Table of Content

29 August 2017, Volume 38 Issue 8

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Contents

2017, 38(8):  0. 

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Paper

Fault Diagnosis of Intake System of Diesel Engine Based on LOLIMOT

WANG Ying-min， CUI Tao， ZHANG Fu-jun， DONG Tian-pu

2017, 38(8):  1457-1468.  doi:10.3969/j.issn.1000-1093.2017.08.001

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Leakage and blocking of intake system of diesel engine may lead to the deterioration of the emissions and fuel economy. An accurate model of intake system is difficult to be established since it is a strong nonlinear system. Thus, a fault diagnosis method based on local linear model tree (LOLIMOT) is proposed for on-line fault diagnosis.The amplitude and phase of intake pressure fluctuation signal and volumetric efficiency are selected as the fault characteristic parameters. LOLIMOT is used to establish the reference models of the parameters. The models are regarded as a function of engine speed and intake density.Three residual signals are generated by using parity equation for calculating their threshold values. The mapping relationship between the residual signal and the fault type is analyzed. Experimental results show that the proposed models give good prediction of fault characteristic parameters, the proposed method can be to diagnose the leakage of engine intake system and the blocking of intercooler. Key

Research on a Triggered Vacuum Switch Pulsed Power Supply

ZHANG Ya-zhou, LI Zhen-xiao, CHENG Nian-kai, TIAN Hui, LI Bao-ming

2017, 38(8):  1469-1475.  doi:10.3969/j.issn.1000-1093.2017.08.002

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The performance of pulsed power supply (PPS) depends on the basic characteristics of the discharge switch. Triggered vacuum switch (TVS) has the advantages of wide working voltage range, high transfer charge, quick dielectric recovery and compact structure. A 2 MJ PPS with rated operational voltage of 13 kV which uses RVU-43 TVS was developed. The PPS is of multi-module parallel structure and composes of 17 118 kJ capacitor-based pulsed power modules. The maximum short-circuit discharge current of every module is about 52 kA. The system is composed of charging, control and measurement subsystems. The synchronous and time sequence discharge tests under dummy load are made for PPS, and PPS is launched from an electrothermal chemical (ETC) launcher. The experimental results show that PPS can output high amplitude and flexible current wave, and has high reliability for ETC launch research. Key

Analysis of Bending Resistance of Composite Barrel for Electromagnetic Railgun Based on 3D Beam Theory

YIN Dong-mei, XIAO Hong-cheng, LI Bao-ming

2017, 38(8):  1476-1482.  doi:10.3969/j.issn.1000-1093.2017.08.003

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An estimation model of effective bending stiffness for filament-wound composite housing of circular railgun barrel is established based on the 3D composite material thick beam theory. Some effects of beam, such as the three-dimensional strain and warping, are considered in the proposed model. The calculation method of effective bending stiffness of composite beam is used to analyze the bending stiffness of the whole filament-wound composite barrel for railgun. The results are compared with those obtained by laminated plate theory and finite element method. The result shows that the calculated results of the three methods have good consistency for bigger winding angle. The effects of the winding angles of fibers and carbon fibers in different radial positions and the different bore insulators on the bending stiffness of barrel are studied. The research result reveals that the bending stiffness of barrel obviously drops with the increase in winding angle while the winding angle is smaller. The winding angle of inner carbon fiber layers has a great effect on the bending stiffness compared with outer carbon fiber layers. The bore insulator with high density and high elastic module can't always enhance the bending stiffness of barrel.Key

Research on Anti-frequency Sweeping Jamming Method for Frequency Modulation Fuze Based on Timing Sequence andCorrelation Detection

