Table of Content

31 January 2017, Volume 38 Issue 1

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Contents

2017, 38(1):  0. 

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Paper

Modeling and Prediction of Muzzle Velocity Degradation of Machine Gun Based on FOAGRNN

CAO Yan-feng, XU Cheng

2017, 38(1):  1-8.  doi:10.3969/j.issn.1000-1093.2017.01.001

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Muzzle velocity degradation prediction of machine gun is a complicated non-linear problem. Generalized regression neural network (GRNN) has been widely used in the modeling of the non-linear problems, but GRNN has rarely been used to predict the muzzle velocity degradation of machine gun. Since the smoothing factor of GRNN obviously affects the prediction performance of neural network, the fruit fly optimization algorithm is used to automatically select the parameters of GRNN. A method to model a muzzle velocity degradation based on general regression neural network with fruit fly optimization algorithm (FOAGRNN) is proposed. A prediction model is established based on the experimental data of muzzle velocity degradation, in which the muzzle velocity degradation is taken as characteristic quantity. The predicted results are basically consistent with the experimental results. The research result shows that FOAGRNN model outperforms GRNN model with default parameter and BPNN prediction model in the prediction of muzzle velocity degradation. Key

Research on Coordination Control Strategy of Driving force of Distributed Electric Drive Tracked Vehicle

ZENG Qing-han, MA Xiao-jun, WEI Wei, YUAN Dong

2017, 38(1):  9-19.  doi:10.3969/j.issn.1000-1093.2017.01.002

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A coordinated hierarchy control strategy of driving torque is proposed for the distributed electric drive tracked vehicle. The coordination control system structure is developed，which is divided into motion control layer, control allocation layer and anti-slip layer. The vehicle is considered to be an unequal over-actuated system. A master-slave multi-motor control allocation law is established. The quadratic programming method is used to design the torque optimization distribution law of in-wheel motors, and the weighted least square (WLS) method is used to solve torque distribution , which could improve adhesion margin and decrease friction loss between motor wheels and track. The anti-slip control law developed by LADRC is used to enhance the adhesive force by restricting the slip of drive wheel. Co-simulation of Matlab and RecurDyn shows that the control allocation could realize torque optimization distribution, and LADRC anti-slip controller could regulate the slip speed in steady margin, which could improve the stability and efficiency of force transfer. Key

Research on Compression Ratio and Fuel Injection Advance Angle Optimization of Two-stage Turbocharged Diesel Engine

SHANG Hai-kun , DONG Chang-long， HE Jian-feng， FAN Feng， LI Ping， HUANG Mian-dun， XIE Liang

2017, 38(1):  20-26.  doi:10.3969/j.issn.1000-1093.2017.01.003

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To address the issue that the maximum combustion pressure is too high after a certain V shape diesel engine is modified into two-stage turbocharged system from one-stage turbocharged system, the effects of fuel injection advance angle and compression ratio on the performance and maximum combustion pressure of two-stage turbocharged diesel engine are simulated by building a simulation model on the software GT-Power and using experimental data, and the united optimization of both the fuel injection advance angle and compression ratio is conducted with the tool DOE of GT-Power by taking experimental maximum combustion pressure of the two-stage turbocharged engines as limitation and taking the maximum torque as goal. The decrease of the compression ratio can effectively reduces the maximum combustion pressure at 1 300 rpm and 2 100 rpm. For every 1 decreased in the compression ratio, the maximum combustion pressure is decreased by 0.8 MPa at 1 300 rpm and 1.16 MPa at 2 100 rpm, respectively. Relative variations of optimized compression ratio and fuel injection advance angle are 14.9°CA and 4.3°CA, respectively. The feasibility of the result is validated according to the structural condition of the testing diesel engine. Verification with trial machine is conducted on diesel engine bench. Key

Research on Flexible Multi-body Dynamics Structure Optimization of Artilleries

XIAO Hui, YANG Guo-lai, SUN Quan-zhao

2017, 38(1):  27-34.  doi:10.3969/j.issn.1000-1093.2017.01.004

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In allusion to the problem of that the existing structural dynamics optimization methods cannot optimize the flexible parts in flexible multi-body dynamic systems, a method combining multidisciplinary agent models and the improved nondominated sorting genetic algorithm (NSGA-II) is proposed. Based on an experimentally authenticated rigid-flexible coupled multibody model, a surrogate model with good generalization ability and forecasting accuracy is established with RBF-BP neural network. In the proposed model, the muzzle vibration parameters are used as outputs, and the modal parameters of flexible part and some general structural parameters are taken as inputs. Nondominated sorting genetic algorithm is used to improve the muzzle vibration characteristics, and the max-min criterion is adopted to select a solution from the Pareto front. The optimized effect is compared with the optimized result of the original model. The result shows that the proposed method can be used for optimization of artillery flexible multi-body dynamics structure. Key

