Table of Content

25 November 2013, Volume 41 Issue 11

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Electronics, Communication & Automation Technology

Generation of Gaussian Random Number Based on FPGA

Yao Ruo-he Xu Xin-cai

2013, 41(11):  1-7.  doi:10.3969/j.issn.1000-565X.2013.11.001

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In order to improve the approximation precision of the Gaussian probability density function ( PDF) ,anew generation algorithm of Gaussian random number is proposed based on the Ziggurat algorithm.In this algorithm,the Gaussian PDF is divided into three subareas including the top,the middle and the tail regions,and thesubareas are further partitioned into rectangles via nested segmentation.After that,one of the rectangles is randomlychosen with the probability being in direct proportion to the rectangle area，and the random points ( x,y),whosePDF is identical to the rectangle,are generated,with x being the output as a Gaussian random number.Moreover,the tail region is treated separately to take into consideration the extreme values occurring in the simulation.Thenew algorithm is implemented on Xilinx Virtex 4,and the simulated results indicate that the proposed algorithmwith simple structure is easy to implement on FPGA,and that the generated random numbers can successfully passthe statistical tests of Gaussian distribution and randomness.

Improved Corner Detection Based on Multi- Direction Latticed Differential and Competitive Suppression

Ma Li- hong Li Jian- hui Tan Xing- jun

2013, 41(11):  8-15,22.  doi:10.3969/j.issn.1000-565X.2013.11.002

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A multi- direction latticed differential (DLD) operator combined with the“Winner Takes All (WTA)”competitive suppression strategy is proposed to remove the false corners along zigzag image edges and the repeatedly-detected corners in smooth regions,which improves the performance of the corner detector.In the investigation,first,a differential operator based on the Directionlet decomposition is proposed to eliminate the zigzag distortion.With the multi- direction latticed complex representation of the operator,image edges in arbitrary direction can bedenoted without zigzag,and false corners with zigzag appearance can be effectively suppressed.Then,a competitivesuppression algorithm,which defines a corner similarity with the constraint of neighborhood size according to theDLD response value,and merges similar corners with the WTA strategy,is put forward to remove slowly- varyingcorners.Experimental results show that the typical GLCP detector and the FAST detector combined with DLD areboth obviously improved.For instance,the ACU value,which is a comprehensive evaluation index of the error de-tection rate and the missed detection rate,increases by 12.14% and 6.32%,respectively.

Three- Dimension Face Recognition Based on Information Fusion

Liao Guang- jun Zeng Wei Liu Yu Li Zhi- fu Hu Yue- ming

2013, 41(11):  16-22.  doi:10.3969/j.issn.1000-565X.2013.11.003

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In order to overcome the disadvantages of two- dimension face recognition,a three- dimension methodusing a Kinect instrument is proposed based on the information fusion.In this method,for the face detection,theeyes' location is used to locate the face,and the skin color model as well as the depth information is employed torealize the face filtering.For the face recognition,the DTW (Dynamic Time Warping) algorithm is applied to therapid extraction of the face contour,and an improved LBP (Local Binary Pattern) matching algorithm is proposed,in which the weight value distribution is determined by analyzing the color image information and the face physiolo-gical characteristics.Experimental results show that the proposed method for face recognition is applicable and is ofimproved real- time capability and robustness.

Target Tracking Algorithm with Structured Sparse Representation Based on Ranks

Hou Yue- en Li Wei- guang Sekou Singare Zeng Shun- xing Rong Ai- qiong

2013, 41(11):  23-29,35.  doi:10.3969/j.issn.1000-565X.2013.11.004

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As the existing tracking algorithms are of poor performance in complex situations,a target tracking algo-rithm with structured sparse representation is proposed based on ranks.In this algorithm,first,a target dictionarycontaining targets and background information is constructed.Next,the candidate targets are represented linearlyvia the structured sparse representation,and the corresponding correlation coefficients are combined and ranked.Then,the residual error scores of the candidate targets are computed by using the residual errors of the target andthe background,and the scores are ranked later,from which the target state is finally determined.Experimental re-sults show that the proposed tracking algorithm is of high tracking accuracy and strong robustness.

