Table of Content

01 June 2012, Volume 33 Issue 6

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Paper

Global Sliding Mode Control for Rocket Launcher AC Servo System

CHEN Fu-hong₁, MA Da-wei₁, YANG Bi-wu₂， ZHU Zhong-ling₁

2012, 33(6):  641-646.  doi:10.3969/j.issn.1000-1093.2012.06.001

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Aimed at wide parameter variations and strong impact moment in a rocket launcher position servo system, a global sliding mode control method was presented. Its stability was proved by using the system’s mathematic model. And, for the high-order derivative term in the control law, a derivative estimator was introduced to obtain the high accuracy estimation. The simulation results show that the proposed approach can inhibit the chattering problem effectively, guarantee the response speed and control accuracy, and possess a strong robustness to parameter perturbation and load disturbance.

Structural Optimization Design for Breechblock Extractor

ZHANG Jian, TANG Wen-xian, XU Xing-xing, PENG Song-jiang, ZHANG Pan

2012, 33(6):  647-651.  doi:10.3969/j.issn.1000-1093.2012.06.002

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The reliability of breech mechanism depends on the strength of extractor directly and affects the warship fighting capacity. Aimed at the extractor yield during extracting process, its topology and shape optimizations were carried out respectively by using HyperWorks software. In order to validate the optimization results, a flexible body dynamics of the breech mechanism was simulated by using ABAQUS software. And, its kinetic energy, internal energy, average extraction speed, strength and stiffness before and after optimization were compared. The analysis results show that the mass of optimized extractor decreases by 20.9%, and its maximal stress decreases by 13% and is lower than the yield limit; the peak of internal energy decreases by 3.44%, and the energy curves are delayed 0.16 millisecond; the trend of kinetic energy is similar to the original one except some fluctuation, the average extraction speed decreases by 0.442% only.

Parameter Optimization of Big-lever Curve of a Dual-purpose Machine Gun

WANG Rui-lin, ZHANG Ben-jun, LI Yong-jian, HAO Gang

2012, 33(6):  652-657.  doi:10.3969/j.issn.1000-1093.2012.06.003

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To solve the problem in first-round loading of a dual-purpose machine gun, the loading test was carried out by using a linear displacement sensor, and the importance factors which affect the first-round loading were revealed, i.e. two maximum values of resistances transferred from feed slide to the loading handle. Five points were taken in two segments of big-lever curve respectively, and the relationship between two maximum values and interpolation points were found out by using cubic spline curve fitting. Taken these two values as objective functions and the Y coordinates of interpolation points as the optimized parameters, the big-lever curves were optimized by using genetic algorithm, and the objective functions were reduced by 47.24% and 39.3%. The method can provide reference for the design and improvement of the similar weapons.

Application of Global Adaptive Fuzzy Backstepping Control in Rocket Launcher Servo System

GUO Ya-jun， WANG Xiao-feng, MA Da-wei， HU Jian

2012, 33(6):  658-662.  doi:10.3969/j.issn.1000-1093.2012.06.004

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A global adaptive fuzzy control method was proposed on the basis of backstepping approach for rocket launcher servo system with unknown nonlinear terms and external disturbances. A Gaussian fuzzy function was applied to compensate some uncertainty factors, such as parameter variation, load disturbances and virtual function. And, the controller parameters were tuned in real-time mode according to the operation conditions. The control law was derived iteratively according to the servo system’s mathematical model and conventional backstepping theory. Then, the controller’s stability was verified by using Lyapunov function. The simulation study on the position tracking under parameters variation and disturbance was carried out, and the change law of the virtual control function was given under complex signal. The simulation results show that the proposed approach can guarantee the response speed and control accuracy and has a strong robustness for the structure parameter uncertainties.