Identification of Interval Uncertainty Parameters of a Howitzer Shell Transfer Arm

ZHAO Qiang-qiang, HOU Bao-lin

2017, 38(1):  35-42.  doi:10.3969/j.issn.1000-1093.2017.01.005

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Shell transfer arm is a complicated mechatronic and hydraulic integrated system of howitzer with multi-parameters. During the modeling process, some parameters are hard or unable to be measured but have significant effect on the performance of shell transfer arm, which can only be achieved by identification. For identifying the parameters of shell transfer arm, the dynamic and control models are built in Simulink, and the uncertainty parameters are described by interval number. The identification problem of interval uncertainty parameters is transformed into a certainty optimization problem via order relation of interval number transformation model. The similarity of angular velocity of shell transfer arm is set as the optimization objective function, and three parameters are identified by differential evolution (DE) method. The proposed method is verified by simulated and test data. The identification results of simulated data show that the identification accuracy satisfies the requirement, and the identification results of test data show that the proposed method is feasible and effective. Key

Influence of shell Structure on Dispersing Velocity of Fuel-air Mixture

WANG Ye， BAI Chun-hua， LI Jian-ping

2017, 38(1):  43-49.  doi:10.3969/j.issn.1000-1093.2017.01.006

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In order to study the dispersal characteristics for different shell structures, the processes of fuel dispersion and shell breakage driven by central explosive are simulated by LS-DYNA code, and the simulated and experimental results are compared. The boundary expansionstate of fuel and the process of shell breakage are obtained. The variation of cutting force with time and the maximum dispersing velocity of different shell structures are analyzed. Results show that the dispersing velocity of fuel could be effectively increased by enhancing the axial tension while satisfying the structural strength and the same radial strength. When axial tension is up to 0.7×10⁶ N, the greater dispersing velocity could be produced by stiffener structure. The maximum dispersing velocity of non-stiffener structure is 285.3 m/s. The maximum dispersing velocity of stiffener structure is 316.3 m/s, that could be increased by 10.8% with the same dose for non-stiffener structure. Key

Research on Aerodynamic Characteristics of Terminal Sensitive Projectile with S-S-shaped Flexible Wings

LYU Sheng-tao, JI Dan-dan, LIU Rong-zhong, GUO Rui, MA Xiao-dong

2017, 38(1):  50-58.  doi:10.3969/j.issn.1000-1093.2017.01.007

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The stabilizing wings are wrapped on the outer wall of terminal sensitive projectile (TSP). The diameter of TSP is generally large to meet the demand of power, which restricts wing thickness. The falling speed of TSP is so quick that the wings deform under the action of aerodynamic force. The effect of the structure parameters of wings on the aerodynamic characteristics of TSP is studied using fluid-structure interaction (FSI) method. The results show that the drag coefficient (C_d) increases with α₂₁ and decreases with other bending angles. The moment coefficient (C_m) increases with bending angles and bending ratios, C_m decreases with length-width ratio of wing. The free flight test results show that C_d and C_m are in agreement the simulated results well. Key

Analysis and Calculation of Non-lethal Efficiency of Tear bomb

WANG Zhi-gang， GUO San-xue

2017, 38(1):  59-63.  doi:10.3969/j.issn.1000-1093.2017.01.008

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The tear bomb is a kind of most effective non-lethal riot bomb for dispersing group targets. Especially for explosive tear bomb, its stimulating agent can be released instantaneously to act on living targets rapidly. But in practical tactical application, no correct measure index is for the non-lethal effectiveness of tear bomb, thus leading to no scientific basis for the use of tear bomb. According to the diffusion characteristics of aerosol smoke, the mathematical models of heavy and non-heavy gas diffusions are used. The two models are combined effectively by calculating the virtual source point. The diffusion process of aerosol smoke is analyzed and studied to get the variation laws of diffusion radius and concentration of aerosol smoke. The effective area of single tear bomb is analyzed and calculated, which is considered as the measure index of non-lethal effectiveness of tear bomb. The results show that, when the wind speed is 2 m per second, the effective diffusion area of a tear bomb can be achieved 602.1 m² after 39 s, and the smoke concentration is no less than 1 mg/m³, the calculated results are consistent with the experimental results. Key

