Table of Content

22 June 2018, Volume 39 Issue 6

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Contents

2018, 39(6):  0. 

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Paper

Influence of Metal Environment on Parameters of Fuze Wireless Setting System Based on Magnetic Resonance Coupling

CAO Juan, LI Chang-sheng, ZHANG He, MIAO Dong-hui

2018, 39(6):  1041-1048.  doi:10.3969/j.issn.1000-1093.2018.06.001

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When the magnetic resonance coupling wireless setting system of fuze is located in cylindrical metal environment, the setting coil will produce the scattering field impedance due to the influence of the metal environment, resulting in change of the working parameters of the system. In order to study this problem, a calculation model of the coil scattering field impedance is established, and the change rules of equivalent parameters of coil with frequency, spacing and metal material are researched experimentally. The theoretical analysis and experimental results show that the proposed model is correct, and the theoretically calculated results are consistent with the experimental results. The equivalent resistance of the coil increases and the inductance decreases due to the existence of metal objects. In addition, the increase in resistance caused by ferromagnetic materials is more than that caused by non-ferromagnetic metal materials, while the decrease in inductance is less. After the scattering field impedance caused by metal environment is calculated by using the proposed model, the setting system can be returned to the resonance state by adjusting the capacitance parameters of the circuit. The proposed model can be used for the quantitative calculation of setting coil parameters under the influence of metal environment. Key

Effect of Altitude on Distribution of In-cylinder Heat Flux

LIU Yong-feng，WANG Long-fei，LIU Sheng，YIN Yu-ting，YANG Zhen-huan

2018, 39(6):  1049-1057.  doi:10.3969/j.issn.1000-1093.2018.06.002

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The computational fluid dynamics (CFD) method is adopted to study the change rule of heat flux distribution in plateau environment. Three-dimensional numerical simulation of combustion process of diesel engine at different altitudes was carried out. The results show that the Han-Reitz model can be used to obtain the satisfied results when the combustion process is calculated, including the process of combustion gas transferring heat to cylinder wall. With the increase in altitude, the excess air coefficient decreases, the ignition delay period is prolonged, the ignition delays, the combustion is deteriorated, the explosion pressure decreases, and the combustion temperature rises. The higher the altitude is, the greater the spray momentum is. The influence of gas flow on the heat transfer coefficient increases after top dead center, and the effect of air intake flow on the heat transfer coefficient decreases, and the heat transfer coefficient increases with the increase in altitude. Under the influences of heat transfer coefficient, gas temperature of wall and wall oil film combustion, the average heat flux on the wall increases greatly during combustion at high altitude, and the instantaneous average heat flux on the wall increases from 1 000 m to 4 500 m, and the instantaneous average heat fluxes on the cylinder head and piston increase to 30% and 26%, respectively.Key

Study of Short-circuit of Fresh Air in Opposed-piston Two-stroke Diesel Engine

LIU Yu-hang, ZHANG Fu-jun, GAO Hong-li, WANG Su-fei

2018, 39(6):  1058-1065.  doi:10.3969/j.issn.1000-1093.2018.06.003

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With the goal of studying the short circuiting phenomenon of fresh air, improving the scavenging quality, and deeply comprehending the scavenging process of two-stroke engines, the effects of pressure difference, back pressure and scavenging system parameters on the short circuit of fresh air during the scavenging process of opposed-piston two-stroke engine (OP2S) are investigated by using the variation of the unburnt gas mass ratio in exhaust pipe to reflect the short-circuited phenomenon of fresh gas. The results show that the increase in the pressure difference can bring the short-circuiting of time a large fraction of fresh air to be ahead of time. In scavenging process, the scaening effect is better at large pressure difference. The increase in the back pressure can postpone the short-circuiting timing of fresh air and worsen the scavenging process. The increase in the intake port height brings the short-circuiting of a large fraction of fresh air to be ahead of time. It is also helpful in improving the scavenging process. The increase in the exhaust port height is benefit for scavenging process. The varieties of the intake port and exhaust port widths have no significant influence on the short-circuiting phenomenon of fresh air. Key

Research on Comprehensive Evaluation Method for Testability of Armored Vehicle Based on Test Result Credibility

