Contents and Abstracts of Journal of Mechanical Engineering ISSN 0577-6686, CN 11-2187/TH*

Vol. 47, No. 1, 2011

Topology Optimization Design of Compliant Mechanisms under Uncertainties

LUO Yangjun1KANG Zhan2WU Ziyan1

(1. School of Mechanics and Civil. & Architecture, Northwestern Polytechnical University, Xi’an 710072, China;2. State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology,Dalian 116024, China)

Various uncertainties exist in the manufacture and operation process of compliant mechanisms. Based on the uncertain description of the multi-ellipsoid convex model for loading and material properties, a mathematical model for topology optimization of compliant mechanisms with the maximization of output displacement as objective and with the constraint on the minimum input performance is proposed. In this model,the artificial spring method and the geometrical nonlinear finite element method are adopted. The adjoint method is employed to give design sensitivity computing formulae, and a simple treatment technique for numerical instabilities is proposed. The optimization problem is solved by the gradient-based mathematical programming method. Design examples of a force-inverting mechanism and a micro-gripping mechanism verify the correctness of the proposed optimization model as well as the applicability of the proposed numerical techniques. The solution comparison between the present design and the deterministic design shows the importance of incorporating uncertainties in the topology design phase of compliant mechanisms.

Compliant mechanism Topology optimization Convex model Geometrical nonlinearity

PP. 1-7

DOI: 10.3901/JME.2011.01.008

An Improved Harmonic Wavelet and Its Application to Rotor Faults Diagnosis

CHEN Guo

(College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China)

Abstract:On the basis of Newland harmonic wavelet, an improved harmonic wavelet is put forward, it has a symmetrical and boxy frequency spectrum, and its expansions and translations will generate a series of wavelet functions which form an orthogonal basis of L2(R) space, the decomposition and reconstitution process of signal by the improved harmonic wavelet is easier than that by the Newland harmonic wavelet,moreover, the improved harmonic wavelet has the same excellent characteristics as the Newland harmonic wavelet. Using the simulation examples, the ability of extracting weak and local signal in strong noise is studied, in comparison to the DB8 wavelet, the effects of the improved harmonic wavelet are better. The improved harmonic wavelet is used to extract the super-harmonics and sub-harmonics components of the rotor faults signals because the harmonics frequencies characteristics reflect the rotor faults very well. The 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 components are extracted by the improved harmonic wavelet from the rotor fault experimental signals including imbalance, misalignment,rubbing, and oil whirling faults, and the results verify the effectiveness and correctness of the new method.

Key words:Harmonic wavelet Signal decomposition and reconstitution Rotor Fault diagnosis

PP. 8-16

DOI: 10.3901/JME.2011.01.017

The Design and Optimization of a Hopping Robot’s Tipping Mechanism

CHEN Diansheng ZHENG Wanjun HUANG Yu SHEN Qi WANG Tianmiao

(School of Mechanical Engineering and Automation,Beihang University, Beijing 100191, China)

Abstract:In order to improve hopping robots’ ground adaptability and solve the overturn problem after hopping robots’ landing on the ground, a kind of tipping mechanism is designed from the research of locust and sea turtle’s tipping process. It features simple structure, easy control, and integration of supporting and tipping functions. The triangle and centre of gravity theory is used to analyze the robots’ tipping principle and process.Based on simulation, tipping mechanism is optimized in configuration and dimension to guarantee the robot with compact structure, light weight and high motor utilization ratio. The tipping mechanism platform is set up to verify the feasibility of the principle and the correctness of optimization design of the tipping mechanism, thus providing the theoretical basis for the further innovation research on hopping robots.

Key words:Hopping robot Tipping mechanism Triangle and centre of gravity theory Simulation and optimization

PP. 17-23

DOI: 10.3901/JME.2011.01.024

Geometrical Design of the Movable Rolling Tooth Transmission with Cam Actuating

LI Jianfeng HE Aiying DONG Xinrui ZHOU Liyan

(College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology,Beijing 100124, China)

Abstract:The problems of parameter selection and geometrical design of the movable rolling tooth transmission with cam actuating are studied. The comprehensive influence of tooth profile parameters, such as transmission ratio, theoretic cam half-axis length, and radius of movable rolling tooth, on tooth profile property of the inner gear is analyzed, and the value selection relationship among tooth profile parameters is established under the condition of no interference appearance on inner gear’ profile. According to the transmission principle and structural characteristics analysis of the movable-tooth-frame, the calculation formulae and selection conditions of the geometrical parameters of movable-tooth-frame for avoiding parts movement interference and meeting the assembly requirement and transmission continuity are proposed. On the basis of the above analysis, the steps for geometrical parameter design of the movable rolling tooth transmission with cam actuating are presented, and the geometrical design process of this kind of transmission equipment is illustrated by means of an example. It’s shown that the design course of the movable rolling tooth transmission with cam actuating can be simplified, and satisfied parameter combination can be obtained on the basis of the value selection relationship of tooth profile parameters, the selection conditions of movable-tooth-frame parameters as well as the parameter design steps presented.

Key words:Movable rolling tooth transmission Cam actuating Parameter analysis Geometrical design

PP. 24-30

DOI: 10.3901/JME.2011.01.031

Neural Sliding Mode Control for Flexible Manipulators with Uncertain Parameters

ZHANG Niaona

(Department of Automation, Changchun University of Technology,Changchun 130012, China)

Abstract:The system is decomposed into the input-output subsystem and the zero dynamics subsystem for flexible manipulators with uncertain parameters through the output of manipulators system is redefined. The neural sliding mode control strategy is proposed for the input-output subsystem. The weights of the radial basis function (RBF) neural network is adjusted online to meet sliding mode arrived conditions. It can guarantee the output of the network to approach non-singular terminal sliding mode control input of the system and avoid chattering phenomenon.The zero dynamics subsystem is approximately linearized nearby the equilibrium point to select the design control parameters. Simulation experiment results demonstrate that the method fulfills the accurate point to point control of the flexible manipultor, and the elastic vibration at the end of flexible manipulator is eliminated.

Key words:Flexible manipulator Non-singular terminal sliding mode Neural network

PP. 31-35

DOI: 10.3901/JME.2011.01.036

2R Pseudo-rigid-body Model of Compliant Mechanisms with Compliant Links to Simulate Tip Characteristic

FENG Zhonglei YU Yueqing WANG Wenjing

(College of Mechanical Engineering and Applied Electronics Technology, Beijing University of Technology,Beijing 100124, China)

Abstract:Compliant mechanism is a kind of new type mechanism and its analysis is very complex because compliant links often under large deflections which introduce geometry nonlinearities. Pseudo-rigid-body model (PRBM) can simplify large- deflection analysis of compliant links.Based on PRBM, a 2R model is proposed for the compliant mechanisms with compliant links and a parametric approximation is made to the deflection angle of a compliant link. This model comprises three rigid links of different length which are connected by two torsional springs of different stiffness coefficient. The characteristic radius factor is used to indicate the length of the rigid links and the stiffness coefficient is used to indicate the torsion capability of torsion springs. A two-dimensional optimization for the optimal characteristic radius factors and a linear regression for the spring stiffness coefficient are presented. This model can simulate accurately both the deflection path and angle of the compliant link. Finally, the expression of strain energy of compliant link and that of PRBMs are derived. The ability of strain energy storage of PRBM is investigated through a comparison study in strain energy among PRBMs.

Key words:Compliant mechanism Pseudo-rigid-body model Parametric approximation Strain energy

PP. 36-42

DOI: 10.3901/JME.2011.01.043

Space Robot Soft-hard Grasping Based on Sliding Mode Control

WEI Cheng ZHAO Yang WANG Hongliu

(Department of Astronautics, Harbin Institute of Technology,Harbin 150001, China)

Abstract:Sliding mode control is applied in space robot capturing floating target with soft-hard grasping. Capturing operations become quite complicated and important for the nonlinear characteristics such as the dynamic coupling between the arm and the base, the impact excitation during grasping when the space robot captures a floating object. The dynamic model of the space robot and floating target is established, and then the impact dynamic model in grasping is introduced. The dynamic grasping area and the sliding mode control is applied for the arm grasping control to reduce the impact interference to the space robot, while the attitude control of the base with the error quaternion method is used to keep the base stable. The sliding mode surface parameters denote the impact-resistance ability of keeping and tracking status, which can be changed for various grasping characteristics: hard grasping as touching and soft grasping as colliding. The simulation results indicate that hard grasping as continuous contact can keep the arm rigidity as the joints change little, while the soft grasping can make the arm moving for energy dissipation as the joints change a lot, but the impact to the attitude of target and the position of base is little, about 50% that of the hard grasping.The results have important academic value and engineering significance.

Key words:Space robot Soft-hard grasping Sliding mode control Dynamic grasping area Grasping impact

PP. 43-47

DOI: 10.3901/JME.2011.01.048

Positioning Accuracy of Robot Vision System Based on Support Vector Machine Regression

YIN Xiangyun YIN Guofu HU Xiaobing ZHAO Xuefeng

(School of Manufacturing Science and Engineering,Sichuan University, Chengdu 610065, China)

Abstract:It is now a key technical issue to improve positioning accuracy of vision-based industrial robots to carry out complex tasks in dynamic and uncertain environment. Considering the accuracy and stability issues that pertain to position-based visual servo control for the monocular industrial robot, a method by combination of a model-based control method and intelligent-based calculation method is proposed. Based on support vector machine regression (SVR) oriented to small sample principle, an error revising model of the vision system for robots is constructed. A practical method based on SVR is designed to revise the planar positioning errors of robot manipulators, and compared with the error revising method based on linear interpolation and neural network.The experimental results demonstrate that this method can improve positioning accuracy of the vision-based robot and satisfy the demand of the location precision for industrial robots to carry through tasks, such as grabbing and assembly.