Research on On-board Reconnaissance Images Quality Assessment

LI Cong-li， XUE Song， LU Wen-jun， YUAN Guang-lin， QIN Xiao-yan

2017, 38(1):  64-72.  doi:10.3969/j.issn.1000-1093.2017.01.009

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Many types of hybrid distortion of on-board reconnaissance images happen due to the imaging platform and constraints. The image quality assessment is carried out in order to provide an important quantitative basis and reference for the performance optimization of the image processing and imaging systems. The characteristics of on-board reconnaissance image are analyzed. In consideration of mutli-degree-of-freedom and multi-attitude change of imaging platform, 11 kinds of image features related to camera shake, structure change and color loss are extracted. The sub-block image features are extracted for multivariate Gaussian (MVG) fitting to obtion benchmark distribution characteristics by using high resolution mapping images as original image set, and the on-board reconnaissance images are also processed to obtain corresponding MVG distribution characteristics. The benchmark distribution characteristics are compared to the MVG distribution characteristics, and Mahalanobis distance is calculated as a score of block quality. The mean score of each sub-block is taken as final score of whole image. The images obtained by the actual on-board imaging platform are verified. The result shows that the proposed method has higher assessment accuracy. Key

Identification of Spinning Projectile Aerodynamic Parameters Using Adaptive Chaotic Mutation Particle Swarm Optimization

GUAN Jun， ZHOU Jia-shen, YI Wen-jun， LIU Shi-ping， CHANG Si-jiang， SHI Ji-gang

2017, 38(1):  73-80.  doi:10.3969/j.issn.1000-1093.2017.01.010

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The maximum likelihood estimation is applied to the identification of spinning projectile aerodynamic parameters. A new algorithm called adaptive chaotic mutation particle swarm optimization is proposed to solve the optimal solution of aerodynamic parameters, thus obtaining the aerodynamic parameters of a spinning projectile. The proposed algorithm is to use an adaptive weight function, generate the initial particles based on chaos theory, and set a discriminant mechanism which judges whether the algorithm falls into the local optimum. If the algorithm falls into the local convergence, the mutation operator is used to make the algorithm jump out of local. The common test function is used to test this algorithm. The test result shows that the proposed algorithm has the advantages of more quick convergence, higher optimization precision and wide range of application compared to basic PSO. Simulated ballistic data is used to test the algorithm. The result shows that the proposed algorithm can identify the aerodynamic parameters effectively with high precision and quickly converging velocity. Key

Topology Optimization Design for Frame Structure of Monolithic Wing of Missile

WEN Jing-jing， WU Bin， LIU Cheng-wu

2017, 38(1):  81-88.  doi:10.3969/j.issn.1000-1093.2017.01.011

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The topology optimization technique is introduced into the frame structure design of monolithic wing of missile for improving the designing quality of missile structure, and a frame structure of missile wing of a missile is optimized. A typical load environment for frame structure of missile wing is constructed with a method of converting aerodynamic load to node load, and the conflict that the element located at a area under design not only participates in load bearing but also is deleted due to optimization is solved. The topologically optimized computer aided engineering (CAE) model can be interpreted as computer aided design (CAD) model which can be redesigned in CAD software directly with CAD-CAE interface technology, and the practicability of topology optimization is improved. By analyzing the empirical and optimized frame models and comparing the mass, strength, deformation and modal of these two models, it is founded that, under the condition of satisfying the structural strength and deformation, the mass of the optimized frame model is reduced by 9.39%, meanwhile the natural frequencies for the first and second bending modes and the natural frequency for the first torsional mode are increased. The proposed method can be seen as supplement and improvement of traditional structure design method of missile wing. Key

A Simple Constrained PSO Algorithm and Its Application in μ-PID Controller Design for Missile Autopilot