KONG Zhi-jie， HAO Xin-hong， LI Ping， WANG Zhe

2017, 38(8):  1483-1489.  doi:10.3969/j.issn.1000-1093.2017.08.004

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Frequency sweeping jamming is a serious threat to frequency modulation (FM) fuze. To improve the anti-frequency sweeping jamming performance of FM fuze, a frequency sweeping jamming mo-del is established, the failure mechanism of FM fuze is analyzed, and an anti-frequency sweeping jamming method based on timing sequence and correlation detection for FM fuze is proposed. The missile-target range information, dual-channel timing sequence information and time interval information are used to control the FM fuze's detonation. The feasibility of the proposed method which is also implemented in hardware is verified through simulation. The simulated and measured results show that the proposed method can be used to improve the anti-frequency sweeping jamming performance and ranging accuracy of FM fuze more effectively compared with the harmonic ranging method, and the complexity and instantaneity of the proposed method can satisfy the fuze's requirement.Key

Effects of Step Recovery Diode Parameters on Narrow Pulse Waveform

LI Meng， HUANG Zhong-hua, SHEN Lei

2017, 38(8):  1490-1497.  doi:10.3969/j.issn.1000-1093.2017.08.005

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Step recovery diode (SRD) is the kernel of ultra-wideband (UWB) fuze generating a narrow pulse signal, and the parameters of SRD can affect the amplitude and width of narrow pulse signal. A SRD model is established based on the semiconductor device theory and SRD operating states, and the effects of SRD parameters on forward bias admittance and reverse bias barrier capacitance are studied. According to narrow pulse generating equivalent circuit, a circuit transient analysis method is used to solve the expression of narrow pulse amplitude and width. The relationships among SRD minority carrier lifetime, reverse saturation current, bias junction capacitance, doping distribution coefficient, narrow pulse amplitude and pulse width are studied through simulation. The simulated results show that the amplitude and pulse width of narrow pulse can be adjusted by changing SRD parameters. The correctness of simulated results is verified by comparing with the generated narrow pulse. Key

Numerical Simulation on the Initiation of Cylindrical Covered Charge Impacted by Tungsten Sphere Fragment

WANG Xin, JIANG Jian-wei, WANG Shu-you, LI Mei

2017, 38(8):  1498-1505.  doi:10.3969/j.issn.1000-1093.2017.08.006

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The interaction of tungsten fragment and cylindrical covered charge with different curvature radius is simulated by using AUTODYN-3D software. The influence of impacting position of fragment on the detonation characteristics of explosive is analyzed, and the “up-down” method is used to obtain the critical detonation velocity. The results show that the impact initiation progress of cylindrical covered charge coincides with that of plane covered charge. The detonation point is at a certain distance from the interface between explosive and casing, and gradually approaches to the interface as the fragment impact velocity increases. The cylindrical covered charge is easy to detonate under the same condition, and its critical detonation velocity increases nonlinearly with the increase in curvature radius. For collision point offset δ=0, the critical detonation velocity is increased by 3.2% for infinite curvature radius r=∞ compared with that for r=40 mm; the critical detonation velocity increases exponentially with the increase in offset δ. For r=40 mm, the critical detonation velocity for δ=0.94r is increased by 35.6% and 31.5% compared to that for δ= 0 and plane covered charge, respectively. Key

Study of Interior Ballistics of Solid Rocket Motor in the Process of Gas Jet Driving Liquid Column

WANG Jian， LIN Qing-yu， RUAN Wen-jun， WANG Hao

2017, 38(8):  1506-1512.  doi:10.3969/j.issn.1000-1093.2017.08.007

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In order to achieve the launch of individual rocket in limited space, a individual rocket launching system of which the liquid column is placed in the tail tube as a balance body is proposed. The system is tested, and the interior ballistics process is analyzed over time intervals. Based on the theory of the classical inrerior ballistics theory, a mathematical model of the launching system is established by assumoffing that the irregular mixing of gas and liquid is regarded as mixing of perforation. Runge Kutta method is used for numerical calculation, and the complete curves of interior ballistics process are given. The analysis result shows that the theoretical results are in good agreement with the experimental results. The relative error of the maximum pressure in combustion chamber is 1.6%, and the relative error of projectile velocity is 0.9%. The calculated results shows that the liquid column can be used to reduce the launching characteristics of rocket, improve the velocity of projectile, and enhance the power of individual rocket for the individual rocket launching systems with and without liquid column under the same launching conditions.Key