XU Bao-rong, LIU Xue-gong, WU Yan-wei, HU Wei-feng

2018, 39(6):  1066-1073.  doi:10.3969/j.issn.1000-1093.2018.06.004

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As the natural fault samples are insufficient in the field test and the evaluated result of the laboratory test is superior to the real testability level of the equipment, a scientific evaluation method of testability is lack for armored vehicles in final stage. For this reason, the test predictive model of testability is modified according to the definition of conditional probability, and the relationship between the test result and the test evaluation mode is studied. A comprehensive test method of testability based on the three test modes, including field test, laboratory test, and analysis and evaluation, is presented, and a calculation model of test result credibility and a comprehensive evaluation model of testability, which determines the weight of different test results according to credibility, are established. The proposed method and models are validated via applied examples. Results show that the comprehensive testability evaluation method based on the credibility of the test results solves the problem that the samples of field test are insufficient and improves the practicability of test operation and the scientificalness of evaluation conclusion. Key

An Analysis of Motion of Projectile in Bore with the Change of Material Properties of Copper Armor due to High Temperature

YANG Yu-zhao, XU Cheng, FAN Li-xia

2018, 39(6):  1074-1081.  doi:10.3969/j.issn.1000-1093.2018.06.005

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A finite element model of projectile and barrel is established to study the motion of projectile in bore at high temperature, in which the pre-bending of barrel under gravity and the mechanical properties of copper armor at different temperatures are considered. The engraving process of projectile and its motion attitude in bore are studied through numerical simulation, and the engraving resistance, material flow and deformation of projectile at different temperatures are analyzed. The mechanical properties of barrel and copper armor were obtained through high temperature tensile tests, and the processes of projectile entering into the barrel at different temperatures are analyzed. The results show that the higher the temperature is, the greater the stress, strain, deformation and swing angle of projectile will be. Key

Kill Probability Calculation Model for Weakly Correlative Firing Error of Anti-aircraft Artillery

YAO Zhi-jun， XIE Jie-tao， ZHAO Zhi-ming， GUO Zhi， WANG Jun

2018, 39(6):  1082-1087.  doi:10.3969/j.issn.1000-1093.2018.06.006

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An equation of state of weakly correlative firing error is established to accurately calculate the kill probability of anti-aircraft artillery, and the recursive calculation formula of hit probability is deduced by strict mathematical deduction, that is, the recursive calculation formula of kill probability under 0-1 damage law. The result is accurate and gives the error bound of finite value, which can be used as the evaluation criterion of other models. Comparison with the existing methods indicates that the error model conversion method, including the national standard, has obvious deviation, and its deviation is more obvious for the multi-barrel anti-aircraft artillery. Key

Design of Jamming Signal on Pseudo-random Code Phase-modulation and Pulse Doppler Combined Fuze Based on Code Reconstruction

LIU Shao-kun, YAN Xiao-peng, LI Ping, YU Hong-hai

2018, 39(6):  1088-1094.  doi:10.3969/j.issn.1000-1093.2018.06.007

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The working principle of pseudo-random code phase-modulation and pulse Doppler fuze with excellent anti-jamming capability is analyzed. On the basis of the analysis, a code reconstruction-based jamming signal method is proposed, and the jamming effect of the proposed method is analyzed theoretically. Third-order correlation function is used to estimate the pseudo-random code sequence, and the signal of jamming the fuze is reconstructed based on the estimated pseudo-random code sequence. The simulated and experimental results demonstrate that the proposed method has deceptive jamming effect on the fuze. The proposed method is more efficient than the traditional jamming method. Key

Echo Characteristic of Planar Target in Pulsed Laser Fuze Detection

CHEN Shan-shan， ZHANG He， XU Xiao-bin

2018, 39(6):  1095-1102.  doi:10.3969/j.issn.1000-1093.2018.06.008

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A pulsed laser echo model is established for the problem of low rangefinding accuracy of pulsed laser fuze in high speed dynamic test. Based on the laser radar equation, the actual emission waveform and light intensity distribution are used to derive the power equation of echo signal by the analytic method. The influences of different parameters on the echo waveform and signal-to-noise (SNR) are analyzed in considering the surface characteristics and structure size of target. The echo experiment of pulsed laser fuze is made. The results show that the peak value decays and the peak time moves forward as incident tilt angle increases. Key