Key words:Industrial robot Visual servo Positioning accuracy Support vector machine regression

PP. 48-54

DOI: 10.3901/JME.2011.01.055

Nonlinear Dynamic Characteristics of Compound Planetary Gear Train Sets Based on Harmonic Balance Method

WU Shijing LIU Zhenhao WANG Xiaosun ZHU Enyong

(School of Power and Mechanical Engineering, Wuhan University,Wuhan 430072, China)

Abstract:A purely rotational model of Ravigneaux compound planetary gear train sets including time-varying mesh stiffness, synthetic mesh errors and gear backlashes is developed to show the nonlinear dynamic behavior of the system with the action of multi-clearances. The gap function is expressed as describing function and harmonic balance method (HBM) is used to convert the differential equations to nonlinear algebraic equations,which is solved iteratively by single rank inverse Broyden method. The steady state response of fundamental frequency is obtained. The influences of gear backlashes, time-varying mesh stiffness and synthetic mesh errors are analyzed by changing the value of the parameter. It is showed from the research that multiple value and amplitude jump discontinuities are presented on the dynamic curves, there the impact phenomenon is reflected. Meanwhile the nonlinearity degree of the system is increased by the coupling of stiffness fluctuation, mesh errors and backlashes. The HBM based on describing function can be used for more complicated model to obtain the steady state response of fundamental frequency, which provides a method for deeply researching the dynamic behavior of compound planetary gear train sets.

Key words:Compound planetary gear sets Transmission system Nonlinear characteristics Harmonic balance method

PP. 55-61

DOI: 10.3901/JME.2011.01.062

Vibration on the Results of the Asymptotic Perturbation Method for Multiple Degrees of Freedom Nonlinear Mechanics Systems with Quadratic Terms

YANG Li HAO Yuxin

(College of Mechanical Engineering, Beijing Information Science and Technology University, Beijing 100192, China)

Abstract:By considering the nonlinear strains-displacement relation and the effect of the shear deformation, the nonlinear governing equations of motion for the structure of plate and shell in the mechanical engineering are a two-degree-of-freedom nonlinear system including the quadratic and cubic nonlinear terms under external excitations. To consider the influence of the quadratic terms on the nonlinear dynamic characteristics of the nonlinear system, it is difficult for one to use the method of multiple scales to obtain the second-order approximate solution which includes the quadratic terms. By using the asymptotic perturbation method, based on the Fourier series and time rescaling, the quadratic terms can be included in the average equations. By introducing proper scale transformations, the asymptotic perturbation method is used to reduce the second-order non-autonomous nonlinear differential equations to autonomous nonlinear differential equations. The resonant case considered is 1:2, principal parametric resonance-1/2 subharmonic resonance. Then numerical analysis of the governing averaged equation is carried through by using Runge-Kutta method. It is found from numerical results that complex periodic, double-period and quasi-period motions exit intle four-degree-offreedom system.

Key words:Asymptotic perturbation method Internal resonance Averaged equations Quasi-period motions

PP. 62-67

DOI: 10.3901/JME.2011.01.068

Inverse Dynamics of 3-RRPR Compliant Precision Positioning Stage Based on the Principle of Virtue Work

JIA Xiaohui TIAN Yanling ZHANG Dawei

(School of Mechanical Engineering, Tianjin University,Tianjin 300072, China)

Abstract:For the realization of high frequency control of the flexure-based micromanipulator, a novel spatial compliant precision positioning stage driven by PZT is designed, and flexure hinge with circular notches and one rotational degree of freedom is utilized to realize the passive adjustment of the three translations of the platform. The position, velocity and acceleration equations are established on the basis of the Pseudo-Rigid-Body model. After calculating the potential energy of the flexure hinges, the inverse dynamic is developed on the principle of virtue work. By the mass matrix and the stiffness matrix, the expression of the natural frequency is derived. Then, the influence of the stiffness of the flexure hinges and the mass on the drive torques are analytically discussed.The model analysis of the stage is carried out by means of ANSYS, a finite element method code. Experiments are conducted to measure the modal frequencies of the stage. The results obtained from experiment,finite element method and formulation are compared to prove the correctness of the established theoretical model and the validity of the numerical analyses.

Key words:Dynamics Compliant mechanism Natural frequency Principle of virtue work

PP. 68-74

DOI: 10.3901/JME.2011.01.075

Analysis of Dynamic Stiffness of 250 t High Speed Dynamic Balancing Machine

SHI Qingxin1YUAN Qi1HU Yongkang2

(1. School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China;2. Department of Product Development, Dongfang Turbine Company Ltd., Deyang 618000, China)

Abstract:The dynamic performance of high speed dynamic balancing machine directly affects the accuracy and safety of the dynamic balance test. The three-dimensional finite element method is adopted to numerically study the dynamic stiffness of a 250 t high speed dynamic balancing machine, which is compared with the experimental results. The dynamic stiffness characteristics of four improved models are evaluated,aiming to investigate how the stiffness of the main stiffness rod influences the dynamic performance of the machine. The results show that the calculated dynamic stiffness curves agree well with the experimental results. The dynamic stiffness of the machine increases with the increment of the structure size and material elastic modulus of the main stiffness rod;a suitable structure and material for the main stiffness rod enables the machine to meet the dynamic balance test requirements of the large-mass rotors. Improving the main stiffness rod cannot lead to a flat dynamic stiffness curve.

Key words:High speed dynamic balancing machine Dynamic stiffness Finite element method Optimization

PP. 75-79

DOI: 10.3901/JME.2011.01.080

Natural Characteristics Analysis on Herringbone Planetary Gear Trains with Slide Bearing Support

BU Zhonghong LIU Geng WU Liyan

(School of Mechanical Engineering, Northwestern Polytechnical University, Xi’an 710072, China)

Abstract:A dynamic model of herringbone planetary gear trains is developed considering the axial vibration of two rings and asymmetry and interaction of oil film stiffness. Four stiffness coefficients are used to describe the oil film stiffness of slide bearings for planets’ support. The free vibration characteristic is analyzed and the vibration modes are divided into five groups: rotational-axial vibration mode of center gears,rotational-axial vibration mode of rings, translational vibration mode of center gears, translational vibration mode of rings and planets vibration mode. For each class of mode, the reduced-order inherent characteristics formulas are derived according to the properties of each vibration mode.The distribution range of natural frequencies is smaller than those of spur and helical planetary gear trains. It reveals that although the asymmetry of oil film stiffness has little influence on the vibration modes properties, the significant changes of translational vibration mode of center gears will happen if there is asymmetry interaction of oil film stiffness: the corresponding twofold natural frequencies will turn into two different frequencies and new characteristics of vibration mode will appear.

Key words:Herringbone planetary gear trains Slide bearing Asymmetric and interaction of oil film stiffness Natural characteristics

PP. 80-88

DOI: 10.3901/JME.2011.01.089

Lubrication Characteristics of GL-5 Gear Oil at High Contact Pressure

XIAO Huaping1LIU Shuhai2GUO Dan1LU Xinchun1LUO Jianbin1

(1. State Key Laboratory of Tribology, Tsinghua University,Beijing 100084, China;2. College of Mechanical and Electrical Engineering,China University of Petroleum, Beijing 102200, China)

Abstract:Lubricants working under heavy load are usually subjected to high contact pressure which may change the feature of lubricants in some way. As a result, the friction pair may fail which sometimes leads to even more serious situation like the collapse of the whole system. However,lacking necessary equipment, researchers perform experiments under the condition that the contact pressure is less than 2 GPa. New equipment is devised and manufactured to obtain interferometer image of lubricants at high contact pressure. The film thickness of GL-5 gear oil is tested with the new machine and its lubrication characteristic is analyzed. The results show that GL-5 gear oil can form thick lubrication film at high contact pressure but low rolling speed; flat and smooth lubrication film is formed at high pressure which makes contribution to reducing peak value of stress in contact area; with the increase of contact pressure measured film thickness gradually deviates from the theoretical value and adjustment is needed to the coefficients of rolling speed and load in Hamrock-Dowson formula.

Key words:High contact pressure Heavy load Lubrication characteristic Gear oil

PP. 89-95

DOI: 10.3901/JME.2011.01.096

Life Prediction Model for Friction Material of Traveling Wave Ultrasonic Motor

QU Jianjun1TIAN Xiu1SUN Fengyan2

(1. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China;2. National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China)

Abstract:Aiming at the dynamic contact process between stator and rotor,it is proposed that wear of friction material is generated by the reciprocating scratch of wave crests on stator surface. The visco-elastic contact model of stator and rotor is used to deduce the functions of normal pressure distribution and relative sliding speed, which are introduced to the traditional wear equation-Archard equation. Then, the wear and life prediction model of TWUSM friction material is established. In the model,the special relationship between time and distance are used to analyze contact interval, and the change of friction material thickness is also considered. Based on this model, the wear and life prediction curve of a TWUSM friction material is simulated. As a result, the life prediction curve is consistent with the experiment which verifies the rationality of the prediction model.

