水下无人系统学报

Based on One-dimensional Attention Mechanism Convolutional Neural Network for Underwater Acoustic Target Recognition

ZHANG Yufei, ZHAO Mei, HU Changqing, GUO Zheng

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0053

[Abstract](0) [FullText HTML] (0) [PDF 1531KB](0)

Abstract:
To address the issues of complex network parameters and high computational costs in deep learning-based underwater acoustic target recognition models, this study proposes a lightweight one-dimensional convolutional neural network with an attention mechanism for underwater acoustic target recognition.First, during the feature extraction stage, spectral, Mel-spectrogram, chroma, spectral contrast, and tonal features are selected and reconstructed into a fused one-dimensional hybrid feature. Next, the hybrid feature is processed by a multi-scale residual convolution (MRC) module to enhance feature representation across different scales. Simultaneously, a Convolutional Block Attention Module (CBAM) is introduced to adaptively adjust feature importance through channel and spatial attention mechanisms, improving the model's focus on critical regions.Experimental results show that the proposed model achieves an average recognition accuracy of 98.58% on the ShipsEar dataset, demonstrating excellent classification performance. Compared to existing models, this model significantly reduces computational complexity. Further validation on real-world data from the East China Sea confirms its effectiveness.

Design and verification of end-face bidirectional self-sealing structure

LI Kaifu, GUAN Youliang, JIG Guotao, JIANG Quan, LIU Yunfan, JIAO Peng

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0020

[Abstract](0) [FullText HTML] (0) [PDF 4562KB](0)

Abstract:
In order to achieve the bidirectional sealing of the end face of underwater large-caliber hatch covers and solve the problem of large reaction force of the sealing ring during the closing process. Innovatively combining the good self-sealing advantage of the tongue-shaped cross-section and the anti-ejection structure of the dovetail structure, five specifications of "high-low tongue" bidirectional self-sealing rings were designed. The stress, deformation, contact pressure and other simulation analyses of the sealing rings were carried out using ABAQUS, and a prototype was trial-produced to conduct internal and external pressure sealing tests as well as loosening and tightening torque tests. The test results are consistent with the results of finite element analysis. The "high-low tongue" sealing ring can achieve bidirectional self-sealing of the end face under low reaction force. The larger the chamfer of the "tongue-shaped" structure, the higher the contact stress value between the sealing ring and the sealing surface, and the better the sealing effect; the smaller the difference in the height of the "tongue" on both sides of the sealing ring, the lower the height of the middle platform, and the easier it is for the sealing ring to be sucked out; reducing the maximum height and the middle platform height of the sealing ring can effectively reduce the sealing reaction force and extend the service life of the sealing ring. Based on the test results, the sealing ring was improved and optimized, and a large-caliber sealing ring was trial-produced. After closing and pressing the cover for more than a thousand times, it can still achieve self-sealing of internal air pressure, internal water pressure and external water pressure. The research results provide a reference for the design and application of end face sealing of large underwater pressure-bearing equipment.

Study on the Dynamic Interaction between Lower Limb Posture and Flow Field Environment during Underwater Diver Motion

ZOU Pengjun, LIN Xinghua, ZHANG Junxia, WANG Xinting, WANG Hao

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0052

[Abstract](0) [FullText HTML] (0) [PDF 1338KB](1)

Abstract:
In this paper, the dynamic coupling mechanism between the posture of the lower limbs and the flow field environment in the underwater movement of frogmen is deeply studied. Firstly, using the fluid-structure interaction simulation method, a numerical model of the frogman's lower limb dynamics with wearable assistive equipment was constructed, and the reliability of the numerical model was verified by comparing the experimental results with the simulation data. Secondly, based on the validated model, the influence of water flow impact on the posture of the frogman's lower limbs at different speeds was analyzed and the rule of joint angles was revealed. Finally, the Pareto optimal solution set of lower limb joint angles at different speeds was obtained based on the NSGA-II multi-objective optimization algorithm, the drag optimization strategy based on attitude compensation was proposed, and the optimization effect was verified through experiments. The results show that at a fixed speed, the lower limb posture experiences three phases: "maximum deformation - reverse adjustment - dynamic equilibrium." As the speed increases, the stable posture of the lower limb tends to flow field adaptive equilibrium point. Within the 1~3 kn speed range, the compensation between the posture stabilization angle and the optimal angle of resistance for the hip, knee, and ankle joints is −0.78°, 2.28°, and −1.05°. In the experimental verification of lower limb attitude optimization, the speed is increased by 9.09% compared with the free state, which indicates that the underwater kinematic performance can be improved by lower limb attitude angle constraints. This provides a quantitative basis for the closed-loop control of the joint module of the underwater assisted exoskeleton and the overall design of the flow field adaptation.

