水下无人系统学报

Current Development of Control Technology for Unmanned Surface Vessel Clusters under Complex Sea Conditions

XIE Shao-rong, LIU Jian-jian, ZHANG Dan

2020, 28(6): 584-596. doi: 10.11993/j.issn.2096-3920.2020.06.001

[Abstract](975) [PDF 369KB](1169)

Abstract:
As highly autonomous systems, unmanned surface vessels (USVs) are a reliable means of improving working efficiency on water in such areas as hydrology research, scientific exploration, hydrographic surveys, emergency search and rescue, and security patrol. Advancements in exchange information and collaborative decision-making have enabled the development of USV cluster systems. These systems can obtain more complete perception information and have a high execution efficiency and greater operating range, which considerably enhance the capabilities of USVs to complete tasks autonomously. However, because of complex and changeable marine environmental factors such as wind, waves, and sea currents, collaborative control and optimization decision-making of USV cluster systems face challenges related to single USV autonomous and complete perception mechanism, rapid and flexible interactive cognition of multiple USVs, and real-time efficient cluster collaboration. This study summarizes the latest developments of USV cluster systems in the following four respects: 1) the single USV complete autonomous perception mechanism, 2) the multiple-USV real-time interactive cognition mechanism, 3) the intelligent collaborative control decision methodology, and 4) the USV verification platform. Finally, problems that remain to be addressed as well as future research directions in the field are also briefly discussed. Single USV autonomous and complete perception, rapid and flexible interactive cognition among multiple USVs, and real-time efficient cluster collaboration are the research directions of cluster control technology.

Maritime Object Detection Method Based on Self-Supervised Representation Learning

ZHANG Qian, ZHANG You-mei, LI Xiao-lei, SONG Ran, ZHANG Wei

2020, 28(6): 597-603. doi: 10.11993/j.issn.2096-3920.2020.06.002

[Abstract](483) [PDF 1380KB](353)

Abstract:
To improve the perception and monitoring ability of marine unmanned equipment, boosting the performance of maritime object detection is critical. However, complex sea environments and limited sensors make it difficult to collect high-quality samples for a large-scale maritime dataset. This results in a dearth of large-scale sea surface target datasets, which in turn hampers the development of maritime object detection based on deep earning. To address this problem, this study introduces self-supervised representation learning into the field of maritime object detection. Specifically, a momentum-contrast based algorithm is proposed to conduct representation learning of ships, where the characteristics of ship targets are learned from large-scale unlabeled maritime data. This provides prior knowledge for subsequent maritime object detection based on Faster R-CNN. Experimental results show that with the aid of model pre-training on a large-scale unlabeled dataset in a self-supervised manner, the proposed maritime object detection method through self-supervised representation learning has a performance comparable with those that employ supervised model pre-training. The proposed method can thus overcome the limitations caused by an inadequate number of labeled maritime samples.

Plots-Centroid Method for USV-Borne Millimeter-Wave Radar Based on Euclidean Distance

LI Rui-wei, LI Li-gang, JIN Jiu-cai, LIU De-qing, LI Fang-xu, DAI Yong-shou

2020, 28(6): 604-610. doi: 10.11993/j.issn.2096-3920.2020.06.003

[Abstract](262) [PDF 1419KB](198)

Abstract:
To solve the problems of false alarm and target-plot splitting of millimeter-wave(MMW) radar used in the detection of obstacles in unmanned surface vessels(USVs) on the sea, most recent studies have reduced false alarms by processing radar echo based on waveform characteristics. These studies have also compared multi-dimensional information such as the distance and angle of plots to determine whether the plots belong to the same target, this studies are cumbersome. And the centroid methods are not sufficiently accurate to represent the target state. Therefore, this study proposes a plots-centroid method based on Euclidean distance that solves the problems of false alarm and target-plot splitting by processing radar plot data. First, using prior knowledge related to radar echo intensity and effective detection range, a threshold filtering method is used to remove invalid plots. Then, based on the rule stating that plots belonging to the same target have the same speed and close distance, the Euclidean distance is used to measure the similarity of information between plots. Finally, target-plot clustering is realized. Finally, the position and section width of the obstacle target are calculated, where the range of the obstacle target is denoted by a rectangular dangerous area to enable accurate detection of the obstacle target in front of the USV. The effectiveness of this method is verified by an actual ship test conducted.