Roll Angle Estimation Algorithm with Improved Sage-Husa Adaptive Kalman Filtering Based on Dual-spin Mortar Shell

WANG Jia-wei, QI Ke-yu, YANG Kai-hua, LIANG Ke, YAN Jie

2018, 39(6):  1103-1108.  doi:10.3969/j.issn.1000-1093.2018.06.009

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Traditional extended Kalman filter (EKF) algorithm is unable to eliminate the bigger measured roll angle error caused by irresistible measuring noise. A roll angle estimation algorithm with improved Sage-Husa adaptive Kalman filtering (SHAKF) based on dual-spin mortar shell is proposed, in which the measured rotation speed of gyro is used as compensation for system noise. Compared with traditional EKF algorithm, the proposed algorithm is used to reduce the measuring error of roll angle significantly, and improve the adaptivity of filter to the innovation changing of roll angles in the upward and downward legs of ballistic trajectory. The new proposed algorithm is verified by in-lab testing with MEMS three-axis turntable. The research results indicate that the mean value and standard deviation of measuring errors are 0.26 degs and 0.35 degs, respectively, in simulating verification, and the in-lab testing results show that the estimation error is always less than 4.2 degs in dynamic range changing from 30 r/s to 1 r/s. Key

Rapid Transfer Alignment for Airbone Smart Bomb Based on Separate Estimation of Weak Observable State

MI Chang-wei， ZHAO Hong-yu， WU Xu， SONG Li-ping

2018, 39(6):  1109-1116.  doi:10.3969/j.issn.1000-1093.2018.06.010

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In order to solve safety the problem of aircraft due to the long transfer alignment of airborne smart bomb, the two-point estimation algorithm for MEMS gyro drift and the fast transfer alignment method based on the separate estimation of weak observable state are presented. The proposed estimation algorithm is used to separately estimate he weakly observable states of gyro zero bias based on the observability analysis of tof velocity and attitude matching method presented by Kain, et al^［1］. Because of the influence of varying parameters of separate estimator, the variational Bayesian adaptive Kalman filtering algorithm is adopted to adjust the twice transfer alignment. The simulated and experimental results show that the estimating accuracy of the two-point estimation algorithm is at least 88% in 2.5 seconds, and the corresponding transfer alignment time is reduced to 8 seconds.Key

Numerical Calculation of Opening Process of Frangible Rear Cover of a Launcher

DUAN Su-chen， JIANG Yi， NIU Yu-sen， ZHANG Ao-lin

2018, 39(6):  1117-1124.  doi:10.3969/j.issn.1000-1093.2018.06.011

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The opening process of rear cover of a launcher involves complex physical phenomena, such as shock wave propagation and jet motion. The dynamic mesh technology is used to get the pressure and temperature distribution of gas jet flow in the process of opening the cover by taking a solid rocket engine as the research object.The opening process of fragile cover is studied, and the gas jet flow is analyzed. The results show that the peak overpressure of shock wave is higher in a radial jet of engine, which may damage the launcher and peripheral equipment; the movement of frangible rear cover has an influence on the gas jet flow. It is shown that the gas jet flows downward with the downward movement of rear cover, and the rear fow of gas jet occurs due to the blocking of rear cover; the shock effect of gas flow decreases gradually in the process of its motion, and the temperature and pressure on the rear cover also decrease gradually except the core area. The simulated results are consistent with the test results. Key

Hydraulic Measurement Method for Equivalent Diameter of Laval Nozzle Throat

ZHANG Xiang， SUN Xiao-hong， PAN Xu-dong， WANG Guang-lin

2018, 39(6):  1125-1131.  doi:10.3969/j.issn.1000-1093.2018.06.012

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The requirements of Laval nozzle size are quite strict, and the existing measurement methods can not be used to measure the equivalent diameter of Laval nozzle throat directly. A hydraulic measurement method for measuring the equivalent diameter of Laval nozzle throat based on the core plug gauge is proposed through the analysis of the orifice flow of the throat’s equivalent diameter measurement model. The relationships among the plug gauge size, orifice flow model and its relative sensitivity are analyzed. On this basis, the short orifice flow model is taken as the model for measuring the equivalent diameter of throat. The measurement parameters are determined, and a measurement prototype device is developed. The repeatability error of the proposed measurement method is ±0.001 8 mm. Key

