水下无人系统学报

Numerical Simulation on Vertical Water Entry Impact of Axisymmetric Body at Supersonic Speed

SUN Kai, DANG Jian-jun, HAO Wei-min, JIANG Bin

2015, 23(1): 002-6. doi: 10.11993/j.issn.1673-1948.2015.01.001

[Abstract](1017) [PDF 417KB](671)

Abstract:
Water entry impact is one of the hot topics in the modern underwater weapons research. With the volume of fluid (VOF) model and dynamic mesh in commercial CFD software, the water entry processes of an axisymmetric body with flat top are simulated at subsonic, transonic and supersonic speeds, respectively. The drag coefficient, head diame-ter, water compressibility and the effect of air shock wave on the water entry processes of the simulated model are ac-quired at three different speeds. Simulation results show that: 1) with the increase of speed, the peak value of drag coef-ficient first decreases then remains stable in the end, and the width of peak value decreases gradually; 2) the peak value and its width of drag coefficient increases with the increase in head diameter; 3) the water compressibility delays the appearance of the peak value of drag coefficient and reduces the peak value; and 4) air shock wave reduces the value of drag coefficient at water surface.

Calculation of Whirling Frequency in Flexural Vibration of Torpedo Propulsion Shafting Based on MATLAB

ZHAO Qi, YIN Shao-ping, WANG Zhong, GUO Jun

2015, 23(1): 007-13. doi: 10.11993/j.issn.1673-1948.2015.01.002

[Abstract](1012) [PDF 503KB](685)

Abstract:
To avoid resonance, it is necessary to calculate whirling frequency of a rotor system. The input parameters of commercial finite element analysis(FEA) softwares are limited, and these softwares can not complete the analysis of special cases. In this paper, according to the differential equation of motion for a rotor system and its solution process, a program is coded to calculate the whirling frequency by the software MATLAB. Comparison between the results of MATLAB and ANSYS shows that this MATLAB program is reasonable, and it can be used to calculate whirling fre-quency in flexural vibration of torpedo propulsion shafting or to perform subsequent development.

A Conformal Array Arrangement Method for Torpedo

YU Yi-ming, HAO Bao-an, JI Bang-jie, LI Tao

2015, 23(1): 014-19. doi: 10.11993/j.issn.1673-1948.2015.01.003

[Abstract](969) [PDF 495KB](594)

Abstract:
To explore the performances of different arrangements of conformal array, three different arrangements of conformal array are established based on the basic rules of arrangement. By using the conventional beamforming method, the directivity formulae of the array element with baffle and any discrete array, the directivity function of the established conformal arrays are calculated. The horizontal and vertical directivities are analyzed and compared. The results show that the cross ring type conformal array is more suitable for torpedo weapon due to its better horizontal and vertical di-rectivities in the main axis.

Noise Source Location Method Based on Near-field Acoustic Holography for Underwater Vehicles

JI Qing, JIANG Pei, SUN Yu-hui

2015, 23(1): 020-25. doi: 10.11993/j.issn.1673-1948.2015.01.004

[Abstract](1005) [PDF 325KB](593)

Abstract:
In regard to the localization of noise source for underwater vehicles, such as torpedoes and mines, the current studies on the near-field acoustic holography(NAH) based on spatial Fourier transform are discussed with emphasis on algorithms′ reconstruction error, reconstruction stability and filtering methods. The problem in NAH technology, which still needs to be solved, is analyzed. Further, corresponding suggestions about applying such new technologies as Patch NAH and vector hydrophone to location of underwater noise source are offered.

Passive Detection Models of Underwater Acoustic Target Based on Time-Frequency Analysis

YAN Kan, LEI Jiang-Tao

2015, 23(1): 026-29. doi: 10.11993/j.issn.1673-1948.2015.01.005

[Abstract](762) [PDF 516KB](424)

Abstract:
To extract the non-stationary or transient features of targets in complicated underwater environment and achieve high detection probability, a novel passive detection method of underwater acoustic target based on time-fre-quency analysis and statistical model is proposed, and three passive detection models are established based on short time Fourier transform(STFT), Wigner-Ville distribution, and wavelet transform, respectively. Target detection is conducted with these three models on the basis of the measured data of ship-radiated noise, and the results show that all three models achieve satisfactory target detection, of which the model based on wavelet transform behaves best.

