水下无人系统学报

Numerical Simulation on the Internal Flow Characteristics in Ventilated Cavity

ZHONG Xiao, WANG Shu-shan, MA Feng

2014, 22(1): 001-6. doi: 10.11993/j.issn.1673-1948.2014.01.001

[Abstract](922) [PDF 3554KB](348)

Abstract:
The distribution of internal pressure in ventilated cavity is affected by ventilation condition, which may in-duces distinct impact effects on the boundary of the cavity and the dynamics rules of ventilated cavity. In this paper, the internal flow structure of ventilated cavity is simulated by using CFD code of FLUENT, and the simulation results are calibrated by digital particle image velocimetry(DPIV) and high-speed camera experiments. Then the effects of different ventilation conditions on internal flow structure of cavity are analyzed. Numerical simulation results indicate that the ventilation conditions impose clear influence on the flow form of gas-jetting region and weak influence on the recircu-lating region, the angle of ventilation affects the structure of gas-jetting region, and the flow rate of ventilation affects the proportion of gas-jetting region and recirculating region to the internal cavity space.

Analysis on Attack Performance of Sleeping Torpedo

ZHOU Tao, ZHANG Chen-guang

2014, 22(1): 007-13. doi: 10.11993/j.issn.1673-1948.2014.01.002

[Abstract](1305) [PDF 1126KB](457)

Abstract:
To improve the operational efficiency of a sleeping torpedo, an attack performance simulation model of a sleeping torpedo is established according to its technical characteristics of launching guidance and the given principle, situation and trajectory flow. The present bearing method and advance bearing method are used to calculate the detection probability when a multi-speed torpedo is running at alternate high and low speeds, and a speed setting scheme for effectively improving the detection probability of a sleeping torpedo is achieved. Aiming at the problem of large miss distance of a torpedo at big enemy board angle, the simulation results of two methods are compared, conclusion is drawn that the advance bearing method can improve detection probability more effectively for a sleeping torpedo.

Longitudinal Motion Modeling and Simulation of Tethered AUV with Length-Variable Towing Cable

YANG Zhi-dong, PAN Guang, DU Xiao-xu

2014, 22(1): 014-19. doi: 10.11993/j.issn.1673-1948.2014.01.003

[Abstract](1029) [PDF 1268KB](419)

Abstract:
A numerical model of towing cable is established based on the lumped mass method to simulate the variation of cable length for tethered autonomous underwater vehicle(AUV). And a longitudinal motion model of the AUV is es-tablished according to the rigid body momentum theorem and the moment of momentum theorem. In addition, the boundary equation of the towing cable for the AUV is deduced based on the two models. The longitudinal motion equa-tions are obtained by jointing the towed motion equation, the longitudinal motion model and the boundary equation of the towing cable. The motions of a tethered AUV and an untethered AUV are simulated and compared by using same control law equation and the fourth order Runge-Kutta method. The results show that the effects of towing cable on the motion parameters of the tethered AUV become greater as the length of towing cable increases, especially for the axial velocity of the tethered AUV, and the acting force on the tethered AUV gets greater.

Unbiased Least Square Estimation for Bearings-Only Target Tracking Based on Sequential Algorthm

SHANG Jin, LI Ya-an, YU Jing, LI Xiao-hua

2014, 22(1): 020-25. doi: 10.11993/j.issn.1673-1948.2014.01.004

[Abstract](982) [PDF 1273KB](399)

Abstract:
Bearings-only target tracking attempts to obtain a target trajectory only based on bearings measurements. This problem is difficult because the measurement equations are nonlinearly related to the target parameters. The pseudolin-ear estimation provides a linearized measurements equation, however the estimation result is severely biased. In order to deal with this problem, this paper proposes an unbiased estimation method with good convergence property, in which constraint least squares minimization is applied to the pseudolinear estimation without assuming initial values. The se-quential filtering algorithm is employed for batch processing of the estimator, thus the estimation accuracy is improved and the computation is reduced. Simulation result shows that the proposed algorithm gets higher tracking accuracy and faster convergence speed than the extended Kalman filter, the obtained estimator approaches the perfect state in the condition of Gaussian noise rapidly and keeps steady when the target is moving at a high speed.

Nonlinear Dynamic Characteristics of Active Homing Echo Signal

SHEN Shen, CHENG Hong, WANG Ming-zhou

2014, 22(1): 026-29. doi: 10.11993/j.issn.1673-1948.2014.01.005

[Abstract](903) [PDF 1127KB](407)

Abstract:
We discuss the phase trajectory motion characteristic of the sinusoidal signal, the active homing echo signal, and the filtered active homing echo signal based on the theories of nonlinear dynamics and nonlinearization of target echo signal. And we conduct a simulation with a certain number of measured active homing echo signal data. Simulation results indicate that the filtered active homing echo signal shows nonlinear characteristics, and its phase trajectory mo-tion characteristic and point distance sum-based parameter exhibit certain regularity and separability.