Optimal Selection of Cell Number of Bus-based Embryonic Electronic System Based on Integer Nonlinear Programming Model

WANG Tao, CAI Jin-yan, ZHANG Min-guo, MENG Ya-feng, ZHU Sai

2018, 39(6):  1132-1143.  doi:10.3969/j.issn.1000-1093.2018.06.013

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In bus-based embryonic electronic system (BEES) with certain scale, the number of electronic cells has a direct effect on the reliability and hardware consumption of BEES. In view of the research status that the selection of electronic cell number is lack of quantitative analysis method, an optimal selection method of electronic cell number for BEES is proposed, which is based on integer nonlinear programming model. A BEES reliability analysis model is established based on n/k system reliability theory. The number of metal oxide semiconductor (MOS) field effect transistors which are consumed in the system is used to measure hardware consumption, and BEES hardware consumption analysis model is established. The selection problem of BEES electronic cell number is transformed into the solving problem of integer nonlinear programming by analyzing BEES reliability and hardware consumption, and the optimal selection of BEES electronic cell number is realized based on genetic algorithm. The simulation experiment and analysis results indicate that the proposed method can be used for the optimal selection of electronic cell number in BEES.Key

Image Mosaic and Positioning Algorithms of Bionic Compound Eye Based on Fiber Faceplate

YANG Chao, QIU Su, JIN Wei-qi, DAI Jia-lin

2018, 39(6):  1144-1150.  doi:10.3969/j.issn.1000-1093.2018.06.014

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In order to study the image mosaic and target location technology of bionic compound eye system, SolidWorks is used to design a lens holder for a bionic compound eye system composed of nine optical lenses. Feature points are extracted using scale-invariant feature transform algorithm. According to the overlapping information between the sub-eye lenses, the binocular distance measurement principle is adopted to locate spatial target in 3D. A vision system with a field of view of 74.3°is built, and a large field-of-view bionic compound eye mosaic image is obtained to locate the target in 4 different positions in space. It is proved that the bionic compound eye system can obtain large field-of-view mosaic images, and can locate the spatial target. Key

Influences of Microbubble and Homogeneous Polymer on Drag Reduction Characteristics of Axisymmetric Body

SONG Wu-chao, WANG Cong, WEI Ying-jie, LU Li-rui

2018, 39(6):  1151-1158.  doi:10.3969/j.issn.1000-1093.2018.06.015

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To reduce the drag of underwater vehicle, the experiment of axisymmetric body is conducted to study the combined drag reduction effect of microbubble injection and the homogeneous polymer solutions by using the high speed camera system and six-component balance system. The axisymmetric body is constructed with sintered porous material. The morphologic changes of microbubble flow are analyzed based on the high speed camera system, and the drag reduction characteristics of axisymmetric body are obtained by the six-component balance system. The experimental results show that the microbubbles are uniformly dispersed throughout the surface of the experimental model. The floating-upward phenomenon of microbubbles is distinct when the microbubbles reach the tail of the experimental model with the dispersed microbubbles. The drag reduction efficiency of combination of microbubbles and homogeneous polymer is larger than that of individual one. With the increase in air injection rate, the drag reduction rates of various homogeneous polymer solutions are all gradually increased but the difference among them declines. As the density of individual homogeneous polymer solution increases, the drag reduction rate of individual homogeneous polymer solution increases as well with the homogeneous polymer saturation effect. The saturation density decreases with the increase in free stream speed. Key

Experimental Investigation into Impact Load during Oblique Water-entry of a Supercavitating Vehicle at 20°

CHEN Cheng, YUAN Xu-long, DANG Jian-jun, XU Qiang

2018, 39(6):  1159-1164.  doi:10.3969/j.issn.1000-1093.2018.06.016

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In order to investigate the impact load characteristics of a supercavitating vehicle with a disk cavitator during oblique water-entry, a series of experiments were carried out at the water-entry angle of 20° . An air cannon is set up to provide the initial velocity of supercavitating vehicle. An inertial measurement unit is embedded at the center of gravity of supercavitating vehicle to record the variation of axial impact load, and the data is extracted and analyzed after the experimental test. A typical research case is set up, and the impact load characteristics varying with time are obtained and described in detail. Subsequently, a series of experiments for different entry speeds and cavitator areas are carried out, and the effects of the influence factors on the impact load characteristics are analyzed. The investigation shows that, when the impact load reaches the peak, the penetration distance is 1.89 times of the diameter of cavitator as a reference dimension, and the resistance coefficient is 1.33 times of that in the steady stage. The resistance coefficient is shown to be independent of entry velocity and cavitator area over a wide range of test conditions. Key

