Robosense AC Calibration

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1. Introduction

Robosense AC Calibration is designed to provide camera intrinsic calibration, camera-lidar extrinsic calibration and camera-imu extrinsic calibration for Robosense Active Camera.

2. Prerequisites

This project is developed and tested based on ROS2. Follow the instructions in the ROS2 Official Tutorial according to your operating system. Additional dependencies include:

sudo apt install libceres-dev

3. Installation and Setup

3.1 Pulling Source Code

You can create a new folder or navigate to your existing ros2 workspace. Then, execute the following command to clone the code into your workspace.

git clone https://github.com/RoboSense-Robotics/robosense_ac_calibration.git -b main

3.2 Build

In your workspace, execute the following command to build and install robosense_ac_calibration.

colcon build --packages-select robosense_ac_calibration

After the build is complete, it is recommended to refresh your workspace's bash profile to ensure the components function correctly.

source install/setup.bash

4. Configuration Files

Calibration parameter configuration: config/calibration.yaml

Calibration extrinsic result file: config/calibration_result.yaml

Calibration board configuration: config/AprilTag_41h12_65-77.yaml

Calibration Board Specifications: Users are recommended to create the calibration board with a size of 60cm×60cm. If the size is modified, update the calibration board configuration file accordingly.

5. Usage

5.1 Rviz Visualization

rviz2 -d src/robosense_ac_calibration/config/default.rviz

5.2 Required Sensor Topics

• /rs_camera/rgb : Camera image topic
• /rs_lidar/points : Lidar point cloud topic
• /rs_imu : IMU topic

5.3 Camera Intrinsic Calibration

• ​Load Configuration File: Click the Open button in the top-right control panel to select the appropriate configuration file. Verify all parameters before loading.

• ​Start Driver: Click the Start Driver button in the control panel. The button will turn gray once initialization is complete.

• Click the Camera Int button in the control panel to enter camera intrinsic calibration mode. The program will display guidance frames (published on /camera/image_indicate) indicating the current calibration progress.

• ​Capture Images:

  • Move the AC1 sequentially to ​center-left-right-top-bottom positions.
  • At each position, capture 6 images by adjusting the orientation of the AC1 according to the guidance frames, ensuring the calibration board is captured from diverse angles for optimal quality.

• ​Alignment Guidance:

  • Move the AC1 to ensure the calibration board fully fits within the guidance frame and occupies as much area as possible.
  • When conditions are met, the program triggers automatic detection and publishes results on /camera/image_detecte.

• ​Calibration Completion:

  • After capturing all images, the program automatically computes the intrinsic parameters and displays results in the output area and terminal.
  • Expected accuracy ​within 1.0 pixel.

• ​References:

  • Demo Video
  • Sample Data

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5.4 Camera-Lidar Extrinsic Calibration

• ​Load Configuration File: Click the Open button to load the correct configuration file.

• ​Start Driver: Click the Start Driver button in the control panel. The button will turn gray once initialization is complete.

• ​Calibration Board Setup Recommendations:

  • Ensure the board is within the ​FOV of both sensors (recommended distance: ​0.8m~1m). Use Rviz for verification.
  • Tilt the board at ​~45° for optimal feature extraction.
  • Mount the board ​suspended to avoid interference from background objects.
  • Keep the AC1 ​stable to minimize motion-induced errors.
  

• ​Start Calibration:

  • Click the Camera-Lidar button. The program automatically checks calibration conditions, computes extrinsic parameters, and displays results upon completion.
  • Expected accuracy within 0.3°.

• ​Reference:

  • Sample Data

5.5 Camera-IMU Extrinsic Calibration

• ​Load Configuration File: Click the Open button to load the correct configuration file.

• ​Start Driver: Click the Start Driver button in the control panel. The button will turn gray once initialization is complete.

• ​Start Calibration:

  • Click the Camera-IMU button in the control panel.
  • To ensure calibration accuracy, the process starts with IMU bias calibration. Keep AC1 stationary for 10 seconds to allow the program to automatically calculate the bias. Wait until the message "imu bias has been calibrated" appears in the output area, then begin rotating AC1 (refer to the demo video for rotation guidance).
  • To ensure calibration accuracy, each rotation of AC1 must provide sufficient angular deviation while keeping the target board within the camera's field of view.
  • To ensure calibration accuracy, after each rotation, keep AC1 stationary again for 3–5 seconds before performing the next rotation.
  • To ensure calibration accuracy, rotate AC1 around different axes to ensure sufficient excitation of motion in all directions.
  • The program automatically detects calibration status. Once sufficient data is collected, the extrinsic parameters are calculated, and results are displayed in the output area and terminal.
  • Expected accuracy within 1°.

• ​Reference:

  • Demo Video
  • Sample Data

6. FAQ

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