Based on the investigation of the current development trends of deep-sea mining technologies, and in combination with the analysis of domestic and international literature and patent hotspots, three key technological fields of deep-sea mining were identified: collection, lifting, and surface support. Based on the systematic sorting of the core technologies in different fields, a review on the domestic and international research progress is presented in 10 core technologies, including ore crushing, ore collection, mining vehicle traveling, long-distance vertical pipeline transportation, anti-clogging and emergency escape for lifting pipelines, pump-free mineral transportation, underwater acoustic communication, mineral processing, launch and recovery, as well as heave compensation. A multi-dimensional quantitative assessment was conducted on China’s advantages and disadvantages compared to the international level in the overall field of deep-sea mining and the three key technological fields of collection, lifting, and surface support. Comprehensive analysis indicates that at the current stage, the main shortcomings of China’s deep-sea mining technologies include the low efficiency of core equipment, insufficient long-term reliability, inadequate understanding of deep-sea environmental disturbance mechanisms, and the lack of integrated coordinated operation in at-sea tests. The global challenges of deep-sea mining technology are mainly manifested in dynamic coordinated control under multi-field coupling, flow assurance and equipment reliability in long-distance vertical transportation, and environmental constraints and plume control. In the future, it is advisable for China to focus on breaking through core technologies, strengthening environmental impact assessment and monitoring, and conducting integrated system at-sea tests, so as to move toward the more systematical, smarter and eco-friendly technology, laying a foundation for China’s future participation in deep-sea resource exploitation.

By reviewing the formulation process of the Draft Regulations on Exploitation of Mineral Resources in the Area (short for the “Exploitation Regulations”) by the International Seabed Authority (ISA) and the US policies and legislations to unilaterally advance deep-sea mining in the international seabed area (short for the “Area”), this paper analyzes the game landscape of international legal regimes governing deep-sea mining from multiple perspectives, including core divergences over the Exploitation Regulations, differentiated interest demands of participating parties, and the impact of US unilateral practice. Based on the analysis results, some countermeasures are proposed, including promoting the ISA to optimize the review procedure of the Exploitation Regulations, petitioning the Seabed Disputes Chamber of the International Tribunal for the Law of the Sea to render an advisory opinion on the legality of US unilateral authorization of deep-sea mining in the Area, and actively applying for new exploration contract within the Area.

This paper reviews the research progress in numerical simulation of transport and dispersion of plumes generated during deep-sea mining. Based on the formation mechanisms of plumes, the differences between dynamics of collector plumes and midwater plumes are compared in terms of discharge, transport driven by buoyancy and passive advection. By comparing the advantages and disadvantages of widely used near-field and far-field numerical frameworks in terms of applicable scales, computational efficiency, and physical accuracy, the parameterization methods for key physical processes are illustrated. Aiming at the bottleneck of insufficient deep-sea environmental data, the limitations and core challenges in current laboratory flume experiments and in-situ observations for model verification are further analyzed. On this basis, a prospect for the development direction are finally offered, including integration of artificial intelligence and advanced data assimilation techniques with establishment of standardized model evaluation framework.

Based on the slope-climbing dynamic analysis of mining vehicles, models for traction, total resistance and sinkage were established with the characteristics of soft deep-sea sediment taken into consideration, and a passable slope threshold was also determined. An improved A* path planning algorithm is proposed, which integrates multi-cost constraints to optimize the search efficiency and path quality, and employs a redundant node removal method and Bézier curve fitting for the post-processing smoothing of the path. Simulation results show that, compared with the traditional A* algorithm, the proposed improved algorithm makes the total length of the path planned shortened by about 3% on average, reduces the travel time and energy consumption costs by over 60% on average, and decreases the total steering angle of the path by over 70% on average. It generates a global path with a lower comprehensive cost and smoother steering, effectively improving the safety and efficiency of deep-sea mining vehicle operations.

Based on sorting out all exploration contracts approved by the International Seabed Authority, progress in negotiations on exploitation regulations, and policy divergences among major countries, it is argued that controversies over deep-sea mining rules focus on environmental protection, benefit distribution, regulatory responsibilities and commercial feasibility. China has established a relatively complete resource layout in international seabed, and also solid technological foundation for deep-sea exploitation, yet still confronts with regulatory uncertainties, environmental pressure and constraints on commercialization. China shall actively participate in the formulation of international deep-sea mining rules, strengthen international cooperation, and coordinate resource security and ecological conservation, for promoting the commercial exploitation of deep-sea mineral resources.

A loosely coupled visual-inertial fusion positioning algorithm based on Extended Kalman Filter (EKF) is proposed, which adopts a visual algorithm for relative pose estimation. It takes a mining vehicle as an observation target to acquire low-frequency and high-precision global coordinates, and then fuses these data with high-frequency global coordinate information from the inertial navigation system (INS). Simulation results show that compared with the INS, the proposed fusion algorithm leads to the average position error reduced from 1.309 m to 0.026 m for rectangular trajectory and from 1.749 m to 0.028 m for serpentine trajectory, indicating a remarkable improvement. Further experiments have verified the feasibility of the proposed algorithm, which provides technical support for cooperative operation of robots under complex deep-sea working conditions.