Experimental Investigation into Noise Characteristics of Water Jet in Anechoic Tank

CHENG Guang-li， LUO Xia- yun， MENG Lu-wen， YANG Qiong-fang

2018, 39(6):  1165-1170.  doi:10.3969/j.issn.1000-1093.2018.06.017

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An experimental system for producing water jet and measuring its radiated noise was designed and constructed to study the noise characteristics of water jet. Performances of free field in an anechoic tank are evaluated, and then the noise characteristics of water jet in the anechoic tank are measured using the proposed experimental system. Analysis of experimental data demonstrates that the source level and spectral distribution of water jet can be obtained exactly using the proposed experimental system with 50 mm diameter jet pipe at the jet efflux velocity of less than 20 m/s. Radiated power of water jet noise obtained from experiment varies approximately in proportion to the eighth power of jet efflux velocity, and water jet noise at efflux velocity of less than 20 m/s is mainly caused from its turbulent motion. Key

6σ Optimization Design of Ring-stiffened Composite Pressure Hull of Underwater Vehicle

LI Bin, PANG Yong-jie, ZHU Xiao-meng, CHENG Yan-xue

2018, 39(6):  1171-1177.  doi:10.3969/j.issn.1000-1093.2018.06.018

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In order to get a more reliable composite pressure hull structure of underwater vehicle, the effects of anisotropy and uncontrollable processing of composite materials on the structural performances should be taken into consideration. 6σ design is introduced into the optimization of ring-stiffened composite pressure hull. Monte Carlo sampling simulation is used for the reliability analysis of hull structure, and the reliability optimization design of pressure hull is conducted by taking sigma level as an evaluation index based on the radial basis function (RBF) neural network approximation model. The results show that, although the structural mass designed by 6σ optimization is 3.11 kg higher than that designed by deterministic optimization, the sigma levels of structural performance constraints are up to 8 and more, and the reliability reaches to 100%. Both structural mass and reliability are considered in the optimal design. The proposed optimization method of RBF approximation model-based 6σ design and reliability evaluation can be used for the accurate, efficient and reliable optimization of ring-stiffened composite pressure hull of underwater vehicle and solve the problem of low structural reliability due to variation of random factors. Key

Study of Time Delay Characteristic of HITL Simulation System for Laser Angle Deception Jamming

LIANG Wei-wei, ZHAO Hong-peng, YIN Rui-guang, LI Hui, CHEN Qian-rong

2018, 39(6):  1178-1185.  doi:10.3969/j.issn.1000-1093.2018.06.019

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The simulation of sequential relationship is an important part in the laser angle deception jamming of hardware-in-the-loop (HITL) simulation system. The time delay characteristic of system is studied to set the ahead time of deception jamming accurately. The laser angle deception jamming of HITL simulation system and jamming theory are introduced, and the primary cause of system time delay is analyzed. A system time delay characteristic model is established based on time delay measurement of single device. The proposed model is verified by means of the laser angle deception jamming for HITL experiment under typical working condition. The measured results show that the peak-to-peak value of system delay time is less than 230 ns, which is coincident with simulated results of the model. Key

Mechanical Properties and Constitutive Model of Aluminum Powder/Rubber Composites

LI Jun-bao, LI Wei-bing, CHENG Wei, WANG Xiao-ming, LI Wen-bin, HONG Xiao-wen

2018, 39(6):  1186-1194.  doi:10.3969/j.issn.1000-1093.2018.06.020

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The mechanical properties and constitutive model of aluminum powder/rubber composites are studied. Quasi-static and dynamic compression tests of aluminum powder/rubber composites were carried out using WGD-1 universal testing machine and split Hopkinson pressure bar, and the stress-strain curve of test samples in the range of 1 400 s^-1-2 800 s^-1 strain rate in the quasi-static compression test are obtained. A rate-dependent constitutive model which can describe the one-dimensional dynamic and static compression behaviors of the test samples is established，and the distribution of aluminum particles in the rubber matrix is observed by scanning electron microscopy.The test results show that the test samples have different hardening modes under quasi-static loading. The aluminum powder particles of composites containing 60 wt% Al are crushed during the later stage of compression, and the test samples are eventually crushed. Under dynamic loading,the test samples show obvious strain-rate effects, and the flow stress is significantly increased under the quasi-static compression, especially for compo-sites containing 60 wt% Al. Key