Improved Algorithm Based on DTR Protocol in Cooperative Networks

Yu Yong-cong Feng Sui-li

2013, 41(11):  30-35.  doi:10.3969/j.issn.1000-565X.2013.11.005

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In order to implement the complex spectrum management in multi- relay channel accesses for distributedwireless cooperative networks,an improved algorithm based on the DTR protocol is proposed,which selects the bestrelay node offering cooperation based on the local game,thus avoiding the large delay due to the backoff or collisioncaused by the random access in the DTR protocol.Moreover,in this algorithm,each source controls its standard ofaccessing channel with threshold scheme adaptively,and the information between relay and source nodes is locally exchanged,thus substituting the centralized control mode for the best relay selection of base station or AP and exten-ding the algorithm to distributed systems.As compared with the backoff and collision transmission in DTR protocol,the proposed algorithm results in less communication overhead.Analytical and simulated results show that the pro-posed algorithm is superior to the traditional DTR- based algorithm because it helps to reduce the average end- to- enddelay and increase the system throughput without significantly increasing the network overhead.

Strategy of Avoiding Conflict Between MRO and MLB in LTE Self- Optimizing Networks

Huang Miao- na Feng Sui- li Chen Jun Zhang Yong- zhong

2013, 41(11):  36-42.  doi:10.3969/j.issn.1000-565X.2013.11.006

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Proposed in this paper is an optimization theory- based strategy of avoiding the conflict between MRO(Mobility Robustness Optimization) and MLB (Mobility Load Balancing).This strategy takes into considerationthe variation of users' received signal reference power in the period of T,so that the handover range for different userscan be dynamically adjusted.Moreover,based on the optimization theory,optimization objectives are designed forthe modeled MLB problem,and the allowed range of handover parameter O is set as the constraint to obtain theoptimal value of the handover parameter.Simulation results indicate that the proposed strategy not only avoids theconflict between MRO and MLB but also balances the cell load effectively,and that it helps to decrease the callblocking ratio and radio link failure as well as increase the network throughput.

Effectivity Analysis and Improvement of GSS Algorithm for Sensor Selection

Wang Xiao- le Huang Hong- bin Deng Su Liu Ming- xing

2013, 41(11):  43-49.  doi:10.3969/j.issn.1000-565X.2013.11.007

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In this paper,first,the optimality of GSS algorithm is discussed,and a theoretical analysis as well asseveral counter- examples is presented to prove that the traditional GSS algorithm does not guarantee the obtaining ofoptimal solution.Then,in the condition that the state vector dimension is larger than the observation vector dimen-sion,an improved GSS algorithm combining the exhaustive search is proposed to avoid the selection result degrada-tion due to the randomness of initial solution selection.Experimental results indicate that the improved algorithm iseffective in practice because it is of a high optimal selection rate of more than 90% and a low solution error of lessthan 0.35% even when the optimal selections are suboptimum.Moreover,the simulated results of the target track-ing in wireless sensor networks demonstrate that the improved GSS algorithm is superior to the traditional one.

Spectrum Sensing System Based on Array Duffing Oscillator Under Ultra- Low SNR

Jia Qiong Li Bing-bing

2013, 41(11):  50-55.  doi:10.3969/j.issn.1000-565X.2013.11.008

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As a rapid,correct and efficient spectrum detection algorithm is necessary for cognitive radio,this papermainly focuses on the spectrum sensing under ultra- low signal- to- noise ratio (SNR,less than －20dB).In the in-vestigation,first,a Duffing oscillator spectrum sensing model with strong nonlinearity is established based on thetheory of chaotic dynamics and the characteristics of spectrum sensing.Next,by introducing a dimensionless coeffi-cient as the transformation parameter of the system,the equivalence relationship between oscillators with differentdriving forces is derived.Then,a spectrum sensing approach based on the array Duffing oscillator is proposed todetect signals in a frequency band, Finally, the detection performance of the established model is numerically ana-lyzed.The results indicate that,as compared with the conventional spectrum detection methods,the proposed ap-proach is simpler to implement and is of higher detection performance.It is thus more applicable in practice.

