Table of Content

26 June 2014, Volume 25 Issue 12

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Dynamics Equation of Cracked Beam Based on Finite Element Displacement Mode

Li Zhaojun, Long Hui, Liu Yang, Qiu Min

2014, 25(12):  1563-1566. 

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Considering the influences of a cracks on the stiffness of cracked beam, the formula of strain energy of a cracked beam was introduced based on the theory of fracture mechanics, which showed that the strain energy of cracked beam will be released due to crack propagation. According to the characteristics of beam material, the dynamics model of cracked beam element was established by the finite element displacement method. Based on the dynamics model of cracked beam element, a dynamics equation of the beam structure with cracks was obtained. The results show that the dynamics equation discovers the actual relation among the macro dynamic characteristics of beam structure with cracks and the structural parameters and cracked parameters; and that the position and length of crack have effects on the dynamic properties of beam structure with cracks. Finally, an example was presented to verify the theoretical results.

Multi-assembly Line Robust Scheduling of Double Resource Constrains under Uncertain Orders

Chen Yong, Wu Yunxiang, Wang Yaliang, Lu Jiansha

2014, 25(12):  1567-1573. 

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Considering the uncertainty of orders and some other factors in the production process, a robust scheduling model was established to maximize customer satisfaction, maximize utilization of the assembly line and minimize completion time span. Combined the differential evolution algorithm and particle swarm optimization characteristics, a hybrid optimization algorithm was proposed based on differential evolution algorithm and particle swarm algorithm, using the hybrid optimization algorithm to simulate and solve the robust scheduling model created, and the feasibility and effectiveness of using hybrid optimization algorithm were proved to solve the robust scheduling model by numerical examples. At last, comprehensively the actual production situation of the multi-assembly line production workshop of Plant Two of PTCN company was analyzed. Applying the established robust scheduling model and the proposed hybrid optimization algorithm in actual multi-assembly line production process excellent scheduling results are achieved.

Topology Configuration Optimization for a Modular Robot

Gao Wenbin, Wang Hongguang, Jiang Yong, Pan Xin'an,

2014, 25(12):  1574-1580. 

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A study of task-oriented topology configuration optimization for a joint type modular robot system was carried out based on genetic algorithm. The topology configuration information such as the module types, parameters, quantity, assembling sequence and orientations of any given manipulator were represented by binary coding. Design requirements were divided into hard ones, soft ones and hard+soft ones according to their properties. The topology structure which did not  meet the “hard” requirements would be processed by filters to improve the computational efficiency. Meanwhile, the others were evaluated and the configuration evaluation function was constructed based on the weighted sum of the evaluation results. Taking the minimized degree-of-freedom as the main optimization objective, a topology architecture optimization design method was given based on the combination of traversal method and genetic algorithm. The effectiveness of the method was verified through an architecture optimization experiment.

Robot Impedance Control Method Adapting to Unknown or Changing Environment Stiffness and Damping Parameters

Li Zhengyi, Cao Huimin

2014, 25(12):  1581-1585. 

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The robot impedance control performance decreases with the efffects of changing or unknown environment stiffness and damping parameters in practical applications,this paper presented a self-adaptive robot impedance control method to resolve this problem. Based on the definition of the robot impedance control performance index and the geometric representation for the impedance model stiffness variation, the calculation method was illustrated for intitial values of the the impedance model stiffness. Designing an artificial neural network to estimate the environmental equivalent stiffness online and combining with critical damping condition of the second-order system, a calculation method was provided for the impedance model damping initial values. The results of robot force control experiments demonstrate  smoother reference trajectory, improved robot force control stability and feasibility in practices compared to the existing robot impedance control methods.

Relationship between Round Link Chain Deformation and Worn Sprocket

Wang Shuping, Yang Zhaojian, Wang Xuewen

2014, 25(12):  1586-1590. 

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To calculate the deformation of the arc segment for round link chains, a finite element model was established, the elastic deformation of arc segment in different load was analyzed. The numerical calculation results show that, the arc segment of round link chain was deformed as ellipsis shape under the tensile load, and the difference between longer axis and shorter axis is bigger with higher load. When the tensile load is close to the elastic maximum, concave arc appeares in the middle of the ellipsis. Scanning the sprocket surface with flexible 3D coordinatograph and analysing the detected dots, results show that sprocket surface wear on the direction of directrix is even, and wear on the direction of generatrix has a relationship with the deformation of round link chain. The wear curve of the detected sprocket on the direction of generatrix is close to the deformation of the outer-side for round link chain with 21.4% elastic maximum load. So elliptical chain, shorter axis of which is aligned with the tensile force, may be a better chain to lower the wear of sprocket surface.

