Tutorial: Running CARMEN-LCAD in Playback Mode

What is Playback Mode?

The Playback mode in CARMEN-LCAD allows the system to run using a previously recorded log instead of live sensor data. This log contains recorded sensor data — mainly odometry, camera, and LiDAR — collected during a real robot execution.

During playback, the system reproduces the data in the same format and temporal sequence in which it was recorded, simulating a real execution using real data. This enables controlled and reproducible testing of perception, mapping, and localization algorithms without requiring the physical robot.

It is important to note that, in this mode, the robot only replicates the originally recorded data and movements. Therefore, route planning modules should not be used, since the robot will not respond to new commands — it will strictly follow what was recorded in the log.

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Preparation

1. Obtain the Log File

Download the log file that will be used for playback:

https://drive.google.com/file/d/1j8njzZm6gyUeRfx9_vKMf29B5oU4HfLQ/view?usp=sharing

After downloading, place the file inside the /dados/ directory and extract it using the following command:

cd /dados/
tar -xvf log_volta_da_ufes_20230422-1.tar.gz

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2. Start the Central Module

Before running the process, it is necessary to start the central module. Open a terminal and execute:

cd ~/carmen_lcad/bin/
./central

Keep the central module running before starting the other modules.

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Running the Process in Playback Mode

To run the playback, execute the process configuration file, which defines:

• Which modules will be started
• Which parameters will be used (such as the log path and the map)

Open another terminal and run:

cd ~/carmen_lcad/bin/
./proccontrol process-volta_da_ufes_playback_viewer_3D.ini

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Starting the Simulation

After starting the process, press Play in the window that appears to begin log playback.

The system will start publishing the log data as if it were being received in real time.

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What Can Be Done in Playback Mode?

In Playback mode, you can:

• Test perception algorithms
• Evaluate localization modules
• Run mapping systems
• Analyze LiDAR and camera data processing
• Debug behavior with deterministic execution

⚠️ Important limitation:
Route planning or reactive control modules cannot be used, since the robot's motion is entirely determined by the recorded log.