Table of Content

30 December 2016, Volume 37 Issue 12

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Paper

Effect of Time-sequence Control on Coupling of Strong Magnetic Field and Shaped Charge Jet

MA Bin, HUANG Zheng-xiang, ZU Xu-dong, XIAO Qiang-qiang, JIA Xin

2016, 37(12):  2177-2184.  doi:10.3969/j.issn.1000-1093.2016.12.001

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Effect of time-sequence control on the coupling of strong magnetic field and shaped charge jet is analyzed based on the relevant depth of penetration (DOP) tests. Two kinds of magnets with different structures (Ⅰ-type andⅡ-type) are used in the experiments. The depth of penetration and the crater form, which is penetrated by the jet impacted by the magnetic field in different time-sequence, are measured and analyzed. Meanwhile, the effect of magnetic field under different time-sequence control on the stability of shaped charge jet is researched. The research results show that time-sequence control is one of the important influence factors. The major penetration ability of jet focuses on its front and middle parts. Its penetration ability is increased effectively if those parts are coupled with the magnetic field by improving the time-sequence control of the system. The penetration ability of jet produced by 56 mm shaped charge is increased from 1.7% to 32.8% under the effect of magnetic field generated by Ⅰ-type magnets, and the penetration ability is improved from 1.6% to 69.4% for Ⅱ-type magnets.

Research on Sliding Mode Control and Energy Management Strategy of Energy-regenerative Suspension System of Vehicle

HUANG Da-shan, ZHANG Jin-qiu, LIU Yi-le, ZHANG Jian

2016, 37(12):  2185-2195.  doi:10.3969/j.issn.1000-1093.2016.12.002

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To solve the high energy consumption of standard active suspension system of vehicle, a 4 DOF energy-regenerative suspension system is established by taking the half-car as research object. A new energy-regenerative absorber, which has an actuator for active controlling and an energy-regenerator for energy harvesting, is designed to solve the problem of enabling to implement the active control and energy harvesting of energy-regenerative absorber at the same time. An energy management strategy based on the performing rate of active control is given according to the running conditions of vehicle. The simulated and experimental results show that, in comparison to the passive suspension, the comprehensive performance of the established energy-regenerative suspension with sliding mode control algorithm is improved by 22.700%, which indicates that the vibration control of the energy-regenerative suspension with sliding mode control is effective; 3 kinds of typical running condition, which are distinguished by road level and running speed, could be used as the criteria of the performing rate of active control.

Analysis and Experiment of Steady-state Steering of Tracked Vehicle under Concentrated Load

WANG Hong-yan， CHEN Bing， RUI Qiang， GUO Jing， SHI Li-chen

2016, 37(12):  2196-2204.  doi:10.3969/j.issn.1000-1093.2016.12.003

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In order to study the steady-state steering performances of tracked vehicle under concentrated load and improve the simulating accuracy of tracked vehicle steering model, the effect of track tension on ground pressure distribution is analyzed, and a computation model of ground pressure distribution of tracked vehicle is proposed. A new steering dynamics model is derived to establish a corresponding dynamics equation set based on shear stress and shear displacement relationships of track and ground. The effect of ground pressure change induced by track width and tension on steady-state steering kinematics and dynamics parameters is analyzed. The analysis result is verified through vehicle test. The test results show that the theoretically calculated result is well fitted with the test data, and the proposed model is proven to be effective.

Analysis of Distribution Characteristics of In-bore Magnetic Field of Electromagnetically Launched Projectile Based on Analytical Method