Optimization of Geometric Structure of Non-coaxial Helical Flank Micro-drill and Its Grinding Processing

GUO Hai-xin, WANG Xi-bin, LIANG Zhi-qiang, ZHOU Tian-feng, LIU Zhi-bing, ZHANG Su-yan

2018, 39(6):  1195-1204.  doi:10.3969/j.issn.1000-1093.2018.06.021

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Non-coaxial helical flank micro-drill has a significant advantage in the tool grinding efficiency and drilling performance compared with the plane flank drill. A slight change in the geometry structure of micro-drill causes a significant change in drilling performance. The mathematical models of non-coaxial helical flank and helical groove are proposed, and the cutting lip shape, rake angle and uncut chip thickness are calculated. The micro-drilling finite element simulation models of stainless steel are established to optimize the geometric structure of non-coaxial helical flank micro-drill, and the effects of helix angle, web thickness and point angle on drilling force, temperature and chip morphology are investigated. The results show that the thrust force increases with the increase in point angle within a certain range of geometric parameters. On the contrary, the torque and temperature decrease with the increase in point angle. The drilling force and temperature decrease with the increase in helix angle. The geometry of chip is continuous chip when the helix angle arrives to 40°, which is easily blocked lead to tool breaking. With the increase in web thickness, the drilling force and temperature increase simultaneously, but the width of chip reduces. The optimized micro-drilling geometric parameters are obtained based on the variation of drilling force, drilling temperature, and chip morphology during the micro-drilling of stainless steel. The non-coaxial helical flank micro-drill is fabricated based on six-axis CNC tool grinder and the mathematical model. The measured results show that the geometrical parameters are basically the same as the designed values. And the experimental results show that the micro-drill with the optimized geometric structure has good drilling performance.Key

Research on Measuring Point Layout for Roundness Measurement of Large Diameter Revolving Parts

WEN Xue, TAN Jian-ping, LIU Su-qi, LI Xin-he

2018, 39(6):  1205-1214.  doi:10.3969/j.issn.1000-1093.2018.06.022

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In order to improve the roundness measurement accuracy of large diameter revolving parts under rotating state, an optimization model is established based on the influences of positions of three measuring points on the measurement accuracy, and an optimization strategy of position of three points is presented on the basis of particle swarm and genetic hybridization algorithm. The influence of sensor position on roundness extraction accuracy is analyzed, and the optimization function of measuring point position based on the error transfer coefficients is established by using the outer contour measurement model and roundness extraction technology. A hybrid algorithm of a new particle population is generated through particle swarm optimization and genetic complement, and the circumferential angles of the sensors are obtained under the given harmonic orders. The circumferential layout angles of the measuring point under the condition of the given harmonic orders (160,240, and 480) are calculated, and the error transfer coefficients before and after optimizing the position of measuring points are compared. The accuracy of roundness extraction was tested with the virtual and real revolving parts. The results show that the error transfer coefficient after position optimization is less than that before optimization, and the extracted roundness value is closer to the true roundness value with accuracy of about 0.010 mm. The proposed optimization strategy can be used to improve the measurement accuracy of the revolving part roundness, and provides an effective detection means for manufacturing high precision and large diameter revolving parts. Key

Research on Selective Maintenance Decision-making Method of Complex System Considering Imperfect Maintenance

WANG Shao-hua， ZHANG Shi-xin， LI Yong, DONG Yuan-sheng, WANG Jin-peng

2018, 39(6):  1215-1224.  doi:10.3969/j.issn.1000-1093.2018.06.023

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A sequential condition deterioration process model is constructed to enhance the mission reliability of complex systems composed of sequential-parallel parts. To better illustrate the effect of varied maintenance behaviors, the minimal maintenance, imperfect maintenance and replacement are taken as optional maintenance actions and modeled. A selective maintenance decision-making model and the attached artificial solving measures are presented to maximize the current mission reliability. The result shows that the imperfect maintenance model can be used to represent the actual reliability of the system better by integrating service age reduction model and risk correction model. Also within given maintenance time, the imperfect maintenance strategy is of help to offer a more feasible maintenance plan and increase the system reliability. Key