Design and Test of a Kind of SMA Torsional Actuator

Wu Jiajun, Wang Bangfeng, Lu Jiyun, Zhang Yong

2014, 25(12):  1591-1594,1599. 

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One kind of plane turbination torque output actuator based on Ni-Ti SMA was introduced herein. This device could achieve forward and reverse torque output corresponding to the high and low temperature state with the interaction of the single trip memory effect of NiTi alloy and the recovery spring. First the basic structure and action principle were declared and the design approach and its basic preparation technology of SMA acting part were discussed. Then the principle prototype was designed and manufactured. The input-output characteristic test was processed. Testing results show that, the device could continuously and stably output torques under the condition of temperature state from 10~60℃. The maximum stroke range is as 0~175°, and the maximum torque is 0.33N·m. The results verify the feasibility of the design and preparation process of this device.

Frequency Veering Properties for Variable Rotating Blades under Thermal Load

Qin Jie, Qi Piqian

2014, 25(12):  1595-1599. 

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Based on sheet bending theory, the dynamic characteristics of a cantilever sheet were studied by the beam function combination method. Considering the centrifugal force, the obtained analytical solutions of frequency and mode shape  might be applied to cantilever sheet. The theoretical foundation of the frequency and mode shape research on cantilever sheet were obtained. A new method of investigation of frequencies veering was presented. The obtained frequency and mode shape solutions are rather practical for the blade fatigue detection.

S form Specimen Cutting Dynamic Performance Testing and Its Key Technologies

Qiu Jian

2014, 25(12):  1600-1604,1629. 

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A systematic analysis was carried out on the advantages and disadvantages of current testing specimens at home and  abroad for five-axis NC machine tools. Combining 3D modelling, theoretical calculations, finite element analysis and cutting experiments, the key technical challenges such as the structural characteristics and surface distribution of S form specimen, structural rigidity and stress and deformation were analyzed, respectively. It is found that there is a clear curvature difference in different locations on the 'S'  form specimen surface. Part-surface exists reversing and alternating across the machine coordinate quadrant. And there are 4 main regions where the structure stiffness of 'S' specimens jumps over the suddenly in single side processing, which leads to cutting deformation, vibration and loss of accuracy  directly. Finally, two stages of rough and finish cutting process were analyzed.

Structure Design and Analysis of Flex-lay System

Liang Xuexian, Zhang Zhonglin, Li Bing, Wang Yanxin, Yang Fen, Wang Liquan, Xi H

2014, 25(12):  1605-1608,1693. 

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Through the research of correlative flex pipe-laying technology at home and abroad, one kind design scheme of flex-lay system was put forward herein. Three-dimensional structure model of the system was established with Pro/E. By using the finite element method, the key parts strengths were checked. Dynamic simulation of the laying of the tower adjoining angle device was put up. Theoretical analysis and checking results indicate that the system can meet flex pipelines laying design and strength requirements.

Pumping Unit Fault Diagnosis Based on Quantum Shuffled Frog Leaping Algorithm and Process Neural Networks

Zhang Qiang, Xu Shaohua, Li Panchi

2014, 25(12):  1609-1615. 

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A quantum shuffled frog leaping algorithm(QSFLA)  was presented herein. In this algorithm, the individuals were expressed with Bloch spherical coordinates of qubits, the evolution search was realized with the rotation of qubits in Bloch sphere. The mutation of individuals was achieved with Hadamard gates to avoid premature convergence. Above operations enhanced the ergodicity of the solution space and approximate global optimal solution fast. The network structure, network parameters and expand the number of items of PNN were encoded uniformly, and were optimized by the QSFLA. The optimizated neural network was used in pumping unit fault diagnosis. The diagnostic results between the new QSFLA and BP algorithm were compared. The conclusion is that the PNN based on QSFLA has better training performance, faster convergence rate and higher accuracy.

Improved Method of EMD and Its Applications Based on Boundary Characteristic Scale Matching Extension Method

Shi Peiming, Jiang Jinshui, Liu Bin, Wang Jun

2014, 25(12):  1616-1623. 