LI Xiang-ping, LU Jun-yong, LI Yu, WU Xiao-kang

2016, 37(12):  2205-2211.  doi:10.3969/j.issn.1000-1093.2016.12.004

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The in-bore magnetic field distribution characteristics of electromagnetic launcher should be considered in the layout design of components in guided projectile. The high in-bore magnetic field generated by electromagnetic launcher is analyzed, and a formula for magnetic field distribution is deduced based on Biot-Savart law, in which projectile displacement and current skin depth are considered. The relationship between inductance gradient, current frequency and projectile’s location is obtained by time-harmonic analysis and data fitting to analyze the in-bore kinetic characteristics of projectile interior trajectory. And the time-frequency analysis method is used to achieve the relationship between current skin depth and time to build a 3-D theoretical calculation model (TCM) for the distribution characteristics of magnetic field along the central axis of projectile. A laboratory electromagnetic launcher is taken for example, and the experimental data is used as input for simulation. The results show that the in-bore magnetic induction intensity frequency is below 450 Hz and the peak of in-bore magnetic induction intensity is up to 0.4 T, which gets weaker along the length direction of projectile and approximates to 0 at 100 mm. The validity of TCM is verified by using the experimental data of magnetic probe.

A Parametric Modeling Method for Gun Barrel and a Meshing Generation Strategy for Worn Barrel

DING Chuan-jun, ZHANG Xiang-yan, LIU Ning

2016, 37(12):  2212-2219.  doi:10.3969/j.issn.1000-1093.2016.12.005

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In order to accurately build the finite element model of worn gun barrel, a piecewise-connection algorithm is designed to generate parametric 3D solid model of bore, and a node-offset algorithm is proposed to construct the finite element analysis model of bore with different wear degrees. Based on the projectile-barrel interaction model of worn barrel, and taking account of the increment in bore's volume, the interior ballistic process is simulated by the thermo-mechanical coupling finite element method. And the main reason of degradation in muzzle velocity and chamber pressure for a 23 mm gun is also studied. The simulated result matches with the experimental data, which verifies the correctness of the proposed modeling method and meshing strategy. The present study not only has important guiding significance for the design and analysis of gun barrel, but also provides an evaluation method for the performance degradation of interior ballistic process.

Prediction of Gun Barrel Wear Based on Improved Non-equal Interval Grey Model and BP Neural Network

YI Huai-jun, LIU Ning, ZHANG Xiang-yan, DING Chuan-jun

2016, 37(12):  2220-2225.  doi:10.3969/j.issn.1000-1093.2016.12.006

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General data fitting and prediction methods are constrained by the unequal time interval, difficult sampling, high cost and small amount of data in predicting of the wear degrees of gun barrel. A combined prediction method based on the improved unequal interval grey model and neural network is proposed. The proposed method is used to predict the wear of gun tube. The predicted results agree well with the experimental values. The results show that the combined prediction method has high prediction accuracy, and therefore can be used to effectively predict the gun bore wear.

Numerical Simulation on Formation and Penetration of Double-layer Liners EFP Warhead Influenced by Multi-point Initiation

LONG Yuan, LIU Jian-feng, JI Chong, ZHONG Ming-shou, LIU Ying, ZHOU Hui

2016, 37(12):  2226-2234.  doi:10.3969/j.issn.1000-1093.2016.12.007

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Initiation modes have important influence on formation and penetration of double-layer liners explosively-formed projectile (EFP). Based on the experimental study of double-layer liners EFP warhead, the effect of multi-point initiation on the formation and penetration of EFP warhead with double-layer liners is analyzed by using ANSYS/LS-DYNA software. Results show that the EFP warhead with double-layer liners can form a large aspect ratio of L/D(the length/diameter) penetrator with good flight characteristics and terminal effects when the number of initiation points are between 4 and 8. As the number of initiation points reach 6, the maximum penetration depth is about 1.07 times of the charge diameter which is increased by 32% compared with an initiation point in the same shape charge structure. The conclusions can supply a theoretical reference for choosing the appropriate initiation point parameters of the double-layer liners EFP warhead.

