LD Lidar ROS 2 Package

ROS 2 package for LDRobot lidar - Based on Nav2 Lifecycle nodes

Get the Lidar • YouTube Videos • Install • Start the Node • Parameters • RViz2 • Robot Integration • Benchmarking

This package is designed to work with the DToF 2D Lidar sensors LD19 made by LDRobot.

It can work also with the LD06 model, but no tests have been performed with it. LD06 cannot work outdoor.

LD19	LD06

Get the lidar

My lidar (LD19) comes from the LDRobot kickstarter campaing ended in 2021.

LDRobot then created also an Indiegogo campaign for the LD19.

LDRobot today distributes the Lidar through third-party resellers:

• Waveshare: LD19
• Innomaker: LD06
• Other: Search on Google

The node in action

LD19 Lifecycle	LD19 outdoor

Install the node

The node is designed to work with

• ROS 2 Humble
• ROS 2 Jazzy

📌 Note: ROS 2 Rolling is not yet supported because of the missing nav2_utils dependency

Clone the repository in your ROS2 workspace:

cd ~/ros2_ws/src/ #use your current ros2 workspace folder
git clone https://github.com/Myzhar/ldrobot-lidar-ros2.git

Add dependencies:

sudo apt install libudev-dev

Install the udev rules

cd ~/ros2_ws/src/ldrobot-lidar-ros2/scripts/
./create_udev_rules.sh

Build the packages:

cd ~/ros2_ws/
rosdep install --from-paths src --ignore-src -r -y
colcon build --symlink-install --cmake-args=-DCMAKE_BUILD_TYPE=Release

Update the environment variables:

echo source $(pwd)/install/local_setup.bash >> ~/.bashrc
source ~/.bashrc

Start the node

Launch file with YAML parameters

The default values of the parameters of the node can be modified by editing the file ldlidar.yaml.

Open a terminal console and enter the following command to start the node with customized parameters:

ros2 launch ldlidar_node ldlidar_bringup.launch.py

The ldlidar_bringup.launch.py starts a ROS 2 Container, which loads the LDLidar Component as a plugin.

The ldlidar_bringup.launch.py script also starts a robot_state_publisher node that provides the static TF transform of the LDLidar [ldlidar_base->ldlidar_link], and provides the ldlidar description in the /robot_description.

Lifecycle

The ldlidar node is based on the ROS2 lifecycle architecture, hence it starts in the UNCONFIGURED state. To configure the node, load all the parameters, establish a connection, and activate the scan publisher, the lifecycle services must be called in sequence.

Open a new terminal console and enter the following command:

ros2 lifecycle set /lidar_node configure

If the node is correctly configured and the connection is established, Transitioning successful is returned. If there are errors, Transitioning failed is returned. Check the node log for details on any connection issues.

The node is now in the INACTIVE state, enter the following command to activate:

ros2 lifecycle set /lidar_node activate

The node is now activated and the /ldlidar_node/scan topic of type sensor_msgs/msg/LaserScan is available to be subscribed.

Launch file with YAML parameters and Lifecycle manager

Thanks to the NAV2 project, you can launch a lifecycle_manager node that handles the state transitions described above. An example launch file, ldlidar_with_mgr.launch.py, demonstrates how to start the ldlidar_node with parameters loaded from the ldlidar.yaml file. It also starts the lifecycle_manager, configured with the lifecycle_mgr.yaml file, to automatically manage the lifecycle transitions:

ros2 launch ldlidar_node ldlidar_with_mgr.launch.py

The ldlidar_with_mgr.launch.py script automatically starts the ldlidar_node by including the ldlidar_bringup.launch.py launch file.

Parameters

Following the list of node parameters:

• general.debug_mode: set to true to activate debug messages
• comm.serial_port: the serial port path
• comm.baudrate: the serial port baudrate
• comm.timeout_msec: the serial communication timeout in milliseconds
• lidar.model: Lidar model [LDLiDAR_LD06, LDLiDAR_LD19, LDLiDAR_STL27L]
• lidar.rot_verse: The rotation verse. Use clockwise if the lidar is mounted upsidedown. [CW, CCW]
• lidar.units: distance measurement units [M, CM, MM]
• lidar.frame_id: TF frame name for the lidar
• lidar.bins: set to 0 for dinamic scan size according to rotation speed, set to a fixed value [e.g. 455] for compatibility with SLAM Toolbox
• lidar.range_min: minimum scan distance
• lidar.range_max: maximum scan distance
• lidar.enable_angle_crop: enable angle cropping
• lidar.angle_crop_min: minimum cropping angle
• lidar.angle_crop_max: maximum cropping angle

Display scan on RViz2

The launch file ldlidar_rviz2.launch.py starts the ldlidar_node node, the lifecycle_manager node, and a preconfigured instance of RViz2 to display the 2D laser scan provided by the LDRobot sensors. This is an example to demonstrate how to correctly setup RViz2 to be used with the ldlidar_node node.