Numerical Study on Effects of Precursor Flow on Muzzle Propellant Flow Field

GUO Ze-qing， WANG Yang, JIANG Xiao-hai, LI Hong-zhi

2012, 33(6):  663-668.  doi:10.3969/j.issn.1000-1093.2012.06.005

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During the gun firing, the in-bore air column compressed by the projectile is ejected from the muzzle to the external ambience to form the precursor flow field, and has a great effect on the development of the subsequent propellant flow and the movement of the projectile even reduces the shooting accuracy. Thus, it is important to study this effect mechanism. The muzzle flow with a complicated projectile is simulated numerically by using second order AUSM+ scheme with MUSCL interpolation method. Multi-domain structured grids are employed to solve ALE governing equations. The real shooting conditions, for example, moving projectile, precursor and propellant flow, interior ballistics conditions are considered in the simulations. Two cases, with or without precursor flow field, are also predicted and the resulted shadowgraphs with precursor flow coincide with the experimental ones. And then flow patterns and development of the propellant flow field in these two cases are discussed in detail to reveal the effect of the precursor flow based on the numerical results. It is demonstrated that the precursor flow is the essential condition for the generation of the bow shock ahead of the projectile. And the maximal stagnation pressure in the area near the muzzle increases more than 2 times for the precursor flow relatively to the condition without it.

Study on Influence of Bore Structure on Gun’s Interior Ballistic Performances

SUN He-yang, MA Ji-sheng, LI Wei, SHENG Long-bo, WU Da-lin, LIU Hai-ping

2012, 33(6):  669-675.  doi:10.3969/j.issn.1000-1093.2012.06.006

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Considered the coupling effects of classical interior ballistic equations and band’s engraving process, the solution of interior ballistic equations was taken as the boundary condition of the simulation for engraving process, and the results of the simulation were taken as the initial conditions for the interior ballistic equations in the next step iteratively. A coupled constitutive model considered visco-plasticity and ductile damage and based on continuum damage mechanics was introduced to simulate the band’s damage process. The Von Mises yield criterion, Johnson-Cook hardening model and Johnson-Cook fracture strain model were adopted, and the model considered large strain, high strain-rate, thermal softening and damage evolution. The model was implemented in the explicit finite element code by using VUMAT subroutine of Abaqus\\Explicit module. The band’s engraving processes of two different bore structures were simulated, and the influences of different engraving conditions on the stress state of the band were analyzed. The effects of band’s stress state and bore structure on the interior ballistic performances were pointed out. It is very useful for the design of bore structure.

Research on Macroscopic and Microscopic Mechanism of Plastic Deformation of Bearing Band

YIN Jun-hui, ZHENG Jian, NI Xin-hua, JIA Chang-zhi, CUI Kai-bo

2012, 33(6):  676-681.  doi:10.3969/j.issn.1000-1093.2012.06.007

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In motion process of projectile in bore, its bearing band is subjected to the high strength impact loads and high-speed friction, and the microscopic mechanism of transient plastic deformation under high temperature is very complicated. According to the load characteristics in bore, the microscopic mechanism of plastic deformation was studied on the basis of metal material theory; the regulation of hardness distribution and microstructure evolution was analyzed; then, the microscopic nature of macroscopic deformation was explored. The research results show that the bearing band has obvious layered characteristics after extrusion; fibrous tissue on its surface is heated up quickly and recrystallized partly because of severe friction; the large scale deformation does not occur inside the bearing band; the melted metal membrane on the surface is an important factor to restrain the plastic deformation extend to the inner region.

Artillery Blast Point Detection Based on Adaboost Algorithm

QIN Xiao-yan, WANG Xiao-fang, CHEN Ping, CHU De-jun, WANG Hai-tao

2012, 33(6):  682-687.  doi:10.3969/j.issn.1000-1093.2012.06.008

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The blast point detection is a foundation of fire emendation, damage evaluation and opposite firepower point estimation. According to the characteristics of artillery blast point, this paper proposes a new center-surround Haar-like feature which can be calculated quickly. An algorithm for the blast point detection is presented based on Adaboost with the new Haar-like feature. The experiment results show that the proposed algorithm has better performance than the Adaboost algorithm without the new Haar-like feature.