Analysis on Coning Motion of High-speed Spin-stabilized Projectile Base on On-board Magnetic Test

ZHANG Long， ZHAO Zhi-qin， FAN Bin-ning， ZHANG Yan

2016, 37(12):  2235-2241.  doi:10.3969/j.issn.1000-1093.2016.12.008

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In order to study the coning motion of high-speed spin-stabilized projectile during flight, the on-board geomagnetic attitude measurement method is used to build a test model. The angular relation among local magnetic vector, projectile velocity vector and projectile-axis geomagnetic component is analyzed. A test model for the angular movement and parameters of high-speed spin-stabilized projectile is built, an experimental method is proposed. The test platform and the calibration devices are constructed too. The on-board geomagnetic test data is obtained through experiment. Signal filtering and attitude resolving are conducted based on geomagnetic test data. The trajectory curve of projectile coning motion is got. Test results of projectile coning motion is anlyzed,and the laws of projectile precession and nutation motion are obtained. Analysis result shows that the on-board geomagnetic test method and the projectile angular motion model can be used accurately to reveal the coning motion law of high speed spin-stabilized projectile.

Research on Model of Ignition of Boron Particle Based on Multiple Oxide Layer Structure

XU Yi-hua, HU Xu, ZOU Hao, LI Yu-lin, ZENG Zhuo-xiong

2016, 37(12):  2242-2250.  doi:10.3969/j.issn.1000-1093.2016.12.009

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In order to study the influence of the related factors on the ignition process of boron particle by using numerical calculation method, an improved ignition model of boron particle is developed under the consideration of the multilayer oxide structure. The physical process of the change of species at the surface of the oxide layer and the formation of surface flame is considered in the model. The simulation results are in good agreement with published experimental data. The influences of ambient pressure, particle diameter, kinds of oxidant and their concentration, ambient temperature on the ignition process of boron particle are studied by using the improved ignition model. The simulation results show that the ignition time is shortened at higher ambient pressure. The larger the particle diameter is, the thicker the oxide layer is, thus delaying the ignition time. The higher oxygen concentration has a good effect on the ignition of boron particle on the larger particle diameter（>5 μm）, but has little significant influence on smaller particle diameter(≤5 μm). The ignition of boron particle is promoted with water vapor available. The higher concentration of water vapor makes the ignition time reduced. The higher ambient temperature is useful for the ignition of boron particle.

Integrated Autopilot Guidanceand Control Design Based on 2-order Sliding Mode for Extended Range Guided Projectiles

YANG Jing， SHI Jin-guang， LI Xiao-yuan, WANG Zhong-yuan， CHANG Si-jiang

2016, 37(12):  2251-2258.  doi:10.3969/j.issn.1000-1093.2016.12.010

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A 2-order sliding mode(2-SM) controller is proposed for an integrated guidance and control (IGC) design of extended range guided projectiles (ERGP). The canard loop is modeled as first-order dynamics. Considering the characteristics of ERGP, a linear model for IGC design is established based on the initial line-of-sight(LOS) with the assumption of a small disturbance. Then the linearized longitudinal integrated dynamics is formulated, in which the discrepancies from the target maneuver and the aerodynamic parameters are included. The quasi-continuous sliding mode control algorithm is adopted for a 2-SM IGC design for regulating the LOS rate to zero in finite time. To demonstrate the benefits of IGC, a separated robust autopilot and guidance law are also presented via the conventional SM control theory. Simulated results show that the proposed IGC controller is superior in that the miss distance is reduced.

A SINS/STAR Integrated Navigation Method Based on Online Estimation of Gyroscope Error in Inertial Coordinate

ZHAO Hui, XIONG Zhi, SHI Li-juan, YU Feng, LIN Ai-jun

2016, 37(12):  2259-2267.  doi:10.3969/j.issn.1000-1093.2016.12.011

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In traditional SINS/STAR integrated navigation system, the stellar attitude information needs to be converted from inertial coordinate system to navigation coordinate system. Since the geographic position information needs to be introduced in the conversion process of attitude information, it is inevitably to introduce the conversion error and is unable to take full use of the correction effect of high precision stellar attitude information on the error of inertial navigation system. In consideration that the gyroscope output information and the stellar attitude information can be directly obtained in the inertial reference frame, a SINS/STAR integrated navigation method based on the online estimation of gyroscope error in inertial coordinate is proposed. The drift error of gyro can be estimated online in inertial coordinate by establishing the mathematical model of SINS/STAR integrated navigation based on gyroscope error. The inertial navigation error caused by the drift error of gyro can be effectively reduced by correcting the gyro error in real-time. The simulated results show that the proposed method can effectively estimate the drift error of gyro, and improve the accuracy of inertial navigation system.