Mechanical Engineering

Collaborative Welding Algorithm of Robots Based on Coupling and Decoupling of Kinematic Chain Ends

Zhang Tie Ying Can Zhai Jing-mei

2013, 41(11):  56-61,67.  doi:10.3969/j.issn.1000-565X.2013.11.009

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With the development of welding automation,multi- robot collaborative welding has become a researchhotspot in the field of welding robots.In this paper,based on the coupling and decoupling idea of kinematic chainends,a robot workstation is regarded as the combination of several open kinematic chains connected with joints,thegeneral constraints that must be satisfied by the kinematic chain ends in the welding process are analyzed,and thecoupling/decoupling method of master/slave kinematic chains is explored.Thus,a collaborative welding algorithmof robot workstation is proposed.In this algorithm,the kinematic chain for grasping weldments is taken as the mainchain and the discrete points of welding seam are successively replaced and adjusted to the optimal welding pose,while the other kinematic chains are responsible for the tracking of current discrete points of the welding seam.Mo-reover,by taking a dual- welding robot workstation with one positioner as an example,the effectiveness of the pro-posed algorithm is verified through simulation.

Design and Analysis of Flexible Connecting Mechanism for Large- Scale Wind Turbine with Coning Rotor

Liu Wang- yu Luo Yuan- qiang

2013, 41(11):  62-67.  doi:10.3969/j.issn.1000-565X.2013.11.010

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By comparing the structural characteristics of two traditional flexible hinges,a flexible mechanism con-necting the blades with the hub of the wind turbine is designed based on straight- beam flexible hinges.Then,a 3Dmodel of the whole wind turbine is established with SolidWorks,and a structural static analysis as well as a modalanalysis is performed with the finite element software ANSYS Workbench 14.0.The results indicate that the designedflexible wind turbine is more flexible than the conventional rigid one,and that the flexible connection between theblades and the hub remarkably reduces the natural frequency of the whole wind turbine,so that it helps to avoid thesympathetic vibration between the whole turbine and the blades,the tower or the wind rotor,protect the parts,andimprove the operation stability and life of the wind turbine.

Mechanical Characteristic Analysis of Tapered Roller of a New- Type Mechanical Vibration Table

Wu Shang- sheng Hu Zi- gao Hu An- tao Zhang Zhi- ming

2013, 41(11):  68-72.  doi:10.3969/j.issn.1000-565X.2013.11.011

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This paper puts forwards the basic structure and working principle of a new- type mechanical vibrationtable.It mainly investigates the mechanical characteristics of the vibration component—tapered roller.In the inves-tigation,the quasi- static method is used to analyze the force situation of the tapered roller,and the hydrodynamicmodel as well as the friction force model of the tapered roller is established.Then,the force and moment balanceequations of the tapered roller are derived,from which it is found that the up- and- down vibration of the mechanicalvibration table can be realized in an equilibrium condition.Finally,a transient dynamic analysis of the tapered rolleris carried out with ANSYS and the stress distribution response of the tapered roller in one movement cycle is simula-ted.The stress deformation curve obtained by simulation shows that the mechanical vibration table meets the designrequirements well,with only a slight stress change occurring during the movement of the tapered roller.

Bifurcation and Stability of Gear System with Random Parameter Excitation

Wang Jing- yue Guo Li- xin Wang Hao- tian

2013, 41(11):  73-78.  doi:10.3969/j.issn.1000-565X.2013.11.012

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By considering the random disturbances caused by the low- frequency internal excitation of torque fluctua-tion,damping ratio,gear backlash,meshing frequency and meshing stiffness,the random vibration equations of asingle pair of spur gear system with three degrees of freedom are established based on Newton's law.Then,the mo-tion differential equations are solved by means of the Runge- Kutta method,and the bifurcation and stability of thegear system with varying gear meshing frequency are analyzed according to the bifurcation diagram,phase diagram,time course diagram and Poincaré mapping graph of the system.Finally,the effect of the random disturbance ofmeshing frequency on the system dynamics is investigated.Numerical simulation results show that (1) there existsabundant period- doubling bifurcation in the random non- smooth gear system; (2) with the decrease of meshing fre-quency,the periodic motion of gear system becomes chaotic via the period- doubling bifurcation; (3) by eliminating6 unstable speed sections,a stable speed section can be obtained in a dimensionless meshing frequency range from0.1 to 6.0; and (4) as the system motion is extremely sensitive to the random disturbance of meshing frequency,the influence degree should be taken into consideration during the system modeling.