Applications of Curvelet Transform in Low Contrast Target Recognition

CHEN Fang-han， ZHANG Su， WANG Wen-sheng

2012, 33(6):  688-694.  doi:10.3969/j.issn.1000-1093.2012.06.009

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The target in low contrast image cannot be discriminated from cluttered scene by using joint transform correlator as its indistinct edge. Aimed at this problem, an image enhancement based on Curvelet transform was adopted to process the target’s joint image. In the wavelet analysis, the Curvelet transform is a better multi-resolution tool to analyze and understand the image feature. Both gray contrast and edge can be enhanced by adjusting the high and low frequency coefficients of Curvelet transform with different methods. As an example, a tank’s image with low contrast was processed by using Curvelet transform. The gray contrast of original image was increased from 4.16% to 29.37%. The computer simulation and optical experiment results show that a bright pair of correlation peaks are obtained after enhancing the image, and the recognition for the target in low contrast image is realized successfully.

Study on Application of Distributed Multi-channel MAC Protocols in WSN

ZHAO Jun， CHEN Xiang-guang， LIU Chun-tao, YU Xiang-ming, YUE Bin

2012, 33(6):  695-701.  doi:10.3969/j.issn.1000-1093.2012.06.010

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In order to detect the running state of oil pipeline in real time, reduce the interference between nodes of wireless sensor network (WSN) and improve network throughput, two multi-channel WSN models for the nodes distributed in a line were proposed; the models of channel assignment for single path and dual path network and their network throughputs were are discussed; the corresponding distributed MAC protocol was presented also. Field experiment results show that the single-path channel wireless sensor network not only reduces the energy consumption but also increases the network throughput; the dual path channel wireless sensor network has some fault tolerance and improves network throughput greatly, although it requires higher energy consumption.

An Improved Tree-based Distributed Group Key Agreement Protocol

LIU Tian-hua, ZHU Hong-feng

2012, 33(6):  702-705.  doi:10.3969/j.issn.1000-1093.2012.06.011

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A distributed group key agreement protocol based on authenticated-BD and logical tree, namely T-BD, was proposed. Although the communication and computation costs are increased at the beginning of the proposed protocol, the protocol can guarantee honesties of participants and prevent attacks from internal malicious members. Since the protocol has authentication ability, it can detect the internal malicious attackers. And, the communication and computation costs decrease when new members join and leave, dealing with members’ joining and quitting efficiently. As the protocol is constructed on top of authenticated-BD, the internal malicious members can not attack initiatively. Compared with the existing protocols, the proposed protocol has low communication cost and efficient modular exponentiation and is more scalable for distributed P2P application.

Forward Image Motion Compensation for Aerial Camera Based on Neural Network Predictive Control

ZHONG Chong-liang， DING Ya-lin， FU Jin-bao

2012, 33(6):  706-711.  doi:10.3969/j.issn.1000-1093.2012.06.012

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In order to compensate forward image motion of a certain aviation camera, the reasons for it were analyzed, and the compensation methods were studied. Firstly, the mechanism of image motion was found out on the basis of the camera’s principle. Secondly, a neural network model (NNM) was used to identify the nonlinear characteristics of the system’s response in time domain. Finally, according to the prediction given by NNM, the control signal was adjusted by using optimal algorithm to make the tracking performance of the scanning mirror optimal. This method overcomes some shortcomings of traditional PID control, such as low accuracy, slow response and weak adaptability. The compensation results show that the compensated angular speed of scanning mirror can track the desired angular speed.

Study on Measurement of Residual Stresses in Forged Barrel Surface

LIU Li-li ， FAN Li-xia ， DONG Xue-hua

2012, 33(6):  712-717.  doi:10.3969/j.issn.1000-1093.2012.06.013

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The theory of the blind-hole method used to measure surface residual stresses in plate was applied to measure surface residual stresses in forged barrel accurately. A kind of FEA software ABAQUS was used to calculate the relaxation coefficients of the blind-hole, and the applicable range of the blind-hole method to measure the surface residual stresses in forged barrel was confirmed by comparing the relaxation coefficients of the blind-hole in the plate and in the forged barrel under the same material, the same force and the same drilling condition. A new method to minimize the off-center error was proposed. The surface residual stresses in a forged barrel were measured by using this method.

