  Loop Closure Detection (LCD) is an essential task in robotics and computer
vision, serving as a fundamental component for various applications across
diverse domains. These applications encompass object recognition, image
retrieval, and video analysis. LCD consists in identifying whether a robot has
returned to a previously visited location, referred to as a loop, and then
estimating the related roto-translation with respect to the analyzed location.
Despite the numerous advantages of radar sensors, such as their ability to
operate under diverse weather conditions and provide a wider range of view
compared to other commonly used sensors (e.g., cameras or LiDARs), integrating
radar data remains an arduous task due to intrinsic noise and distortion. To
address this challenge, this research introduces RadarLCD, a novel supervised
deep learning pipeline specifically designed for Loop Closure Detection using
the FMCW Radar (Frequency Modulated Continuous Wave) sensor. RadarLCD, a
learning-based LCD methodology explicitly designed for radar systems, makes a
significant contribution by leveraging the pre-trained HERO (Hybrid Estimation
Radar Odometry) model. Being originally developed for radar odometry, HERO's
features are used to select key points crucial for LCD tasks. The methodology
undergoes evaluation across a variety of FMCW Radar dataset scenes, and it is
compared to state-of-the-art systems such as Scan Context for Place Recognition
and ICP for Loop Closure. The results demonstrate that RadarLCD surpasses the
alternatives in multiple aspects of Loop Closure Detection.