ZHANG Min, CHEN Liang, CHEN Xin

2017, 38(1):  89-96.  doi:10.3969/j.issn.1000-1093.2017.01.012

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The existing constrained particle swarm optimization(PSO) algorithms have the disadvantages of algorithm complexity, limited application and poor optimization. A kind of novel constrained particle swarm optimization algorithm is proposed. The proposed algorithm converts a constrained optimization problem into an unconstrained one using the method of objective function substitution method. It is tested with the typical test functions. The algorithm shows its superiority in handling the constrained conditions clearly compared with other constrained PSO algorithms. In order to verify the feasibility of the proposed constrained PSO algorithm applying in the engineering, the proposed algorithm is used to design a μ-PID fixed-structure robust controller by taking a sample missile longitudinal model for the classical Raytheon control structure. The simulated results indicate that the sample missile controller can not only satisfy a variety of time domain indexes but also have strong robustness, and the proposed algorithm is effective. Key

Effect of Rocket Engine Jet Flow with Water Injection on Air-flow Exhaust of Gas-flow-guided Channel

WANG Shu-man, MA Yi-qing, YU Shao-zhen

2017, 38(1):  97-105.  doi:10.3969/j.issn.1000-1093.2017.01.013

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To study the influence of rocket engine jet flow with water injection on the gas-flow exhaust of gas-flow-guided channel, the scaled models of rocket engine and gas-flow-guided channel are designed, by which the mooring ignition and water injection are tested. The results show that the temperature of mixed gas in the gas-flow-guided channel could be decreased to half of the original temperature. The cooling effect is obvious. However, a large amount of water vapor is generated and enters into the gas-flow-guided channel after mixing with combustion gas, thus influencing the exhaust of combustible air-flow. A numerical model based on the Mixture multiphase flow model is established. The interphase heat and mass transfer equations are added into the unsteady gas-liquid two-phase flow field model . The comparison of calculated data with experimental data shows that the proposed model has higher calculation accuracy and reliability，and the interaction of gas and liquid flow fields and its influence on the patency of gas-flow-guided channel are clearly shown. For further study, the influences of the number of nozzles and the type of surface curve are analyzed. Key

The Target Designation and Handover Method of Early-warning Radar and Multifunction Phased Array Radar

ZHENG Yu-jun, TIAN Kang-sheng, LIU Jun-kai, TIAN Geng

2017, 38(1):  106-113.  doi:10.3969/j.issn.1000-1093.2017.01.014

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A new method to cue and hand over a target is presented in order to solve the problems, such as unreasonable distribution of search area, long time consuming due to inaccurate beam position arrangement, overused radar resource and even wrong handover, which exist in target designation and handover of the early-warning radar and ground-based radar. Based on a nonlinear characteristics of target trajectory and the transformation of coordinates, the proposed method uses KEF to determine the orbits of target smoothing, and the search area is distributed and upgraded by the probability of target occurrence. This is a dynamic beam position arrangement designed based on the probability density of target occurrence. The target designation and handover and the beam position arrangement are experimented. The experimental reults show that the proposed method is better than the conventional method in error control, and the hit probability of beam position arrangement method based on probability density of target is bigger than that of conventional beam position arrangement method. The success probability of target designation and handover of the phased array radar is efficiently optimized, thus resulting in the saving of the radar resources. Key

A Novel ICA-based DOA Estimation Method for Underwater Wideband Source

LI Zi-gao, LI Shu-qiu, WEN Shu-lin

2017, 38(1):  114-122.  doi:10.3969/j.issn.1000-1093.2017.01.015

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The estimation of high-resolution and high-accurate direction-of-arrive (DOA) of underwater wideband acoustic sources in the cases of limited array aperture and lack of target feature information is studied. Considering the independent statistical characteristics of underwater bandwidth acoustic sources, a state coherence transform (SCT) method based on independent component analysis (ICA) is utilized to obtain DOA estimation. For the Gaussian distribution characteristics of additive noise, the wavelet denoising pre-processing is used to reduce the Gaussian components in the mixed signals. A spatial resampling method is proposed to fix the performance degradation of SCT in low-frequency range. In the computer simulation and sea trial, the proposed algorithm has the advantages of higher resolution, fewer sensors, less dependence on the priori knowledge and better low-frequency performance compared with other traditional algorithms. The signal processing results confirm the feasibility and performance superiority of the proposed algorithm.Key

Research on the Characteristics of Flow Noise Induced by Fish-like Flexible Deformation Motion

