RINO: Accurate, Robust Radar-Inertial Odometry with Non-Iterative Estimation

Precise localization and mapping are critical for achieving autonomous navigation in self-driving vehicles. However, ego-motion estimation still faces significant challenges, particularly when GNSS failures occur or under extreme weather conditions (e.g., fog, rain, and snow). In recent years, scanning radar has emerged as an effective solution due to its strong penetration capabilities. Nevertheless, scanning radar data inherently contains high levels of noise, necessitating hundreds to thousands of iterations of optimization to estimate a reliable transformation from the noisy data. Such iterative solving is time-consuming, unstable, and prone to failure. To address these challenges, we propose an accurate and robust Radar-Inertial Odometry system, RINO, which employs a non-iterative solving approach. Our method decouples rotation and translation estimation and applies an adaptive voting scheme for 2D rotation estimation, enhancing efficiency while ensuring consistent solving time. Additionally, the approach implements a loosely coupled system between the scanning radar and an inertial measurement unit (IMU), leveraging Error-State Kalman Filtering (ESKF). Notably, we successfully estimated the uncertainty of the pose estimation from the scanning radar, incorporating this into the filter's Maximum A Posteriori estimation, a consideration that has been previously overlooked. Validation on publicly available datasets demonstrates that RINO outperforms state-of-the-art methods and baselines in both accuracy and robustness. Our code is available at https://github.com/yangsc4063/rino.

4D Millimeter-Wave Radar in Autonomous Driving: A Survey

The 4D millimeter-wave (mmWave) radar, capable of measuring the range, azimuth, elevation, and velocity of targets, has attracted considerable interest in the autonomous driving community. This is attributed to its robustness in extreme environments and outstanding velocity and elevation measurement capabilities. However, despite the rapid development of research related to its sensing theory and application, there is a notable lack of surveys on the topic of 4D mmWave radar. To address this gap and foster future research in this area, this paper presents a comprehensive survey on the use of 4D mmWave radar in autonomous driving. Reviews on the theoretical background and progress of 4D mmWave radars are presented first, including the signal processing flow, resolution improvement ways, extrinsic calibration process, and point cloud generation methods. Then it introduces related datasets and application algorithms in autonomous driving perception and localization and mapping tasks. Finally, this paper concludes by predicting future trends in the field of 4D mmWave radar. To the best of our knowledge, this is the first survey specifically for the 4D mmWave radar.