水下无人系统学报

Study on Design of Shape and Hydrodynamic Layout for Ultra-low-speed AUV

JIANG Jun, SONG Bao-wei, PAN Guang, CHANG Ming

2011, 19(5): 321-324. doi: 10.11993/j.issn.1673-1948.2011.05.001

[Abstract](1613) [PDF 273KB](800)

Abstract:
An axisymmetric body based scheme of shape and hydrodynamic layout for an ultra-low-speed autonomous underwater vehicle (AUV) is presented to obtain high stability at low speed (<0.5kn) according to the characteristics of its underwater laying and recovery. Theoretical calculation and simulation with the software FLUENT verify that the scheme may be taken as a reference in the study of ultra-low-speed AUV.

Damping Design for Shell Structure of Underwater Vehicles

LI Wei-sheng, ZHOU Yu-tao

2011, 19(5): 325-331. doi: 10.11993/j.issn.1673-1948.2011.05.002

[Abstract](1632) [PDF 464KB](604)

Abstract:
Anti-vibration protection and noise control of such cable-shell structures as torpedo′s and submarine′s shells, and cabin wall of autonomous underwater vehicle(AUV) are important to their purposes. The cable-shell structure is composed of different shell structures with different geometric dimensions. This paper performs finite element calculation of damping sandwich shells with the method of modal damping ratio extraction, applies damping anti-vibration structure to shell design, and analyzes anti-vibration effect of different damping structure, material, thickness and distribution location. The result shows that this method can facilitate anti-vibration design of vehicle cable-shells.

Trajectory Planning and Simulation of Mine for Water Exit Attack

YUAN Xu-long, LIU Wei, LI Bing, WANG Ya-dong

2011, 19(5): 332-336. doi: 10.11993/j.issn.1673-1948.2011.05.003

[Abstract](1716) [PDF 218KB](724)

Abstract:
In the background of information and network warfare, water exit attack of a mine against target can increase its blockage radius, and expand its blockage area from surface to low air, which remarkably enhances the operational effectiveness of the mine. In this study, the characteristics of the water exit attack of a mine are analyzed. The water exit attack trajectory scheme and trajectory planning method are proposed. And the trajectories in three kinds of typical warfare conditions are simulated. Simulation results indicate that the mine can hit target effectively.

A New Concept Sonar —— Cognitive Sonar

LI Xiao-hua, LI Ya-an, CUI Lin, LIU Wang-sheng

2011, 19(5): 337-343. doi: 10.11993/j.issn.1673-1948.2011.05.004

[Abstract](1777) [PDF 154KB](719)

Abstract:
Sonar system performance to some extent depends on the marine environment and the target characteristics from sonar receiver．In dealing with echoes, a conventional active sonar system takes no account of the influences of environmental information and prior knowledge of target characteristics perceived by sonar receiver on the transmitter, and its transmitting signal parameters are fixed, which leads to a difficulty in obtaining desired detection. In this paper, inspired by bat’s echolocation system, a cognition-based intelligent sonar system, named cognitive sonar (CS), is proposed based on the basic principle and key technology of sonar. The cognitive sonar is capable of jointly optimizing the transmitted waveforms and received echoes according to the environmental variation and the prior knowledge to significantly improve its target detection and identification performance underwater.

Target Detection Algorithm Based on Fractional Fourier Transform Cumulant

HU Guang-bo, HE Xi-bing, GAN Xin-nian

2011, 19(5): 344-348. doi: 10.11993/j.issn.1673-1948.2011.05.005

[Abstract](1050) [PDF 303KB](610)

Abstract:
Conventional signal detection and noise separation methods are limited in time domain or frequency domain, and satisfactory detection result is hard to be obtained in time-frequency domain if intensive time-frequency coupling occurs between signal and background noise. Therefore, a fractional Fourier transform(FrFT) cumulant algorithm is presented for solving this problem. The algorithm can get rid of the time-frequency coupling and reduce the noise. Perfect detection result would be achieved in fractional Fourier domain if a suitable rotation angle is selected to match with the processing signal. Simulation results of moving target detection show that the detection performance of the FrFT cumulant algorithm is better than that of the FrFT and the fourth-order cumulant method.