Research on Output Performance of Al/KClO₄ Igniter in Closed Bomb

LIANG Xiao-ai, NIE Jian-xin, WANG Shuai, ZHANG Zhi-feng, ZHANG Hai-jun

2017, 38(8):  1513-1519.  doi:10.3969/j.issn.1000-1093.2017.08.008

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The output performance of Al/KClO₄ igniter is a key parameter for the overall design of pyrotechnically actuated separation device. In order to describe the output performance of Al/KClO₄ igniter more accurately, an improved interior ballistics analysis model of Al/KClO₄ is established by modifying the hypotheses of classical interior ballistics equations and introducing the correction coefficient of powder force. The Matlab numerical algorithm is written to calculate the pressure peak, pressure rise time and impulse per unit area of Al/KClO₄ igniter in closed bomb. The changes of these parameters with charge mass and cavity volume are analyzed. And the calculated results are in good agreement with the experimental results. The results show that the pressure peak of Al/KClO₄ igniter increases with the increase in charge mass, and decreases with the increase in cavity volume. In a small volume (<5 mL), the cavity volume is increased by two times, and the peak pressure is decreased by about 40%. Key

Simulation of Transient Internal Flow Field of Solid Rocket Motor Based on Level-set Method

WANG Ge, LI Dong-dong, HAN Wan-zhi, ZHANG Ying

2017, 38(8):  1520-1531.  doi:10.3969/j.issn.1000-1093.2017.08.009

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A method considering combustion surface regression is developed to simulate the transient flow field of solid rocket motor. The method combining the level-set method with the porous media model can accurately simulate the transient flow field. In this method, the level-set method is used to capture the fluid-solid interface, and the porous media model is used to constrain the flow characteristics of grain region. The transient flows in the circular tube channel with interface regression and the solid rocket motor with short tube and complex wing-shaped charge are simulated to demonstrate the simulation accuracy of the proposed method. The calculated results agree well with the results obtained from dynamic grid method and zero-dimensional internal trajectory theory. It shows that the method can accurately simulate the transient flow with combustion surface regression. Key

Effect of Charge Size on Cook-off Characteristics of AP/HTPB Base Bleed Propellant

LI Wen-feng, YU Yong-gang, YE Rui

2017, 38(8):  1532-1540.  doi:10.3969/j.issn.1000-1093.2017.08.010

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To investigate the effect of charge size on the cook-off characteristics of ammonium perchlorate (AP)/ hydroxyl-terminated polybutadiene (HTPB) base bleed propellant, a cook-off model of base bleed propellant grain is established based on the two-step decomposition reaction mechanism of AP/HTPB. The AP/HTPB propellant is 72 mm in charge length and 43-53 mm in grain diameter, as well as 43 mm in grain diameter and 72-90 mm in charge length. The cook-off characteristics of AP/HTPB base bleed propellant are simulated at the heating rates from 1.0 K/min to 10.0 K/min. The results show that the cook-off time is shortened with the increase in the grain diameter of charge. As the charge length of AP/HTPB propellant with same grain diameter is added to 90 mm, the cook-off time is shortened remarkably. The charge size has little influence on ignition position. At the medium heating rates of 1.0-2.5 K/min, the ignition temperature rises with the increase in grain diameter and charge length. At the fast heating rates of 5.0-10.0 K/min, the charge has a less effect on the ignition temperature of AP/HTPB propellant. Key

Cook-off Test and Numerical Simulation of Small Booster Device of fuze

YUAN Jun-ming, ZHANG Lin-yan, TANG Xin, LIU Yu-cun, ZHANG Xi-liang, CHEN Yin-gang, LI Shuo

