Table of Content

30 July 2013, Volume 34 Issue 7

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Research Papers

Analysis and Application Study on the Extended Trajectory Shaping Guidance Law

WANG Hui, LIN De-fu, QI Zai-kang, ZHANG Di

2013, 34(7):  801-809.  doi:10.3969/j.issn.1000-1093.2013.07.001

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The extended weighted and object functions are proposed based on the time-to-go exponential function. The optimal control theory is used to deduce a family of extended optimal trajectory shaping guidance laws for the constant maneuvering target. According to Schwartz inequality, the analytical solution of the guidance law acceleration command is derived by introducing the initial displacement, initial heading error, target maneuver and final impact angle into the lag-free guidance system. The analysis shows that the final acceleration command approaches to zero when the exponent of the time-to-go exponential function is greater than zero. The non-dimensional position and angle miss distance of guidance system with first order lag are studied using the non-dimensional method and the adjoint method. The results show that the position and angle miss distance induced by the heading error and final impact angle approach to zero when the missile terminal guidance time is about 15 times of the system lag time constant. And also, the position and angle miss-distance are smaller when the signs of initial heading error angle and final impact angle are opposite.

Simulation of Solidification Process for DNAN-based Melt-cast Explosives

MENG Jun-jiong, ZHANG Xiang-rong, ZHOU Lin

2013, 34(7):  810-814.  doi:10.3969/j.issn.1000-1093.2013.07.002

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In order to simulate the pouring and solidification process of DNAN based melt-cast explosives, flow and thermal fields were calculated using structured mesh, and stress field was calculated usingunstructured mesh. This numerical scheme can obtain an accurate interface between solid and liquid,reasonable shrinkage and stress data. By comparison research, on the condition of certain mould andcharge size, the optimized scheme for DNAN-based melt-cast explosives is that thermal insulation on upper mould surface for an hour with 30℃ water on lower mould surface, in order to decrease shrinkage,thermal stress value and solidification time by overall consideration.

Fusion Method for Visible and Infrared Images Based on Non-subsampled Contourlet Transform and Sparse Representation

WANG Jun, PENG Jin-ye, HE Gui-qing, FENG Xiao-yi, YAN Kun

2013, 34(7):  815-820.  doi:10.3969/j.issn.1000-1093.2013.07.003

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An image fusion method based on NSCT and spare representation is presented for the lowersparseness of low-frequency sub-band coefficients unfavorable to fusion. Firstly, the infrared and visibleimages are transformed by NSCT, the common and innovation coefficients are extracted from the sparsecoefficients of low-frequency sub-band, and the sparse coefficients are adaptively weighted by the specificcoefficients. Secondly, the high-frequency sub-band coefficients with higher sparseness are fused by usinga method which takes the sum of absolute values of its coefficients be maximal at the same scale. Finally,the fusion image is reconstructed by the inverse NSCT. The method has better fusion performance than thetraditional fusion method based on DWT, NSCT, and the SOMP, JSR fusion method based on sparse representation.

Optimization Analysis of Frequency Stabilization Servo System of Prisms Laser Gyro

LIU Jian-ning, JIANG Jun-biao, SHI Shun-xiang, MA Jia-jun, GUO Qiang

2013, 34(7):  821-827.  doi:10.3969/j.issn.1000-1093.2013.07.004

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A physical model of frequency stabilization process of gyro is established based on the analysis of the operating principle of frequency stabilization servo system and the study of actual operating conditions of the system in total reflection prism laser gyro. The law of the distribution change of temperature gradient field in cavity with the servo system control in the control process of mode jump is obtained by using finite element method. The relationship between the number of longitudinal mode jumping and frequency stabilization servo parameters is derived. Finally, the experiments are designed to verify the best servo parameters by calculation. The experimental results show that the theoretical analysis is valid. This study is vital to insure the stable operation of servo system for laser gyro, and the results are useful to improve the control precision of digital circuits.

