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Table of Content

    10 January 2008, Volume 19 Issue 1
    Simulation Research on System Dynamic Reliability Based on General Stochastic Petri Net
    Su Chun
    2008, 19(1):  1-5. 
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    The limitation of traditional reliability modeling methods was analyzed, the dynamic reliability modeling method based on general stochastic Petri net (GSPN) for complex system was proposed, the transitions were divided into instant transitions and timed transitions,the timed transitions were used to express the failure and maintenance process of elements.The inhibitor arc was used to express the changeover among failure states and restore states,a typical GSPN model of repairable system was established. Aiming to deal with the problem of non-exponential distribution and state explosion in complex repairable system, the Monte Carlo simulation was uesd to solve the GSPN model, by calculating the parameters such as the occurring times and sustained time of transitions and places, the dynamic reliability data of the elements and system are obtained. A hydraulic loop of digging machine was selected as an example, the feasibility of the method was validated.

    Time-dependent Reliability Model of System with Common Cause Failure
    Wang Zheng, Xie Liyang, Li Bing, Zhang Junyi
    2008, 19(1):  5-9. 
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    Common cause failure as an important mode of dependent failure was considered and the reliability models of systems with common cause failure were built with the stress-strength interference model in system-level directly. Based on the analysis of models proposed, the cumulative distribution functions and probability density functions of strength of systems were derived respectively. The process of random load action was described with the Poisson stochastic process and the time-dependent reliability models of series system, parallel system and k/n system were developed with the probability differential equation and total probability formula when strength degenerated as time. Taking the degeneration of strength following the exponential rule as an example, the relationships between the reliability and failure rate of system and time were studied. The result shows that the reliability of system decreases gradually as time, the reliability of k/n system is between that of series system and parallel system, and the failure rate of system has the feature of bathtub curve.

    Coupled Vibration Analysis of Wind Turbine
    Jin Xin, He Yulin, Du Jing, Liu Hua
    2008, 19(1):  9-13. 
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    The aerodynamics characteristics of wind turbine were calculated by applying GDW theory and were programmed in MATLAB/Simulink. The drive chain was calculated by applying state space method and also programmed in MATLAB/Simulink. The model of the wind turbine was built in Adams. The simulation of vibration characteristics was carried out so that the aerodynamic loads and the torque were applied to the structure of the rotor. Simultaneously the deformation of the structure also affected the loads. The results show that the method has excellent ability to simulate the vibration characteristics almost the same as test measured.

    Research on Wear Calculation Method for Friction Disc of Wet Shifting Clutch
    Wang Liyong, Ma Biao, Li Heyan, Zheng Changsong
    2008, 19(1):  14-17. 
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    Working principle of power-shift steering transmission wet shifting clutch was introduced. Based on the law of oil pressure and speed of sliding friction in the course of clutch combine and apart, the characteristic equation of clutch oil pressure and speed of sliding friction was draw up. And the mathematical model for calculating the wear of wet shifting clutch friction disc was found. According to the wear experimental results of clutch friction disc, the relationship between oil pressure influence exponent and combine time and the relationship between speed of sliding friction influence exponent and combine time were confirmed. 18000 times clutch shifting experiments was accomplished by the experimental system witch was built to test the wear of power-shift steering transmission wet shifting clutch, It is indicated that the wear of wet shifting clutch can be expressed by a function of the oil pressure and the speed of sliding friction.

    Study on Normal Tracking in NC Quick-point Grinding of Curve Parts
    Luo Yumei, Wu Qi, Hu Dejin
    2008, 19(1):  18-21. 
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    A new technology, which is called non-interference normal tracking for NC curve grinding was presented. By controlling the worktable to rotate in x-y plane, the superposition between the rotary surface of the grinding wheel and the normal vector of the curve was realized. Based on the geometric characteristic and the kinematic relationship between the wheel and the workpiece, a mathematic model was established and an algorithm for calculating the normal tracking angle was proposed. From simulations and experiments, it is shown that the normal tracking grinding can effectively overcome the problems lies in tranditional NC curve grinding.