Key words:Traveling wave ultrasonic motor Friction material Wear Life prediction

PP. 96-101

DOI: 10.3901/JME.2011.01.102

Effect of Friction on Maximum Pressing Load of Scaling-up Equal Channel Angular Pressing

XU Xiaojing1ZHANG Zenglei1WANG Hao1CHENG Xiaonong1PAN Li1GONG Xinlan2DAI Fengyang2

(1. Institute of Advanced Forming Technology, Jiangsu University,Zhenjiang 212013, China;2. Machinery Branch, Nanjing Sanle Electron Information Industry Group Co., Ltd., Nanjing 210009, China)

Abstract:The finite element dynamic simulation using Deform-3D software and the experimental investigation of a large-scale equal channel angular pressing (ECAP) are carried out, with the special focus on the effect of both the friction coefficient between workpiece and ECAP die and the orifice size in exit channel of ECAP die on maximum pressing load. The finite element simulation results show that the shear friction model can be used in the finite element simulation of ECAP deformation.The friction coefficient between workpiece and ECAP die has very great effect on the maximum pressing load. With the increase of friction coefficient, the maximum pressing load increases considerably. As the friction coefficient varies from 0 to 0.6 (approximately equal to the friction coefficient between aluminum and steel under dry friction condition), the maximum pressing load increases up to 5.1 times. The effect of the orifice size on maximum pressing load is found to be dependent on the magnitude of the friction coefficients. When the friction coefficients are smaller than 0.6, enlarging the orifice size has little effect on the maximum pressing load. On the other hand, when the friction coefficients are bigger than 0.6, the maximum pressing load can be obviously decreased with an enlarged orifice size, but the impact is not always improved with the increase of the orifice size. The experimental results demonstrate that the realization of ECAP scale-up and commercialization strongly depends on finding an approach to effectively reduce friction, and that the maximum pressing loads by the finite element simulation and the experiment are in accordance.

Key words:Equal channel angular pressing Scale up Maximum pressing load

PP. 102-107

DOI: 10.3901/JME.2011.01.108

Modeling and Analysis of Real-time Properties of Open Architecture Computerized Numerical Control Systems

CAO Yunan1ZHANG Hui1YE Peiqing1WANG Tianmiao2

(1. Department of Precision Instruments and Mechanology,Tsinghua University, Beijing 100084, China;2. Robot Research Institute, Beihang University,Beijing 100191, China)

Abstract:A novel modeling method called timed transition model/all-time real-time temporal logic (TTM/ATRTTL) for specifying open architecture CNC (OAC) systems is proposed. TTM/ATRTTL provides full support for specifying hard real-time property and feed-back characteristics needed for modeling OAC systems. The formal method is used to model OAC systems from different aspects by specifying the TTM structure of an open-loop OAC, a system-level logic controller, and task communication and synchronization, and obtain the closed-loop OAC TTM with scheduling mechanism is given, which is the foundation of the verification framework. Finally, a verification framework is proposed and implemented with STeP and SF2STeP. In the verification, several problems are solved including rewrite rule, verification rule, state explosion problem, and time bound restriction when STeP is used for verification, and then experiments are conducted for verifying an OAC system for dead-lock and system time bound checking. The results show that the method can effectively model and verify OAC systems.

Key words:Open architecture computerized numerical control system Formal specification and verification Timed transition model/all-time real-time temporal logic Real-time property Modeling

PP. 108-116

DOI: 10.3901/JME.2011.01.117

A Middle-point-error-control Method in Strip-width Maximization-machining

CHEN Zhitong1,2YUE Yi3XU Rufeng1,2

(1. School of Mechanical Engineering and Automation,Beihang University, Beijing 100191, China;2. Research and Application Center of Advanced CNC Machining Technology, Beijing 100191, China;3. Beijing Spacecrafts, Beijing 100190, China)

Abstract:The tool center fluctuation problem commonly exists in the current machining strip-width maximization methods for 5-axis finish machining of complex surfaces with abrupt curvature change by using a torus cutter. This has negative impact on machining efficiency and quality improvement. After analyzing the tool position adjusting process of those strip-width maximization machining methods, the reasons for fluctuation caused by cutting strip-width (FCCS) and fluctuation caused by tool axis(FCTA) are decomposed. FCCS is the tool center fluctuation caused by the different machining strip-widths between two adjacent tool positions,and FCTA is the tool center fluctuation caused by tool freedom resulted from surface curvature variation. Although the influences by FCCS and FCTA may counteract with each other, the tool center fluctuation may be aggravated when they are both positive and both negative. A mid-point-error-control method (MPEC) for tool position optimization which can eliminate FCCS is proposed. Thus, FCTA is the only causation of the tool center fluctuation in this method. The torus cutter is firstly positioned by the mid-point on the effective-character-curve-segment(ECCS), and the other 2 degrees of freedom (DOF) are adjusted to obtain the maximum strip-width. The corresponding program of this method for an airscrew part is developed and the cutting experiment is conducted.Through comparison among the proposed method, the Sturz algorithm and the multi-point method, the effectiveness of MPEC in tool path smoothing and machining efficiency improvement for complex surface machining is validated.

Key words:Tool center’s fluctuation Middle-point-error-control Strip-width maximization machining Complex surface

PP. 117-123

DOI: 10.3901/JME.2011.01.124

Vehicle Routing Problem in Material Distribution under Condition of Much Fuzzy Information

LI Jinhang1,2HUANG Gang1,2JIA Yan1

(1. School of Mechanical Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074, China;2. State Key Laboratory of Digital Manufacturing Equipment &Technology, Huazhong University of Science and Technology,Wuhan 430074, China)

Abstract:Material distribution of mixed-model assembly is a complex system for supporting assembly line operation. Accurate distribution in time can ensure continuous production and greatly improve production efficiency. However, there often exist uncertain factors, such as work station demand for goods, appointed goods arrival time, and vehicle transportation time, so the traditional route programming model cannot truly reflect the field situation and on the contrary will cause low productivity. The uncertain factors are taken into consideration, the chance constraint programming model under the condition of fuzzy information is built, and traditional hybrid intelligent algorithm is improved to solve this model. In the selection of initial solution, roulette heuristic algorithm is adopted to reduce the search range. In the crossover operator, generalized hamming similarity degree is used to distinguish the similarity degree of two chromosomes in order to avoid inbreeding. Duplicate selected and mutated operator is chosen for increasing the convergence speed. A practical example proves the feasibility and high efficiency of the algorithm in dealing with uncertain factors, and different values of confidence of key factors in the fuzzy parameters are selected for comparison and analysis, thereby giving the suggestion on selection.

Key words:Material distribution Vehicle routing programming Fuzzy chance constraint programming Improved hybrid intelligent algorithm

PP. 124-131

DOI: 10.3901/JME.2011.01.132

Methods on Parameter Calibration and Tolerance Identification of Master Product Variant Model

XU Xinsheng1CHENG Xin1YAN Tianhong2

(1. Institute of Industrial Engineering, China Jiliang University,Hangzhou 310018, China;2. Institute of Mechatronics Engineering, China Jiliang University,Hangzhou 310018, China)

Abstract:In order to improve the validity of variant product，calibration and tolerance identification to the parameters of master variant model is proposed. Aiming at calibration issue，quality characteristic indicators associated with customization product and its synthesis model are constructed, and then the range of key parameters attained from customized product instances is used as constraints. Based on these，parameter calibration value that makes synthesis indicator achieve its optimization is worked out by using multi-objective optimization genetic algorithm. Aiming at tolerance identification，the tolerance range of parameter is calculated within the allowance range of synthesis indicator by analyzing the product cost loss and indicator excursion on the basis of the three stage design of Taguchi method. As a result，a validity variant instance that satisfies the requirement of quality characteristics can be derived from the master product variant model，so the ratio of successfully deriving variant instance is increased. Finally，an example is given to verify the above-menotioned principle and method.

Key words:Master product variant model Parameter calibration Tolerance identification Multi-objective optimization Three stage design of Taguchi method

PP. 132-137

DOI: 10.3901/JME.2011.01.138

Generation and Evaluation of Porous Structure of Bionic Bone Scaffold

YOU Fei YAO Yuan HU Qingxi

(Rapid Manufacturing Engineering Center, Shanghai University,Shanghai 200444, China)

Abstract:According to the analysis on porous structure of human bone and factors influencing scaffold performance, the generation and evaluation method of porous structure of bionic bone scaffold is proposed. Based on the structure of multi-constrained knapsack problem model and an ellipsoid taken as the unit body, the hybrid genetic algorithm is used to solve the inverse model of porous structure. Moreover, porosity and connectivity are used as the constraint condition to ensure the bioactivity of bionic bone scaffold. The model of bionic bone scaffold with pores is generated by Boolean operation between the model of scaffold without pores and the inverse model of porous structure. The evaluation system of porous structure of bionic bone scaffold is established with five evaluation indexes, i.e.porosity of scaffold, connectivity of pore, uniformity of pore distribution,twisting degree of pore canal and specific surface area of scaffold. Based on the inverse model of porous structure of scaffold, the calculation methods of porosity, connectivity, uniformity, twisting degree and specific surface area of scaffold are proposed to evaluate and optimize the porous structure of bionic bone scaffold. The bionic bone scaffold generated with this method has good bioactivity, better mechanical properties and uniform degradation rate.

Key words:Bionic bone scaffold Knapsack problem model Porous structure Porosity Connectivity

PP. 138-144

DOI: 10.3901/JME.2011.01.145

Robust Design of Aircraft Skin Stretch Forming Process Based on Transmitted Variance Model

SHEN Lijuan YANG Jun ZHAO Yu

(School of Reliability and Systems Engineering, Beihang University,Beijing 100191, China)

Abstract:Conventional optimization design in skin stretch forming process rarely considers the uncertain factors existing in materials, process conditions and parameters such as modulus, thickness and residual strain,thus causing great fluctuation in forming quality. Aiming at this problem, a robust design approach for aircraft skin stretch forming based on transmitted variance model is proposed, which combines robust design with finite element method. The main quality defects and key design parameters in skin stretch forming process are analyzed, and the fluctuation of design parameters and noise factors are considered. Based on the transitive relationship among the variances of design parameters,noise factors and response, the estimations of response mean and variance are obtained on the basis of the transitive relationship among response variance, design parameter variance and noise factor variance. Robust design of parameters is realized by taking the minimized mean square error as the criterion of robust optimization and by combining with ideal point to carry out multi-objective optimization. The stretch forming process of a certain skin part is taken as an example to verify the proposed method. The result shows that in comparison with the traditional optimization design, this method can effectively reduce the quality fluctuation and improve the robustness of skin stretch forming process.