Analysis of Tactical Missile Three-loop Lateral Acceleration Autopilot in the Time and Frequncy Domain

WANG Jia-xin, LIN De-fu, QI Zai-kang

2013, 34(7):  828-834.  doi:10.3969/j.issn.1000-1093.2013.07.005

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Based on the linearized and small perturbation model of the longitudinal missile control system, the configuration, response time, robustness and capability of stabilizing a static unstable missile are studied for the aforementioned systems. A non-dimensional model of the autopilot is established and analyzed, and a new method for the three-loop autopilot design is put forward. The results indicate that thestabilizing loop system is more robust and capable of stabilizing a static unstable missile compared withthe damping loop system,but its response time is longer; while the three-loop autopilot is more robust,and faster than the stabilizing loop system by designing a chief pole at lower frequency and a pair of higher frequency conjugate poles with a appropriate damping ratio.

Analysis Method for the Noise Characteristics of Fiber Optic Gyroscope Based on Fitting Model of Six Noise Items

LI Jing-shu, XU Jiang-ning, CHA Feng, HE Hong-yang

2013, 34(7):  835-839.  doi:10.3969/j.issn.1000-1093.2013.07.006

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A kind of fitting model and piecewise fitting method based on six kind of noise is proposed to solve the problem that the fitting model will probably be inaccurate by the traditional analysis method for the noise characteristics of fiber optic gyroscope. The reason of leading to the inaccuracy of fitting model is analyzed according to the data of a fiber gyroscope. It is found that a low frequency sinusoidal noise exists in the random noise of fiber-optic gyroscope. Compared with other gyroscope noises, this noise is small so that it was ignored in the traditional fitting model for five noise items, which may lead to the irrationality of fitting model and the inaccuracy of fit coefficients for optical fiber gyroscope,especially high precision optical fiber gyroscope. A fitting model for six noise items, including sine noise, is established by analyzing the time and frequency domains of measured gyroscope signal to determine the frequency of sinusoidal signal. A subsection fitting method is proposed to reduce the fitting error coupled by the approximating correlation time of sinusoidal noise, quantization noise, zero offset instability and rate ramp. The measured data of fiber optic gyroscope is analyzed with Allan variance based on the fitting model for six noise items. The results show that the fit error of the fitting model is small, and the fit error coefficient is accurate and credible.

A Neural Network-Based Prediction Method of Machining Deformation for Thin-walled Workpiece

QIN Guo-hua, ZHANG Yun-jian, YE Hai-chao

2013, 34(7):  840-845.  doi:10.3969/j.issn.1000-1093.2013.07.007

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During the cutting operation of thin-walled workpiece, the tool parameter is an important factor causing the workpiece deformation. The deformation law of workpiece which is caused by the single tool angle can be obtained by finite element method. However, if multiple tool angles are synchronously considered only by using finite element method, the deformation law of workpiece is difficult to reveal. Therefore, the 3D finite element analysis model is established for the milling process of thin-walled work-piece. The comparison of the simulated values with the experimental results is carried out to validate the proposed finite element model. Thus, the viable finite element method can be used to obtain the training samples of neural network. And then, with the nonlinear mapping of neural network, the prediction model of workpiece deformation is suggested according to the finite training samples. Finally, the relative error in less than 3% of the predicted deformation to the corresponding simulated result shows that the proposed prediction model can be used to correctly obtain the workpiece deformation.

Modeling and Experimental Research on Drilling Temperature Field of Carbon Fiber/ Epoxy Reinforced Composites

BAO Yong-jie, GAO Hang, LIANG Yan-de, ZHU Guo-ping

2013, 34(7):  846-852.  doi:10.3969/j.issn.1000-1093.2013.07.008

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Carbon fiber/ epoxy (C/ E) composites are characterized by light weight, high modulus and high specific strength, which make their use especially attractive to aerospace applications. But heat is easy to aggregate during drilling of C/ E composites because of their anisotropy, low interlayer strength and the low thermal conductivity. It can result in a high temperature gradient which has a significant effect on the quality of the workpiece and the tool wear. A drilling temperature field model of the unidirectional composites is developed. Based on the finite difference method (FDM), the temperature distribution and changes are simulated. A carbide twist drill is used in the experiments. The rise in temperature rise at different fiber directions and distribution of temperature field at the exit are measured by using thermocouples and infrared camera, respectively. The results show that the temperature distribution is in agreement with the temperature field model, the distribution of temperature field at the exit oval, and the in temperature rise is higher in parallel with the fiber direction.

