Most autonomous mobile robots are often equipped with monocular cameras and 3D LiDARs to perform vital tasks such as localization and mapping. In this paper, we present a two-stage extrinsic calibration method as well as a hybrid-residual-based odometry approach for such camera-LiDAR systems. Our extrinsic calibration method can estimate the relative transformation between the camera and the LiDAR with high accuracy, allowing us to better register the image and the point cloud data. After the calibration, our hybrid-residual-based odometry can be used to provide real-time, accurate odometry estimates. Our approach exploits both direct and indirect image features. The sensor motions are estimated by jointly minimizing reprojection residuals and photometric residuals in a nonlinear optimization procedure. Experiments are conducted to show the accuracy and robustness of our extrinsic calibration and odometry algorithms using both public and self-owned real-world datasets. The results suggest that our calibration method can provide accurate extrinsic parameters estimation without using initial values, and our odometry approach can achieve competitive estimation accuracy and robustness.

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Purpose – The purpose of this paper is to design intelligent robots operating in such dynamic environments like the RoboCup Middle-Size League (MSL). In the RoboCup MSL, two teams of five autonomous robots play on an 18- × 12-m field. Equipped with sensors and on-board computers, each robot should be able to perceive the environment, make decision and control itself to play the soccer game autonomously. Design/methodology/approach – This paper presents the design of our soccer robots, participating in RoboCup MSL. The mechanical platform, electrical architecture and software framework are discussed separately. The mechanical platform is designed modularly, so easy maintainability is achieved; the electronic architecture is built on industrial standards using PC-based control technique, which results in high robustness and reliability during the intensive and fierce MSL games; the software is developed upon the open-source Robot Operating System (ROS); thus, the advantages of ROS such as modularity, portability and expansibility are inherited. Findings – Based on this paper and the open-source hardware and software, the MSL robots can be re-developed easily to participate in the RoboCup MSL. The robots can also be used in other research and education fields, especially for multi-robot systems and distributed artificial intelligence. Furthermore, the main designing ideas proposed in the paper, i.e. using a modular mechanical structure, an industrial electronic system and ROS-based software, provide a common solution for designing general intelligent robots. Originality/value – The methodology of the intelligent robot design for highly competitive and dynamic RoboCup MSL environments is proposed.

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