Key words:Stretch forming Robust design Transmitted variance model Response surface method Finite element method

PP. 145-151

DOI: 10.3901/JME.2011.01.152

Integrated Modeling and Optimization of Printed Circuit Board Assembly Process Planning and Scheduling

DU Xuan1,2LI Zongbin2

(1. College of Mechanical & Material Engineering, China Three Gorges University, Yichang 443002, China;2. National Key Lab of Mechanical Manufacturing Systems Engineering, Xi’an Jiaotong University,Xi’an 710049, China)

Abstract:Aiming at the integrated optimization problem of printed circuit board (PCB) assembly process planning and scheduling, an integrated optimization model is built, and an new optimization method by combining polychromatic set (PS) with genetic algorithm (GA) is presented. On the basis of logical contour matrix and numerical contour matrix of PS, a constraint model of PCB assembly process planning and scheduling is built. which is combined with GA genetic coding, genetic operation and fitness value calculation, so as to guarantee the GA to search always in an effective solution space. The efficiency and effectiveness are improved significantly. Moreover, PS model holds unified standard form,it can help to dynamically describe various uncertain events such as machine fault and urgent order and improve the adaptability of PSGA. The calculation results indicate that PSGA can achieve the integrated optimization of PCB assembly process planning and scheduling efficiently.The completion time for PCB assembly is shorten, the delay of delivery date is reduced, and the workloads of machines are balanced.

Key words:Printed circuit board assembly Process planning Scheduling Polychromatic set Integrated optimization

PP. 152-160

DOI: 10.3901/JME.2011.01.161

New Research Progress in Design and Manufacture of Artificial Optical Compound Eye

CHEN Mingjun LIU Yesheng LI Ziang CHU Xin

(Center for Precisison Engineering, Harbin Institute of Technology,Harbin 150001, China)

Abstract:With the advantages of small volume, light weight, large field-of-view, high sensitivity and measuring speed, the artificial optical compound eye has broad application prospects in both advanced equipment of national defense and civilian industries and has attracted more and more attention. The characteristic of insects’ compound eye is analyzed briefly and the structure, function and classification of compound eye are concluded; the new progress in both design and manufacture of artificial optical compound eye is discussed in detail; the disadvantage in design using the optical micro lens array and the deficiency in manufacture process, such as the special processing, are made clear through comprehensive analysis and discussion of the imaging test results of the artificial optical compound eye. The merits of designing optical compound eye by using cross-section hexagon higher-order curved surface and the advantage of manufacture by using ultra-precision machining technology are discussed. A new idea of modeling and processing of the curved surface is given in order to provide a useful reference for further study.

Key words:Artificial optical compound eye Large field-of-view Micro-lens array Ultra-precision machining technology

PP. 161-168

DOI: 10.3901/JME.2011.01.169

Key Technology Research of Combined Electrical Machining of Closed Integral Structure

ZHAO Jianshe LIU Chen WU Rui WANG Jun XU Jiawen

(College of Mechanical & Electrical Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016, China)

Abstract:In order to solve the worldwide difficult problem of how to machine closed integral structure made of difficult-to-cut material, a new process of combined electrical machining is put forward and studied, that is an organic combination of numerically controlled electrochemical machining (NC-ECM) and numerically controlled electrical discharge machining (NC-EDM). As an example of trial processing of several typical closed integral structures, its overall technological scheme and main key technologies are discussed,including the design of auxiliary apparatus, electrode and its moving tracks based on digital technology, the computer simulation of combined electrical machining, the working areas partition of integral structure and the arrangement of technological parameters and machining allowance among the processing procedures. Combined with tackling key manufacturing technology of closed integral structure, the machining scheme is verified and improved through technological experiments, and qualified closed integral structures are machined finally. Then, the machinability problem of typical closed integral structure is solved, and the machining efficiency can be improved by above 40% compared to the use of NC-EDM alone, at the same time,the electrode wear can be reduced effectively. With the increase of production lot and the deepening of technological experiments of NC-ECM, there is ample room for improving overall machining efficiency. The above research achievements have been successfully used in the development of new aero-engines, airspace engines and turbo-machines, thus promoting the development of manufacturing technology of closed integral structure.

Key words:Closed integral structure Combined electrical machining Electrochemical machining Electrical discharge machining Numerical control

PP. 169-176

DOI: 10.3901/JME.2011.01.177

Monitoring of Drill Process and Prediction for Remaining Useful Life of Drill Tool

AO Yinhui WANG Baosheng

(Faculty of Electromechanical Engineering, Guangdong University of Technology, Guangzhou 510090, China)

Abstract:The real-time detection of drill wear is helpful to the preventive maintenance which will give caution of tool change in drilling production process. For the problem of tool monitoring during automatic production, a strategy of drill bit wear monitoring and remaining life time prediction system is presented for drilling machine with the use of spindle current signal. The spindle current information is acquired by closed loop current sensor, and a moving window technique is used to extract the real parts of data for drilling from the sampled data sequence. The wavelet packet decomposition is used to extract features.Critical features are selected according to their ability of discriminating the wear under Fisher criterion. Logistic regression (LR) combined with auto-regressive moving average (ARMA) model are used to evaluate the failure possibility and remaining life of the drill bit. Experimental results show good performance of the proposed algorithm and it can provide the basis for tool change.

Key words:Tool wear Wavelet packet decomposition Feature selection Prediction of remaining life

PP. 177-181

DOI: 10.3901/JME.2011.01.182

Model of the Instantaneous Undeformed Chip Thickness in Milling Based on Real Tooth Trajectory

YAN Xue1TAO Hua1,2CAI Jin1LI Haibin2

(1. Sino-French Common Research Group on Virtual Prototyping for Design and Fabrication, Northwestern Polytechnical University, Xi’an 710072, China;2. The Key Laboratory of Contemporary Design and Integrated Manufacturing Technology of Ministry of Education,Northwestern Polytechnical University,Xi’an 710072, China)

Abstract:Instantaneous undeformed chip thickness is one of the key parameters in modeling of milling process. Through analyzing the tooth trajectory, accurate instantaneous undeformed chip thickness can be obtained by solving cumbersome transcendental equation. Traditional chip thickness models always simplify the tooth trajectory to get approximate results. A novel instantaneous undeformed chip thickness model is proposed. Based on real tooth trajectory of end milling cutter,compensation is made for the simplified model. The chip thickness obtained by this new model is more accurate and simpler compared with traditional models. Comparison of cutting forces under different chip thickness models and experimental data indicate that this new model can provide better cutting force prediction than prior ones.

Key words:End milling cutter Real tooth trajectory Instantaneous undeformed chip thickness Dynamic cutting force

PP. 182-186

DOI: 10.3901/JME.2011.01.187

Finite Element Simulation and Experimental Research of Residual Stresses in the Cutting Based on the Coupled Thermo-mechanical Model

SUN Yazhou LIU Haitao LU Zesheng

(School of Mechatronics Engineering, Harbin Institute of Technology,Harbin 150001, China)

Abstract:Aviation precision thin-walled parts have complex internal structures; and cutting induced residual stresses are important influencing factors for their precision stability. So, it is necessary to research on residual stresses in cutting. According to the thermal-elastic-plastic finite element theory, a 3D finite element model is established, the aviation material aluminum alloy Al2A12 is analyzed in a nonlinear elastic-plastic finite element simulation of orthogonal cutting, and residual stresses on the machined surface are predicted and calculated. By means of FEA, simulation results of residual stresses on the machined surface are obtained when different cutting speeds, tool angles, tool edge radiuses are used. By analyzing and comparing the results, the basic influence rules of various factors on residual stresses are found. Residual stresses induced by different cutting processes are simulated, the influence rules of a secondary cutting on residual stresses are obtained. At last, experiments are carried out to research the influences of different cutting parameters on residual stresses, and the validity of the 3D finite element model is proved.

Key words:Residual stress Finite element simulation Coupled thermo-mechanical model Cutting experiment

PP. 187-193

Vol. 47, No. 2, 2011

DOI: 10.3901/JME.2011.02.001

Deviation Propagation Model of Assembly Sequence and Quality Evaluation Approach Based on Degree of Dimensional Variation

ZHOU Sihang LIU Zhenyu TAN Jianrong

(State Key Laboratory of CAD & CG, Zhejiang University,Hangzhou 310027, China)

Abstract:To accurately and effectively evaluate the influence of cumulative deviation in different assembly sequences on the product assembly quality,an assembly sequence deviation propagation model and a quality evaluation approach based on degree of dimensional variation are established. To acquire degree of dimensional variation, assembly-feature adjacency matrix and geometrical-feature tolerance matrix are established. According to the matrixes mentioned above, deviation propagation model with information of assembly sequence is automatically created. On the basis of the cumulative deviation calculated through deviation propagation model, the degree of dimensional variation is acquired. Following the evaluation rules, the assembly sequence can be comprehensively evaluated. The designer is able to obtain the assembly sequence with best assembly quality and improve the design tolerance of parts. Finally, a special machine for artificial gemstone is taken as an example to verify the effectiveness of the approach.

Key words:Degree of dimensional variation Assembly sequence Deviation propagation Evaluation of assembly quality

PP. 1-8

DOI: 10.3901/JME.2011.02.009

Simulating Modulated Thermography of Cladding Debond in Solid Rockets

GUO Xingwang LI Ransheng DING Mengmeng

(School of Mechanical Engineering and Automation,Beihang University, Beijing 100191, China)

Abstract:Modulated infrared thermal wave nondestructive testing (IR NDT)is an advanced technique of internal flaw inspection, and has certain application prospect in detecting cladding debond in solid rocket motors(SRM). The numerical simulation of modulated IR NDT for cladding debond in SRM is carried out by using finite element method, and the influences of heating condition and structure on the detectability are studied.The evolutions of informative parameters (i.e. the amplitude, phase and phase difference of surface excessive temperature) versus heating condition(i.e. the modulation frequency and heat flow intensity) and structural parameters (i.e. materials, defect size, depth and thickness) are obtained. The optimal modulation frequency, blind frequency and phase difference for typical material and structural size are predicted. Modulated thermography can be used in detecting cladding debond in SRM, and the test condition can be optimized through computer simulation.