2017, 38(8):  1541-1546.  doi:10.3969/j.issn.1000-1093.2017.08.011

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The thermal reactions of booster device during slow heating are investigated. A small cook-off test is completed to assess both the reaction temperature and exothermic behavior of the material at a slow heating rate. The reaction kinetics of JH-14C are determined using differential scanning calorimetry (DSC) experiments, and the thermal decomposition characteristics are implemented into a 3D fully transient hydrocode and corrected by direct comparison with the subscale cook-off test results. The decomposited activation energies and pre-exponential factor of JH-14C are 2.04×10⁵ J/mol and 5.59×10¹⁷ s^-1, respectively. Based on the available thermal decomposition characteristics, the cook-off processes of booster device are simulated at four different heating rates. The results show that the booster charge explodes first and than the detonating explosive detonates. The explosion of detonating explosive is caused by the detonation wave which is produced by the explosion of booster charge. The ignition locations inside the booster charge at different heating rates differ, and remove from the center of booster charge cylinder to its edge with the increase in heating rate. The heating rate has no much influence on ignition temperature. Key

Data-level Fusion for Emitter Signal Identification Based on Compressed Sensing

WANG Zhi-peng， WANG Xing， TIAN Yuan-rong， ZHOU Yi-peng

2017, 38(8):  1547-1554.  doi:10.3969/j.issn.1000-1093.2017.08.012

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A novel data-level fusion method for emitter identification is proposed for the large scale communication in cooperative reconnaissance, which uses the superiority of compressed sensing in representing an original signal by using few measured data. In the proposed method, the Gabor time-frequency data of intercepted signal in a receiver is compressively measured with a Gaussian random measurement matrix. By transmitting few compressively measured data rather than the original signal, the large scale communication problem is alleviated. In the fusion center, a correlation fusion rule is proposed to calculate the combined weight of measured data according to the correlation among compressively measured data. To identify the signal type, a dictionary library is trained with every possible signal, and the reconstruction error in the sub-dictionary is calculated. The signal type with minimum reconstruction error is just the identification result. The simulated result proves that the proposed method achieves a pretty good balance in identification rate and communication scale, especially under low signal-to-noise ratio. Compared to the existed algorithms, the correlation fusion rule keeps more details of original signal. Key

A Satellite Selection Method for Missile-borne Detection System Based on Opportunity Illuminators

XIAO Ze-long， WANG Hua， ZHOU Peng， HAN Lu-xia， WANG Yuan-kai， LI Xiao, LU Xuan

2017, 38(8):  1555-1562.  doi:10.3969/j.issn.1000-1093.2017.08.013

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The geometric configuration relationship of detection system changes rapidly due to the high speed movement of missile-borne passive detector. The detection ability of the system highly relies on the selection of satellites. To solve this problem, BDS (BeiDou navigation satellite system) satellites are selected as opportunity illuminators, and the resolution of missile-borne passive detector is figured out. The quantitative relationship between the resolution of detector and the geometric configuration of detection system is deduced by using bistatic ambiguity function and angular resolution function. The constraint of the geometric configuration relationship is reversely derived depending on the resolution requirements. Optimization principle of BDS satellite selection is then concluded. The simulated results verify the feasibility and effectiveness of the proposed optimization principle of BDS satellites selection. Key

Research on Dual Optimized Broadband Beamforming Algorithm

BI Yang， WANG Ying-min，WANG Qi

2017, 38(8):  1563-1571.  doi:10.3969/j.issn.1000-1093.2017.08.014

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When the focusing matrix is identified in the coherent signal-subspace method, the deviation of the initial direction and the deviation of focusing frequency selection have an effect on the final focusing effect, even making the algorithm fail. A dual optimized broadband beamforming algorithm is presented. The algorithm is to use the robust Capon beamforming algorithm to correct the focusing matrix, the broadband signals are focused on the best focusing frequency by the corrected focusing matrix, and the narrowband signals are beamformed by the second-order cone programming algorithm. The computer simulation results and lake experiments show that the proposed algorithm can make the beam constant, and lower the sidelobe level at each frequency point. Key