WANG Ya-dong, YANG Xiao-guang, ZHANG Ji-hua

2017, 38(1):  123-128.  doi:10.3969/j.issn.1000-1093.2017.01.016

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Fish swimming has the characteristics of low noise, high efficiency, and the swing of fish body can be abstracted as a flexible wall deformation motion. Flexible deformation can induce a complex vortex structure in the flow field, of which the flow noise formation mechanism and characteristics are different from the conventional problems in a large extent. The NACA0012 airfoil developed by National Advisory Committee for Aeronautics is used as the research object. Considering the demand of flow noise calculation, a numerical model based on the acoustic analogy theory is set up to simulate the flexible deformation, revealing the mechanism of the effect of the flexible deformation on noise characteristics, and radiation directivity of flow noise is obtained. The results indicate that the complex vortex structure evolution induced by flexible deformation is the major source of flow noise; the total sound pressure levels at different orientations decrease with the increase in distance; the total sound pressure level tends to be maximum just above and below the flexible deformation wall, and the noise radiation directivity is most similar to the radiation directivity of a dipole source. Key

Dynamic Analysis of Offshore Parallel Stabilized Platform in Considering Joint Clearance

LI Hao-jie, ZHANG He, LI Ke-xiang, XIE Ke-feng

2017, 38(1):  129-134.  doi:10.3969/j.issn.1000-1093.2017.01.017

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An improved serial-parallel mechanism based on less DOF parallel mechanism is designed for a floating stabilized platform with compact structure and high load inertia. Based on the structural characteristics of the platform, the kinematics is analyzed, the system Jacobian matrix is derived, and a dynamic model is established and analyzed by using Lagrange equation. A simplified rigid body-spring model is proposed to analyze the chains with clearance joints. A non-linear spring-damper model is introduced to calculate the contact force by using improved Hertz contact theory, and a dynamic model considering joint clearance is established. The numerically computated and experimental results show that the dynamic model is effective, and the clearance has significant impact on the structure,position accuracy and dynamic characteristics of moving platform. Key

Research on Bonding Technology for Installation of Protective Armor of Armored Vehicles

LI Yi-shu, CAO He-quan, HAN Hong-wei, DU Hou-jun, DENG Jia-hao, SHI An-shun

2017, 38(1):  135-142.  doi:10.3969/j.issn.1000-1093.2017.01.018

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To solve the issues of armored vehicle's protective area reduction, relatively complex installation process and so on, which are led by those conventional installation ways like bolting or rack supporting, a novel protective armor installation technology, called bonding technology, is presented. The kind and preparation technology of bonding agent are determined by the characteristics of installing structures. An optimal glued structure design for protective armor is proposed by studying the effects of different glued joint thickness and bonding areas on bonding strength. The bonding technology for installation is proved to be feasible and reliable through the simulated car broadband vibration test and the environmental extreme temperatures suitability assessment test. For the tests mentioned above, the bonding thickness is 2~3 mm; multi-point small area is glued ; the bearing capability is more than 3 MPa shear stress per square centimeter of bonding area; the bonding strength at extreme temperature from -50 ℃ to 70 ℃ is not less than 70% of corresponding strength at normal temperature. The results show that the two-component polyurethane adhesive is able to satisfy the dynamic broadband vibration requirement. Key

Numerical Simulation on Inside Load Characteristics of Broadside Cabin of Defensive Structure Subjected to Underwater Contact Explosion

WU Lin-jie, HOU Hai-liang, ZHU Xi, CHEN Peng-yu, KAN Yu-long

2017, 38(1):  143-150.  doi:10.3969/j.issn.1000-1093.2017.01.019

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The inside load characteristics of broadside cabin of defensive structure subjected to underwater contact explosion is researched. The interaction between underwater explosion bubble and broadside empty cabin at the time when is three fold of the first pulsation period of underwater explosion bubble and the inside load characteristics of broadside empty cabin are numerically analyzed by using LS_DYNA software. The model experiment is performed to validate the creditability of simulation results and analysis. The research shows that the blast gas flows into or out the broadside empty cabin from the plate crevasss along with bubble expansion or contraction, and the broadside plate is sunken or upheaved at the same time. The broadside empty cabin is separated by plate petals into two regions, and the load in the front of plate petals is different from that in the back of plate petals. If the largest plate damage is evaluated by using finite element method, the calculation time could be just 5% of the first pulsation period of underwater explosion bubble.Key

Research on Multi-source Data Equivalent Methods for Testability Integrated Evaluation