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For the end effects of EMD, an improved extension method was proposed based on boundary local features. By calculating the mathcing errors between the boundary wave and any internal signal wave, the regularity strength of signal was determined. In the case that the inherent regularity was strong, the internal wave form matching extension was conducted to maintain the inherent tendency to the greatest extent. While the signal was weak regularity and the signal edge was changed abnormally, the local information at the edges was considered only to conduct the extreme point extension. Thus the extreme points were used to fit envelope curve to realize extension. This method ensures that the decomposition of valid data is correct, and improves the decomposition accuracy. Simulation results show that the method can suppress end effect of EMD method.

Selective Method of Accelerated Stresses in Accelerated Reliability Growth Test for Machining Centers

Zhang Genbao, Guo Shuheng, Liu Jian

2014, 25(12):  1623-1629. 

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Based on the definition of failure characteristic attribute, the attribute collection was used to represent the failure. The fuzzy relation between system failures and failure stresses could be established according to the fuzzy theory. On the basis of the expert knowledge, the fuzzy relation matrix could be calculated by binary sorting. The failure attribute weight and system failure weight could be calculated by using the fuzzy consistent matrix. According to the fuzzy transformation theory, the fuzzy comprehensive evaluation of the failure stress alternative set could be achieved, and the problem of the selection of the accelerated stresses in a accelerated reliability growth test could be solved. With the analysis of how the end-toothed disc dividing type NC rotary works, this paper gained the results of the fuzzy comprehensive evaluation of the system failure stress and picked up the best accelerated stress combination. In addition, this paper also testified the availability of this method by comparing with the traditional methods.

Bridge Crane Energy-saving Evaluation Based on Fuzzy Optimization Model

Ye Wei, Tong Yifei, Li Xiangdong

2014, 25(12):  1630-1633,1638. 

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Based on energy consumption of a bridge crane in “full life cycle”,this paper put forward bridge cranes energy saving evaluation index system. Rough set theory knowledge was adopted to reduce the index of the bridge crane energy saving evaluation index system. The optimized bridge crane energy saving index system could be obtained after reduction and all index weights were acquired as well. Finally the fuzzy optimization theory was applied to build energy-efficient evaluation model of the bridge crane and this model was used to evaluate the energy consumption of the overhead crane. This paper selected  five bridge cranes of different designs and materials and analyzed  their advantages as well as disadvantages of power consumption. Via calculation and analyses, the optimal design of energy saving of bridge can be obtained and it may provide a reference for the bridge crane design and manufacturing.

Path Planning and Motion Control of an Automatic MFL Inspector for Tank Floors

Song Xiaochun, Chen Yu, Xu Zhengwang, Wu Ying

2014, 25(12):  1634-1638. 

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In order to overcome such disadvantages as the low-level automation, high labor intensity and low efficiency for the current tank floor testing system,an automatic MFL inspector for tank floors was developed. And the inspector composition and function modules were introduced, the automatic positioning principle of testing trolley was analyzed based on binocular laser ranging. According to the structural characteristics of tank floors and the technical features of MFL inspection, the planned motion path for floor inspection were presented, and the differential direction control algorithm and the velocity control algorithm based on incremental PID controller were studied. Experimental results indicate that the automatic MFL inspector has good performance of trajectory tracking, and can scan the floor well with setting control parameters along the planned path, and the maximum time of deviation angle rectification is about 1.7s.

Information Transformation between CAD and XNA Based on XML

Xing Yingjie, Li Jiangnan, Huang Xuewen

2014, 25(12):  1639-1644. 

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To realize the information transformation between CAD and XNA virtual environment, an information transformation method of the model was proposed. Firstly, a hierarchical assembly information model for virtual assembly was constructed, which consisted of six hierarchy layers, including product layer, assembly layer, part layer, feature layer, geometry layer, triangle facet layer. Secondly, based on the information separation method, the model information was divided into geometry information, assembly information, facet information and other information, and the assembly information was extracted by Pro/ToolKit secondary development tool, then with the transformation of model facet information, the information transformation between the CAD and XNA was solved. Finally, a virtual assembly platform in the XNA was developed by programming, and a real assembly example was held to verify this method.

Roundness Evaluation Method Based on Error Transformation and Image Domain

Zhang Xuechang, Liang Tao, Tang Yanmei

2014, 25(12):  1645-1650. 

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For solving the problems of roundness error assessment methods with profound theory, complex computation, low detection efficiency and inapplicable to sample points with large capacity in engineering application, a new method was proposed based on error transformation and image domain. The method transformed the roundness errors from the field measurements to the image domain and made it meet the requirements of error estimation. The method took the least square circle as the initiative round to seek the  “minimumin maximum” of its radius or radius difference. And then through small scale translation of the least square circle and getting the translation planning coordinate by genetic algorithm, the ideal circle after translation and roundness error value were obtained. Experimental results of a certain type of part show that the roundness error can be evaluated effectively and exactly by using this method because it is very close to the results measured by coordinate measuring machine.