Inverse Optimal Cooperative Control for Unmanned Surface Vessel Cluster

ZHANG Zhen-hua, LI Yao, YU Cheng-pu

2020, 28(6): 611-617. doi: 10.11993/j.issn.2096-3920.2020.06.004

[Abstract](416) [PDF 819KB](345)

Abstract:
To realize an optimal cooperative control strategy of unmanned surface vessel(USV) clusters under artificial control through data-driven learning, a linear quadratic closed-loop differential game inverse optimization algorithm is proposed. The algorithm can identify the cooperative strategy objective function according to the optimal system state and control input trajectories. In this study, an optimal feedback matrix is first identified based on the observed optimal system state and control input trajectories with additive white noise. The cooperative strategy objective function is then identified after solving the coupled algebraic Riccati equations derived from the necessary and sufficient conditions for Nash equilibria. The proposed inverse optimization algorithm can obtain the optimal cooperative strategy objective function to satisfy the given system state and control input trajectories. The objective functions identified by the inverse optimization algorithm can then be used to achieve an optimal cooperative control of USV clusters for specific task scenarios and provide new ideas and solutions for cluster adversarial games.

Scale Adaptive Sea Surface Target Tracking Algorithm Based on Deep Learning

WU Xiang, ZHONG Yu-xuang, YUE Qi-qi, LI Xiao-mao

2020, 28(6): 618-625. doi: 10.11993/j.issn.2096-3920.2020.06.005

[Abstract](743) [PDF 3993KB](252)

Abstract:
Compared with target tracking in common scenes, sea surface target tracking presents unique challenges such as changes in the target scale and perspective as well as intense dithering of targets. Accordingly, a scale-adaptive sea surface target tracking algorithm based on deep learning is proposed. The algorithm classifies samples according to whether the central point of the sample falls to the ground truth and then regresses the distances from the target location to the four sides of the bounding box to predict the position and scale of the target. An evaluation platform for the sea surface target tracking algorithm is also established to verify the effectiveness of the proposed algorithm. Experimental results show that compared with the anchor-based algorithm, the tracking accuracy of the proposed algorithm is improved by 4.8% and its success rate is improved by 11.49%, thus effectively solving the problem of target scale adaptation.

Collaborative Path Tracking Control Method of USV Cluster Based on RBF Integral Sliding Mode

SHI Wen-yu, LIANG Xiao, QU Xing-ru, TENG Jian-ping

2020, 28(6): 626-633. doi: 10.11993/j.issn.2096-3920.2020.06.006

[Abstract](769) [PDF 515KB](168)

Abstract:

To meet the requirements of ship escorts and target enclosure, a collaborative path tracking control method for underactuated unmanned surface vessel(USV) cluster based on a path parameter cycle is proposed in this study. In a kinematics design that includes line-of-sight guidance and a consistency algorithm, a collaborative guidance law is designed for the USV cluster. This design realizes symmetrical formation on a closed curve and target enclosure. In a dynamics design in which model uncertainties and chattering induced by the traditional sliding mode are considered, a distributed integral sliding mode controller based on an adaptive radial basis function neural network is designed. This distributed integral sliding mode controller uses the approximation characteristics of the neural network and the saturation function to ensure that the USV can track guidance signals accurately, thereby improving the anti-interference of the system and path tracking accuracy. The study also conducts a Lyapunov stability analysis to show that the errors of the closed-loop system are globally asymptotically stable. Simulation results reveal the effectiveness of the proposed collaborative path tracking control method.

Collaborative Traversal Path Planning Algorithm of for Multiple Unmanned Survey Vessels

WENG Lei, YANG Yang, ZHONG Yu-xuan

2020, 28(6): 634-641. doi: 10.11993/j.issn.2096-3920.2020.06.007

[Abstract](419) [PDF 1804KB](383)

Abstract:
To obtain underwater geomorphological information of islands, reefs, and surrounding waters and improve surveying and mapping efficiency, collaborative surveying, and mapping using multiple unmanned survey vessels should be employed. In this study, a collaborative traversal path planning algorithm in conjunction with the scanline polygon method is used to obtain a dynamic grid map. A water environment model is then constructed, task areas are allocated based on the K-means++ algorithm, and a full traversal path is obtained by the heuristic path planning algorithm. Simulation results meet the requirements of uniformity and connectivity of the traversal path. A dynamic reprogramming algorithm is then proposed to reallocate the untraversed areas based on the number of unmanned vessels that can work in real time. The collaborative traversal algorithm is shown to improve the mapping efficiency of the grid map with different spacing, and the path repetition rate is low, meaning that dynamic reprogramming can be realized quickly and efficiently.