    An Operational Condition Forecasting Model for Power Devices Based on Fractal & Support Vector Regression
    Li Yue, Wen Xisen
    2008, 19(1):  22-25. 
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    The operational condition characteristics and the forecasting requirements for power devices were analyzed. A condition forecasting model based on the fractal theory and support vector regression method was presented. As a condition feature, vibration intensity was adopted to construct a time series. Minimum embedding dimension of the phase space was calculated by using phase space restructure technique, which was used to decide the input nodes of the support vector regression model.The forecasting ability and the validity of the model were studied and validated by means of application case and contrastive experiments.The research results demonstrate that relative mean error (RME) of the forecasting model is only 1.7881% for one step forecasting and 3.3983% for thirty steps forecasting; and the model can better meet the requirements of the condition forecasting for power devices.

    Design and Simulation for a Novel Shock Wave Regulator
    Wang Gongxian, Cui Hongfei, Chu Deying, Zhang Zhiyi
    2008, 19(1):  26-30. 
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    Based on the concept of energy dissipation, a novel structure of a regulator was presented herein with thorough analyses of its working mechanism. The design comprised a set of valves connecting with a hydraulic bumper. By virtue of orifice throttling, the hydraulic bumper dissipated the kinetic energy of a moving load with high speed and decelerated it to generate the desired shock pulses. By establishing motion equations of each component and simulating the dynamic behavior of the whole system, the shock wave regulator was demonstrated numerically to be able to change the width and amplitude of shock pulses. Prompt and easy adjustment is achieved by changing the equivalent flow area of damping orifices and consequently the closing velocity of the flow area of a valve, which makes it applicable to different impact tests.

    Research on the Basin Grinding Wheel for Elliptical Groove of Constant-velocity Universal Joint
    Wang Junming, Tang Yangping, Bin Hongzan, Feng Qingxiu, Xiong Zhengpeng
    2008, 19(1):  31-34. 
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    A basin wheel for grinding the elliptical groove of constant-velocity universal joint was presented. When the design parameters were optimized, it will avoid the trouble that the validity and accuracy was restricted by the interference of the head, and will ensure the machining precision and the sectional shape of raceway to the greatest extent. The paper designed the basin grinding wheel directly under the equation for the elliptical groove by means of simulating the elliptical arc, established the mathematical model, studied the principles of processing in detail, and analyzed the machining errors. The simulation results indicate that the theoretical error for elliptical groove ground by basin wheel will be reduced to 0.7μm.

    Robust Optimization Design Based on the Compromise Decision Support Problem
    Cheng Xianfu
    2008, 19(1):  34-37. 
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    Robust optimization design is essentially multiple objectives. The compromise Decision Support Problem (DSP) was used to support design decisions in problems involving multiple objectives, it included concepts from mathematical and goal programming.The compromise DSP was introduced to robust optimization design, and mathematic model of a compromise DSP for robust optimization design was presented. Both the robustness and feasibility of constraints were satisfied and various design goals were achieved by compromising goals. To demonstrate the proposed framework, the design of the compensation of pulley block in derricking mechanism was presented. The results indicate that the proposed method effectively attains solution that is robust to variations in design.

    Design of Partial Porous Air Thrust Bearing
    Wang Jianmin, Dai Yifan, Li Shengyi
    2008, 19(1):  38-43. 
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    A nonlinear model based on the finite element method was provided to compute the static characteristics of partial porous air thrust bearing considering the tangential velocity slip at the bearing-film interface. Good agreement is achieved between theoretical and experimental results of static load capacity, mass flow and static stiffness. The modified Reynolds equation is verified to be proper to investigate the characteristics of externally pressurized partial porous air thrust bearing. The effects of slip on the steady state characteristics, such as mass rate of flow, load capacity and static stiffness were studied, when the feeding parameters of permeability coefficient, height or diameter of partial porous restrictors were changed. Then the results are presented in form of charts. Based on the analysis, the criterion of designing partial porous air thrust bearing was provided. Furthermore, the performance comparison between the thrust bearings with partial porous restrictors and porous restrictors shows that this kind of bearings have prosperous application for their good performance.

