your computer to the robot. It bridges 2 ROS2 systems using the Zenoh protocol.

Important

You can only connect to the robot from the Desktop Computers in the UoL Computer Labs. You cannot access it through eduroam or the University's VPN.

On the display on the back of the Limo, you should now see a screen which tells you the state of the robot.

The hostname is displayed in big text, and it is the serial number of the Limo. We use this to track and maintain the robots we have.

The IP is the numbers that start with 10.82.0., you will need to use this to connect to the Limo from your developer machine.

Then you will see some text which shows the state of the container.

• If the container is running you can continue with the next steps.
• If the container is shutdown you will need to start the container. You should see on the desktop a blue icon that says 'Zenoh Docker On' press this, and wait a few seconds. It will then update to say it is running. Once it is running — you can continue.
• If the container is in a error state, ask for some help from the staff in the room. But, you may be able to resolve it by turning 'Zenoh Docker' off and then back on again.

Connect your DevContainer to the robot using Zenoh

In your developer machine, go to the devcontainer running in VSCode (the one you also run the simulation in), see Using the Docker Image.

1. Make sure you are not running the simulation when connecting to the real robot! Stop it if you have to ([Ctrl-c])
2. Open a terminal in VSCode, and start the start the bridge with the IP of your robot:

   zenoh-bridge-ros2dds -e tcp/10.82.0.XXX:7447

   (you need to add your robot's IP again here, see above!) and keep it running. If you get an error, check the IP is correct and is for YOUR robot!
3. run ros2 topic list -v in a different terminal (inside of VSCode) and you should see the relevant topics from the robot. Check which topic names are different to the simulation and which are the same.

To disconnect from the robot's ROS system, simply stop the zenoh-bridge-ros2dds process by pressing [Ctrl-c] in the terminal where it is running.

Note: As you have noticed, will need to open multiple terminals in VS Code. You can do this by pressing either the + button for a new terminal window, or you can press the two boxes button to split the current window.

Moving the robot around and getting some data back

Moving the robot

⚠️ It is now extra important to make sure that the robot is on the floor

You should have VS Code running with a Zenoh connection to your robot (see above). Open a new terminal using the instructions provided previously.

And then run the command

ros2 run teleop_twist_keyboard teleop_twist_keyboard

Now with the keys i j l , you can move around your robot. You can also use the k key to stop all movement.

RViz

We can use the graphical visualiser RVIZ to look at the robot and its sensor topics. You should know this already from your work with the simulator. But now, as we are connected to the robot via the Zenoh bridge, you will see the live data from the robot.

Open rviz with the command:

rviz2 -d /opt/ros/lcas/install/share/limo_description/share/rviz/model_sensors_real.rviz
or
rviz2 -d /opt/ros/lcas/install/limo_description/share/limo_description/rviz/model_sensors_real.rviz

Now it is open you can click the the add button in the bottom left to see which topics you can add to the window.

You should play around with it and see what you can do!