Calculation Model of SGR Based on Operational Environment Configuration Resources

PENG Ya-xin, Huang Qi, YU Ming-hui, YANG-Jie, SU Hou-sheng

2020, 28(6): 642-649. doi: 10.11993/j.issn.2096-3920.2020.06.008

[Abstract](303) [PDF 502KB](167)

Abstract:
The sortie generation rate(SGR) of naval weapons such as aircraft carriers and unmanned surface vessels (USVs) is the key index for judging the comprehensive operational capabilities of a system, where the resource configuration will greatly affect such a system. Therefore, research on the optimal combination of configuration resource of an operational system can improve the system’s operational capabilities. Using an aircraft carrier SGR as an example and based on the sortie-by-waves model, this study develops a simulation calculation model of the SGR. To avoid the problem of having to repeat the calculation to reduce the randomness of the results, a simulation calculation model is fitted by a back-propagation(BP) neural network, and a BP-SGR calculation model of is obtained. An optimization of the deck resource configuration with the BP-SGR calculation model is also studied. Through a simulation, all of the SGR combination values of 21 groups optimal resource configurations obtained by the BP-SGR calculation model fall within a 99% prediction range of the simulation model’s SGR calculation results. In addition, all relative errors are shown to be less than 1%, thus verifying the applicability of the model to resource configuration optimization. The BP-SGR calculation model can thus be used to solve configuration problems related to aircrafts and USVs.

Position Optimization Method for an Active Vibration Control Actuator of a Cylindrical Shell

GENG Xiao-ming, YIN Shao-ping, ZHOU Jing-jun, WANG Qian

2020, 28(6): 650-656. doi: 10.11993/j.issn.2096-3920.2020.06.009

[Abstract](227) [PDF 956KB](135)

Abstract:
In this study, with a cylindrical shell used as a research object, the actuator position optimization problem in the active vibration control of the cylindrical shell is studied. A controllability optimization configuration criterion is employed, a derivation analysis is conducted, and the cylinder is constructed using a genetic algorithm to quickly identify the position of the actuator in the shell. Results show that this method for optimizing the position of the actuator with the cylindrical shell as the control structure can improve the vibration control effect. The method can thus be applied for use in vibration control and vibration transmission suppression in a compact space structure.

Effects of Hull States on the Control Parameter of the Current Compensation Electric Field Stealth

SUN Qiang, JIANG Run-xiang, YU Peng, CHENG Jin-fang

2020, 28(6): 657-662. doi: 10.11993/j.issn.2096-3920.2020.06.010

[Abstract](184) [PDF 510KB](141)

Abstract:
To produce a stealth control technology for the static electric field of a ship with current compensation based on the control parameter (i.e., the ratio of the compensation current to the shaft current), this study analyzes variation trends in the underwater electric field and the optimal value of . Specifically, the study employs boundary element simulation software to assess a ship with different degrees of coating damage and different coating damage positions. Results show that the optimal value of gradually increases with the rate of coating damage. In addition, damage localized near the propeller affects the optimal value of , unlike that in the middle anterior of the hull. The effect of propeller rotational velocity on the optimal value of is also studied based on a scaled ship model experiment, with results showing that the optimal value of is not affected by the rotational velocity. Results also show that the maximum suppression ratios of the underwater electric field are different under different rotational velocities.

Sliding Backward Recursive EKF Bearings-Only Target Tracking Method

ZHENG Yi, WANG Ming-zhou

2020, 28(6): 663-669. doi: 10.11993/j.issn.2096-3920.2020.06.011

[Abstract](837) [PDF 513KB](176)

Abstract:
In the field of target location and tracking, when only one observer is present and only the bearings of the target can be obtained, passive bearings-only underwater target tracking by a single observer is difficult. In engineering applications, the time of observation is short and the amount of data is sometimes small, which makes target location and tracking more difficult. In this study, the principle of a conventional extended Kalman filter(EKF) is studied and the characteristics of state estimation changes in bearings-only target tracking by a single observer are analyzed and proved by formula derivation. Considering the special background of short-term observation and the existence of a small amount of data, this study proposes a sliding backward recursive EKF method. Through a combination of backward and forward recursion, the data are reused and estimation errors are reduced. In a simulation of different observation noises and noise covariance estimates, results show that the proposed method generates lower errors than the conventional EKF for bearings-only target tracking by a single observer using a small amount of short-term observation data.

Midwater Navigation Algorithm Based on Single-Beacon Ranging-Aided SINS

LIU Xiang-heng, WANG Ya-bo, LIU Xian-jun

2020, 28(6): 670-676. doi: 10.11993/j.issn.2096-3920.2020.06.012

[Abstract](227) [PDF 497KB](163)

Abstract:
Global navigation satellite system and Doppler velocity log cannot be used for deep-diving undersea vehicles in midwater. Therefore, this study proposes an economically feasible midwater navigation algorithm to solve this problem. The algorithm utilizes the one-way arrival time mechanism to measure the distance from a beacon of a known position to a deep-diving undersea vehicle. To suppress error divergence of the strapdown inertial navigation system(SINS), an extended Kalman filter based on SINS error propagation and a single-beacon ranging model is designed to execute information fusion for single-beacon ranging-aided SINS. Simulation results show that the midwater navigation algorithm based on ranging-aided SINS can obtain localization results whose errors do not accumulate over time. In addition, for analytical observability, this study analyzes the accuracy of static and circular motion trajectories, where the theoretical analysis is shown to be consistent with the simulation results.