Research on Magnetic Target Location Method Based on a Single Magnetic Gradiometer

JIA Wen-dou, LIN Chun-sheng, SUN Yu-hui, ZHAI Guo-jun

2017, 38(8):  1572-1577.  doi:10.3969/j.issn.1000-1093.2017.08.015

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Euler method can be used to realize the accurate positioning of magnetic dipole source. The magnetic gradient tensor data can be calculated using the magnetic field strength data, which is measured by rotating the magnetic gradiometer. A magnetic target location method based on the rotation of a single vector magnetic gradiometer is proposed. A rotating detection model of magnetic gradiometer is established. The influences of rotational angle, inclination angle and baseline length on the positioning accuracy of target are analyzed, which provides a reference for the design of rotating device. The proposed detection method has a higher positioning accuracy in the region near the magnetic target compared with the detection method using an array of seven magnetic sensors.Key

Quantitative Experimental Analysis on Crater Wear of Cemented Carbide Tools

WANG Kai， SUN Jian-fei， DU Da-xi， CHEN Wu-yi

2017, 38(8):  1578-1585.  doi:10.3969/j.issn.1000-1093.2017.08.016

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The effects of cutting parameters on the developing rate and volume of crater wear of uncoated cemented carbide tool during turning of TC4 alloy are investigated. Contour maps are used to describe the crater morphologies and study the relationship between the area of contour region and its wear depth in the case of the different cutting parameters. The evolution rate of crater wear is introduced to describe the variation rate of the area of contour region with its wear depth. The effects of cutting parameters on the developing rate of crater wear are analyzed. The volume of crater wear is obtained in the case of the different cutting parameters, and the effects of cutting speed, feed rate and material removal rate on the volume of crater wear are analyzed. The research result shows that the cutting speed is the primary factor in determining the volume of crater wear. Key

Step Stress Accelerated Degradation Test Modeling and Remaining Useful Life Estimation in Consideration of Measuring Error

LIU Xiao-ping， ZHANG Li-jie， SHEN Kai-kai， GAO Qiang

2017, 38(8):  1586-1592.  doi:10.3969/j.issn.1000-1093.2017.08.017

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Accelerated degradation test (ADT) has been developed into a main test method, which can be used to estimate the reliability and remaining useful life (RUL) of products with high reliability and long life. In order to study the effect of measurement error on the estimation of RUL in the step stress accelerated degradation test, a degradation process modeling based on Wiener process model considering the measurement error and the individual variation is proposed. The drift coefficient of Wiener process is randomized to describe the individual variation in different equipment, and the probability density function of life distribution is obtained at first hitting time. The maximum likelihood estimation method is used to estimate the unknown parameters introduced in the model. Monte Carlo method is used to simulate the performance degradation of laser. The results show that the fitting of model and the accuracy of RUL estimation in the degradation model considering the measurement error are better than those in the model without considering the measurement error, which can enhance the estimation accuracy of reliability and the prediction accuracy of RUL.Key

Multi-objective and Dynamic Scheduling of Battlefield Rush-repair Tasks Based on Non-ergodicity

CHEN Chun-liang, CHEN Wei-long, CHEN Kang-zhu, LIU Yan, SHI Xian-ming

2017, 38(8):  1593-1602.  doi:10.3969/j.issn.1000-1093.2017.08.018

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In the offensive operation, equipment is constantly damaged, but the battlefield rush-repair time and power are limited. The dynamic scheduling of battlefield rush-repair tasks in the offensive operation is studied. A multi-objective and dynamic scheduling of battlefield rush-repair tasks based on non-ergodicity, which is a real military problem, is presented. A mathematical model of multi-objective programming is established. Three key factors, including non-ergodicity, repair ability difference and priority of equipment to be repaired, are analyzed. A scheduling example of 39 equipment to be repaired and 3 repair groups is simulated and analyzed by using Matlab. The simulated result shows that the proposed model is scientific and reasonable, and the algorithm is correct and efficient, which can effectively solve the difficult problem of non-ergodic optimization and dynamically track the change of the optimal solution. Key