Research on the Extraction and Recognition of Space-Time-Frequency Features for Underwater Moving Targets

LIU Xiaochun, YANG Yunchuan, HU Youfeng, WANG Chenyu, LI Yongsheng

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0067

[Abstract](0) [FullText HTML] (0) [PDF 1231KB](0)

Abstract:
Aiming at the issue of inadequate bearing-angle adaptability in active sonar target recognition, this paper elaborates on the physical mechanism of active sonar target information perception from wave equation theory. Based on generalized multiple signal classification(MUSIC) spatial spectrum estimation, a novel method is proposed for acquiring the pseudo three-dimensional spatial feature of underwater targets by incorporating distance information, thereby effectively enhancing the adaptability of spatial features across different bearing angles. Additionally, research is conducted on methods to enhance Pseudo Wigner-Ville Distribution(PWVD) time-frequency features and extract Doppler frequency shift distribution features of moving targets. By leveraging the complementary advantages of these two algorithms, the bearing-angle adaptability is further improved. To address the challenge of scarce and imbalanced underwater target samples, the concept of meta-learning is integrated to construct a data-level fusion target recognition network that incorporates spatial, time-frequency, and Doppler domain features. The network is trained and tested using simulation and experimental data. The results demonstrate that the fusion features significantly improve the bearing-angle adaptability and anti-interference capability, providing a novel approach for the development of intelligent underwater target recognition technology.

A Review of Research Progress on Liquid Metal-Driven Soft Robotics

CAI Yueyao, WANG Shenlong

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0080

[Abstract](2) [FullText HTML] (0) [PDF 4002KB](2)

Abstract:
With the rapid advancement of key technologies in soft robotics, liquid metals have emerged as a focus in this field due to their unique properties, including low melting point, high electrical conductivity, superior thermal conductivity, and excellent fluidity. Gallium-based alloys have significantly enhanced their auxiliary application potential in actuation systems through approaches like magnetic reinforcement, electroactive enhancement, and structural optimization. As conductive materials and flexible electrodes, they demonstrate further promise in actuation, sensing, and multi-degree-of-freedom(multi-DOF) motion through approaches like magnetic reinforcement, electroactive enhancement, and structural optimization. This review systematically summarizes the functional characteristics, actuation mechanisms, and sensing technologies of liquid metals, with particular emphasis on their current applications and challenges in underwater soft robotics. To date, liquid metal-based actuators have achieved diverse actuation modes, including electrothermal, electrochemical, and magnetic driving mechanisms, while corresponding sensors have made breakthroughs in high-sensitivity strain detection, pressure sensing, and multimodal signal monitoring. Nevertheless, the realization of multi-DOF motion in underwater environments still faces technical challenges, such as complex actuation mechanisms, insufficient material stability, and imperfect control systems. Future research needs to further overcome these technical bottlenecks to advance the practical application of liquid metal-driven underwater soft robots.

An Engineering Approach for Obstacle Avoidance Path Planning of Unmanned Vessel Based on Optimized Artificial Potential Field

ZHANG Yabo, WANG Hongrui, ZHANG Haiyan, XIAO Qiang, LIU Yuxin

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0030

[Abstract](28) [FullText HTML] (11) [PDF 1259KB](6)

Abstract:
Aiming at the local path planning problem of obstacle avoidance for unmanned surface vessel, relying on the artificial potential field framework, a local path planning method for obstacle avoidance based on the dynamic construction of the water surface situation in longitude and latitude coordinates is proposed. Initially, the basic operations in the longitude and latitude coordinate system are sorted out and organized, and then the forms of the gravitational and repulsive force functions of the traditional potential function method are derived. The problems existing in the traditional potential function method and its improved methods, such as the difficulty in determining the virtual target point in the project and the inability to accurately predict the trajectory of the controlled object, are expounded. An improved potential function local path planning algorithm relying on the dynamic construction of the water surface situation is designed. Finally, the designed method is verified by simulation and sea trials. The simulation and test results show that the proposed engineering method of obstacle avoidance path planning can guide the unmanned surface vessel to complete the obstacle avoidance task, and has strong reliability and robustness.