Detection of Underwater Weak Acoustic Signal Based on Radial Basis Function Neural Network

MENG Xian-chao, LIU Chun-wu, LIU Ye

2011, 19(5): 349-354. doi: 10.11993/j.issn.1673-1948.2011.05.006

[Abstract](1544) [PDF 213KB](531)

Abstract:
To enhance the detection efficiency of underwater weak acoustic signal, we analyze the chaotic characteristic of ocean reverberation, establish a prediction model by combining the theory of phase space reconstruction with the radial basis function neural network (RBF NN), and detect the frequency spectrum of the weak harmonic signal from the absolute error of the predicted value and the observed value. From the spectrum we calculate the target information, thus present a chaotic serial prediction method of ocean reverberation. Compared with the traditional random signal processing method, our prediction model overcomes the detection shortcoming of detection with low signal to noise ratio(SNR) due to simplifying background noise to white noise, and can obtain detection result accurately and efficiently. The proposed model can be suitable for weak signal detection in underwater acoustic.

Design of Warship Target Recognition System Based on Fundamental Frequency Extraction

YAO Zhen-xuan, ZHANG Xiao-min, ZHAO Yan-an, GUO Si-ming

2011, 19(5): 355-359. doi: 10.11993/j.issn.1673-1948.2011.05.007

[Abstract](1701) [PDF 263KB](746)

Abstract:
With the development of minesweeping gear technology, we present a fundamental frequency extraction method of a warship according to the difference between the low-frequency power spectrums of warship and minesweeping gear in order to distinguish a warship target from a minesweeping gear. Considering these factors, we use ultra-power devices OPA378, ADS7951 and TMS320VC5509A to design a fundamental frequency extraction system of warship with low power, quickness and real time. This system uses difference frequency algorithm to estimate target base-band. Experiments verify the stability and reliability of the system.

Fuzzy Sliding Mode Control for Near-Surface AUV in Longitudinal Plane

SHEN Jian-sen, ZHOU Xu-chang, GAO Xuan

2011, 19(5): 360-364. doi: 10.11993/j.issn.1673-1948.2011.05.008

[Abstract](1488) [PDF 259KB](659)

Abstract:
To solve wave turbulence problem when an autonomous underwater vehicle(AUV) is running in near-surface sea, we apply fuzzy sliding mode control to AUV longitudinal motion control. Based on the approximation and simplification of a six-degree-of-freedom model, linear equations of motion in longitudinal plane are established. Wave force and moment on AUV are computed and simulated according to the theory of random long-crested wave and the function of wave spectral density. An AUV longitudinal motion controller is designed based on the sliding mode control method. Depth control performance of sliding mode under first-order wave frequency turbulence is analyzed and evaluated with Matlab, and fuzzy logic is introduced to eliminate the input shake caused by the first-order wave frequency turbulence. The simulation results demonstrate that the proposed controller achieves good control performance, and reduce the high frequency shake of input rudder angle.

Three-dimensional Path Planning for UUV with Multiple Constraints

YAN Zhe-ping, ZHAO Yu-fei, CHEN Tao

2011, 19(5): 365-369. doi: 10.11993/j.issn.1673-1948.2011.05.009

[Abstract](1544) [PDF 246KB](637)

Abstract:
A three-dimensional (3D) path planning approach on the basis of safe sail surface and threat map is proposed for a UUV in multi-constraint condition. A safe sail surface is constructed to predigest the 3D search space, reducing the 3D path planning to 2D path planning. Then, a threat map is established for unification of hostile threat and terrain threat, and a threat cost and threat level heuristic factor are introduced. In the end, the A* algorithm is applied to path search to obtain an optimum path. Simulation results illustrate that the proposed approach is simple and fast, and the generated path can meet the requirements of terrain following, terrain evading and threat evading.

Numerical Investigation on the Tip Leakage Flow of Rotor Blade of Torpedo Turbine

YI Jin-bao, ZHAO Wei-bing, SHI Hai-chao

2011, 19(5): 370-375. doi: 10.11993/j.issn.1673-1948.2011.05.010

[Abstract](1549) [PDF 565KB](759)

Abstract:
A three-dimensional(3D) viscous and steady computational fluid dynamics(CFD) analysis is performed for calculating turbine rotor tip leakage flow field of a torpedo by solving RANS-Navier-Stocks equations. The effect of different seal structure on turbine passage efficiency and rotor tip leakage flow is studied. Different numbers of sealing fins at the rotor blade are simulated, and the influence of the number of sealing fins on turbine passage efficiency and rotor tip leakage flow characteristic is analyzed. The results show that the turbine efficiency is improved remarkably after applying the seal technology. Compared with comb-type seal structure, the labyrinth seal exhibits better airtight performance. The leakage flow in the labyrinth seal housing forms 3D vortex current which transform the kinetic energy of the leakage flow into heat energy, and leads to a decrease in the seal leakage flow rate of the labyrinth seal. Airtight performance gets better with increasing number of fins.