Key words:Non-destructive testing Modulated thermography Simulation Solid rocket motor Infrared thermal wave

PP. 9-15

DOI: 10.3901/JME.2011.02.016

Image Vehicle Motion Trajectory Prediction Method under Complex Environment

ZHANG Runsheng1HUANG Xiaoyun1LIU Jing1MA Lei1HAN Rui1ZHAO Yuqin1YANG Xinhong2

(1. College of Vehicle and Energy, Yanshan University,Qinhuangdao 066004, China;2. School of Transportation Science & Engineering,Beihang University, Beijing 100191, China)

Abstract:The charge coupled device(CCD) installed in front of vehicle acquires road image in real-time, objective function is constituted by gray level and gradient character, and the road boundaries are fitted by using a parabola modal , so the identifications of the linear lane and the bent lane are unified. Identification is divided into three phases, the ROI of parabola parameters in each phase is set The parameters of parabola are optimized by using genetic algorithm. The parabola with approximately maximum objective function value is searched out through processes of initialization coding, calculating fitness, multi-point crossover and mutation, that is the optimal solution. The road identification result is used to obtain the direction deviation and lateral deviation of preview point and the road curvature, thus providing information for trajectory prediction. Based on the dynamic characteristics, the vehicle front steer angle of kinematics model is modified.The vehicle front steer angle and the road curvature are used as input of system, the preview dynamic continuous model is built. According to the sampling frequency of system, the continuous model is discretized. Kalman filter theory is used to design the state observer for observing real-time lateral speed and yaw velocity of vehicle, thus obtaining the vehicles trajectory. The tests show that the method not only simulates the boundaries of road exactly under complex environment and predicts vehicle trajectory accurately, but also has strong real-time performance.

Key words:Intelligent vehicle Road boundary identification Genetic algorithm Kalman filter State observer Vehicle trajectory prediction

PP. 16-24

DOI: 10.3901/JME.2011.02.025

The Philosophy and Application of Failure Study

ZHONG Qunpeng1ZHANG Zheng1FU Guoru2WU Sujun1LUO Hongyun1YOU Yiliang1

(1. School of Materials Science and Engineering, Beihang University,Beijing 100191, China;2. Institute of Aviation Equipment, Air Force Armament Research Institute, Beijing 100076, China)

Abstract:Failure Study is the science and technology focusing on success and safety based upon failures and aiming at the future and development from study of the past and history. The philosophical idea of failure study is with universal applicability. Basic principles, philosophical concepts and application of failure study are described from epistemology, contradictions,systematology and methodology. The theory and application of failure study are studied, explored and analyzed, to raise the concept and application of failure study to the height of philosophy, which is an initial attempt to open up a new field. Epistemology of failure study shows that failure is inevitable.It is necessary to establish a correct view on safety and risk management concept, to fully understand important role of security risk management and safety process management. Contradiction analysis in Failure Study considers that it is important to establish a point of view that every coin has two sides and contradictions can be transformed, and to fully understand the leading role of internal cause in transformation process and the importance of all-staff and self safety management. Systematology of failure study believes it is significant to establish the view that system is the starting point and destination of failure analysis, and to fully understand the important role of the hierarchy and the importance of safety management systems.Methodology of failure study indicates that it is crucial to master the system analysis method, the outside-to-inside type of analysis methods and the forward-backward iterative exploration methods.

Key words:Failure study Philosophical idea Application

PP. 25-30

DOI: 10.3901/JME.2011.02.031

Automatic Tool Assembly Algorithm of Sheet Metal Forming Based on the Background Mesh Projection

FAN Rong1ZHENG Guojun1,2HU Ping1

(1. School of Automotive Engineering, Dalian University of Technology, Dalian 116024, China;2. Engineering Analysis Division, Geely Automobile Research Institute Co., Ltd., Hangzhou 311228, China)

Abstract:According to the research of tool pre-assembly in automotive body panels forming simulation, three preconditions for effective automatic assembly algorithm are presented: Normal consistent algorithm, definite tool property and correct initial normal direction; the automatic assembly algorithm based on the background mesh projection is also presented. Nodes of sheet and tools are projected and distributed onto background mesh along the overall normal direction, and according to the corresponding relation between tools, sheet and background mesh the minimum values of tool nodes and sheet elements are calculated, thereby determining the distance that tools need to be moved. Ultimately, the correct assembly is accomplished automatically. The algorithm eliminates the coupling relationship between stamping type and stamping direction to improve the adaptability of the program and efficiency of the algorithm, it also simplifies the user operation. The practice in the complex industry model proves the feasibility and efficiency of the new self-assemble algorithm satisfying the requirement of the automotive body panels forming simulation.

Key words:Automatic assembly Finite element method Stamping Mesh generation

PP. 31-35

DOI: 10.3901/JME.2011.02.036

Application of Twin Shear Unified Elastoplastic Finite Difference Method in Metallic Structures

MA Zongyuan LIAO Hongjian LI Hangzhou

(Department of Civil Engineering, Xi’an Jiaotong University,Xi’an 710049, China)

Abstract:Twin shear unified strength theory is applied to the numerical simulation of metallic structures with the method of elastoplastic finite difference. This work has actual significance for the problem of metallic structures strength or processing research. Firstly, the twin shear unified strength theory and the method of Lagrangian finite difference are briefly introduced. Secondly, the finite difference formulation of twin shear failure criteria and flow rule is derived and the model is loaded into FLAC code with dynamic-link library file compiled by language of C++. Finally,the cases of thick-walled cylinder under internal pressure and perforated plate in tension are calculated. The calculation results of analyses suggest that the precision of Lagrangian finite difference method and finite element method are similar. Twin shear unified strength theory can be applied to the metallic materials with a ratio of shear strength to tension strength between 0.5 and 0.667, so that it will have wide application in numerical simulation of metallic structures.

Key words:Twin shear unified strength theory Metallic structures Lagrangian finite difference Numerical simulation

PP. 36-43

DOI: 10.3901/JME.2011.02.044Analysis and Experiment on Central Buckling and Post Buckling of Thin Cold-rolled Sheet

DAI Jietao ZHANG Qingdong

(School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China)

Abstract:The mechanism and deformation behavior of the thin strip central buckling are studied by using analytical and experimental methods.The analytical model of thin strip buckling and post buckling is established in order to verify the results of the analytical model, the rolling experiment is carried out in test rolling mill. In those experiments, a variety of different central buckling models are obtained by designing different roll-shaped curves for work roll, and the geometric parameters of the central buckling are measured. The corresponding parameters of rolling equipment and the aluminum sheet are also obtained. By using the analytical model, the critical central buckling stress for the conditions of rolling experiment is achieved on the basis of the principle of least work,the path generation of post buckling is found with perturbation-variational solution, and the model of the post buckling is in good agreement with the result of experiment. Simulation analysis for the conditions of rolling experiments is established by using ANSYS, the model of buckling is obtained, which is in good agreement with the experimental results, and the critical buckling stress of this buckling model is also achieved, thus proving the correctness of the finite element model and its calculation results, and further verifying the analytical calculation results.

Key words:Thin cold-rolled sheet Buckling Post buckling Rolling experiment Analytical method Finite element method

PP. 44-50

DOI: 10.3901/JME.2010.02.051

Fatigue Life Prediction of Ball Bearings by Modified Paris Law Based on Critical Curved Surface

XU Dong1XU Yongcheng1CHEN Xun1LI Xinglin2YANG Yongmin1

(1. College of Mechatronical Engineering and Automation,National University of Defense Technology,Changsha 410073, China;2. Hangzhou Bearing Test & Research Center (HBRC),Hangzhou 310022, China)

Abstract:Microstructures of flaws of ball bearings are investigated by using field emission scanning electron microscope and it is found that both crack initiation and crack propagation are always along a certain curved surface. Propagating to a certain degree, the crack will fracture and form an elliptic flaw. Along with the ball bearing operating, not only the flaw continues to flake away, but also some new cracks initiate and propagate along new curved surfaces and fracture ultimately. There are many cross sections in the flaw. Based on this phenomenon, the critical curved surface of ball bearing is proposed and crack initiation and propagation are assumed to be on this critical curved surface. In virtue of this method,three dimension problems are converted to two dimension ones. Based on this, a modified Paris fatigue life prediction model is proposed. The fatigue life is divided into two sections: crack propagation and flaw size gain, and fatigue life are predicted by sectional Paris law. The model is validated by fatigue test life data of SKF 6205 deep groove ball bearings.In comparison with the prediction of traditional SKF L-P formulary, the proposed model produces more accurate results.