Aerodynamic Characteristics of Small Coaxial Rotor Considering the Wind Gust

LEI Yao， JI Yu-xia

2018, 39(6):  1225-1232.  doi:10.3969/j.issn.1000-1093.2018.06.024

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The wind resistance of coaxial rotors in hover is tested considering the horizontal and vertical light breezes with the wind velocity varied from 1.6 to 3.3 m/s and the gentle breeze with the wind velocity varied from 3.4 to 5.4 m/s in the natural environment. A velocity distribution model of blade in the natural incoming flow is established, and a low-speed wind tunnel is also introduced to simulate the natural disturbance on the coaxial rotors. The sliding mesh method is adopted to calculate the flow field and capture the aerodynamic interference in the natural incoming flow, mainly including the distribution of tip pressure, the streamline distribution of flow field and the velocity vector of blade tip. Results show that the proposed simulation method can accurately reflect the influence of natural incoming flow on the aerodynamic characteristics of coaxial rotors. Compared to the case with no wind gust, the performance of coaxial rotors is declined due to vertical incoming flow. It is noted that the coaxial rotors can effectively resist the wind disturbance in the horizontal incoming flow, and eventually the rotor performance is greatly improved with the increase in wind velocity.Key

Design of Admittance Control with Sliding Mode for Elbow Joint Actuated by Pneumatic Muscle

WANG Bin-rui, JIN Ming-tao, SHEN Guo-yang, JIN Ying-lian, CHEN Di-jian

2018, 39(6):  1233-1238.  doi:10.3969/j.issn.1000-1093.2018.06.025

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The compliance control is a research focus of human-robot collaboration. For the dynamic model of the cascaded elbow joint actuated by pneumatic muscle, a control structure is established with sliding mode position control as inner loop and contact force admittance control as outer loop. A sliding mode controller with disturbance observer (SMCDO) is designed, and the convergence of SMCDO control algorithm can be illustrated. An admittance controller is designed as the outer loop and the control law is given by treating the environment as a spring model. A real experimental platform is built to test the threshold force, security threshold force, and collision for the handshaking action, and also analyze the influence of stiffness parameter on the angle modified trajectory and contact force. Experimental results show that the compliance is related to stiffness parameter, and the control accuracy of SMCDO admittance controller is higher than that of the SMC admittance controller without disturbance observer. The proposed control algorithm is stable and effective.Key

Research Notes

Analysis of Dynamic Load of Spur Gears Considering the Gear Body Stiffness and Tooth Profile Modification

LI Chun-ming, WANG Cheng, DU Ming-gang, ZHAO Zhi-gang

2018, 39(6):  1239-1248.  doi:10.3969/j.issn.1000-1093.2018.06.026

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The influences of gear bodies, input speed, torque and tip relief on dynamic load of gear pair are studied to solve the low power density and high dynamic load of spur gear for high speed heavy-duty vehicles. A gear mesh stiffness model is established for spur gear, in which the gear body stiffness, profile modification and actual motion state of gear are considered. The gear mesh stiffness model is coupled into the 10 degrees-of-freedom lateral-torsional-rocking nonlinear dynamic model of a single stage gear system. The results show that the dynamic load of gear changes in the form of hump-like shape with the increase in speed, and the change trend of dynamic load remain almost the same at many rotating speeds. While the dynamic load of light-weight gear are much larger at various speeds, especially the amplitudes corresponding to the second- and sixth-order harmonics of mesh frequency of dynamic mesh force are obviously increased. With the increase in torque, the dynamic load of gear body is reduced in the form of a parabola, while the dynamic load of light-weight gear reaches to its local maximum. With the increase in tip relief amount, the dynamic load changes in the form of “U” type, and an optimal amount of tip relief exists to make the dynamic load reach to the minimum. While the amount of tip relief exceeds the optimal value, the dynamic load of light-weight gear changes more slightly. For short length of tip relief, the dynamic load appears in the form of “U” type. For long length of tip relief, the dynamic load factor is sharply reduced, which means that the long length of tip relief can more effectively reduce the dynamic load.Key