Anti Positioning Range Ambiguity Algorithm with Simulation for Underwater Synchronous Acoustic Positioning System of Torpedo

YANG Zhi-quan, SHANG Fan

2014, 22(1): 030-34. doi: 10.11993/j.issn.1673-1948.2014.01.006

[Abstract](1153) [PDF 1325KB](413)

Abstract:
The reason why positioning range ambiguity problem is created in an underwater synchronous acoustic posi-tioning system of torpedo is analyzed, and an anti positioning range ambiguity algorithm is proposed to completely solve this problem. Accordingly, a quick positioning method is proposed for the underwater synchronous acoustic positioning system of torpedo based on the horizontal equidistant line array technology and the correlative wave gate technology for correcting time-delay difference. Simulation result shows that this method has such advantages as less addition in hard-ware cost, non-exhaustion of all fuzzy solutions, and non-prior position information. It may be applied to eliminating range ambiguity and locking tracked target in design of medium- and long-range positioning system of torpedo, and to design of short/ultra-short baseline underwater acoustic positioning system.

A Filtering Method of Anti-waves Disturbance Real-time Control Signal

ZHAO Jiang, XIAO Chang-mei, LEI Fei-lin, JIANG Tao, WANG Chao

2014, 22(1): 035-38. doi: 10.11993/j.issn.1673-1948.2014.01.007

[Abstract](863) [PDF 1251KB](330)

Abstract:
To solve the problem that filtering effect is incompatible with phase margin in servo control system, while eliminating high-frequency noise will lose useful low-frequency signal, we present a filtering method of anti-waves disturbance real-time control signal based on Kalman filter algorithm. In this method the system is described by state space method, the second-order autoregression model is used to calculate the system parameters, and recursive algorithm is adopted to achieve real-time process of computer, thus the high-frequency noise can be significantly removed, the gyro drift can be suppressed and the useful signal can be extracted. Simulation result shows that this method is simple and convenient in implementation, and has good disturbance suppression performance. Moreover, it effectively reduces the loss of system phase, eliminates the high-frequency interference, and greatly contribute improvement to the system bandwidth and the open loop gain.

An On-line Modifying Algorithm of Lightweight Torpedo Attitude Angle without Data from MINS

YANG Guan-jin-zi, HONG Jian-ying, WANG Li-wen, GUO Lin-na

2014, 22(1): 039-43. doi: 10.11993/j.issn.1673-1948.2014.01.008

[Abstract](1416) [PDF 1380KB](362)

Abstract:
The sensors in a lightweight torpedo in service often employ framed gyroscope. However, some problems are br- ought to launch control system interface of lightweight torpedo launch platform in updating the framed gyroscope by strapdown inertial technology. In this paper, an on-line modifying algorithm of lightweight torpedo attitude angle is proposed. The algorithm doesn’t need any navigation parameter data from launch platform before launch, extracts the attitude angle by accelerometer after launch, and on-line modifies the attitude angle error in steady motion segment in order to achieve stable control. And it supports the original launch control system interface of lightweight torpedo launch platform. Simulation result shows that this algorithm greatly reduces the torpedo preparation time on launch platform, and keeps steady control of lightweight torpedo attitude angle during running.

Analysis on Heat Transfer Characteristic of Super-speed Mechanical Seals Based on FLUENT

ZHANG Jia-he, YANG Cheng-shi, PENG Bo, WAN Rong-hua, GUO Zhao-yuan, GAO Yu-ke

2014, 22(1): 044-48. doi: 10.11993/j.issn.1673-1948.2014.01.009

[Abstract](957) [PDF 1509KB](559)

Abstract:
To understand the heat transfer characteristic between mechanical seals and flushing fluid in super-speed condition and to obtain the intensity of the heat transfer, a fluid-solid model of the mechanical seals is built based on the numerical calculation method. Subsequently, the temperature field is calculated, the temperature distributions of some surfaces are achieved. Moreover, the convection heat transfer coefficient is calculated by the formula, which coincides with the analytic solution. It is concluded that the calculated convection heat transfer coefficient is accurate; the heat transfer capability of the flushing liquid in contact with moving loop is slightly higher than that in contact with static loop; the heat transfer on some walls can be significantly enhanced by increasing the flow rate of flushing liquid at inlet.