WANG Jing， LI Tian-mei， HE Hua-feng， XU Cong-qi

2017, 38(1):  151-159.  doi:10.3969/j.issn.1000-1093.2017.01.020

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The form of prior data for testability integrated evaluation is too multiply to match with the binomial data which is processed under the framework of Bayes theory. For this issue, five kinds of prior data, including expert data, preexposure test data, growth test data, replaceable unit data and virtual test data, are studied. Furthermore, five corresponding equivalent methods which transform the different types of data into the system-level binomial data are proposed based on Bayes theory. The proposed methods are validated via applied examples. Results show that the proposed methods have wide applicability, and also enlarge the amount of data used for testability evaluation indirectly. Key

UCAV Robust Maneuver Decision Based on Statistics Principle

GUO Hai-feng, HOU Man-yi, ZHANG Qing-jie, TANG Chuan-lin

2017, 38(1):  160-167.  doi:10.3969/j.issn.1000-1093.2017.01.021

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An UCAV (unmanned combat air vehicle) robust maneuver decision method based on statistics principle is proposed for UCAV robust autonomous combat decision. A mathematic model of UCAV is built to reduce the sensibility of the combat maneuver decision. The typical maneuver library is improved, and the robust membership functions of the air combat situation parameters are designed. The statistics method is introduced in the robust maneuver decision, and the simulations are carried out with two typical air combat cases of UCAV confront maneuver and non-maneuver objects. The simulated results indicate that the robust maneuver decision method has the robustness and optimizing capability in guiding UCAV to the advantage situation. Key

Frost Formation and Defrost Methods of Electric Vehicle Heat Pump Air Conditioning System

LIANG Zhi-hao, WU Jiang-hong, JIN Peng, LI Hui-xi

2017, 38(1):  168-176.  doi:10.3969/j.issn.1000-1093.2017.01.022

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Heat exchanger frosting deteriorates the heat performance of electrical vehicle heat pump air conditioning system ( HPACS ) in winter. Specially designed micro-channel heat exchangers are applied to electrical vehicle HPACS here. The system is tested at different surrounding air temperature, different surrounding air relative humidity and different air flow rate. Frost area proportion and frosting rate of outdoor heat exchanger are monitored and analyzed to understand different factors that could influence frosting performance of HPACS. The results show that the increase in air relative humidity, and the decrease in ambient temperature and air flow rate lead to quick frosting and bigger frost area proportion. The relationships between dynamic coefficient of performance (COP) and frosting rate are observed in detail. It reveals that frosting rate keeps the same change tendency to COP. At the period of frost beginning to form, COP and frosting rate increase at almost the same time, and as frosting rate curve start to drop, COP curve also drop at the same time. This phenomenon has been validated at different conditions. It is considered as the switch point of defrosting when the frosting sharply drops and the frost area proportion reaches to 30%. On the other hand, the frost area proportion calculated from binary image of frosting is taken as switch point of defrosting finish. When sharp drop of frosting rate and frost area proportion of 30% are detected, HPACS starts to defrost; when frost area proportion is reduced to same value as non-frosting’s, HPACS stops defrosting. The defrosting control strategy may save defrosting energy and improve the heating performance of electrical vehicle HPACS. Key

Research Notes

Extraction of Precession Period of Projectile Based on Phase Differential

LIU Zhi-xue, GONG Zhi-hua, LENG Xue-bing

2017, 38(1):  177-183.  doi:10.3969/j.issn.1000-1093.2017.01.023

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For uncontrolled projectile, such as cannonballs, rockets, etc, precession period is an important parameter of the trajectory characteristic. To obtain the precession period of projectile effectively, a precession period extraction method based on phase differential is introduced. Precession of projectile brings micro-Doppler modulation on echoes of continuous-wave radar, and its mathematic model indicates that the micro-velocity produced by precession changes with the law of sine, and the change rate of its phase is inversely proportional to precession period. The phase of the micro-velocity can be obtained by Hilbert transform, and then the precession period can be derived by the phase differential of the micro-velocity. The experimental results show that, for the micro-velocity signal which S/N is greater than 7 dB, precession period can be effectively extracted with the proposed method, and this method is more precise and smooth for actual measuring data. Key