Task Allocation Method for Wartime Equipment Maintenance under Multiple Constraint Conditions

ZAN Xiang, CHEN Chun-liang, ZHANG Shi-xin, WANG Zheng, LIU Yan

2017, 38(8):  1603-1609.  doi:10.3969/j.issn.1000-1093.2017.08.019

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A model of equipment maintenance task allocation is established for lack of constraint conditions of existing wartime equipment maintenance task allocation. The model can be used for optimal decision of maintenance task allocation in the case of time constraint and maintainability limitation. And the equipment repair time, maneuver time and maintainability are comprehensively considered in the model. A two-stage heuristic algorithm, including genetic algorithm and neighborhood searching method, is designed to solve the model. The effectiveness of the proposed algorithm is verified through example analysis and comparison.Key

Rotation Control Modeling of Triaxial Rotating Inertial Navigation System

ZHA Feng， QIN Fang-jun， LI Jing-shu， YE Bin

2017, 38(8):  1610-1618.  doi:10.3969/j.issn.1000-1093.2017.08.020

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A control model of triaxial rotating inertial navigation system (RINS) is established to reduce the influence of carrier movement on the error modulation. A reasonable coordinate system is defined based on the triaxial frame structure, and then the transfer process of the carrier motion from the base to initial measurement unit (IMU) is analyzed to find the mathematical relationship between carrier motion and IMU motion. A dynamic model of triaxial frame motion, motor torque and carrier transport power is established based on Euler dynamic equation. A dynamic model of triaxial frame motion，motor torque and carrier motion is established according to Euler dynamic equation. And a control model of triaxial RINS under the condition of carrier motion isolation is established by using the proposed dynamic model and the motion transfer process. Accordingly, the analytical form of real-time change in rotary inertia on the outer ring axis is obtained, which is verified by simulation and actual test. Key

Dynamic Modeling and Driving Parameter Prediction of Mechanical Leg of Wheel-leg Hybrid Robot

QU Meng-ke， WANG Hong-bo， RONG Yu

2017, 38(8):  1619-1629.  doi:10.3969/j.issn.1000-1093.2017.08.021

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A new type of wheel-leg hybrid quadruped robot is proposed, which has four 6-DOF mechanical legs based on 3-UPS parallel mechanism. The dynamics of mechanical legs are modeled, and their driving parameters are predicted. The vector chain method is used to establish a transfer model of 3-UPS parallel mechanism, and the Jacobian matrix is established. A dynamics model of mechanical legs is established based on the Lagrange equation, and the drive force acted on the mechanism is given. The peak prediction model of servo motors for driving speed and torque is analyzed based on the dynamics model. The calculated result shows that the peak value of rotating speed of driving motor is 19.7 r/s, and the peak value of torque of driving motor is 71 mN·m. A design scheme of mechanical leg and its structure parameters are used to obtain the changes of driving speeds and torques of 6 motors over time. The calculated results show that the peak speed of driving motor is 15.3 r/s, and its peak torque is 48.1 mN·m, which are all less than the predicted limit values. The predicted peak power of servo motors is 77 (W). It proves that the dynamic analysis and the peak prediction model of driving parameters of the mechanical leg are very reasonable. Key

Muli-sensor Calibration Optimization Method of Mobile Robot Based on Stationary and Moving Object Observation ConsistencyConstraint