Key words:Critical curved surface Paris law Fatigue life prediction Prediction model Ball bearing

PP. 51-57

DOI: 10.3901/JME.2011.02.058

Development of Nb Microalloyed Low Carbon Steel Plate with Ultra-fine Grains in Surface Layer

DU Haijun LI Chun ZHAO Dewen WANG Guodong

(The State Key Laboratory of Rolling and Automation,Northeastern University, Shenyang 110004, China)

Abstract:A 10 mm thick Nb microalloyed high strength steel with ultra-fine grains (1～5 µm) in surface layer is obtained by applying the accelerated cooling intermediate slab-rolling-post rolling accelerated cooling process, the thickness of ultra-fine grains layer lies between 0.5 and 2.0 mm. It has 640 MPa yield strength, 740 MPa tensile strength, 27% elongation and more than 130 J impact absorbing energy at –40 ℃. Microstructure investigation is done by using optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show the mechanism of ultra-fined ferrite is deformation induced undercooling austenite to ferrite transformation (DIT), and conjunction with dynamic recrystallization (DRX)of proeutectoid ferrite and DIF ferrite. The strengthening mechanism is fine grain strengthening, Nb precipitation strengthening, dislocation and substructure strengthening. Before accelerated cooling of intermediate slab ,to obtain refined austenite grains through recrystallization region rolling or deformed ones through non-recrystallization region rolling, or to increase the rolling compression ratio after accelerated cooling of intermediate slab , and to decrease the final cooling temperature of post-rolling accelerated cooling ,all help obtain ultra-fine grains in surface and increase the proportion of ultra-fine grains over the whole plate thickness.

Key words:Strain induced transformation Ferrite dynamic recrystallization Surface layer Ultra-fine grain Nb microalloyed low carbon steel Accelerate cooling

PP. 58-64

DOI: 10.3901/JME.2011.02.065

Fatigue Damage Performance of Metal Rubber Material

WANG Youyan BAI Hongbai HOU Junfang

(Department of Guns Engineering, Ordnance Engineering College,Shijiazhuang 050003, China)

Abstract:The fatigue damage test of disk type metal rubber piece is performed. The results show that fatigue damage performance of metal rubber is different from conventional solid materials. The damage of metal rubber is accumulated with its inner partial wires wearing and fracturing,so it does not rupture as sudden failure of solid material. The load-bearing capacity and energy dissipation are tapered in macroscopic view. The fatigue damage mechanism of metal rubber material is revealed through analysis of the variation of energy dissipation modes of two typical linking structures of inner wires along with the vibration cycle, which is mainly the difference between the slip extrusion modes of inner linking structures and the fretting friction, wear, fracture of metal wires. The stiffness damage and damping damage are used to accurately describe the fatigue damage process of metal rubber, and the comprehensive damage factor D is proposed to be the fatigue failure criterion.

Key words:Metal rubber material Elastic porous material Fatigue damage Fretting friction

PP. 65-71

DOI: 10.3901/JME.2011.02.072

Optimum Design of Flywheel Rotor Made of Functionally Graded Materials

YAN Xiaolei ZHONG Zhihua ZHA Yunfei MO Xuhui SUN Guangyong

(State Key Laboratory of Advanced Design and Manufacture for Vehicle body, Hunan University, Changsha 410082, China)

Abstract:Functionally graded materials(FGMs) are new materials whose properties change continuously in the spatial position. Using FGMs instead of uniform materials for high speed energy storage flywheel rotor can reduce stress concentration effectively and give full play to the material properties, thereby improving the rotor performance . In view of the big error of plane stress(PS) solution when the axial thickness of flywheel rotor is big compared to its radius, a three-dimensional semi-analytical solution that is a modified plane stress(MPS) solution of FGMs flywheel rotor is derived by dividing the rotor into finite ring elements with constant thickness and homogeneous material, and then its accuracy is verified by finite element method. At last, by taking thickness,material volume fraction and rotating speed as design variables, and maximized energy storage density of the rotor as objective function, both shape and material distribution are optimized for FGMs flywheel rotor by using sequential quadratic programming(SQP) method, in addition, the effect of material properties on optimization results are also analyzed.Calculation results indicate that rational shape and material distribution can make stress distribution more even, and greatly increase the energy storage performance of flywheel rotor.

Key words:Flywheel rotor Functionally graded materials(FGMs)Modified plane stress(MPS)Sequential quadratic programming(SQP)

PP. 72-79

DOI: 10.3901/JME.2011.02.080

Effect of Welding Parameters on Corrosion Resistance of 5383 Al Alloy Friction Stir Welding Joint

ZHANG Liguo1,2JI Shude1ZOU Aili1LUAN Guohong3WANG Shan3

(1. Academy of Astronautical Technology, Shenyang Institute of Aeronautical Engineering, Shenyang 110034, China;2. Shenyang Aircraft Design & Research Institute,Shenyang 110035, China;3. China FSW Center, Beijing 100024, China)

Abstract:On the basis of preparing the friction stir welding joint of 5383 Al alloy under different welding conditions, the macrocosmic appearance and the microcosmic appearance are all researched, and the effects of welding parameters, such as welding speed, stirring head speed and pressure, on the corrosion resistance of joint are obtained . The results show that the “S” line appears in the weld zone under certain welding conditions. The most serious region of corrosion is the “S” line, which results from three factors: the segregation of Mg, the aggregation of many micropores, and the formation of ferromanganese compounds. The corrosion resistance of weld zone other than “S” line and its nearby regions is better than that of the parent metal. Moreover, the reasons why the three factors make the corrosion resistance decrease are analyzed. The effects of different welding parameters on the “S” line are described.Decreasing the welding speed , increasing the stirring head speed and pressure can improve the corrosion resistance of friction stir welding joint of 5383 Al alloy.

Key words:5383 Al alloy Friction stir welding Corrosion resistance Welding parameters

PP. 80-84

DOI: 10.3901/JME.2011.02.085

Influence of Heat Treatment on Mechanical Properties of 2205 Duplex Stainless Steel Welds

ZOU Dening HAN Ying LI Jiao CHEN Zhiyu

(School of Metallurgy and Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China)

Abstract:2205 duplex stainless steel (DSS) joints welded by manual arc welding are subjected to solution treatment at 1 050 ℃ and aging treatment at 850 ℃ for various holding time. The microstructure evolutions and the distribution of σ phase in each joint region are observed by optical microscope. Hardometer, tensile and impact testers are used to evaluate the mechanical properties of the welded joints. Meanwhile, the impact fractographs and fracture mechanism are analyzed through scanning electronic microscope. The results show that the solution treatment at 1 050 ℃ for 2205 DSS welded joint can effectively improve the microstructure and properties. After aging at 850 ℃, σ phase precipitated at the γ/α interface can be found in all the joint regions,including base metal, weld metal and heat affected zone (HAZ). With increasing aging time, σ phase grows into the adjacent ferrite grains and the amount of σ phase increases. The weld metal is more sensitive to σ phase precipitation. The hardness in the base and weld metal markedly increases due to the σ phase formation, and the increment rate is faster in the weld region. Furthermore, the extent to which brittle σ phase improves the ultimate strength is found to be in evidence, being more pronounced in reducing the ductility and impact toughness. The fracture mechanism of impact fracture is a transformation from the mixed rupture as-solution treated to the brittle fracture after aging at 850℃, characterized by cleavage crack.

Key words:Duplex stainless steel Welding Solution treatment Aging Mechanical properties

PP. 85-89

DOI: 10.3901/JME.2011.02.090

Mechanical Property of the Sintering Layer at the Interface of Natural Yellow Clay-bonded Sand Mould and Iron Casting

ZHANG Rui LUO Yilan YIN Liang ZHU Shigen

(College of Mechanical Engineering, Donghua University,Shanghai 201620, China)

Abstract:Natural yellow clay-bonded green sand casting process is suitable for producing iron casting. It can avoid burnt-on sand and improve the casting surface quality, and has the comprehensive advantages of low cost, less pollution and high efficiency. The big difference between natural yellow clay bonded green sand process and usual clay bonded green sand processis that the former can form a dense sinter skin at the interface of casting and mold, which can resist the scouring and infiltration of liquid metal, and can firmly adhere to the casting surface after the liquid metal is solidified. So, elevated temperature knockout can be realized without too fast cooling of casting and too high surface hardness, thus improving production efficiency. At room temperature, it can easily shed from the casting surface, thus reducing the amount of sand-removing work.In order to understand this phenomenon in depth, the mechanical performances of sinter layer of natural yellow clay-bonded sand at elevated and room temperatures are investigated . The results show that the sinter layer sample has excellent plasticity at elevated temperature, and with the decreasing of temperature, the plasticity decreases and the compression strength increases. At room temperature, it exhibits obvious brittleness. This accounts for the agreement of the variation of mechanical performance of sinter layer with its behavior in the casting process.

Key words:Natural yellow clay bonded sand Casting mold Burning-on sand Stinter skin Elevated temperature property

PP. 90-94

DOI: 10.3901/JME.2011.02.095

Improving Resistance of Cobalt-based Alloy Coating Formed Laser Fine Cladding on High-hardness and Microporous Small Parts

SHI Yan ZHANG Hong LIU Shuangyu XU Chunying

(School of Electromechanical Engineering, Changchun University of Science and Technology, Changchun 130022, China)

Abstract:The surface hardening of high-hardness and microporous small parts is difficult owing to its special structure characteristics. The valve seat, as a representative of such small parts, is hardened by laser fine cladding Cobalt-based alloy coatings by using the auxiliary processing device and the co-axial powder feeding system. The macromorphology,microstructures and microhardness are characterized by using laser microscope, SEM, XRD and microhardness tester . Comparison tests of service lives of the laser cladding specimens and the uncladding specimens are carried out on the fuel injection test rig. The results show that the phenomena of ablation and high tempering of the valve seat during the process of cladding are avoided while good forming of clad layer is ensured by using the pure copper auxiliary processing device . The problem of micropores blocked by cladding layer is solved by the method of inlaying kryptols. The laser cladding layer is comprised of a hypoeutectic structure, which contains primary dendrites and interdendritic eutectics. The primary phases are γ-Co, CoCx, Cr23C6,W5Si3 and etc. The metallurgical bonding forms well between the cladding layer and the matrix of GCr15 steel. Compared with the uncladding specimens, the erosion resistance of the laser cladding specimens is increased by 40%.