Two-Torpedo Salvo Active Homing Method Based on Fractional Fourier Transform

JIANG Shuai, FAN Shu-hong, HAO Bao-an

2020, 28(6): 677-684. doi: 10.11993/j.issn.2096-3920.2020.06.013

[Abstract](219) [PDF 969KB](98)

Abstract:
A two-torpedo salvo can effectively improve hit probability, but it may cause mutual interference problems. Therefore, a two-torpedo salvo active homing method based on fractional Fourier transform is proposed in this study. The echo signals of two torpedoes can be separated and detected by transmitting linear frequency modulation (LFM) signals at different chirp rates and by applying the focus characteristics of the fractional Fourier transform to those LFM signals. Accordingly, a general scheme for two-torpedo salvo target detection is proposed, and the main factors that affect the target parameter estimation results are further analyzed. Simulation results under different signal-to-noise ratios show that using fractional Fourier transform can effectively realize target detection of a two-torpedo salvo and has strong anti-interference capabilities. In addition, two torpedoes can work in the same frequency band without frequency division, thus making the method feasible for use in two-torpedo salvo active homing.

Study on Nonlinear Wake Interaction

WANG Cheng-ying, ZHANG Jian-sheng

2020, 28(6): 685-693. doi: 10.11993/j.issn.2096-3920.2020.06.014

[Abstract](164) [PDF 2708KB](113)

Abstract:
The most important feature of the wakes of fast ships in restricted waters is that solitary waves can be generated ahead of the ship. Using the Korteweg de Vries equation and the sign and auxiliary results of the Hirota bilinear form, this study derives a two-soliton solution with different phase changes. All possible waveforms of the two-soliton solution of the Kadovtsev-Petviashvili(KP) equation for different phase changes and the waveforms of the decomposition structure and linear superposition of the two-soliton solution are obtained using Mathematica. This establishes a foundation for understanding the two-soliton solution of the KP equation, two-soliton interaction, and its morphological characteristics. Based on the two-soliton solution of the dimensionless KP equation, the study simulates the surface height of the interaction region of equal and unequal amplitude incident solitons with standard coordinates. The results show that the amplitude difference between the equal amplitude incident soliton and the amplitude of the reference soliton is 0.01% larger than that of the 1% difference in the space of the interaction peak. The interaction of two incoming solitons with unequal amplitudes results in the bending of their wave humps. The different wave humps of the incoming soliton and two-soliton solution at the center of interaction area are obtained using MATLAB. Finally, the slopes of the interacting solitons are compared by adjusting the parameter k. Results show that for a higher value of k, the profile of the interacting soliton is narrower and the slope along the propagation direction of the wave crest is greater.

A Design Scheme of Low-Speed High-Torque Permanent Magnet Synchronous Motor

ZHANG Guo-nan, HU Li-min, WANG Jian-ping, DUAN Kai-yuan

2020, 28(6): 694-698. doi: 10.11993/j.issn.2096-3920.2020.06.015

[Abstract](379) [PDF 1034KB](637)

Abstract:
This study focuses on the requirement of reducing vibration and noise in low-speed, high-torque propulsion motors used by large unmanned undersea vehicles(UUVs). Furthermore, a low-speed high-torque permanent magnet synchronous motor with a rated power of 100 kW and a rated speed of 250 r/min is designed. First, a motor electromagnetic scheme is designed based on the magnetic circuit method. Subsequently, the finite element model of the motor’s segmented skewed slot is established, and the no-load back electromagnetic force, cogging torque, electromagnetic torque, and other parameters are analyzed. Finally, the prototype is developed and tested. Test results indicate the feasibility of the design scheme for achieving a low-speed, high-torque, permanent magnet synchronous motor.

Research on Anti-Torpedo Torpedo Interception Strategy of Surface Ship

SUN Zhen-xin, GU Tian-jun

2020, 28(6): 699-705. doi: 10.11993/j.issn.2096-3920.2020.06.016

[Abstract](265) [PDF 707KB](291)

Abstract:
As the capability of torpedo intelligence continues to improve, anti-torpedo torpedoes (ATTs) have become a major research focus in many countries, where the interception strategy directly affects ATT interception probabilities. In this study, four ATT models of rough-position, head-on, direct and current-location interception are established to defend against incoming torpedoes. The defense strategy is divided into four processes: long-range, medium-range, close-range, and near-boundary. Based on a simulation of the ATT interception probability under different situations, an optimal interception method of the ATT at different ranges is then obtained, and an optimal interception strategy for surface ships to defend against incoming torpedoes is proposed, thus providing a significant means of improving survivability of surface ships.

2020 Vol. 28, No. 6

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