Fixed imu joint missing (for jazzy)

[Jabee7531]

Hello!

While testing the EKF with the simulation, I noticed that the IMU sensor data was behaving abnormally. Upon closer inspection, I found that in Gazebo, the IMU was falling infinitely.

After checking the model, I discovered that the imu_joint was missing in the gz_waffle.sdf.xacro file.

To fix this, I added a fixed joint between base_link and imu_link:

      <joint name="imu_joint" type="fixed">
        <parent>base_link</parent>
        <child>imu_link</child>
        <pose>0.0 0 0.068 0 0 0</pose>
      </joint>

After applying this fix, the IMU remains correctly attached to the robot, and the EKF output is stable.

Please let me know if any adjustments are needed. Thank you!

[SteveMacenski]

@Jabee7531 can you open this for main too and I'll merge both?

[Jabee7531]

I'm very sorry — I mistakenly deleted the source branch for this PR, which caused it to close.

I'll reapply the fix and submit a new PR by tomorrow.
Thank you for your patience and understanding.