Fault Pattern Recognition Based on Bispectrum Entropy Model

HUANG Jin-ying， PAN Hong-xia， BI Shi-hua， CUI Bao-zhen

2012, 33(6):  718-723.  doi:10.3969/j.issn.1000-1093.2012.06.014

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A fault pattern recognition method was developed on the basis of information entropy and bispectrum theory. The bispectrum features of vibration signal were analyzed. And a bispectrum entropy algorithm based on energy distribution was derived under the condition of subspace distribution probability. Then, the vibration signals of a gearbox under four conditions were extracted experimentally. And a BP neural network for the fault pattern recognition was established by using the bispectrum entropy feature as input. Finally, this method was verified by successfully recognizing four fault patterns of the gearbox.

Layering Shaping Mould Gasbag Polishing Trajectory Planning Method for Equal Residual Figure Error

CHEN Guo-da， JI Shi-ming， JIN Ming-sheng， ZHANG Cai

2012, 33(6):  724-729.  doi:10.3969/j.issn.1000-1093.2012.06.015

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A new approach called as layering shaping gasbag polishing trajectory planning method was proposed to deal with equal residual figure error. It can be used to the whole polishing process for the workpiece with equal residual facial contour error and certain polishing stage for the workpiece with non-equal residual facial contour error. The optimal selection method of dwelling point interval under grating polishing trajectory was presented on the basis of one-time removal depth function, and the contrast experiment was designed to validate its feasibility. The experiment results show that it is reasonable to choose twice of the corresponding Y value in material removal model as the dwelling point interval if X direction is feed direction of polishing.

Magnetic Flux Leakage Defect Reconstruction Method Based on Wavelet Neural Network Iteration

XU Chao, WANG Chang-long, SUN Shi-yu, CHEN Peng, SHENG Hui

2012, 33(6):  730-735.  doi:10.3969/j.issn.1000-1093.2012.06.016

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To reconstruct 2-D defect profile from magnetic flux leakage (MFL) signals, a dual wavelet neural network iteration model, including a forward model and an inverse model, based on radial wavelet basis function neural network was proposed. It iteratively adjusts the weights of the inverse network to minimize the error between the measured and predicted MFL signals. The network can be trained respectively by the same training samples from measurement and FEM calculation. To improve the network’s adaptability and accuracy, a novel training algorithm was proposed. Firstly, confirm the optimal number of layers, and then update the weights based on the conjugate gradient algorithm. The reconstruction results in different resolutions and SNRs indicate that the method is rapid, accurate and robust, and it is effective and feasible for reconstruction of 2-D defects comparing with other approaches.

Research Notes

Measurement Methods for Muzzle-leaving Time of Projectile

WANG Bao-yuan， CHAO Hong-xiao， SHAO Xiao-jun， ZHANG Peng-fei， CAO Xin， HONG Li-na

2012, 33(6):  736-740.  doi:10.3969/j.issn.1000-1093.2012.06.017

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In order to obtain the muzzle-leaving time of projectile accurately, a small caliber gun was taken as tested object, and four methods, such as high-speed photography, on-off target, photoelectric and recoil displacement methods were simultaneously used for the same projectile and a data acquisition system was used to acquire four signals, in order to search the best measurement method. Taken the result obtained by high-speed photography as time benchmark, four signals were unified in the same time coordinate. The results show that the high-speed photography is a direct and reliable method, on-off target is broken by high-speed burning gas flow before the projectile, and the powder gas triggers the photoelectric sensor earlier.