    Research and Design of Measurement and Control System for Pump and Motor
    Guo Yanwen, Huang Zhenxiang, Zhou Shu
    2008, 19(1):  43-47. 
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    A multi-sensor fusion and control system was designed ,with a dual-CPU structure based on ADμC812 and TMS320F206. The architecture, configuration, interface circuits, working principles and workflow of this system were introduced. This system was the subsystem of a testing platform for pump & motor. This system can implement those duties such as multi sensor data fusion, high-speed and high-accuracy data acquisition, real-time computation with complex algorithms for mass data and multi channel control of both of analogy signals and on-off signals, etc. The hardware structure in the system is simple. This system is validated that it can meet the experimental requirements and has good reliability and in real-time for the experiments of pump & motor performance testing.

    Cloud Data Filter Based on Morphological Operator in Photogrammetry
    Yan Long, Zhao Zhengxu, Zhou Yiqi
    2008, 19(1):  48-51. 
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    Much noise exists in cloud data due to deviation of system and matching algorithm in photogrammetry. This paper presented an algorithm for scan line cloud data filtering. It fulfiled the noise filtering, and rectified data in creep region. Experiments show that it has higher speed and better results than that of comparison algorithm. The filtered results are most applicable to curve or surface reconstruction.

    Collaborative Optimization for Mechanical Products under Multi-Agent Environment
    Tao Ye, , Huang Hongzhong, Liu Zhijie
    2008, 19(1):  52-57. 
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    Based on the principles of collaborative optimization, this paper presented an intelligent Multi-Agent model, which employed ANN to build response surface of subspace agent, and used subtask-programming agent to perform the traditional optimization processing. By the approximate satisfactory degree calculated by result analysis agent, task assignment agent was able to select different executive routes autonomously. The response surface agent acquired gradually the accurate response surface of subspace objects and constrainted in accordance with updating criterion. When subspace agent received the target vector from system level, it can use the response surface to fastly produce the optimal solution and sent it to global blackboard structure, by which system level agent coordinated the inconsistent information of different subspace agents. Finally, an engineering example was applied to prove the proposed method can improve the efficiency and accuracy of collaborative optimization for complex mechanical products.

    Semantic Integration of Distributed Manufacturing Information System Based on OWL Ontology
    Zhang Kaisheng, Sun Yanming, Zheng Shixiong
    2008, 19(1):  58-60. 
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    Different descriptive criterion of units in distributed manufacturing information system (DMIS) will cause unshared information and unrealized function. To make the system work normally, the unit ontology was presented and its properties were described in OWL (Web Ontology Language), which was recommended by W3C (World Wide Web Consortium). Then system semantic was integrated and information was shared in the DMIS. Finally, the integration of information system based on OWL ontology was instantiated by a ceramics manufacturing information system. The application of OWL to semantic integration in DMIS resolves the problems of unrealized function suffers from different descriptive criterion.

    Dynamic Optimum Design of Tower Crane Based on Neural Networks and Genetic Algorithms
    Yu Lanfeng, Wang Jinnuo
    2008, 19(1):  61-63. 
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    塔式起重机;动态优化;有限元法;正交试验法;BP神经网络;遗传算法
    Study on Manufacturing Grid Fuzzy Resource Reservation Technology Based on SLA
    Xie Xiaolan, Zhou Dejian, Li Chunquan
    2008, 19(1):  64-68. 
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    The fuzzy resource reservation technology based on SLA was proposed. On the basis of analyzing the necessity of manufacturing grid resource reservation, a basic framework for resource reservation was built, and resource reservation admission control strategy based on the fuzzy theory was carefully researched. Taking the rate of resource reservation and request admission as the decision-making indicators, and also taking the different SLA level of resources reservation fuzzy projection as decision-making basis, the paper carried out algorithm description and analysis. Finally, it was testified.

    A Study of Frequency Characteristics of Rotor System with Pedestal Looseness at Two Supports
    Zhang Jing, Wen Bangchun
    2008, 19(1):  68-71. 
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    A mathematical model with nonlinear oil film force was employed to study the pedestal looseness fault at two supports in a rotor-bearing system. By using Runge-Kutta numerical method, the motion equations were solved, and frequency characteristics of the rotor system was obtained after applying Fast Fourier Transformation(FFT) on these stable solutions. The simulation results show that when the vibration displacement is smaller than the maximum inner-space value, there are many low frequencies; when the vibration displacement is larger than the maximum inner-space value, there exist some apparent high frequencies. The simulation results will be helpful to diagnose the fault of pedestal looseness in this system.

