Ubuntu Linux for Robotics · Lesson 87 of 96

Multi-robot coordination

Namespaces, shared resources, priorities and deadlock avoidance.

Estimated time · 60–90 min

Learning goals

What you will understand

Explain multi-robot coordination in your own words
Use it in a small workstation example
Verify the result instead of assuming it worked

Understand the idea first

The mental model

Robots that share corridors, doors or chargers need rules. A reservation table gives a resource to one robot at a time: robots request it, wait, and release it when done. Requests are served first-come or by priority. Deadlock (each robot holds what the other needs) is avoided by reserving whole routes or ordering resources.

Technically each robot needs its own namespace, unique TF frame names or namespaced TF, and its own Nav2 instance; they may share the map. Use ROS_DOMAIN_ID to separate independent fleets, and check ros2 node list and ros2 topic list for name clashes.

Guided lesson

Work through these steps

1.
Open a terminal and record the current state before changing anything.
2.
Read the multi-robot coordination commands and predict what each one does.
3.
Run the commands one at a time and compare each output with your prediction.
4.
Write the commands that worked in a setup note you can repeat later.

Worked example

Read it before you run it

ros2 launch fleet_bringup robot.launch.py namespace:=robot1 x:=0.0 y:=0.0
# Start robot 1 in its own namespace at its start pose.
ros2 launch fleet_bringup robot.launch.py namespace:=robot2 x:=2.0 y:=0.0
# Start robot 2 at a different pose.
ros2 topic list | grep -c '^/robot1'
# Count the topics that belong to robot 1.
ros2 topic echo /traffic/reservations --once
# Read the shared reservation table (custom topic).
ros2 run tf2_tools view_frames
# Check that each robot has its own connected frame tree.

What the example is doing

1.Lines without sudo only inspect or change files you own; sudo authorizes a system-wide change.
2.Read command output before moving to the next line. Stop if names, versions, disks, or paths differ from the lesson.
3.Comments beginning with # explain safety checks and are not executed by the shell.

Watch it run · Mobile robot

See what this code does

The terminal types this lesson's practice solution and runs it. The scene shows the kind of robot behaviour that code drives. It plays by itself and loops.

Practice code

Now type it yourself

Open a terminal, run the starter line by line (or save it as practice.sh and run bash practice.sh), and replace every TODO with your own command.

# TODO: start robot2 from the launch file robot.launch.py of fleet_bringup with namespace:=robot2

Expected output

Two robots are running in separate namespaces

Stuck? Show the full solution (try it yourself first)

ros2 launch fleet_bringup robot.launch.py namespace:=robot2 x:=2.0 y:=0.0

Expected result

How you know it worked

Each command completes without an unexplained error.
Your notes contain the command, the important output, and what it proves.

Practical exercise

Apply the lesson

Start two robots in namespaces, make both cross the same corridor, show they collide or block without reservations, then add a reservation node and show the conflict is gone.

Before you continue

You recorded the starting state
Every command and output is understood
The change can be repeated from your notes

If something goes wrong

A command says permission denied.

Check ownership and permissions first. Do not add sudo unless the command changes a documented system location.

A command or package is not found.

Check spelling, Ubuntu version, enabled repositories, and whether the previous installation command succeeded.