A Method of Parameter Identification Based on Least Squares for Torpedo Propulsion Motor

WANG Chong-wu, XIE Jia-peng, LI Hong

2011, 19(5): 376-379. doi: 10.11993/j.issn.1673-1948.2011.05.011

[Abstract](1258) [PDF 199KB](617)

Abstract:
The torpedo propulsion motor′s parameters, such as resistor, inductor, and viscous coefficient, vary with the ambient temperature, which usually leads to structure change and uncertain influence on the control system. In this paper, an objective function based on least squares is established by making use of the differential equations of propulsion motor to obtain the motor′s parameters. This method only adopts the excitation source of pulse width modulation to achieve ideal parameter identification without needing specific excitation (such as M sequence), which can preserve the system operation from the interference of pseudo-random sequence. And this method has the features of simple principle, small amount of calculation, high real-time performance, and wide application.

Mechanical Characteristics Analysis of New Plunger Piston Wobble-plate Engine

TIAN Bing, LIAN Yong-qing, WANG Shu-zong, MA Shi-jie

2011, 19(5): 380-384. doi: 10.11993/j.issn.1673-1948.2011.05.012

[Abstract](1014) [PDF 234KB](446)

Abstract:
Traditional piston wobble-plate engine can not solve essentially the problem of excessive vibration noise due to the complicacy of force and restrain condition in the join with wobble-plate. To reduce the noise of torpedo engine, a new type of plunger piston wobble-plate engine is proposed in this paper. The structure and principle of the engine are introduced. The mechanical characteristics and the movement rule of plunger piston with cylinder and wobble-plate are analyzed. The force balance equation is built based on the piston force analysis, and the relationship formula between the minimum length inside the cylinder and the whole length of the piston is derived. The conclusion may provide a theoretical evidence for the design of plunger piston wobble-plate engine. There is no restraining mechanism on the wobble-plate. The autorotation of the plunger piston during working process can improve lubrication, and reduce friction and noise.

Study on Friction-induced Noise of Thermal Torpedo Engine

LIANG Wei-ge, ZHANG Zhen-shan, ZHU Rui

2011, 19(5): 385-390. doi: 10.11993/j.issn.1673-1948.2011.05.013

[Abstract](1110) [PDF 155KB](479)

Abstract:
Noise intensity is one of the important tactical and technical indexes for a thermal torpedo.To enhance the operational effectiveness of the thermal torpedo, experimental and simulation methods to investigate the friction-induced noise of the thermal torpedo engine on the basis of current studies and methods were introduced. The Stribeck curve for a system in the presence of friction was analyzed, the friction-induced noise parameters were listed, and the expression of the friction-induced noise was derived. In addition, considering three axioms in tribology, three research aspects about the friction-induced noise of the engine were discussed, including the generating mechanism of the friction-induced noise, the quantification of the friction-induced noise, and the formation, size, and number of worn-out particles with their effect on the friction-induced noise.

Simulation and Analysis of Operational Capability of Mobile Acoustic Decoy for Defending Against Acoustic Homing Torpedo

YE Hao-liang, Liu Ming-yong, GAO Jiang

2011, 19(5): 391-395. doi: 10.11993/j.issn.1673-1948.2011.05.014

[Abstract](1161) [PDF 235KB](606)

Abstract:
Presuming an operational posture that a submarine lays a mobile acoustic decoy to defend against an acoustic homing torpedo, this paper adopts the methods of uniform design experimentation and time sequence simulation to simulate and calculate the survival probability of a submarine in different alarming distances and board angles, according to the relative position and state among submarine, torpedo and mobile acoustic decoy, the active sonar equation, and the criterion of capturing and hitting a target by a torpedo. The simulation results are analyzed, and a favorable evading way of submarine is hence suggested. This study may offer a reference to theoretical research, test design and operation of mobile acoustic decoys in defending against acoustic homing torpedoes.

A Method for Attacking Low-Speed Surface Ship with Submarine’s Straight Running Torpedo

LI Chang-jun, WANG Shun-yi

2011, 19(5): 396-400. doi: 10.11993/j.issn.1673-1948.2011.05.015

[Abstract](1175) [PDF 247KB](350)

Abstract:
In order to effectively attack a surface ship with low speed, this paper puts forward a method for a straight running torpedo or a homing torpedo with straight running way to attack the low-speed ship, and establishes a hit probability model of double straight running torpedoes parallel salvo. The hit probability of double straight running torpedoes parallel salvo against the low-speed ship is simulated with this model by means of Monte Carlo method. Simulation results show that the hit probability of the double torpedoes parallel salvo against a ship with a speed lower than 12 kn gets up to 0.5 when the distance is within 2 000~4 000 m, and the submarine occupies a broad angle within 50~80°.

2011 Vol. 19, No. 5

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