The Application of Fractal Theory in Electrical Discharge Truing/ Dressing Diamond Grinding Wheels

CAI Lan-rong, RUAN Wen-yu, HU De-jin, LI Min

2013, 34(7):  853-857.  doi:10.3969/j.issn.1000-1093.2013.07.009

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Electrical discharge dressing (EDD) process is a non-traditional promising truing and dressing technology for superabrasive wheels. The process makes use of electrical energy to melt and vaporize the wheel bond, and make the abrasive grains stick from the grinding wheel. The development of lightning leader displays a stochastic discharge channel with branching and tortuous structure during EDD. It obviously has characteristic of self-similarity, which can be well described by fractals. A discharge channels simulation model based on the fractal theory shows the thermal energy distribution of various discharge mediums on the diamond wheel. And various discharge mediums including kerosene-based oil,impressed air and misted deionized water, are applied on EDD bronze-bonded diamond grinding wheels. The surface topography of dressed diamond grinding wheel is observed by VHX-1000 three-dimensional digital microscope. The analyses indicate that the surface topography of dressed diamond grinding wheel is consistent with the feature of simulation discharge channel based on the fractal theory. At the same time, the fractal simulation model of discharge channels is benefit to predict the wheel dressing microstructure and fressing quality.

Study on the Mechanism and Influencing Factors of Rotational Orientation of Crystals in Melt Under a High Magnetic Field

LOU Chang-sheng, WANG Qiang, WANG Chun-jiang, YUAN Yi, LI Wen, HE Ji-cheng

2013, 34(7):  858-864.  doi:10.3969/j.issn.1000-1093.2013.07.010

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The rotating mechanism of second phase particles in melt under the action of high static magnetic fields is analyzed, and the thermodynamic criterion and the law of rotational motion are given. Some important factors, such as temperature, gravity and particle shape, which play key role in the rotation of the second phase are clarified in detail. The results of theoretical analysis and experiments show that the rotational movement of the second phase is attributed to the resultant movement, the critical sizes of the second phase particles depend on temperature and gravity, and the shapes of the second phase particles have an effect on the orienting time. It can be concluded the high oriented metal-matrix composite can be fabricated under the action of an appropriate high static magnetic field by altering the factor mentioned above based on the differnce of intrinsic magnetic susceptibility of matters.

Research on Crack Propagation in the Crack Process of 1Cr18Ni9Ti Tube Under Uniaxial Tension

CHEN Ji-sheng, E Da-xin, ZHANG Jing-wen

2013, 34(7):  865-868.  doi:10.3969/j.issn.1000-1093.2013.07.011

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Based on a series of explorations on tube bending, the true mechanical property parameters of 1Cr18Ni9Ti tube are obtained through uniaxial tensile test. An approximate equation of true tensile stress at any moment in the uniform deformation process is derived and the corresponding result could be obtained by merely measuring the outer diameter of tube. Crack propagation law and stress-strain distribution in the necking process are discussed by experiment and simulation. The result shows that there exists a discrepancy in the stress states in the inner and outer tube walls during necking. Crack occurs first in the area which is close to the inner tube wall and subsequently propagates to the outer tube wall. In the meanwhile, the maximum axial stress energes in an area close to the inner tube wall due to unloading in the outer tube wall and the maximum axial strain yields in the outer tube wall where the crack occurs last.

Mechanical Properties of Epoxy Resin Composites Reinforced by Short Carbon Fibers Treated with Ball Milling-liquid Phase Oxidation Method

ZHANG Zhong-wei, TAN Ye-fa, TU Yi-qiang, DONG Gui-yang, YANG Zi-shuang

2013, 34(7):  869-875.  doi:10.3969/j.issn.1000-1093.2013.07.012

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Ball milling-liquid phase oxidation method was adopted to obtain the surface modified short carbon fibers (SCF). The modified SCFs with different dimensions are used to fabricate the short carbon fiber/ epoxy resin composites (SCF/ EP) by extrusion process. The surface morphology and wettability of the modified SCFs are characterized by atomic force microscope (AFM) and contact angle measuring method. Scanning electron microscope (SEM), tensile and impact test characterization are used to study their microstructures and mechanical properties. In addition, the reinforcing mechanisms of the short carbon fibers are elucidated. The results show that the surface wettability of fibers and epoxy is improved using the ball milling-liquid phase oxidation method. The maximum values of tensile and impact strength of SCF/ EP are up to 71-2 MPa and 27-75 kJ/ m2, respectively, which are increased by 103-4% and 63-9% compared with pure epoxy, respectively. The reinforcing mechanisms involved are mainly fiber debonding and pull-out, crack deflection and fiber bridging.