Design of Hierarchical Control Strategy for Antiaircraft Multiple Rocket Launcher

YANG Fan， MA Da-wei， LE Gui-gao， YAO Jia

2012, 33(6):  741-746.  doi:10.3969/j.issn.1000-1093.2012.06.018

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An improved 2-level hierarchical control strategy was designed to overcome parameter perturbation and load disturbance in antiaircraft rocket launcher systems. Its decision-making level was used to calculate the moment of inertia according to the system status, and a novel 2-order sliding mode controller was adopted in the real-time control level to smooth the control input curve and restrain the parameter variations and external load disturbances. Both simulation and experiment show that this strategy can guarantee the dynamic performance of system and has strong robustness.

Simulation Research on Dynamics of Ramming System and Action Reliability Considering the Randomnessof the Parameters

LI Wei， MA Ji-sheng， DI Chang-chun， WU Da-lin

2012, 33(6):  747-752.  doi:10.3969/j.issn.1000-1093.2012.06.019

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A mechanical-electrical-hydraulic coupling dynamic model of ramming system was built by using MSC.Adams and Easy5. Its confidence was proved by using VV&A. A virtual prototyping-Monte Carlo simulation-support vector machine (VP-MCS-SVM) method was proposed to reduce the large computational volume of MCS method in solving the random dynamics of complex system，and the random dynamics simulation of ramming system was carried out efficiently and precisely. Based on the theory of statistic inference and reliability, the action reliability of ramming system was analyzed and the distribution parameters’ shift was considered. It provides a new idea for the action reliability evaluation for large complex system.

Study on Allowable Quantization Level of Variance-constrained Filtering in Quantized Measurements

WU Yun-gang， TANG Zhen-min

2012, 33(6):  753-758.  doi:10.3969/j.issn.1000-1093.2012.06.020

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In order to determine the quantization level of sensors in quantized measurements, a new filter with allowable quantization level as low as possible was designed for given constraints of variance. The condition of the stability of error covariance matrix and a LMI method for current-estimation-type steady filter were presented. It means that, on the premise of meeting the system estimation variance, the designers can choose the sensors with lower resolution. A numerical example shows the usefulness and flexibility of the proposed approach.

Study on Automatic Long-distance Dimension Measurement System Based on Machine Vision

QIAO Yang， XU Xi-ping， LU Chang-li, LIU Yu-long, WANG Ji-yuan

2012, 33(6):  759-763.  doi:10.3969/j.issn.1000-1093.2012.06.021

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Because of the limitation of measurement methods in traditional visual detective systems, the measured objects are always confined to those parts with small size, and the measurement systems are also lacking in versatility. When the targets are buildings or tanks having bulky size and fixed location, it is very difficult to measure their size with traditional visual detective systems. A vision measurement system proposed in this paper avoids the limitations of light source and standard parts on the measurement distance in traditional measurement methods. It utilizes two laser spots emitted by two laser range finders to determine the proportion relationship between the pixel and the actual geometric size and then calculate the measured dimensions. The experiment results show that the measurement accuracy of the system is better than 0.15 mm within distances of 200 m. Since this measurement method has no limits for the placement and distance of measured objects, it can be widely used in the dimension measurements of random objects. It can also be extended to the size measurement of dynamic targets.

Performance Analysis of Time Delay Estimation for Linear Frequency-modulated Pulse Based onFractional Fourier Transform

DENG Bing， WANG Xu， TAO Ran， LIU Xian-zhong

2012, 33(6):  764-768.  doi:10.3969/j.issn.1000-1093.2012.06.022

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The time delay estimation for linear frequency-modulated (LFM) pulse based on the fractional Fourier transform was analyzed in the fractional Fourier domain, taken the time domain performance of linear frequency-modulated pulse compression as reference. Also, the difference between these two methods was discussed in digital signal processing. It is found that they have almost the same output signal to noise ratio, pulse-width compression ratio and peak amplitude ratio. Furthermore, the latter has higher precision in the time delay estimation in digital implementation, needs less data rate, and has more potential.