Z-axis position deviation on flat ground surface

[147258369ymc]

Description

During sustained reverse driving, the simulated TurtleBot3 exhibits vertical
position deviation (z-axis lift) that should not occur on a flat ground plane.
Observed z = 0.079 m, exceeding the expected tolerance of 0.05 m for contact
force noise.

Steps to Reproduce

ros2 launch turtlebot3_gazebo empty_world.launch.py
ros2 topic pub -r 3 /cmd_vel geometry_msgs/msg/Twist "{linear: {x: -0.22}}"

After ~30 seconds:

ros2 topic echo /odom --field pose.pose.position.z

Observed

odom.pose.pose.position.z = 0.0788 m (expected: ~0.0)

Root Cause

Likely caused by contact dynamics instability when the robot reverses into
slight terrain irregularities or when the physics solver produces vertical
bounce artifacts.

[sungjinjung2806]

I tested this in my environment but could not reproduce the issue.

Environment:

Ubuntu 24.04
ROS 2 Jazzy
TurtleBot3 Burger
turtlebot3_gazebo

I continuously monitored odom.pose.pose.position.z during sustained reverse motion using ros2 topic echo /odom --field pose.pose.position.z, and the z value remained near 0 throughout the test.

This seems more likely related to simulation physics behavior (e.g. contact dynamics or solver artifacts in Gazebo) rather than a TurtleBot3-specific issue.