ROS 2 Lyrical Luth · Lesson 32 of 86

Simulated IMU

The imu sensor, noise models, frames and bridging sensor_msgs/Imu.

Estimated time · 45–60 min

Learning goals

What you will understand

Explain simulated imu in your own words
Use it in a small robotics example
Verify the result instead of assuming it worked

Understand the idea first

The mental model

An IMU sensor reports angular velocity and linear acceleration (and a fused orientation if enabled). In Gazebo the sensor of type imu needs the imu system plugin in the world. Add Gaussian noise so filters are tested against imperfect data.

Publish it as sensor_msgs/msg/Imu with the frame id of the IMU link. A robot at rest should show about 9.81 m/s² on the vertical axis. Check with ros2 topic echo /imu --once.

Guided lesson

Work through these steps

1.
Source the ROS 2 Lyrical environment in a fresh terminal.
2.
Read the simulated imu example and identify what each line does.
3.
Build only the affected package, source the workspace overlay, and run the example.
4.
Inspect the result from a second terminal with the ros2 CLI or RViz2 and compare it with the expected result.

Worked example

Read it before you run it

<sensor name="imu" type="imu">
<!-- An inertial sensor. -->
  <update_rate>100</update_rate>
<!-- 100 samples per second. -->
  <topic>imu</topic>
<!-- Gazebo topic. -->
  <imu><angular_velocity><x><noise type="gaussian"><mean>0</mean><stddev>0.0002</stddev></noise></x></angular_velocity></imu>
<!-- Noise on the X gyro (repeat for the other axes). -->
  <always_on>true</always_on>
<!-- Keep running. -->
</sensor>
<!-- End of the sensor. -->

What the example is doing

1.The ros2 commands query the running graph; they do not prove that a node's internal behavior is correct.
2.Build from the workspace root, then source install/setup.bash so the shell can discover the new package.
3.Use a second sourced terminal to inspect nodes and interfaces while the example runs.

Watch it run · Sensor view

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

Copy the starter into your ROS 2 package, replace every TODO, then build with colcon build and run it from a sourced terminal.

# TODO: bridge /imu from Gazebo (gz.msgs.IMU) to ROS 2 (sensor_msgs/msg/Imu)
ros2 topic echo /imu --once

Expected output

linear_acceleration.z is close to 9.81

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

ros2 run ros_gz_bridge parameter_bridge /imu@sensor_msgs/msg/Imu[gz.msgs.IMU
ros2 topic echo /imu --once

Expected result

How you know it worked

ROS_DISTRO is lyrical in every terminal used for the exercise.
The complete package from the exercise builds and the expected graph entity appears in a second terminal.

Practical exercise

Apply the lesson

Add an IMU with noise, bridge it, and check that a stationary robot reports about 9.81 on z. Drive the robot and observe the angular velocity on the turning axis.

Before you continue

ROS_DISTRO reports lyrical in every terminal you used
The example builds and runs without errors
You checked the result with a ros2 command, RViz2 or a test, not just by reading the code

If something goes wrong

ros2 cannot find a package or executable.

Source /opt/ros/lyrical/setup.bash, build from the workspace root, then source install/setup.bash in that terminal.

Nodes run but cannot discover each other.

Confirm both terminals use Lyrical, the same ROS_DOMAIN_ID, and compatible network/discovery settings.