Yajuan Kang

In view of the requirements and characteristics of a deep-sea polymetallic nodule collector’s movements according to a planned path and speed during operation, a collector trajectory tracking system scheme based on virtual target vehicle reference is proposed. In this system, the virtual target vehicle moves according to the planned path and speed, thereby generating a dynamic target path and speed. A fuzzy controller calculates the collector’s angular-velocity command based on the lateral position deviation and the heading-angle deviation between the collector and the target vehicle, and a proportional controller calculates the collector’s body linear velocity control command based on the longitudinal position deviation between the collector and the target vehicle. By integrating these two commands, the collector tracks the target vehicle and thereby realizes trajectory tracking of the planned path and speed. A control system is designed, and simulation studies are carried out. The results show that the designed system enables the collector to track the planned path and speed well under operational conditions. The trajectory tracking method based on virtual target vehicle reference can also form an organic integration of path planning and trajectory tracking, generate dynamic planned paths and speeds for the entire mining area, and realize movement of the collector along the planned path and speed throughout the whole operation.

In view of the requirements and characteristics that a deep-sea polymetallic nodule collector must travel according to a planned path and speed during operation, a collector trajectory tracking system scheme based on virtual target vehicle following is proposed. In this system, the virtual target vehicle travels according to the planned path and speed, thereby generating a dynamic target path and speed. A fuzzy controller calculates the collector’s angular-velocity command based on the lateral position deviation and the heading-angle deviation between the collector and the target vehicle, and a proportional controller calculates the collector’s body linear velocity control command based on the longitudinal position deviation between the collector and the target vehicle. By integrating these two commands, the collector follows the target vehicle and thereby realizes trajectory tracking of the planned path and speed. A tracking system is designed and simulation studies are carried out. The results show that the designed system enables the collector to follow the planned path and speed well under operational conditions. The trajectory tracking method based on virtual target vehicle following can also form an organic integration of path planning and trajectory tracking, generate dynamic planned paths and speeds for the entire mining area, and realize tracking travel of the collector along the planned path and speed throughout the whole operation.

Prior research has proposed a basic configuration for a deep-sea mining system integrating slurry transport and wastewater discharge, and examined the operational characteristics of water-driven diaphragm pumps. Against the backdrop of commercial deep-sea polymetallic nodule exploitation, this study focuses on the technical design of seabed diaphragm pump groups and hydraulic parameter matching for a coupled slurry transport-wastewater discharge system. The solid–liquid two-phase output characteristics of the water-driven diaphragm pump were analyzed, leading to the proposal of a four-pump staggered configuration to ensure continuous particulate discharge throughout the full operating cycle. To meet commercial mining capacity requirements, the system consists of two sets (each with four pumps) operating with a phase offset to reduce fluctuations in slurry output concentration. A centralized output device was developed for the pump group, and a centralized mixing tank was designed based on analyses of outlet pipe length and positional effects. CFD-DEM simulations show that the combined effects of phased pump operation and centralized mixing tank mixing result in the slurry concentration delivered to the riser pipeline staying within ±1% of the mean for up to 57.8% of the system’s operational time. Considering the characteristics of both diaphragm and centrifugal pumps, the system is designed to output high-concentration slurry from the seabed diaphragm pumps, driven solely by wastewater, while centrifugal pumps provide lower-concentration transport by adding supplementary water from a buffer—thus reducing the risk of clogging. Under the constraints of centrifugal pump capacity, the system’s hydraulic parameters were optimized to maximize overall slurry transport efficiency while minimizing the energy consumption from wastewater discharge. The resulting configuration defines the flow rate and slurry concentration of the diaphragm pump group. Compared with conventional centrifugal pump-based transport schemes, the proposed system increases the slurry pipeline efficiency from 53.14% to 55.43% and reduces wastewater discharge-related pipeline resistance losses from 475.9 mH₂O to 361.7 mH₂O.

The development of heave compensation systems in marine engineering and deep-sea mining applications is analyzed, and their functional requirements and key features are summarized. Based on this analysis, a system is proposed that uses flexible joints to compensate for pitch and roll motion, along with a single-chamber valve-controlled compensation cylinder with a high-pressure accumulator to compensate for heave motion. An active heave compensation system based on this design is studied using a fuzzy PID control method. A dynamic model of the system is then established for this control system. Numerical simulations are carried out to evaluate the control process and performance under different sea conditions. The results show that the proposed heave compensation system offers distinct advantages such as a simple and compact structure, minimal deck space requirements on the mining vessel, and large compensation angles for both pitch and roll. Furthermore, the use of a fuzzy PID control method for heave compensation achieves a relatively good compensation effect, and can be adapted to varying sea conditions.

Deep-sea polymetallic nodules are a mineral resource with potential for commercial development. Due to the unique deep-sea environment in which they are found, specialized technology and equipment are required for their extraction. In this paper, firstly, the development of deep-sea polymetallic nodule mining technology is classified into three stages, and its characteristics are summarized. Moreover, the results from research into deep-sea polymetallic nodule mining technology are analyzed, including proposals for mining systems, research into key technologies, basic scientific problems, and proof of technical feasibility from sea tests. Secondly, the testing of the collector prototype and the environmental impact assessment study of Global Sea Mineral Resources NV, as well as the progress of the deep-sea polymetallic nodule mining test project in China, are introduced. On this basis, the opportunities and challenges brought by the fast-growing demand for electric vehicles to the development of deep-sea polymetallic mining technology is analyzed, and a possible technical scheme for a mining system and the trends in its development towards high reliability and high standards of environmental protection according to the requirements of commercial exploitation are explored. This provides a reference for the research and development of high-efficiency technology and equipment for the mining of deep-sea polymetallic nodules.