Modeling of Telescopic Hydraulic Cylinder and Research on Inter-stage Buffer

FENG Jiang-tao， GAO Qin-he， GUAN Wen-liang， LI Liang

2016, 37(12):  2268-2276.  doi:10.3969/j.issn.1000-1093.2016.12.012

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Telescopic hydraulic cylinder is widely used in large erecting devices. Telescopic cylinder can provide longer stroke compared to single stage cylinder. However, its structure is complex. In order to get the characteristics of telescopic cylinder, a motion model is established based on the cavity node method. The LuGre friction model is improved by considering the lubricant film. The contact force model is improved using the equivalent damping model of the hysteresis factor. The process of erection driven by telescopic cylinder is simulated. The action area mutates when the telescopic cylinder converts one stage to other stage, which leads to the sudden change in pressure and velocity, and excessive impact. In order to reduce the impact, many buffer holes are arranged on the cylinder barrel. The simulated results show that the cylinders synchronously move in the replacement of stage after the buffer structure is used. The sudden change in pressure is transferred into slow change. The pressure is raised to the next working pressure in advance, thus greatly reducing the fluctuations of velocity and acceleration.

Experimental Investigation of Ground Reflected Overpressure of Shock Wave in Air Blast

DUAN Xiao-yu, CUI Qing-zhong, GUO Xue-yong, JIAO Qing-jie

2016, 37(12):  2277-2283.  doi:10.3969/j.issn.1000-1093.2016.12.013

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In order to investigate the parameters of shock wave in air blast, the ground reflected overpressures of TNT, HL0（RDX 95%+Wax 5%）and HL15（RDX 80%+Wax 5%+Al 15%） at different locations were tested. Test resultes show that the peak overpressures of HL15 are maximal at 3 m, 4 m and 5 m from the center of explosion compared with TNT and HL0. The peak overpressures of three explosives get closer to each other at 7 m, 9 m and 12 m from the center of explosion with the increase in distance. Power exponential formulas are used to fit the relationship between peak overpressure and scaled distance. The fitting results show that the magnitude order of peak overpressures is HL0≥HL15>TNT for R≤ 2.6 m; the magnitude order of peak overpressures is HL15> HL0 >TNT for 2.6 m

Research and Design of a Dual-mode Tri-band Antenna for BDS Navigation and Integrated UHF Communication Terminal

WANG Dan-qing， LI Ping， ZHU Yong-zhong

2016, 37(12):  2284-2292.  doi:10.3969/j.issn.1000-1093.2016.12.014

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In order to satisfy the requirements of communication terminal in an individual soldier combat system for navigation and ultra-high frequency (UHF) communication, a novel antenna for the individual soldier communication terminal is proposed, which is compatible with navigation and UHF communication functions. A novel capacitors loaded-FPQHA is designed by loading series capacitors at the top of folded printed quadrifilar helix antenna (FPQHA), which realizes the coverage of B1 and B3 bands for Beidou satellite navigation system (BDS). The proposed antenna has a compact structure and can be tuned conveniently by adjusting the capacitance values. Given that the current UHF radios typically employ an external whip antenna for communication, the proposed capacitors loaded-FPQHA is coaxially located with the existing monopole antenna, which reduces occupation of antenna system on the terminal, and the compatibility issue is solved through structure optimization, especially with a sleeve added around the monopole. The proposed antenna can be easily integrated with existing individual soldier system and reduce the maintenance costs. It satisfies the performance requirements of high-precision BDS navigation in warfare, and UHF communication is also supported.