Modal Strain Energy Method for Damage Detection of an Elastic Beam

Liu Wenguang, Li Jun, Yan Chen, He Honglin

2014, 25(12):  1651-1654. 

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Based on the problems of vibration fatigue damage in an elastic beam which was widely used in aircrafts, a novel method was proposed for structural damage detection via change of the unit modal strain energy. A principle was employed that the modal properties will be changing as the structure was damaged. An indicator was built through comparing the modal strain energy before and after an elastic beam was injured. Firstly, an elastic beam's stiffness was regarded that it was built by unit stiffness, and a formula was defined for unit stiffness sensitivity. Thereafter, the contact between elastic beams before and after damaged was built by modal strain energy. Results are given after simulation and experiments, the accuracy and efficiency of this method were verified.

Precise Scale Invariant Feature Matching and Its Application

Hua Chunjian, Chen Ying

2014, 25(12):  1655-1659. 

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In object detection and localization system based on local feature matching,the number of match and false match effects directly on localization accuracy. An improved SIFT matching algorithm was proposed to decrease false match and meanwhile kept the sufficient correct match number. After analyzing different match result with different match threshold in conventional SIFT feature match method, an iterative strategy for adaptive dual-threshold for image match was presented. Then a geometry constrained model based on sparse but accurate match achieved with high threshold was establish to eliminate false match in dense match set achieved with low threshold. Experimental results show that compared with other methods, the proposed method has higher match accuracy which improves the performance of object detection and localization.

Fault Feature Selection Method for Axial Piston Pump Based on Quantum Genetic Algorithm

Li Sheng, Zhang Peilin, Li Bing, Wang Guode

2014, 25(12):  1659-1644. 

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In order to reduce feature dimension, shorten calculation time and improve classification accuracy, a fault feature selection method for axial piston pump was proposed based on quantum genetic algorithm. In this method, chromosomes were coded by quantum bits, and population was updated with quantum gate. Firstly, the vibration signals of axial piston pump were decomposed by wavelet transform, and the statistic features were extracted from original signals and each wavelet coefficient. Then, the optimal feature set was selected form original feature set by QGA. Finally, by using neural network as classifier, the optimal feature set was used as input for fault diagnosis. This proposed method was used for distinguishing different operating states of axial piston pump. The experimental results show, compared with common genetic algorithm, QGA can reduce feature dimension more effectively and improve classification accuracy greatly.

Optimization of Contact Line for Form-grinding Modified Helical Gears Based on Neural Network

Wang Zhonghou, Zhu Wenmin, Li Gang, Geng Zhi

2014, 25(12):  1665-1671. 

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Since the contact line equation is a transcendental equation, the relationship between the installation angle and the shape could not be expressed by explicit functions, which made it difficult to obtain the optimal shape, this paper firstly took three evaluation parameters of the shape, overrun, shift and offset as the objective function as  well as the installation angle as variables then the contact line optimization model was establish. Secondly, a neural network was introduced to solve the evaluation parameters. Through training the neural network by setting the installation angle as the input, the evaluation parameters as the output, the results show that the trained neural network can respond correctly, and has the advantages which the other methods do not obtain. As an example of end relief modified helical gear, the results show that the method can reduce the grinding errors effectively. Finally, the grinding experiments  proven the effectiveness of the method.

Forming Experiments on Precision Bending of Sheet Metal Using Plasma Arc

Wang Maolu, Yang Lijun, Wang Yang

2014, 25(12):  1672-1675. 

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In order to achieve precision bending of sheet metal using the plasma arc, forming experiments were carried on the sheet metal of 1Cr18Ni9Ti. The CMOS1303uc digital cameras and related software were used to detect the bending angle, and a closed-loop control of the forming process was established according to the detection. The experimental results show that: when the scanning number is small, the plate bending angle will be linearly increased with the increase of the scanning number. When the scanning number becomes more and more, due to thickening effect, this scanning increment of bending angle will be  decreased continuely, and the bending effectiveness reduced significantly. In order to ensure the reliability of the machining process and improve the forming efficiency, the forming process was divided into three stages according to the forming margin, and different process parameters were determined in different stages. The effective of the method was verified by the forming of bending angles 20° and 30° respectively for  stainless steel sheet.