Key words:Laser cladding Small parts Micropore Cobalt-based Microstructure Erosion resistance

PP. 95-101

DOI: 10.3901/JME.2011.02.102

Multidisciplinary Design Optimization of Vehicle Body Structure Based on Collaborative Optimization and Multi-objective Genetic Algorithm

WANG Ping1ZHENG Songlin1,2WU Guangqiang1

(1. College of Automotive Engineering, Tongji University,Shanghai 201804, China;2. School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China)

Abstract:Multidisciplinary and multi-objective optimization design method is applied in the researches of vehicle side impact crashworthiness and NVH performances. Design of experiment(DOE) is explored to obtain the experimental scheme and perform data sampling, the response surface model(RSM) taking into account the vehicle side-impact safety, body-in-white modal frequency, static bending stiffness, torsional stiffness and lightweight is built. Determined optimization, Reliabilityoptimization and lightweight design are operated independently on the basis of genetic algorithm. Finally,collaborative optimization which is one of the best feasible multidisciplinary design optimization approaches is combined with multi-objective genetic algorithm to carry out the optimization of vehicle body structure. Then the Pareto optimal set is obtained. The results show that the reliability optimization which considers the uncertainties of product design and production process can ensure product stability, and is more accurate than deterministic optimization. The coupling and interdisciplinary relationships of lightweight, NVH and crash safety performancesare comprehensively considered during the multi-objective optimization of vehicle body structure.Thus the Pareto set is obtained and designers can choose the satisfactory optimization results according to their demands, so as to significantly reduce product development cycle and costs.

Key words:Multidisciplinary design optimization Multi-objective genetic algorithm Reliability-based design optimization Lightweight Collaborative optimization

PP. 102-108

DOI: 10.3901/JME.2011.02.109

Electric Power Steering on Low Friction Coefficient Road

ZHAO Linfeng CHEN Wuwei QIN Weihua YANG Jun

(School of Mechanical and Automotive Engineering, Hefei University of Technology, Hefei 230009, China)

Abstract:On the slippery road surface, the alignment torque decreases evidently and the conventional control strategy of electric power steering(EPS) can not respond to this particular situation equally in time.Moreover, this status leads to poor steering-wheel returnability and false road feeling, and even results in incorrect handling. The EPS model based on a whole vehicle dynamics is established to obtain the self alignment torque on the current road based on the electric motor current and torque value measured by the torque sensor. Then the ratio of self alignment torque and nominal alignment torque are used to estimate the road friction,which is divided into three levels: high, middle and low, and a new assistant torque control strategy based on the road friction estimation and a time-varying sliding mode return control strategy are proposed. The simulation results show that the new control strategy can improve road feeling and steering-wheel returnability on the slippery road. The Labview PXI hardware-in-the-loop test platform for EPS is established, the assistant torque control strategy based on road friction and the time-varying sliding mode return control strategy are validated on the platform.The test result is consistent with the simulation result.

Key words:Electric power steering system Slippery road Control strategy Road feeling Returnability

PP. 109-114

DOI: 10.3901/JME.2011.02.115

Wheel Profile Numerical Optimization Technique

ZHANG Jian1,2JIN Xuesong1,2SUN Liping2ZHANG Jun2

(1. Traction Power State Key Laboratory, Southwest Jiaotong University, Chengdu 610031, China;2. School of Traffic & Transportation Engineering, Dalian Jiaotong University, Dalian 116028, China)

Abstract:Wheelset rolling radius difference (RRD) is taken as the design objective, a numerical optimal design model for railway vehicle wheel profile is built on the basis of the cubic spline theory. The cubic spline is used to efficiently smooth the wheel profile, and RRD determines the vehicle dynamics performance. As an example, to improve curving ability of LMA wheelset, the present model is used to improve the wheelset rolling radius difference, which mainly optimizes the flange root region of the LMA wheel profile. The rolling contact and dynamic behavior of the improved wheel profile are analyzed in detail. The results show that, in comparison with the LMA profile, though contact pressure and stress increase in the flange root region of the wheel, the improved wheel profile significantly improves the vehicle curving performance, other indices such as vehicle critical speed, performance, and safety index are basically unchanged. The optimization of LMA wheel profile reaches the expected goal. The example demonstrates the effectiveness and the feasibility of the proposed model based on the wheelset rolling radius difference control.

Key words:Wheel profile design Wheelset rolling radius difference Numerical optimization Curving behavior Vehicle dynamics

PP. 115-122

DOI: 10.3901/JME.2011.02.123

Effect of Non-circular Cylinder Bore on Oil Consumption in Cylinder of the Engine

WANG Hu SUN Jun ZHAO Xiaoyong GUI Changlin

(School of Mechanical and Automobile Engineering, Hefei University of Technology, Hefei 230009, China)

Abstract:The piston ring and cylinder of a four-stroke four-cylinder engine is taken as the research object. A study on effect of non-circular cylinder bore on oil consumption in cylinder is carried out, taking into account the non-circularity of the cylinder bore under real working condition. The oil film thickness between piston ring and non-circular cylinder is firstly calculated. Then, major oil consumption patterns are identified and characterized. A numerical model to calculate oil consumption in cylinder is proposed and demonstrated. Compared with the oil consumption in the ideal round cylinder bore, the effect of non-circular cylinder bore on oil consumption is discussed. Results indicate that non-uniform distribution of the film thickness between piston ring and cylinder along the circumferential direction is quite remarkable. Overall, compared with that between piston ring and ideal round cylinder, mean value of oil film thickness along circumferential direction between piston ring and non-circular cylinder bore is bigger. The amount of oil scrapped by top ring, thrown by inertial force or pushed by reversed gas pressure in non-circular cylinder is bigger than the corresponding one in ideal round cylinder. The oil consumption calculation considering non-circular cylinder bore is much closer to the real one.Non-circularity of the cylinder bore plays a very important role in oil consumption calculation, and should not be neglected.

Key words:Non-circular cylinder bore Oil consumption in cylinder Non-uniform distribution of oil film thickness along circumferential direction

PP. 123-129

DOI: 10.3901/JME.2011.02.130

Influence of Independent Suspension Automotive Steering Clearance and Coulomb Friction on Hopf Bifurcation Characteristic

WANG Wei1,2SONG Yuling2,3LI Guixian1

(1. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China;2. Northwest A&F University, College of Mechanical and Electric Engineering, Yangling 712100, China;3. Harbin North Special Vehicle Manufacturing Limit Corporation,Harbin 150056, China)

Abstract:Huge danger to security and stability caused by nonlinear vibration of automotive steering occurs during vehicle running, so, it’s very important to reduce the vibration and analyze the parameters acting on system. In order to analyze the issue in the round and eliminate vibration reasonably, four degrees of freedom equivalent nonlinear dynamic model of independent suspension automotive steering is established which includes some important nonlinear factors, e.g.clearance, coulomb friction of automotive steering and lateral force. Going with analyzing Hopf bifurcation of multi-DOF system self-excitation vibration concretely, influence of clearance and coulomb friction on critical speed of vehicle and limit cycle amplitude after Hopf bifurcation is discussed in detail and validated by numerical method. Another research is developed on stability of balanceable position and its stable time. The rule derived from the numerical simulation using different nonlinear conditions has instructive significance to avoiding vibration and controlling Hopf bifurcation behavior of automotive steering.

Key words:Independent suspension automotive steering Equivalent nonlinear vibration model Hopf bifurcation characteristic Coulomb friction nonlinearity

PP. 130-135

DOI: 10.3901/JME.2011.02.136

Real-time Tracking of Ride Height for Bus with Electronically Controlled Air Suspension

XU Xing1CHEN Zhaozhang1QUAN Li1LI Zhongxing2ZHOU Kongkang2

(1. School of Electrical and Information Engineering,Jiangsu University, Zhenjiang 212013, China;2. School of Automobile and Traffic Engineering,Jiangsu University, Zhenjiang 212013, China)

Abstract:To exactly track the ride height of bus and satisfy the control demand of air suspension, a height tracking circuit based on the inductance sensor is designed. The inductance of sensor and the designed tracking circuit are jointly controlled by the single chip for the inductance charge-discharge, and the single chip calculates the time constant of different inductance to indirectly obtain the real-time bus height.Temperature compensation and components of low temperature-drift property are adopted to fit the ambient temperature change of the bus.Additionally, a special filtering software is developed to track the dynamic ride height exactly and simultaneously. According to the test results, the height tracking system comes to be stable soon, and the change of ride height is about 1 mm; the relative error is about 1.9% and the max value of tracking error is less than 5 mm when the ambient temperature rises from 30 ℃ to 80 ℃. So, the designed tracking circuit can ensure the veracity of ride height control.

Key words:Bus Electronically controlled air suspension(ECAS)Ride height Tracking circuit

PP. 136-141

DOI: 10.3901/JME.2011.02.142

Numerical Investigation on Discharge Behavior and Predication Formula Establishment of Leakage Flow Rate of Honeycomb Seal

LI Zhigang LI Jun FENG Zhenping

(Institute of Turbomachinery, Xi’an Jiaotong University,Xi’an 710049, China)

Abstract:The effects of honeycomb cell on the discharge behavior of honeycomb seal and referenced labyrinth seal are numerically investigated based on the Reynolds-Averaged Navier-Stokes (RANS) equations and standard k- ε turbulent model using commercial CFD software ANSYS CFX. The leakage flow characteristics of the honeycomb seal at three cell sizes, three cell depths, six pressure ratios, constant sealing gap and rotational speed flow condition are analyzed. Numerical simulation results show that the leakage of labyrinth seal and that of honeycomb seal both increase with an increase in pressure ratio. The honeycomb seal with appropriate cell diameter and depth can improve its sealing performance at the same rotational speed, pressure ratio and sealing clearance. The leakage flow rate of honeycomb seal increase with increasing cell diameter at the fixed cell depth. At the same cell diameter, the leakage flow rate of honeycomb seal decreases firstly and then increases with the increase of cell depth. An improved prediction formula of leakage flow rate of honeycomb seal is presented on the basis of classical Egli equation of labyrinth seal through introducing effective seal fins coefficient and honeycomb cell structural coefficient. The reliability and accuracy of the presented prediction equation for honeycomb seal is demonstrated by the CFD computational results.