Measurement and Analysis of IR-UWB Channel in Minefield Near-ground Environment

YANG Li， JI Mao-rong， LIU Qiang， GAO Zhen-ru

2016, 37(12):  2293-2300.  doi:10.3969/j.issn.1000-1093.2016.12.015

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In order to research the propagation properties of impulse radio ultra wideband（IR-UWB）signals in the minefield near-ground environment and provide a technology support for the future development of landmines, the IR-UWB signals were test experimentally in three typical propagation environments. The features of received signals are researched based on the measured data. An analytic method with energy ratio detection and multipath component criterion is proposed. The channel impulse responses (CIRs) and main parameters are statistically calculated and analyzed. The calculated result shows that the path loss coefficient in near-ground environment is smaller than that in free space since the signal reflects from the ground and surrounding obstacles. With the calculation, the path loss coefficients range from 1.50 to 1.85 for the antenna heights of 0.3 m and 0.5 m. According to the CLEAN algorithm with self-adaptive threshold, the error ratios of the original signals and recovered signals from CIRs are not more than 30%. The result shows that the calculated channel parameters correspond with the characteristics of the propagation environment. The feasibility of the proposed method and the accuracy of the channel analysis results were verified.

A GPS-based Camera Calibration Method

KONG Xiao-fang, CHEN Qian, GU Guo-hua, QIAN Wei-xian, REN Kan, WANG Jia-jie

2016, 37(12):  2301-2307.  doi:10.3969/j.issn.1000-1093.2016.12.016

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The calibration templates have been widely used for camera calibration. The calibration templates could not cover a large field of view at a long distance due to its limitation. The method could not realize precise calibration. Combining the high-precision coordinate information access technology with GPS RTK mode, a GPS-based camera calibration method is proposed. In the proposed method, the coordinate information of GPS centroid in WGS-84 coordinates is obtained under the GPS RTK mode. The coordinate system transformation method is used to transform WGS-84 coordinates to system world coordinates. The images of GPS at different positions are taken by the camera under calibration, and Harris corner detection algorithm is used to get the corresponding image coordinates. The projection matrix is calculated according to the camera model, and the camera calibration is realized. Experimental results show that the proposed method can be used to obtain omnidirectional spatial coordinate information with high precision. Compared with traditional camera calibration methods, the calibrated RMS error of the proposed method is only 0.125 36.

A Hybrid Routing Protocol for Differentiating Route Frequencies in MANET

LI Xu, HE Hao-xiong, PENG Jin-lin, SONG Gu-yang, SHAO Xiao-tao

2016, 37(12):  2308-2316.  doi:10.3969/j.issn.1000-1093.2016.12.017

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As a result of the widely use of mobile Ad Hoc network (MANET) in formation communication and emergency communication, the high and low frequency routes appear in real situations. In these scenarios, no matter what routing protocol is used, on-demand routing protocols or proactive routing protocols always use fixed maintenance strategy, and obviously none of them can bring their advantages into play. Regarding this scenario, a totally new hybrid routing algorithm is put forward based on Ad Hoc on-demand distance vector (AODV) routing protocol, which makes use of both on-demand and proactive strategies. In this new protocol, the high frequency route is obtained by estimating the traffic flow to maintain the frequently used route through proactive strategy and deal with the low frequency route with on-demand strategy. The qualitative analysis and simulation show that the new hybrid routing algorithm makes the end-to-end packet average transmission delay is reduced by about 20% when compared with AODV protocol.

Anti-fracture Technology of Ad Hoc Network Routing in Tropospheric Scatter Channel

HE Shao-tong, XUE Lun-sheng, CHEN Xi-hong, ZHANG Kai

2016, 37(12):  2317-2323.  doi:10.3969/j.issn.1000-1093.2016.12.018

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Most of the existing Ad Hoc network routing researches are to use the single receiver power as the basis of the ideal channel. In order to enhance the performance of anti-missile network, the tropospheric scatter channel with long communication distance and anti-interference ability is introduced, and the overall effect of the channel and device characteristics on Ad Hoc network routing is studied. According to the AODV optimization protocol, a monitoring model for the routing status of scatter channel is proposed, which can quickly locate the end nodes of “ weak ” routing and initiate a reverse search for damaged routes before the routes break. Simulated results show that the improved routing protocol RE-AODV reduces the average end-to-end delay by 17.1% and the maximum control packet overhead by 21.8%. The packet delivery ratio of RE-AODV algorithm maintains at 70% or even higher, which proves that it can prevent the routing fault of high-speed mobile nodes.