Speed- Switching Characteristics of Hydraulic Motor of Excavator with Shift Valve

Tang He- sheng Yin Yao- bao Wang Kang- jing

2013, 41(11):  79-84.  doi:10.3969/j.issn.1000-565X.2013.11.013

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In order to meet the variable speed drive requirements of the hydraulic motor of excavators under com-plex operation conditions,a variable speed control system with a shift valve was designed for the hydraulic motor.Then,the system model of the hydraulic motor was established,and the effects of some main parameters,such asthe diameter of the damper orifice at the pilot pressure port,the initial displacement of the valve spool,the diame-ter of the damper orifice at the valve pool and the spring stiffness,on the speed- switching stability,were analyzed.Theoretical and experimental results show that (1) setting a damper orifice at the pilot pressure port helps to im-prove the commutation performance of the shift valve and shorten the speed- switching time of the motor; (2) the ini-tial displacement of the valve spool,the diameter of the damper orifice and the spring stiffness all remarkably influ-ence the speed- switching stability of the hydraulic motor; and (3) the calculated results obtained by the theoreticalmodel accord well with the experimental ones.

Effects of Texture Slip Surface on Load- Carrying Capacity and Cavitation of Bearing

Lin Qi- yin Wei Zheng- ying Wang Ning Chen Wei

2013, 41(11):  85-90.  doi:10.3969/j.issn.1000-565X.2013.11.014

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In order to reveal the effects of surface texture on the tribological performances of journal bearings for themicro- texture optimization design,a numerical slip boundary condition with double coefficients was determined tocharacterize the comprehensive effect of the macroscopic/microscopic interaction and was applied to the journalbearing surfaces with controlled micro- textures.Then,the cavitation was modeled by using a phase change model,and the effects of such macroscopic parameters as the surface texture location and its area on the load- carrying ca-pacity and the cavitation were investigated.Finally,the proposed numerical slip boundary condition with double co-efficients was verified by using an experimental bearing reported in a reference.Theoretical analysis results showthat (1) the surface texture in the cavitation region has no effect on the pressure of the lubrication film and theload- carrying capacity of the bearing; (2) there exists a low- pressure effect at the front of the texture region but adynamic- pressure effect at the end; (3) the textures in the hydrodynamic pressure- rising region may increase theload- carrying capacity in a positive correlation with the area of texture surface in this region,while the textures inthe pressure- dropping region may reduce the load- carrying capacity and aggravate the cavitation.

Calculation of Structural Hybrid Dynamic Reliability Under Multiple Interval Loads

Fang Yong- feng Chen Jian- jun Yan Bin Cao Hong- jun

2013, 41(11):  91-95.  doi:10.3969/j.issn.1000-565X.2013.11.015

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This paper deals with the prediction model of structural hybrid dynamic reliability under multiple intervalloads and with or without structural stochastic strength degradation.In the investigation,first,equivalent intervalloads are used to substitute multiple interval loads and are taken as random variables with uniform distribution.Next,the random variables and the structural random strength are equivalently normalized.Then, the structural dy-namic reliability under multiple interval loads is calculated by using the first- order second- moment method accordingto the stress- strength interference theory.Finally, three numerical examples are presented to demonstrate the rationa-lity,practicability and accuracy of the proposed method.

Modeling and Contouring Performance of Networked CNC System with Delay

Zhang Chun- hua Li Di Zhai Zhen- kun Wang Shi- yong

2013, 41(11):  96-101.  doi:10.3969/j.issn.1000-565X.2013.11.016

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Aiming at the significant influence of timing parameters (i. e. sampling period and delay) on the con-touring performance of networked CNC (Computer Numerical Control) systems due to the involved networks,thispaper sets up a networked CNC system model with delay based on the modified Z transformation,and constructs therelationship between timing parameters and the contouring performance index, with the corresponding influence lawsbeing also obtained. The results show that (1) both the delay and its jittering increase the contour errors of multi-axis processing; (2) the sampling period is the primary factor influencing the contouring performance; (3) themulti- axis control actuation asynchrony caused by delay leads to the degradation of contouring performance; and(4) more attention should be paid to the influence of timing parameters on the contouring performance of high-speed networked CNC systems.