WU Ming, ZHANG Guo-liang, LI Lin-lin, FU Guang-yuan, LI Cheng-jian

2017, 38(8):  1630-1641.  doi:10.3969/j.issn.1000-1093.2017.08.022

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A calibration optimization method of camera and laser rangefinder based on stationary and moving object observation consistency constraint is proposed to address the problem of spatial observation consistency from heterogeneous multi-sensor in the process of mobile robot navigation in unknown environment. A covariance intersection method is used to fuse the bearing state of moving object on image plane, and Kalman and probabilistic data association filters are used to resolve the bearing state fusion of corner feature in the situations of “one-to-one” and “one-to-many”. On this basis, the objective function is generated using the bearing errors before and after fusion of image projections of stationary and moving objects, and the calibration parameters of camera and laser rangefinder are optimized using nonlinear optimization method. Experimental results show that the proposed method can be used to improve the observation consistency of multi-sensor, and the effectiveness of the mentioned methods is verified. Key

Machine Learning-based Road Terrain Recognition for Land Vehicles

WANG Shi-feng， DU Kai-yue， MENG Ying， WANG Rui

2017, 38(8):  1642-1648.  doi:10.3969/j.issn.1000-1093.2017.08.023

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The acquisition of information about the road terrain helps to improve the passengers' safety and comfort when a vehicle runs on different road terrains. Different road terrains have significant impacts on the driving acceleration, braking and manipulation of vehicle. A machine learning-based recognition method is proposed, which is to recognize the road terrain by fusing the feature data from accelerometer and camera. The road profile is estimated by using acceleration and vehicle speed data. The spatial features are extracted from the road profile for terrain classification. The texture features extracted from terrain images captured by a camera are used for the same classification task. And the task of recognition of road terrain is accomplished by fusing the data features from two sensor data sets. The experimental results show that the proposed method is used to improve the accuracy of road terrain recognition, and the reliability and comfort of passengers in vechile. Key

Linear Discriminant Analysis and Back Propagation Neural Network Cooperative Diagnosis Method for Multiple Faults of ComplexEquipment Bearings

HUANG Da-rong, CHEN Chang-sha, SUN Guo-xi, ZHAO Ling，MI Bo

2017, 38(8):  1649-1657.  doi:10.3969/j.issn.1000-1093.2017.08.024

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The fault diagnosis accuracy of bearing for complex equipment is not high due to the structural complexity of complex equipment and the poor working environment. A method of multiple bearing fault diagnosis based on linear discriminant analysis (LDA) and BP neural network is presented. A linear discriminant analysis is utilized for the linear dimension reduction of the dimensionless bearing multiple fault index, which is taken as an indicator of fault data. Lagrange extremum method is used to obtain an optimal projection vector. The bearing multiple fault data is projected on a category most likely to distinguished direction. The projected samples are used as the input samples of BP neural network and the test network. The simulation experiment of a certain large rotating machinery units shows that the proposed method can effectively reduce the dimensional mapping of multi-fault, achieve better classification, and has good validity and practicability. Key

Research Notes

Application of Rolling Device in 0.6m×0.6m Transonic and Supersonic Wind Tunnel

RONG Xiang-sen, TANG Lin-wei, WANG Wei-zhong, LI Zeng-jun, PU Hong-yu

2017, 38(8):  1658-1664.  doi:10.3969/j.issn.1000-1093.2017.08.025

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A rolling device is developed for the continuous change of model's rolling angle, the improvement of test efficiency and test range in the 0.6 m×0.6 m transonic and supersonic wind tunnel. The designs of rolling device, hollow built-in torque servomotor and the software and hardware of control system are introduced. The key technical problems are analyzed and summarized, and the conclusions are finally validated by a wind tunnel test. The test data shows that the rolling device and the central support of the normal force test, as model's supporting mechanisms, can be used to acquire better repeatable data. Meanwhile, the system has a high level control precision (rolling angle≤±3′), and the engineering reliability of the loads meets the wind tunnel test requirements. Key