Research on Collapse Characteristics of Ventilated Cavities around an Underwater Vehicle

ZHANG Xiao-shi， WANG Cong， WEI Ying-jie， SUN Tie-zhi

2016, 37(12):  2324-2330.  doi:10.3969/j.issn.1000-1093.2016.12.019

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The collapse characteristics of ventilated cavities around an underwater vehicle are studied through water tunnel experiment, and a behavior of a ventilated cavity stopping subsequent cavity from generating is analiyzed. In order to analyze the oscillation characteristics of cavities during collapse, the high-speed camera and dynamic force-measuring systems are used to record the evolution process of ventilated cavities and the change in pressure on underwater vehicle. The experimental results show that the changing process of shed cavity can be classified into four periods: generation, cavity breakage, cavity shedding, and collapse. Cavity collapse depends on the state of flow field. The cavity collapses when the flow is in turbulent state. The cavity collapse at a fixed point can be captured by the pressure sensors. As a shed cavity moves near mode boundary, the cavity collapses. The shed cavity and pressure are investigated experimentally, and the experimental results of collapse pressure are compared with the calculated results based on Rayleigh-Plesset equation. The experimental value of collapse are in good agreement with the theoretical value.

Research on Relationship between Crack Propagation Speed of TC4 Alloy and Loading Speed under Mode II Dynamic Loading

MIAO Run， WANG Wei-li， SONG Yang

2016, 37(12):  2331-2339.  doi:10.3969/j.issn.1000-1093.2016.12.020

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In order to ascertain the crack initiation time of TC4 in Mode II crack experiment, the energy absorption in plastic zone and the crack propagation speed are calculated. Split Hopkinson pressure bar (SHPB) is used to experiment upon Mode II crack propagation of TC4. High-speed digital speckle correlation method (HS-DSCM) is used to get displacement-time curve at a observation point, the Mode II crack initiation time of TC4 is determined, and the propagation speed of Mode II crack is calculated. A finite element model is established using ABAQUS/Explicit. The simulated results is compared to the experimental results. The propagation forms of crack at different impact velocities under loading condition are researched. Mode II crack propagation speeds at different loading speeds are calculated. Relation between loading speed and Mode II crack propagation speed is obtained.

Precision Generated Grinding Method and Its Technology of Large Diameter SiC Aspheric Surface

HU De-jin

2016, 37(12):  2340-2346.  doi:10.3969/j.issn.1000-1093.2016.12.021

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In order to improve the grinding accuracy and efficiency of large diameter aspheric surface, a generated grinding method for aspheric surface based on the normal track is proposed, and a motion control model is designed. In grinding process, the rotation centerline of grinding wheel spindle always coincides with normal line of grinding point on aspheric surface. A detecting device is designed for tracking shaping precision in real-time, and a mathematical model and a related grinding process for automatic compensation of grinding wheel wear are established. Results show that the proposed method can be used to avoid the principle error of grinding motion trajectory, make the motion mechanism simple, and ensure the motion accuracy; grinding ratio and grinding efficiency are increased by using the end face of the grinding wheel for aspheric surface grinding.

Reconstruction of Transient Nonuniform Temperature Field in Solid Structures Using Inverse Methods

SHI You-an, WEI Dong, GUI Ye-wei, QIAN Wei-qi, ZENG Lei, LIU Xiao

2016, 37(12):  2347-2355.  doi:10.3969/j.issn.1000-1093.2016.12.022

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A new method is presented for reconstruction of internal transient nonuniform temperature field in solid structures . The proposed method consists of a joint of heat conduction calculation and an inverse analysis for boundary parameter estimation using ultrasonic time of flight by conjugate gradient method or sensitivity method. The principle for internal temperature sensing is based on temperature dependence of the velocity of ultrasonic wave that propagates through solid material. Serial simulation and stability analysis are made， in which classic function form of heat flux or constant temperature is estimated to illustrate the calculating accuracy and the factors of influencing two parameter estimation methods. Comparison experiments with a steel plate which single side is heated by hot water are referred. The temperature gradient and its variation estimated by the two methods agree well with the data measured using thermocouples installed in a steel structure. The results show that the proposed method is a promising means for high accurate reconstruction of internal transient temperature field in solid structure.