Research on the Microstructure and Properties of Multiple-dimensioned Cold Sprayed WC-Co Cermet Coatings

WANG Hong-tao, CHEN Xiao, BAI Xiao-bo, JI Gang-chang, DONG Zen-xiang, YI Deng-liang, YANG Fen-geng

2013, 34(7):  876-882.  doi:10.3969/j.issn.1000-1093.2013.07.013

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Three kind of multiple-dimensioned WC-Co cermet coatings were prepared by cold spraying of WC-12Co, WC-10Cr-4Cr and WC-17Co powders. The microstructure and phase structure of three kinds of multiple-dimensioned WC-Co coatings are analyzed. Their micro hardness, Young爷s modulus and fracture toughness are investigated, and the wear performances of three coatings are tested on a pin on disk tester. It was revealed that three cold sprayed multiple-dimensioned cermet coatings had dense microstructure and similar phase structure with that of feedstock powder. The allotropic transformation of metal Co occurred due to its intensive plastic deformation. The coatings have no lamellar structure of conventional thermal spraying coating and the WC particles in the coatings are distributed in a size range of micrometer, submicrometer and nanometer scale. Moreover, the micro hardness and Young's modulus ofcoatings decreased, fracture toughness and wear weight loss increased with increasing binder phase content. The wear mechanism was mainly the micro-cuts effect of abrasive particle on the coating surface.

Research on the Properties of Ultrasonic Vibration Amplitude and Actual Cutting Depth in Rotary Ultrasonic Machining

ZHANG Cheng-long, FENG Ping-fa, WU Zhi-jun

2013, 34(7):  883-888.  doi:10.3969/j.issn.1000-1093.2013.07.014

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The determinations of actual cutting depth and ultrasonic vibration amplitude, and the influences of input variables on ultrasonic vibration amplitude have important significance on the high efficiency and precision processing of rotary ultrasonic machining (RUM). The features of actual cutting depth during RUM are presented by analyzing the kinematics and cutting characteristics of diamond tool. Experiments are conducted to explore the relations of actual cutting depth and ultrasonic vibration amplitude,and the effects of spindle speed, feedrate and cutting depth on ultrasonic vibration amplitude. The results show that actual cutting depth is determined by effective superpositied ultrasonic vibration amplitude and cutting depth. The ultrasonic vibration amplitude stays unchanged with the changes in input variables (spindle speed, feedrate, and cutting depth), which can ensure the dimensional accuracy of the workpiece during RUM.

The Application of Robust Estimation and Allan Variance Method in Land Vehicle Navigation

WU You-long, WANG Xiao-ming, CAO Peng

2013, 34(7):  889-895.  doi:10.3969/j.issn.1000-1093.2013.07.015

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In order to solve the problems existing in integrated navigation system, such as global positioning system (GPS) signal interruption, interference and short operating time of inertial navigation system (INS), a fault detection and isolation module is integrated in the navigation system, with which the faulty GPS measurements could be excluded so as to improve the system reliability and availability. Meanwhile, the inertial sensor errors are analyzed with Allan variance method and compensated in the computation procedure so that the navigation system can operate with an acceptable accuracy as long as possible when GPS signal interruption happens. The experimental results show that the proposed method can effectively enhance the performance of the integrated navigation system, especially when GPS signal is interrupted.

Nature Frequency Tracking System for the Electromagnetic Resonance Fatigue Crack Propagation Test

GAO Hong-li, ZHANG Li-bin, JIANG Wei, ZHOU Yin

2013, 34(7):  896-903.  doi:10.3969/j.issn.1000-1093.2013.07.016

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A nature frequency tracking system based on the crack on-line measurement is established to ensure the stability of test load in the resonance fatigue crack propagation test, and its applied method which is an improved adaptive hill climbing nature frequency tracking method for crack length on-line measuring is proposed. First, the designed crack on-line measuring system is used to acquire the crack length, the related nature frequency is calculated according to the theoretical relationship between crack length and nature frequency, and then the theoretical nature frequency value is set as an original frequency point to track the accurate nature frequency. The accurate nature frequency near the original frequency point can be obtained by applying the proposed nature frequency tracking method. A vibrating system mathematical model with two degrees of freedom and double mass and a sample stiffness model are established, and the law of nature frequency changing with crack length is theoretically obtained and verified by experiment. The experimental results show that the nature frequency tracking accuracy is 0-3 Hz, the tracking time is 3-5 s, the proposed method has the higher tracking accuracy, faster tracking speed , and more stable and reliable tracking process compared with the general hill climbing nature frequency tracking method. It can meet the resonance fatigue crack propagation test requirements.