A Reverberation Elimination Method Based on Adaptive Step Size Blind Source Separation

WANG Wei-long, YANG Yun-chuan, WANG Ming-zhou, LI Jin-ming, ZHAO Wei, SHI Lei

2015, 23(1): 030-34. doi: 10.11993/j.issn.1673-1948.2015.01.006

[Abstract](1028) [PDF 532KB](537)

Abstract:
To suppress active sonar reverberation, overcome the shortcomings of huge computing consumption and slow convergence in existing algorithms, we propose an adaptive step size blind source separation algorithm, and perform simulation test to verify the algorithm with active sonar echo reverberation. The result shows that the proposed algorithm can separate the echo and reverberation effectively, and improve the signal to reverberation ratio(SRR) and the detection performance of the rear algorithm. The proposed algorithm has a faster convergence and lower computing complexity than conventional algorithms. Compared with the fix step size blind source separation algorithm, it has equivalent steady-state error. The proposed algorithm may facilitate engineering implementation of reverberation elimination.

Formation Path Following Control of Multiple AUVs Based on Serret-Frenet Coordinate System

ZHAO Ning-ning, XU De-min, GAO Jian, ZHANG Qin-nan

2015, 23(1): 035-39. doi: 10.11993/j.issn.1673-1948.2015.01.007

[Abstract](1181) [PDF 446KB](670)

Abstract:
A virtual structure formation control method based on a Serret-Frenet coordinate system is proposed for the formation path following control of multiple autonomous underwater vehicles(AUVs). The formation control system is composed of two parts, namely, the path following control for each AUV and the consistency coordination control for the path following reference points of multiple AUVs. Firstly, a path following reference point is defined for each AUV which moves along the desired path, and a Serret-Frenet coordinate system, which takes the reference point as its origin, is built to describe the formation path following errors and the dynamic model. The course angle and velocity are prop-erly controlled to make the AUV converge to its predefined desired position in the Serret-Frenet coordinate system. Secondly, a proportional-integral consistency algorithm for path parameters is designed for all AUVs to make the virtual reference points synchronously move at a given change rate along the desired path with the desired velocity. At last, three AUVs in following a desired path with a certain formation are simulated, and the results validate the effectiveness of the proposed control method.

Application of Variable Structure Control Technology to Torpedo Steering Gear

LI Qiang, ZHANG Qin-nan, LI Jun, WANG Li-wen

2015, 23(1): 040-43. doi: 10.11993/j.issn.1673-1948.2015.01.008

[Abstract](907) [PDF 349KB](483)

Abstract:
To improve the maneuverability of a torpedo and anti-interference capability of the steering gear control system, a variable structure control system of torpedo steering gear is designed with the sliding mode variable structure control technology, and a steering gear control model is established. System simulation is carried out for a certain type of torpedo, and the results show that this control system using sliding mode variable structure achieves faster response speed, smaller overshoot, stronger anti-interference capability, and better stability compared with the conventional proportion-integration-differentiation(PID) control method, and this design method can improve the performance of torpedo steering gear control system.

A Closed-loop Rotary Velocity Controller for Underwater Turbine Propulsion System

LUO Kai, ZHANG Xue-lei, WANG Xiao-xin, LUO Xin

2015, 23(1): 044-48. doi: 10.11993/j.issn.1673-1948.2015.01.009

[Abstract](869) [PDF 565KB](493)

Abstract:
Abstract: The open circle turbine propulsion system applied to high-speed autonomous underwater vehicle (AUV) has the outstanding characteristics of low gas consumption, large enthalpy drop and simple structure. But this system is sen-sitive to varying conditions. In this study, the closed-loop control strategy was adopted by adjusting the fuel pump angle to establish mathematical models of the open circle turbine propulsion system and the pump angle actuator. A reasonable control algorithm was designed. Based on the models and the algorithm, a closed-loop rotary velocity controller was developed. Thus, the stepless speed control of underwater turbine was achieved. Hardware-in-the-loop simulation result shows that the proposed controller can keep the system′s rotary velocity following the command velocity in varying conditions (variable depth or velocity). The transition time of the rotary velocity regulation is less than 7 s, and the maximum deviation of rotary velocity is less than 20 r/min. The combustion chamber pressure overshoot is less than 5%，which ensures the security of the system. The controller may effectively support the implementation of new guid-ance law of an AUV.