Development of Electronic Impact Hammer and Corresponding Application to Modal Test of Cutting Tool

Liu Lu- ning Zhang Yang- guang Shi Zhen- yu Song Qing- hua Liu Zhan- qiang

2013, 41(11):  102-108.  doi:10.3969/j.issn.1000-565X.2013.11.017

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In order to overcome the disadvantages of the manual hammer for the modal test of cutting tool,the existingautomatic hammer is comprehensively analyzed,and a test device using an electronic impact hammer is developed.The developed device consists of a workbench,a controller,a trigger,a switching power supply and an actuator,etc.It controls the traction electromagnet on/off based on the electromagnetic theory,thus driving the impacthammer by the traction force and realizing the hammer impact on the test object.Moreover,by controlling the con-tact time between the impact hammer and the test object,an ideal force pulse signal with repeatability and adjust-ability can be obtained.Finally,the frequency response functions of the cutting tool shank,the milling tool holder,the boring tool holder and the face milling cutter are respectively tested by using the developed device,and the fre-quency response curve and the modal parameters are obtained.The results show that the developed device is of sim-ple structure and easy operation,and that it helps to produce repeatable and adjustable impact force.

Temperature Rise of Electromagnet of Large- Gap Magnetic Drive System

Xu Yan Tan Jian- ping Wang Jun- feng Liu Yun- long Zhu Zhong- yan

2013, 41(11):  109-113.  doi:10.3969/j.issn.1000-565X.2013.11.018

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In order to guarantee stable and reliable operation of micro axial- flow blood pumps,the temperature riseof electromagnet in the large- gap magnetic drive system should be investigated and accurately controlled.In thispaper,the temperature distribution,heat loss,heat flux and thermal gradient of various components of the systemwere analyzed,and a simulation model of the thermal field of the electromagnet was established.Then,the distri-bution and variation law of the system temperature field were obtained via finite element simulation and experimentinvestigation.Finally,to meet the requirements of human body adaptability and long- term running of the electro-magnet,the electromagnetic and environmental parameters of the electromagnetic drive system were simulated andoptimized by taking a suitable temperature rise of the electromagnet as the target.The results show that the tempera-ture rise of the electromagnet can be effectively reduced by decreasing the loss and improving the heat emission con-dition of the electromagnet; and that the highest temperature of the electromagnet does not exceed 50 ℃ when thecurrent of electromagnet coils is lower than 0.56A and when the air velocity is higher than 3.5m/s.

Automotive Engineering

Vertical Load Control of Tires for Vehicle with Tire Burst

Chen Dong Shi Neng- fang Wu Nan

2013, 41(11):  114-119.  doi:10.3969/j.issn.1000-565X.2013.11.019

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In this paper,first,mathematical models are established based on the whole- vehicle model with 7 de-grees of freedom and the change of radial stiffness of a burst tire.The mathematical models are used to investigatethe vertical load characteristics of burst tires.Then,a simulation based on these models is performed to analyze theredistribution of vertical load after tire burst.As the load redistribution seriously impacts the handling stability ofvehicles,a strategy depending on active suspension control is proposed to control the vertical load on each tire,andPID controllers are used to adjust the dynamic response performance.Thus,excellent mechanical performance oftires for the handling and stable control of tire- burst vehicles can be obtained.Simulated results show that the pro-posed vertical load control system is of high efficiency in damping the dynamic oscillation of vertical load on eachtire and accurately regulating the steady- state vertical load to a desired value.

Solving of Inverse Dynamics for Lane- Change Steering Maneuver Based on Model Predictive Control

Liu Ying- jie Zhao You- qun

2013, 41(11):  120-124.  doi:10.3969/j.issn.1000-565X.2013.11.020

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As the traditional control methods are infeasible in dealing with multiple constraints in the lane- changesteering maneuver process,the model predictive control (MPC) method is adopted to solve the inverse dynamics forlane- change steering maneuver.In the investigation,the steering angle input is used as the control variable,theoptimal trajectory to complete the collision avoidance process of lane- change steering maneuver is taken as the con-trol objective,and the optimal control problem is converted into a quadratic programming problem,which is thensolved via the active set method.Simulated results show that the proposed method based on MPC is of potential ad-vantage for calculating the optimal steering input of vehicle trajectory with heavy computational complexity and mul-tiple constraints,and that it is effective in solving the inverse dynamics for the lane- change steering maneuver.