Hybrid Routing Protocol for Wireless Multi-hop Ad Hoc Networks

LIU Ying， TANG Yi-wei， SHAO Xiao-tao， LI Xu

2017, 38(1):  184-189.  doi:10.3969/j.issn.1000-1093.2017.01.024

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Since the large-scale wireless multi-hop ad hoc networks have been widely used in military communications, emergency communications and other fields, the zone routing protocol (ZRP), as a hybrid routing protocol, has been paid more attention in the large scale network application because of its more flexible routing discovery and maintenance strategy. The selection of intrazone routing protocol and interzone routing protocol of ZRP has great impact on the overall protocol performance. An improved zone routing protocol based on the traditional ZRP framework is proposed for large-scale wireless multi-hop ad hoc network that has certain topological changes. In the improved protocol, the intrazone routing protocol uses a more effective and less resource consumption routing strategy, and the interzone routing protocol uses an expired routing cache mechanism to reduce network overhead. The modeling and analysis results show that the improved routing protocol has higher validity. It is verified through NS2 simulation that the improved protocol has better performance. Key

A Surendra-based Improved Detection Method of Moving Target Camouflage Effect

YANG Jun-tang, XU Wei-dong, QU Yang, CUI Guang-zhen

2017, 38(1):  190-194.  doi:10.3969/j.issn.1000-1093.2017.01.025

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The existing camouflage detection is mainly for static targets, which can not objectively reflect the effectiveness of camouflage in combat operations of mobile equipment. The moving object detection technology and the principle of camouflage are synthetical used for target detection, and the military truck model is used as the research object. Based on Surendra background update model and Lab three-channel, a new method for detecting the camouflage effect of moving objects is proposed. According to the established experimental system, the Euclidean distance between the shape feature parameters of the military truck before and after camouflage is calculated, and the average Euclidean distance of the image sequences is 189.45. It showes that the shape feature parameters of the moving objects before and after camouflage are very different. The target after camouflage has a certain characteristics of dynamic deformation camouflage. At the same time, with the aid of the performance evaluation module, the correlation coefficient range of target image before and after camouflage is 0.003 5~0.127 5. The scientific and reliability of the detection method is proved. According to the principle of moving target detection algorithm, it can be known that the images of moving target after camouflage has a certain fusion with the images of central background. Key

Study of Bolt Joint Stiffness Based on Contact Surface Characteristics

ZHANG Yi-hua, PANG Kui, LIN Dan-yi, MAI Yun-fei, SUN Xiao-meng, YANG Guo-yu

2017, 38(1):  195-201.  doi:10.3969/j.issn.1000-1093.2017.01.026

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Bolt joint is widely used in industry because of its reliability and effectiveness. The joint stiffness plays a very important role in bolt joint structure. A finite method of bolt joint structures under the optimal preload is proposed. The joint stiffness is analyzed for different structural parameters in consideration of the nonlinear factors,such as of force, contact property and friction. The effects of bolt pretightening force, thickness and external diameter of joint member, and nut parameters on joint stiffness are studied. The dimensionless stiffness function expression is derived through the experimental verification of contact surface compressive stress distribution and the assumption of joint stiffness continuity, and the model dimensionless stiffness data is fit. The formula for calculating bolt joint stiffness is developed based on the results of finite element analysis (FEA). The effectiveness and accuracy of joint stiffness calculation formula is verified by comparing FEA results with those from previous studies. Key

An Air-gap Magnetic Field Analysis Method of Electromagnetic Angular Vibrators Based on Equivalent Magnetization IntensityMethod

TANG Bo， HE Wen， JIA Shu-shi

2017, 38(1):  202-208.  doi:10.3969/j.issn.1000-1093.2017.01.027

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The finite element method (FEM) takes much more memory space and computing time for establishing a magnetic circuit geometrical model for the analysis of the air-gap magnetic field . An efficient analytical approach is presented to solve the air-gap magnetic field of electromagnetic angular vibrators based on the equivalent magnetization intensity method (EMIM). The differential equations of the magnetic potential vector are built up based on the EMIM, and an analytical expression of magnetic flux density (MFD) that contains the geometrical parameters of magnetic circuit is derived. The effectiveness of EMIM is verified by comparing the calculated results of FEM and EMIM. The magnetic circuit parameters are optimized by using EMIM. The results show that the region of the effective uniform MFD is widened with the increase in the sector angle of permanent magnet (PM), and MFD in the air-gap becomes strong with the increase in the thickness of PM when the thickness of air-gap remains constant. MFD decreases with the increase in the thickness of air-gap when the sector angle and thickness of PM remain constant. The proposed method can be used to quickly analyze the parameters of magnetic circuit that impact on the air-gap magnetic field, and provide the theoretical reference of the magnetic circuit optimal design in electromagnetic angular ribrators. Key