Effect of Processing Route on Deformation Behavior of Pure Al Powder Consolidation during Multi-pass ECAPT

Wang Xiaoxi, Xue Kemin, Li Ping

2014, 25(12):  1676-1680. 

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Considering the real deformation process, numerical simulation of pure Al powder consolidation during multi-pass  ECAPT under different routes was carried out by using DEFORM-3D program. By comparing and analyzing the simulation results, it is indicated that route A and C are two optimal ECAPT routes, which possesse many advantages over route BA and BC in terms of increasing strain accumulation, promoting powder consolidation and improving deformation homogeneity. In addition, the experimental results of electron Backscattered diffraction(EBSD) show that bulk ultrafine grained Al with average grain size of around 0.8μm and excellent compressive strength of 123.3MPa can be produced under route A after four passes of ECAPT process, which has good consistency with numerical simulation results and confirmed the reliability of established finite element model.

Effects of Unsteady Stream on Transient Characteristics of Automotive Aerodynamic Lift

Yang Yi, Xu Yongkang, Nie Yun, Fan Guanghui, Wu Yihua

2014, 25(12):  1681-1686. 

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An approach of combining the large eddy simulation and wind tunnel experiment was employed to study the variation of transient characteristics of automotive aerodynamic lift under the unsteady stream.The effects of velocity perturbation frequencies on aerodynamic lift were analyzed and the physical mechanism contributing to the variation on the aerodynamic characteristics was discussed. Simulation results show that velocity perturbation frequencies have a great impact on lift coefficient.Specifically, in terms of short period oscillating stream, lift coefficient changes in accordance with sinusoidal curve. With respect to the long period oscillating stream, however, lift coefficient firstly increases and then decreases. Finally, it tends to stable oscillation. The primary analysis shows that trail flow field structure largely affects the magnitude and direction of the aerodynamic lift. Additionally, the change of velocity perturbation leads to the change of pressure difference between upper and lower of the body, thereby giving rise to the change of aerodynamic lift.

Reliability Analysis of Continuously Variable Transmission Clamping Force Control Algorithm

Hao Yunzhi, Sun Dongye, Lin Yupei,

2014, 25(12):  1687-1693. 

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From three respects including clamping force computing method, control algorithm development and clamping force reliability validation, several key points of CVT clamping force control process were studied. The obscure concepts of absolute safety factor and relative safety factor were explained. Normal relative safety factor method could not ensure the safety of clamping force. Inertia torque and computing process were analyzed to determine the influence factors of primary pulley torque computing error. The right computing method and process of clamping force target value were presented. Coupling effects between clamping force control and ratio control were studied by experiments. To avoid metal-belt slipping, ratio shift rate had to be limited while the vehicle was in low speed and heavy duty. The most likely condition leading to metal-belt slipping was analyzed. To validate the reliability of control methods, vehicle running process from ice surface to cement road was simulated.

Frame's Nonlinear Reliability Optimization Based on Interval Uncertainty

Li Weiping, Wang Zhenxing, Zhang Baozhen, Dou Xiandong, Liu Chao

2014, 25(12):  1694-1699. 

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Nonlinear finite element analysis method was used herein, and using ABAQUS software to analyze the stiffness and strength of the frame. Based on the results of the finite element model, the thicknesses of some beams which were more effects on the structural strength and the mass were chosen as the interval of design variables. The frame material density and Poisson's ratio were taken as uncertain variables. Building an approximate model between the design variables and stress by using TPS-HDMR, the Kriging model was utilized to build an approximate model among the design variables and mass. NSGA-Ⅱ and IP-GA was used to carry two objective optimization, at the same time a reliability index was introduced as the constraint, and then the Pareto optimal solution set was obtained.

Development and Testing of Test Bench for Transmission Efficiency of Automobile Drive Axle

Zhang Deping, Mo Yimin, Zhao Muqing

2014, 25(12):  1699-1703. 

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A test bench was developed for transmission efficiency testing. With this test bench, the key factors that had impacts on the transmission efficiency of automobile drive axle could be found, the influence regularity of these factors on the transmission efficiency could be determined, and finally, an effective method to improve transmission efficiency was proposed, which had very important significance to improve the dynamic performance and fuel economy of automobile. Adopting the modularization design, the test bench has the advantages of quick installation, convenient operation and high automation degree. The torque and speed controls of the test bench were achieved through direct torque control, dynamic loading was realized through harmonic drive and planetary transmission, and system energy feedback was  brought to a reality through DC bus technology. The practice indicates that the control precision of the test bench has achieved the anticipated target.