Application of Improved Quantum Genetic Algorithm to Optimization Design of Motor Structure

WU Song, CHEN Gang

2015, 23(1): 049-54. doi: 10.11993/j.issn.1673-1948.2015.01.010

[Abstract](1210) [PDF 373KB](1136)

Abstract:
Considering the features of a large number of physical dimensions and complex constraints in electromagnetic design of a motor, a brushless DC motor(BLDCM) model with 10 physical dimensions and 11 constraints is built to optimize the quality of the counter-rotating BLDCM with an outer rotating magnetic system. The quantum genetic algo-rithm is improved by introducing dynamic adjustment mechanism of rotation angle of quantum gate, and quantum crossover and mutation operations to obtain a group of physical dimensions. Thus, an optimum structure design scheme is achieved with lighter weight of the motor, and the constraint indexes meet the requirements. In addition, the searching effects of different parameters are compared to provide a basis for further improving the algorithm.

Finite Element Analysis of Rigidity Characteristics of Elastic Ring for Gas Turbine Rotor System

LI Ri-zhao

2015, 23(1): 055-60. doi: 10.11993/j.issn.1673-1948.2015.01.011

[Abstract](1202) [PDF 511KB](456)

Abstract:
Elastic support stiffness is vital to adjustment and control of critical speed of gas turbine rotor system. In this study, a rigidity computation model of elastic ring was established with finite element method to analyze the effects of elastic ring′s structural parameters, whirling angle and fit clearance on its rigidity. Tests and measurements verified the feasibility and accuracy of the finite element method for calculating the support rigidity of the elastic ring. The results show that the main parameters in rigidity design of the elastic ring should include the number of bosses, the wall thickness and width, and the fit clearance.

Simulation on Seawater Jet Noise after Submarine Underwater Launching

LIAN Yong-qing, GUO Yu, ZHANG Xiao-fang

2015, 23(1): 061-65. doi: 10.11993/j.issn.1673-1948.2015.01.012

[Abstract](980) [PDF 929KB](580)

Abstract:
To study the noise of the seawater jet from a submarine launch tube after a weapon leaving the tube, simula-tion on three-dimensional flow field of the launching process is conducted, and the fluid field of the seawater jet at noz-zle after the weapon leaving the tube is obtained. The free jet noise of underwater round pipe is calculated using the Lighthill acoustic analogy integral method based on the seawater jet fluid characteristic. Calculation result shows that the energy of seawater jet noise concentrates in the low frequency noise (lower than 100 Hz), and the seawater jet noise is not the main component of the overall launching noise.

Simulation on Complicated Inner Flow Field in False Sea Test Facility

DONG Ming-yang, WANG Yun, DUAN Hao

2015, 23(1): 066-70. doi: 10.11993/j.issn.1673-1948.2015.01.013

[Abstract](985) [PDF 848KB](395)

Abstract:
To obtain a detailed, intuitive and accurate description of the pressure field and velocity field distribution of inner flow field in false sea test facility for an air-turbine pump launcher during launching, a mathematical model of inner flow field in false sea test facility is established, and simulation is conducted by using dynamic mesh of FLUENT. The results illustrate the distributions of pressure field and velocity field of inner flow field in false sea test facility at every stage of the launching process, which may be taken as a reference for test design. In addition, explanation is given for the phenomena appeared during the launching test by considering the simulation results of false sea test. And the recovery state of the inner flow field is predicted according to the simulation results to provide a theoretical basis for determining time interval between two continuous launching.

Verification Methods of Testability Indicators for Torpedo

WANG Wen-bin, HUO Jun-long, WANG Zhong

2015, 23(1): 071-74. doi: 10.11993/j.issn.1673-1948.2015.01.014

[Abstract](990) [PDF 184KB](552)

Abstract:
With the development of torpedo technology, testability becomes one of the most important topics in torpedo research. In this study, verification methods of torpedo built-in test(BIT) prediction, fault detection rate and fault isolation rate were proposed to solve the problems in engineering application of testability. Effective methods were provided to predict torpedo testability in design and development phase, and applications showed that these prediction methods meet the requirements of engineering.

Integrative Verification Test Method of Quantitative Indexes of Torpedo Testability

DENG Xin-wen

2015, 23(1): 075-80. doi: 10.11993/j.issn.1673-1948.2015.01.015

[Abstract](817) [PDF 231KB](478)

Abstract:
An integrative verification test method of the quantitative indexes of testability is proposed for a torpedo in its design approval phase, in which spontaneous and simulated faults are taken as the test sample at the test site. The con-cepts of the quantitative indexes are presented, the implementation procedure of the test is described, and the test meth-ods based on minimum acceptable value under certain confidence and point estimation are discussed. The results verify the correctness of the proposed method in terms of fault detection rate, fault isolation rate and false alarm rate of a tor-pedo. This study may be of benefit to assessing torpedo′s general quality characteristic.

2015 Vol. 23, No. 1

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