Key words:Honeycomb seal Discharge behavior Prediction formula Numerical simulation

PP. 142-148

DOI: 10.3901/JME.2011.02.149

Fractal Correlation Dimension Analysis on the Variation of AHU Supply-air-temperature

YANG Xuebin JIN Xinqiao DU Zhimin ZHU Yonghua

(Institute of Refrigeration and Cryogenics Engineering,Shanghai Jiaotong University, Shanghai 200240, China)

Abstract:For evaluating the performance of system by using quantitative model-based method, the fractal correlation dimension technique is proposed to take the place of conventional direct-comparison method. The supply air temperature in air handling unit (AHU) is faken as an example,the temperature variations are analyzed by using fractal correlation dimension under three loads and four disturbances. The measured temperatures are obtained from transient system (TRNSYS) simulation platform and the simulated temperatures are acquired from AHU process model. The results show that the fractal correlation dimension technique can employ only one dimension value to represent the variation characteristic for parameter curve and thus the number of compared parameter pairs is considerably reduced. The noise intervals beyond certain value often have so strong impacts on dimension calculations that data filtering should be preprocessed for these disturbed measurements until measured and simulated dimension calculations are close to each other. Also, the unprocessed minimum disturbing intervals are available for the curve variation of AHU supply air temperature.

Key words:Parameter estimation Fractal correlation dimension Noise Supply air temperature Air handling unit

PP. 149-153

DOI: 10.3901/JME.2011.02.154

Numerical Study on Heating and Viscosity Reduction of Circulating Hot Water in Hollow Rod Top Pump

SHI Weixiu LI Weiyi PAN Lisheng TAN Xifeng

(Department of Thermal Energy and Refrigeration Engineering,Tianjin University, Tianjin 300072, China)

Abstract:It is of great significance that well bore temperature and viscosity of crude oil are predicted accurately for the selection of oil production technology in the process of exploiting heavy oil.Computational fluid dynamics (CFD) numerical simulation method is used and the numerical simulation model of heating and viscosity reduction of circulating hot water in hollow rod top pump is established. The curves of oil temperature and viscosity along the tube are obtained by using numerical solution for the flow field with different circulating water inlet temperature. The viscosity reduction rate along tube is calculated and drag reduction effect is analyzed by using objective function. The results show that the temperature of crude oil reaches peakvalue at 30～35 m away from the inlet, then the temperature decrease; when the inlet temperature of circulating water are 80 ℃, 70 ℃ and 60 ℃, the viscosity reduction rate of the tube reach 97.3%, 96.7% and 94.6% respectively.

Key words:Heavy oil Computational fluid dynamics simulation Viscosity reduction

PP. 154-158

DOI: 10.3901/JME.2011.02.159

Dynamical Stress Reliability and Sensitivity Analysis of Nonlinear Rotor System with Rigid-flexible Structure

ZHANG Yimin ZHU Lisha TANG Le LU Hao

(School of Mechanical Engineering and Automation,Northeastern University, Shenyang 110004, China)

Abstract:A nonlinear rotor system with complex structure in engineering is studied and the finite element analysis software and the multi-body dynamics simulation software are used to establish and analyze the parametric dynamic model of the rigid-flexible rotor system. The dynamic simulation of the rotor system is carried out and the dynamic stress model for reliability analysis is established on the basis of artificial neural network (ANN) technique, stochastic perturbation method, reliability design and reliability-based sensitivity design theory. Thus, an efficient method is proposed to compute the reliability-based sensitivity of the non-linear rotor system with complex structure. The influence degree of the designed parameters on the reliability of rotor system is discussed, and the sensitivity of reliability to the mean value and variance of original random parameters is obtained. On condition that the units of original random parameters are different, the sensitivity is transformed into dimensionless value and each basic random variable is then sequenced by the influence degree of reliability. The proposed method provides theoretical reference for the mechanical product design, thus having realiseic significance and theoretical value.

Key words:Rotor system Non-linear Dynamics Reliability Sensitivity

PP. 159-165

DOI: 10.3901/JME.2011.02.166

Application of Deterministic Stresses Model in Simulation of Centrifugal Compressor Stage Flow Field

GAO Limin LI Xiaojun GAO Jie LIU Bo

(School of Power and Energy, Northwestern Polytechnical University,Xi’an 710072, China)

Abstract:The passage-averaged N-S equations proposed by ADAMCZYK is proved to be a more rigorous and complicated model than the mixing plane model in the flow prediction of multistage turbomachinery using steady state methods，in which the deterministic stresses represent the time-averaged effect of the flow unsteadiness. Like the RANS, the average-passage N-S equations do not contain sufficient information to determine its solution. Based on reduced passage averaged N-S equations, a semi-empirical deterministic stresses model is introduced instead of overlapping domain approach. By combining the interface approach with the deterministic stresses model, a steady simulation method is developed to predict the effect of the time-averaged unsteadiness in the centrifugal compressor stage. To verify the developed deterministic stresses model and the corresponding numerical method, two computations for two centrifugal compressors are performed: one is the solution of reduced passage-averaged N-S with the developed deterministic stresses model; the other is of the steady N-S equations with the mixing plane. Two computations cost the similar time. Compared with the mixing plane method, results with deterministic stresses model has a better agreement with the experiment due to considering the time averaged effects of the flow unsteadiness; deterministic stresses compensate the influence of the “artificial mixing” with the interface plane, and the deterministic stress model provides more realistic flow field prediction than the mixing plane model.

Key words:Passage averaged N-S equations Multistage environment Deterministic stress Centrifugal compressor

PP. 166-172

DOI: 10.3901/JME.2011.02.173

Application and Control Strategy of Servo Motor Driven Constant Pump Hydraulic System in Precision Injection Molding

PENG Yonggang WEI Wei

(College of Electrical Engineering, Zhejiang University,Hangzhou 310027, China)

Abstract:Precision and energy-saving are development tendencies of injection molding industry. In view of the high energy consumption and low response of the traditional hydraulic system for injection molding machine , a servo motor driven constant pump hydraulic system is designed for precision injection molding process, which uses servo motor,constant pump and pressure sensor instead of common motor, constant pump, pressure and flow proportion valve. This hydraulic system has the advantages of energy saving, quick response easy and accurate control.Then a pressure and speed control strategy based on fuzzy sliding mode control is proposed for accurate control of pressure and flow of hydraulic system in the injection molding process. Moreover, according to the characteristics of pressure/flow coupling in the injection molding process,a control strategy for pressure/speed switching is proposed. Test results show that this hydraulic system features quick response, high-accuracy control of pressure and speed, and good energy-saving effect.

Key words:Servo drive Precision injection Slide mode control Hydraulic system Energy-saving

PP. 173-179

DOI: 10.3901/JME.2011.02.180

µ Synthesis Robust Control of Thrust Vector Control Electric Servo Mechanism Driving Large Inertia and Low Stiffness Load

LU Hao1,2LI Yunhua1TIAN Shengli2CHEN Jiantao1

(1. School of Automation Science and Electrical Engineering,Beihang University, Beijing 100191, China;2. The 18th Institute of 1st Academe, China Aerospace Science& Technology Group Corporation,

Beijing 100076, China)

Abstract:Addressing on the uncertainty problems resulting from the parametric perturbation and the modeling error existing in the electric servo mechanism, the robust control technology for a class of electric servo mechanism used to drive the load with large inertia and low stiffness in aircrafts is researched via µ synthesis theory. For this class of electric servo mechanism, modeling according to one-DOF system will bring about big deviation. In order solving the problem, its two-DOF mathematic model is built by analyzing the dynamic characteristic of thrust vector control electric servo mechanism. Aiming at the performance requirements of controlled plant in position command tracking and torque disturbance restraint, the µ synthesis controller is designed by managing parametric perturbation and modeling error, whereas an optimization design method of weighting functions is put forward. The closed-loop system with µ synthesis controller in the normal case and the positive &negative perturbations is simulated by using MATLAB software, and its control performances are researched and compared with the performances of H∞controller. The simulation results show that for this class of servo mechanism, the µ synthesis controller can effectively improve the conservative results of H∞controller with condition of selecting the same weighting functions, and can make the closed-loop system not only have preferable performance robustness but also satisfy the requirements of dynamic performance targets for controlling system. The proposed optimization design method of weighting functions is good for the application of robust control technology in engineering field.

Key words:Large inertia and low stiffness load Electric servo mechanism Thrust vector control µ synthesis Robust control Disturbance restraint

PP. 180-188

DOI: 10.3901/JME.2011.02.189

Simulation and Experimental Investigation of Immersion Flow Field in Immersion Lithography

FU Xin ZHAO Jinyu CHEN Hui CHEN Wenyu

(The State Key Laboratory of Fluid Power Transmission and Control,Zhejiang University, Hangzhou 310027, China)

Abstract:Immersion lithography is the only actual applied technology for up to 45-mm IC production line . The high refractive index liquid filled between the last one projective lens and wafer is used to improve the optical resolution of the immersion lithography, but the photoresist leaching and liquid heating can occur during immersion exposure process. The liquid renovation must be considered in the immersion lithography because of its ability of pollution elimination and heat dispersion. A CFD model is established to study the influence of structural parameters on the updating efficiency of immersion flow field.The visual flow field test system composed of high-speed camera and data acquisition instrument is used to carry out the research of visualization of immersion flow field, and which is compared with the simulation result, thereby a set of optimized parameters of injection and recovery ports is obtained.

Key words:Immersion lithography Immersion flow field Flow visualization Updating efficiency

PP. 189-194