Contrastive Research on Warship Formation Spare Part Support Plans

JIN Jia-shan, CAI Zhi-ming, CHEN Yan-qiao

2016, 37(12):  2356-2365.  doi:10.3969/j.issn.1000-1093.2016.12.023

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Warship formation spare part support plan plays an important role in forming the warship formation readiness. The spare part support plan which is in accordance with the engineering practice is established by using inventory optimization management strategy. The support plan can be used to reduce the spare parts support funds while satisfying the minimum requirement of warship formation availability. A warship formation inventory optimization model which was based on spare part`s multi-echelon demand rate is built by taking the very low utilization rate of spare parts in the waters off Somalia as studying background, and the system support funds as the optimizing goal which is constrained by the minimum requirement of warship formation availability, and the calculation steps and the solution method are given. the decision and recommendations of warship formation spare part configuration is proposed by using the contrastive research on the different warship formation spare part support plans.

Elaborate Simulation of Interaction Effect between Internal Weapon Bay and Missile

ZHANG Qun-feng，YAN Pan-pan，LI Jun

2016, 37(12):  2366-2376.  doi:10.3969/j.issn.1000-1093.2016.12.024

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To study the strong interaction effect between internal weapon bay and missile during the weapon release, the unsteady flow around a simplified weapon bay and missile model is simulated using SST k-ω improved delayed detached eddy simulation (IDDES) method, six-degrees-of-freedom rigid body dynamics equations and overset mesh method. The fluctuation of pressure in the weapon bay is analyzed using the smooth pseudo Winger-Vile distribution (SPWVD) method, and the time-frequency characteristics of pressure are obtained. The research results show that, when a missile is delivered from the weapon bay, the shear layer is destroyed to lead to the change in the flow structure, the self-sustained oscillation disappears in the weapon bay, and there is no obvious cavity tone. Stronger vortexes concentrate in the trailing edge of cavity, and thus the sound pressure level (SPL) in the trailing edge of the weapon bay increases. After the missile is delivered from the weapon bay, the shear layer is rapidly reestablished and the self-sustained oscillation shows up again. The impact of the accelerated flow near the head of the missile leads to enhance the instability in shear layer. Accordingly, the sound pressure level in the weapon bay is enhanced. The missile flies at a large angle of attack since it is affected by upward force moment during passing through the shear layer. After the missile is delivered from the weapon bay, it begins to be affected by vertical upward force and pitch down moment. The vertical upward force can hinder the missile from falling. Meanwhile, the force and moment acting on the missile fluctuate strongly under the effect of the unsteady flow in the weapon bay.

Research Notes

Trajectory Tracking Algorithm for Motion Compensation of Loitering Munition under Wind Environment

LI Zeng-yan， LI Xiao-min， LIU Qiu-sheng

2016, 37(12):  2377-2384.  doi:10.3969/j.issn.1000-1093.2016.12.025

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The trajectory tracking process of loitering munition is affected by wind speed and wind direction. A motion model with wind is established, and a nonlinear guidance law based on the variable gain virtual reference point and outer loop motion compensation is proposed. According to the fixed distance limit of the guidance law parameters, the variable gain virtual reference point is designed, and the stability condition of trajectory tracking is analyzed. Then the dynamic feedback compensation factor is designed for the hysteresis characteristic of the system’s outer loop, and the calculation method of the parameters and the kinematic constraints are also given. The guidance law is verified with wind and without wind through mathematical simulation. Considering the difficulty of actual flight, the tracking performance is tested on the semi physical real-time simulation platform which is built based on vc++. The results show that the improved guidance law can effectively overcome the wind disturbance, and it has high tracking accuracy but is easy to be realized.