    Humanoid Design and Movement Simulation of a New Knee Prosthesis
    Yang Yiyong, Wang Rencheng, Wang Yanli, Jin Dewen, Tian Shangyun
    2008, 19(1):  72-74. 
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    According to the functional analysis, several knee prostheses had been proposed. The structure of the knee prosthesis was determined by a multi-factor fuzzy composite judge method. Technological design was carried out, and using movement simulation,the movement range of the cycle-cylinder and the torque with squatting were established. This technological method can be used in the design of the knee prosthesis,and can be used in the design of Humanoid robot.

    Differential Motion Equations of 5R Flexible Parallel Robot
    Du Zhaocai, Yu Yueqing
    2008, 19(1):  75-79. 
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    To obtain the kinematic and dynamic characteristics of a planar 5R parallel robot with physical flexible links and distributed mass, operating at higher prescribed input speeds, a finite element-based differential motion equation was proposed. Considering the kinematic coupling between the flexible links and rigid moving platform, a modeling method suitable for the mechanism systems which contained flexible bodies and rigid bodies was modified. The transformation matrices of element variables were derived from the system kinematics property. The governing equations for the deflections of the robot members were obtained using the Lagrange equation. The set of equations was discretized using the finite element method. The equations derived herein give a more accurate model by including additional terms as Coriolis damping, centrifugal stiffness and geometric stiffness. The element equations were transformed and assembled to generate the governing differential equations for the robot. In this manner the defects brought by kinematic and dynamic constraints equations were avoided. The procedure was illustrated by a detailed analysis of a planar flexible 5R parallel robot. The model can be used for Kineto-Elastodynamics analysis and optimal design. The flexibility of links is demonstrated to have significant impact on the performance and stability of the flexible robots.

    A MEMS CAD Methodology from 3D Model to 2D Mask Layout
    Xu Jinghui, Yuan Weizheng, Xie Jianbing, Chang Honglong
    2008, 19(1):  80-84. 
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    A transfer methodology from 3D model to 2D mask layout in MEMS CAD field was put forward after studied respectively the format of the standard 3D model file and the 2D mask layout file. The direct file-to-file’s transfer procedure from 3D model to 2D mask layout was realized, and the corresponding interface has been developed in C++ programming language. Finally, the feasibility and the efficiency was validated by the structures of typical MEMS devices-micro accelerator and micro gyroscope, the result shows that the methodology is feasible and highly efficient, which provides a efficient approach for realizing MEMS top-down and discretional flow design, simplifying the process of drawing the mask layout.

    Rough Set-genetic Algorithm-neural Network Compositive Classifier and Its Application in Rotor Faults Diagnosis
    Chen Guo
    2008, 19(1):  85-90. 
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    The fault diagnosis problem of rotor system was aimed at, on the basis of synthesizing the advantages of Rough Set (RS) theory, Genetic Algorithm (GA) and Neural Network (NN), a new RS-GA-NN compositive classifier was put forward. In the model, the RS was used to carry out selection of sample features; the NN was used to realize the mapping between features and fault type of sample; the GA was used to optimize the structure of NN model in order to make it to reach the best generalization.The rotor fault experimental rig was used to simulate unbalance, misalignment, rubbing and oil whirling faults, and 127 faults samples are obtained. Finally, the RS-GA-NN compositive classifier of multi-faults recognition was established, and the intelligent fault diagnosis experiment was finished, and a very satisfied result is obtained.

    Research on Ultrasonic Vibration Multi-dielectrics Electrical Discharge Milling Machine Tool
    Su Shupeng, Zhang Qinhe, Zhang Jianhua, Huo Mengyou, Ai Xing
    2008, 19(1):  90-94. 
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    Through the analysis of unique machining characteristics of electrical discharge milling(ED-Milling) in distinctive dielectrics with the aid of ultrasonic vibration, the requirements for machine tool were brought forward. On the basis of these requirements, the overall architecture of the new-type EDM machine tool was designed herein. The main machine body, CNC hardware system and CNC software system were described in detail. The initial experiments show that the machine tool works well and has satisfied to the requirements of the new-type EDM process.