Research Notes

Modeling and Analysing of Air-defense Threat Netting

FU Xiao-wei, LI Jin-liang, GAO Xiao-guang

2013, 34(7):  904-909.  doi:10.3969/j.issn.1000-1093.2013.07.017

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The effect of connectivity between air defense units on the kill probability of penetration target is researched from the aspects of communication command and control structure and firepower collaboration. An air defense unit is used as a threat unit to create a threat netting model. A interconnectivity model for the threat units, the reliability of information routing in the network and the connectivity between the threat units. An information fusion model is established for target designation probability and radar detection probability. Based on the joint detection probability of multiple threat units which infers from the principle of radar networking using the networking fire control technology for multiple intercepting and coordinate attack on the penetration target, an final threat netting model is established. Finally,the simulating result in the C++ 6.0 environment proves the validity of the threat netting model.

Dynamics Modeling of Guided Dual-spin Rocket

WANG Zhi-gang,LI Wei,ZHANG Zhen-ning

2013, 34(7):  910-915.  doi:10.3969/j.issn.1000-1093.2013.07.018

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On the basis of multi-body characteristics of dual-spin rocket, a dynamics model, including motions of nose and afterbody is established by Kane method. Considering the interaction of the nose and the afterbody, the axial constraint forces between the nose and the afterbody is treated as active force rather than ideal constraint. Finally, seven scalar dynamic equations can be obtained. Theoretical analysis and simulation results show that the Kane model can present the flight characteristics of dual-spin rocket as accurately as the Newton Euler model. At the same time, the Kane model also can reduce the number of differential equations and has some applicability.

Analytical Model of Rocket-assisted Torpedo's Acquisition Probability

TIAN Heng-dou, CAO Qing-gang, HOU Dai-wen, YANG Xu-sheng

2013, 34(7):  916-921.  doi:10.3969/j.issn.1000-1093.2013.07.019

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According to the analysis of rocket-assisted torpedo operation mode and trajectory, the searching area, water entry point dispersion and target dispersion are found to be the key factors of rocket-assisted torpedo acquisition probability, and mathematical descriptions of each factor are provided. Considered of relative relationship of three factors, and the differences between two typical attacking modes, namely pre-point and current point, two analytical models are presented for rocket-assisted torpedo acquisition probability, based on error synthesis and total probability respectively. The calculated values agree well with the results of simulation experiment.

Attitude Control of Underwater Vehicle out of Water Based on Implicit Nonlinear Dynamic Inversion

BAI Yu-liang, CUI Nai-gang, GUO Ji-feng, XU Jian-gtao

2013, 34(7):  922-928.  doi:10.3969/j.issn.1000-1093.2013.07.020

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In explicit nonlinear dynamic inversion (NDI) control, a system is linearized accurately using nonlinear offset. However, because of the inversion errors in offset from the uncertainties of real models, the robustness of control system is hard to be guaranteed. Explicit NDI is found facing serious challenges when solving the motion issue of underwater vehicle exceeding water. Considering the severe change in hydrodynamic force and the strong impact of waves, its attitude control has become a research focus. Firstly, the control law of dynamic inversion in the form of implicit increments is derived and obtained, and the system is divided into a slow loop and a fast one using the idea of stepped construction on the base of affine motion model of underwater vehicle out of water. Then the feedback of state variation rate is introduced, the implicit control law independent of accurate models and with better robustness is designed based on these two time-scale separated loops. Finally, based on the implicit NDI control algorithm, the attitude of underwater vehicle in its out-of-water process is traced under the influence of waves and perturbation of hydrodynamic parameters and measurement noise, and the validity and rationality of the control law are verified.