A Review on Search and Rescue Robots in Complex Scenarios: Key Technologies of Simultaneous Localisation and Mapping

This paper presents a comprehensive review of robotics research in search and rescue (SAR) operations conducted in caverns, underground environments, disaster zones, and other areas where Global Navigation Satellite System (GNSS) signals are unavailable. The majority of applications for Simultaneous Localisation and Mapping (SLAM), despite its maturity, are still restricted to structured indoor settings or outdoor environments under normal weather conditions. Standard SLAM frameworks often experience degradation and malfunction or even fail when deployed in increasingly complex and unstructured scenarios. This review identifies three major challenges that robots face in SAR environments: (i) increasingly complex terrain, (ii) changing environments and visibility, and (iii) autonomous exploration requirements, along with corresponding technological evolutions in robot mobility, sensor technologies, and SLAM algorithms. A comprehensive and quantitative evaluation of existing approaches is provided, focusing on SLAM on uneven terrain, multisensor fusion, and active SLAM. Additionally, this paper outlines ongoing challenges for guiding future development toward more robust and reliable deployment‐oriented SLAM solutions for SAR applications. These include: (i) short‐term dynamics and structural changes that undermine data association and loop closure, (ii) observability loss and degeneracy in confined and cluttered spaces, and (iii) multirobot consistency under constrained communication. Two cross‐cutting constraints, which are sensor non‐stationarity and safety‐critical autonomy, are highlighted as key factors that turn deployable SAR SLAM into a system‐level reliability problem. Finally, potential research directions and a practical research roadmap toward robust, real‐time, and evaluable SAR SLAM are outlined.