    Research on Automatic Gauge Control Model of Strip Mills
    Zhang Wei, Wang Yiqun, Sun Menghui
    2008, 19(1):  95-98. 
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    Theoretical analysis of strip mills AGC had been processed and a three-DOF mathematical model of hydraulic screw-down system had been built, which was specified cylinder displacement and inner gap and adapt to varied control way. Three typical AGC model, e.g. GM (Gauge Meter) control model, MGM (Modification Gauge Meter )control model,DS(Dynamic Setting )control model were researched contrastively, and pointed out two important parameters: rolling mills rigidity factor and strips plastic coefficient, which were corresponded to static criterion and dynamic criterion of a system individually. Theoretical factor was provided for selecting parameter in control process. Compared with traditional P-h chart, this method reflects essence of thickness control process profoundly.

    Simulation on the Stress Field of Plate with Circular Hole at Hole-edge and Aperture by Different Loads
    Li Cheng, Zheng Yanping, Tie Ying
    2008, 19(1):  99-102. 
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    A calculation model was developed upon the elastic theory and the complex function theory. According to the calculation model, both of the stress field and that of the area near the hole edge can be analyzed. Some instructive conclusions were drawn. Comparisons were made on the stress components,and comparisons on the stress field were made when the distance away from the aperture changed. The influences of different loads and different distance away from the hole-edge on the stress field were explored.

    An Automatic Determination and Optimal Algorithm of Mold Parting Direction
    Wang Huifeng, Zhou Xionghui
    2008, 19(1):  103-107. 
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    An automatic algorithm for determining the optimal mold parting direction was proposed. Features were recognized from the part firstly and treated as the investigation subjects in the following. Operations among the visibility analysis of features were implemented to get the candidate parting directions, then the determination principles of parting direction were introduced and the main parting direction was gained. This algorithm can determine the optimal parting direction and gain the information about the undercuts synchronously. Automated mold parting direction determination system was developed on UG flatform using C++ language and the efficiency and precision of this segment in mold design are improved. It supplies the solid foundation for the following mold design.

    Electromagnetically Assisted Sheet Metal Stamping of Aluminum Alloy
    Li Chunfeng, Yu Haiping, Liu Dahai
    2008, 19(1):  108-113. 
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    The formability of aluminum alloy at room temperature is very low, which can be improved significantly by high velocity forming process. The new sheet metal forming technology needs to develop to facilitate the use of aluminum alloy in automotive, aerospace and 3G manufacture. In the electromagnetically assisted sheet metal forming (EMAS), by embedding electromagnetic coils in conventional forming tools, improving and controlling of the strain distribution of parts are enabled. The state-of-the-art of EMAS was introduced and focused, and the importance to study the technology was presented.

    Study and Development of Mobile Robot’s Control Framework
    Li Wenfeng, Zhang Fan, Yan Xinqing, Yang Xiaozhu, Du Juan, Han Rui
    2008, 19(1):  114-119. 
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    Based on the discussion of features and applications of mobile robots, a survey of their researches was made from the viewpoint of the technologies of their control framework and autonomy. Then control modes and popular systems of mobile robots were discussed and the relative advantages and disadvantages were summarized. The characteristics of the control frameworks of mobile robots were concluded and a few of existing control frameworks were analyzed. According to the development of sensor networks, the combination and cooperation of mobile robots and sensor networks was predicted and the challenges that control frameworks of mobile robots must face to work with sensor networks were pointed out, and a new and reasonable one was put forward at the end.

    New Progresses of Error Analysis Modeling and Calibration of Parallel Kinematic Machine
    Shen Huiping, Zhang Huifang, Xing Xiumei
    2008, 19(1):  120-125. 
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    The latest achievements and development of Parallel Kinematic Machine (PKM ) in error analysis modeling and calibration in Germany were overviewed, including the statistical approach , redundant measurement method, minimal linear combination method, neural network error identification method, the fixed point method and the total self-calibration approach and some new measurement devices or elements. Up till now, there were about 40 PKM models or prototypes in the world which had found practical use successfully in the Europe countries in die making, aerospace, automobile and modeling industry. There were always some errors between ideal parameters and practical ones because of the manufacturing and assembling errors. Manufacturing precision was an important index of the PKM performance, which was the basis to obtain effective workspace and better position precision as well as dynamic performance. Therefore, error-reducing and calibration are the key technical measures, which is necessary for successful applications of PKMs.