Prediction method for buckling of deepwater explosion cylindrical shell based on random forest

FU Gaojun, MA Feng, ZHU Wei, JIA Xiyu, WANG Shuang

, Available online , doi: 10.11993/j.issn.2096-3920.2024-0162

[Abstract](20) [FullText HTML] (11)

Abstract:
Under deep-water explosion conditions, pressure-resistant structures such as cylindrical shells will have a different failure mode from that in shallow water - instability buckling. In order to study the conditions for the occurrence of instability buckling of cylindrical shells under deep water explosion conditions and realize the prediction of the buckling state, a numerical simulation model was firstly established to simulate and analyze the results of the buckling of cylindrical shells under the conditions of different charge amount, blast distance and water depth. Based on the simulation results, a random forest model was designed to predict the buckling state. The results show that under the loading conditions of axial explosion in deep water environment, the cylindrical shell may present two macroscopic responses of unbuckling and buckling, and the prediction model constructed by the random forest algorithm can better realize the prediction of the instability state of the cylindrical shell under the specific structural parameters, and the prediction accuracies under the two structures reach 0.9375 and 0.875 respectively, which can provide references for the study of the buckling conditions of the cylindrical shell.

Analysis of the Impact of Shock Waves on the Safe Exit of the Rocket-assisted Vehicle Nose Cap during the Thermal Emission Process of a Concentric Canister Launcher

LIU Gangqi, YUAN Xin, GAO Shan, CUI Canli, HUANG Yuxuan

, Available online , doi: 10.11993/j.issn.2096-3920.2024-0156

[Abstract](31) [FullText HTML] (13) [PDF 1755KB](6)

Abstract:
In response to the impact of shock waves on the safety of the rocket-assisted vehicle nose cap during the concentric tube thermal launch process, computational fluid dynamics (CFD) software was used to numerically simulate the ignition and launch process. The propagation process of shock waves and gas generated by solid rocket motors in the concentric tube was analyzed in detail, and the force variation curve of the nose cap under the action of shock waves was obtained, revealing the force mechanism of the nose cap inside the tube under the action of shock waves. The test data of the shock wave opening process during the field test of a certain product further illustrates the force variation process of the nose cap in the shock wave environment. The research results contribute to a clear understanding of the mechanism of force changes on the nose cap under the shock wave during the thermal emission process of concentric cylinders, and can be used to guide the safety design of the nose cap exiting the cylinder.

The 3D Reconstruction Method of Submarine Cables Based on High-Speed ROV Cruising with Multibeam Sonar

XU Haining, WANG Yong, JING Qiang, DING Tongzhen, YU Fei, SHEN Qingye, CAO Shengzhe

, Available online , doi: 10.11993/j.issn.2096-3920.2025-0036

[Abstract](50) [FullText HTML] (8)

Abstract:
Submarine cables, serving as the critical conduits for power transmission in offshore wind farms, are pivotal to the system's stability. However, due to their complex environments, three-dimensional (3D) reconstruction technology for these cables has become a key method for their inspection and maintenance. Currently, conventional 3D reconstruction methods for submarine cables are costly and less effective in deep-sea environments. Therefore, this paper proposes a 3D reconstruction method for submarine cables based on high-speed Remotely Operated Vehicle (ROV) cruising with sonar, drawing on the concept of synthetic aperture and simplifying calculations through spatial carving. This method comprehensively processes the multiple sonar observation information obtained during the ROV cruising to collectively reflect the spatial occupancy. In the simulation experiments of submarine cable 3D reconstruction, a comparison with mainstream methods was conducted. It is evident that the proposed method not only reduces the cost of submarine cable reconstruction by using conventional multibeam sonar but also achieves higher reconstruction accuracy, demonstrating significant application value and promotion potential.

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