Open a terminal console and enter the following command:

ros2 launch ldlidar_node ldlidar_rviz2.launch.py

Integrate the LDLidar sensor in your robot

Follow these steps to integrate the LDLidar sensor into your robot configuration:

1. Provide TF Transform: Ensure there is a TF transform from base_link to ldlidar_base, positioned at the center of the lidar scanner base. The ldlidar_base -> ldlidar_link transform is provided by the robot_state_publisher started by the ldlidar_bringup.launch.py launch file.

2. Modify Configuration: Update the ldlidar.yaml file to match your robot's configuration.

3. Include Launch File: Add the ldlidar_bringup.launch.py to your robot's bringup launch file. Refer to the example provided.

4. Handle Lifecycle: Properly manage the node's lifecycle. You can use the Nav2 lifecycle_manager by including it in your bringup launch file. Follow the example provided.

5. Deploy and Test: Deploy your configuration and test the system to ensure everything is working correctly.

Enjoy your fully integrated lidar system!

SLAM Toolbox example

The launch file ldlidar_slam.launch.py shows how to use the node with the SLAM Toolbox package to generate a 2D map for robot navigation.

Benchmarking

It is possible to benchmark the node to evaluate the overall performance by using the NVIDIA® ISAAC ROS ros2_benchmark package.

First of all install the ros2_benchmark package.

Launch the benchmark:

cd ~/ros2_ws/src/ldrobot-lidar-ros2/ldlidar_node/test/
launch_test ldlidar_benchmark.py

the final result should be similar to

+--------------------------------------------------------------------------------------------+
|                                  LD Lidar Live Benchmark                                   |
|                                        Final Report                                        |
+--------------------------------------------------------------------------------------------+
| [Scan] Delta between First & Last Received Frames (ms) : 4900.138                          |
| [Scan] Mean Playback Frame Rate (fps) : 9.936                                              |
| [Scan] Mean Frame Rate (fps) : 9.936                                                       |
| [Scan] # of Missed Frames : 0.000                                                          |
| [Scan] # of Frames Sent : 49.000                                                           |
| [Scan] First Sent to First Received Latency (ms) : 0.075                                   |
| [Scan] Last Sent to Last Received Latency (ms) : 0.113                                     |
| [Scan] First Frame End-to-end Latency (ms) : 0.075                                         |
| [Scan] Last Frame End-to-end Latency (ms) : 0.113                                          |
| [Scan] Max. End-to-End Latency (ms) : 0.172                                                |
| [Scan] Min. End-to-End Latency (ms) : 0.049                                                |
| [Scan] Mean End-to-End Latency (ms) : 0.098                                                |
| [Scan] Max. Frame-to-Frame Jitter (ms) : 100.142                                           |
| [Scan] Min. Frame-to-Frame Jitter (ms) : 0.000                                             |
| [Scan] Mean Frame-to-Frame Jitter (ms) : 17.865                                            |
| [Scan] Frame-to-Frame Jitter Std. Deviation (ms) : 12.793                                  |
+--------------------------------------------------------------------------------------------+
| Baseline Overall CPU Utilization (%) : 0.000                                               |
| Max. Overall CPU Utilization (%) : 79.167                                                  |
| Min. Overall CPU Utilization (%) : 0.000                                                   |
| Mean Overall CPU Utilization (%) : 1.179                                                   |
| Std Dev Overall CPU Utilization (%) : 3.964                                                |
+--------------------------------------------------------------------------------------------+
| [metadata] Test Name : LD Lidar Live Benchmark                                             |
| [metadata] Test File Path : /home/walter/devel/ros2/ros2_walt/src/ldrobot-lidar-ros2/ldlidar_node/test/ldlidar_benchmark.py |
| [metadata] Test Datetime : 2024-11-25T22:12:54Z                                            |
| [metadata] Device Hostname : walter-Legion-5-15ACH6H                                       |
| [metadata] Device Architecture : x86_64                                                    |
| [metadata] Device OS : Linux 6.8.0-40-generic #40~22.04.3-Ubuntu SMP PREEMPT_DYNAMIC Tue Jul 30 17:30:19 UTC 2 |
| [metadata] Idle System CPU Util. (%) : 0.333                                               |
| [metadata] Benchmark Mode : 3                                                              |
+--------------------------------------------------------------------------------------------+