Fault- Tolerant Control of 4WID/4WIS Electric Vehicles Based on Reconfigurable Control Allocation

Liu Jie Liu Chao Zong Chang- fu Zheng Hong- yu Liu Ming- hui

2013, 41(11):  125-131.  doi:10.3969/j.issn.1000-565X.2013.11.021

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Proposed in this paper is a fault- tolerant control (FTC) algorithm for the 4WID/4WIS electric vehiclesafter faults,which takes the maximum post- fault vehicle stability as the control objective.The fault- tolerant control-ler adopts a hierarchical structure consisting of an upper motion controller based on the model predictive control(MPC) theory and a lower reconfigurable control allocator based on the reconfigurable control allocation method.Moreover,a re- allocation law considering multiple fault conditions of the driving motor is designed off line so as tomaintain the desired vehicle dynamics after faults.Simulated results show that the proposed FTC algorithm guaran-tees the desired dynamics and trajectory even under multiple fault conditions of the driving motor,so that it im-proves the post- fault stability and safety as well as the handling of vehicles.

Integrated Braking Algorithm Based on Brake Temperature and Wear Loss Control

Zheng Hong- yu Liu Zong- yu Xu Wen- kai

2013, 41(11):  132-136,142.  doi:10.3969/j.issn.1000-565X.2013.11.022

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In order to integrate the security and the economy of bus braking,an algorithm integrating the control ofthe main brake system and auxiliary brake systems is proposed based on the EBS (Electronic Controlled BrakingSystem).In this algorithm,according to the ECE regulation,the wear loss of brake linings and the thermodynamicproperties of brake systems,the braking force is rationally distributed among the brake systems of the bus,thusachieving the economy on the premise of brake security. Moreover,based on the co- simulation platform of Matlab/Simulink and TruckSim,the proposed algorithm is verified by simulations.The results show that,during the down-hill braking,the algorithm helps to keep the temperature of brake systems at an optimal value and facilitate a ba-lance wear of brake linings; and that,during the level- road braking,the algorithm helps to achieve the desired bra-king force effectively. It is thus concluded that the proposed algorithm is feasible in improving the security and theeconomy of bus braking.

Numerical Analysis of Grease Elastohydrodynamic Lubrication of Automotive Wheel Hub Bearing Under Actual Working Conditions

Chen Ying- jun Huang Ping

2013, 41(11):  134-148.  doi:10.3969/j.issn.1000-565X.2013.11.024

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Due to the high initial viscosity,obvious non- Newtonian property and small equivalent radius in thegrease lubrication of automotive wheel hub bearing under actual working conditions,great difficulties arise in thecorresponding elastohydrodynamic lubrication (EHL) calculation.In order to solve this problem,basic grease lu-brication equations are derived,non- dimensionalized and difference- solved sequentially.After that,the numericalsolutions of EHL of greased and lubricated wheel hub bearing,such as the pressure distribution and the thicknessshape of lubrication film,are obtained.The results show that (1) in greased and lubricated wheel hub bearings,there exist a second pressure peak and thickness necking similar to those under oil lubricated condition; (2) lightload,high velocity and large rheological exponent all help to form thicker lubrication film with a more obvious se-cond pressure peak; and (3) the lubrication between the rolling ball and the rolling cave is actually in an alternatestate of EHL and boundary lubrication.

Energy Data Clustering and Fault Recognition of Engine Based on Principal Component Entropy

Li Huai- jun Xie Xiao- peng Huang Heng

2013, 41(11):  137-142.  doi:10.3969/j.issn.1000-565X.2013.11.023

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Proposed in this paper is a fuzzy recognition method of engine fault modes based on the initial classifica-tion strategy with principal component entropy and oriented to energy data. In this method,first, the principal com-ponent data extraction method is used to reduce the highly- relevant multi- dimension data dimension.Next,the firstprincipal component data that maintain the maximum energy are clustered according to the number of possible classi-fications,and the optimal category number as well as the initial cluster centers is determined based on the kerneldensity estimation and the maximum entropy principle. Then,the best cluster center is produced via the fuzzy clus-tering of the principal component data only.Finally,the fault mode is recognized by calculating the maximum near-ness. Test results show that the proposed method effectively avoids the random selection of initial data due to theadoption of an independent initial classification algorithm,and that it is superior to the traditional algorithm due toits high classification accuracy,low computational overhead and excellent recognition performance.