An Improved Direct Torque Control Method for Brushless DC Motor

WANG Song-lin, XIE Shun-yin, ZHANG lin-sen

2014, 22(1): 049-53. doi: 10.11993/j.issn.1673-1948.2014.01.010

[Abstract](1229) [PDF 1163KB](420)

Abstract:
Conventional 3-phase brushless direct current-direct torque control (BLDC-DTC) scheme usually adopts 2-phase conduction mode with simple control system. However, like the pulse width modulation(PWM) current control, this control scheme will lose restriction on torque ripple due to phase commutation at high speed. This paper presents an improved DTC method and applies it to BLDC motor control system to reduce the torque ripple. The present method combines the voltage space vectors of 2-phase conduction mode and 3-phase conduction mode to form twelve voltage space vectors for the quality enhancement of torque hysteresis control. Simulation results show that this method can adjust the phase current waveform to maintain constant torque, especially to restrain the torque ripple quite effectively at high speed.

Visual Simulation of Seafloor Topography Based on Biharmonic Interpolation

LIU Feng, ZHANG Yan, CHEN Yan-yong

2014, 22(1): 054-59. doi: 10.11993/j.issn.1673-1948.2014.01.011

[Abstract](1350) [PDF 2718KB](590)

Abstract:
The electronic chart only includes the vector data of marine environment, however it doesn′t give seafloor topography information. We extract the depth vector data from S-57 original document by using the ISO8211 library, calculate a set of grid points data based on the water depth data by Biharmonic curved surface spline interpolation, so as to visually simulate underwater terrain. The interpolated data are used to simulate depth contour, and the result shows consistency with that of the special electronic chart software. Error analysis demonstrates the validity of the proposed method in constructing seafloor topography. Regularly distributed interpolated data can be used for path planning of an autonomous underwater vehicle.

Modeling and Simulation of Monostatic Scattering and Reverberation for Rough Seafloor

WANG Song, LIANG Hong, YANG Chang-sheng

2014, 22(1): 060-66. doi: 10.11993/j.issn.1673-1948.2014.01.012

[Abstract](1088) [PDF 1632KB](413)

Abstract:
Reverberation strength calculation has long been based on the simple scattering model, which is semi-empirical in nature, without considering environmental parameters. In fact, environmental parameters impose im-portant effects on reverberation generation. In this paper, the geoacoustic bottom interaction model (GABIM) is utilized to divide seafloor into two layers, and the cross-sections for interfacial scattering and volumetric scattering in each layer are calculated to obtain the formula of seafloor scattering strength. Based on GABIM, a monostatic reverberation model is set up, in which bottom monostatic reverberation strength depends on seafloor environment. Single frequency signal is adopted in this model to simulate the seafloor reverberation signal. The results indicate that the reverberation signal is consistent with the reverberation theory, and its strength changes with the environmental parameter.

Data Analysis and Processing for Test and Evaluation of Rocket-assisted Torpedo

CAO Qing-gang, YANG Xiao-feng, LI Bing, FANG Yi

2014, 22(1): 067-71. doi: 10.11993/j.issn.1673-1948.2014.01.013

[Abstract](765) [PDF 1106KB](377)

Abstract:
We present a test data usage and processing method of a rocket-assisted torpedo for its indexes evaluation, in which the information in both development phase and simulation phase is integrated by means of some mathematical statistic methods, such as conversion of environment factor, test for outliers, and compatibility check. The method re-duces the number of samples for test, therefore it may facilitate the comprehensive evaluation of tactical and technical indexes with small sample.

Experimental Research for Exploring Frequency Variation Characteristics of Underwater Electromagnetic Wave

SUN Chang-cun, YUAN Peng, REN Zhi-liang, TAN Si-wei

2014, 22(1): 072-77. doi: 10.11993/j.issn.1673-1948.2014.01.014

[Abstract](763) [PDF 1413KB](449)

Abstract:
An experimental scheme was designed for exploring frequency variation characteristics of underwater elec-tromagnetic wave based on the analyses of experimental principle and experiment items of electromagnetic wave propagation characteristics, and a water-tank experiment was performed. The results after data processing and quadratic polynomial fitting are given, and are compared with simulation ones. Conclusions are drawn that the theoretical values show some error to the measured data, but the fitting curve of the measured data show consistent trend with the theo-retical curve, which verifies the feasibility of the proposed scheme. In addition, some existing problems and further re-search topics are presented.

Verification Test Method of Mean Time to Repair for Torpedo

GAO Jiang, LI Chun-feng, XIONG Qian-kun

2014, 22(1): 078-80. doi: 10.11993/j.issn.1673-1948.2014.01.015

[Abstract](802) [PDF 967KB](313)

Abstract:
Verification test of mean time to repair (MTTR) is an important item in appraisal of torpedo. MTTR is a cru-cial index for evaluating testability, maintainability and operational readiness of a torpedo. In this paper, the basic rou-tine of the verification test method of MTTR is illustrated, the test method and process are programmed via real and analog faults, and the corresponding criteria are proposed. This verification test method may be applied to finalizing design of torpedo.

2014 Vol. 22, No. 1

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