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Table of Content

    25 February 2014, Volume 25 Issue 4
    Method for De-nosing Based on Optimal Threshold of EMD Optimized by Ant Colony Algorithm
    Zhang Genbao, Fan Xiujun
    2014, 25(4):  427-432. 
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    To further enhance the de-noising performance of EMD algorithm, this paper proposed a de-noising method based on adaptive threshold of EMD referred to the method of threshold-based wavelet de-noising. First, the relationship between the mean square error(MSE) and the threshold function were established, then the optimal threshold of each intrinsic mode function(IMF) level were searched and obtained by the ant colony algorithm which realized to get the minimum MSE. So this method eliminates the disadvantages of soft and hard threshold de-noising method effectively. The experimental results indicate that the method is more effective in noise reduction in comparison with the conventional soft and hard threshold-based EMD de-noising methods, the method works better.

    Locomotion and Adhesion Mechanisms of Gecko Climbing Vertically on Different Material Surfaces
    Ji Aihong, Gu Wei, Wang Zhongyuan, Ni Yong, Wang Zhouyi, Dai Zhendong
    2014, 25(4):  432-438. 
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    By using an animal locomotion behavior and 3D reaction force measurement system, gekko gecko's locomotion behavior and ground reaction forces on vertical glass, acrylic and aluminium substrate were acquired, respectively. Then the relationships among adhesive and kinematic performance of gecko and substrates' surface properties were analyzed. The results show that geckos employ trot gait when climbing upward on vertical glass, acrylic and aluminium substrates but hardly adhere and climb on stainless steel. Among these substrate locomotion and adhesion ability of gecko decrease one by one and gecko decrease the ground reaction forces either. On glass substrate motion velocity is more than doubled on aluminium substrate. Animal increases its velocity greatly by increasing stride frequency. But on substrate of weakly adhesion geckos try to decrease motion speed, ampify the duty factor and extend adhering time to keep stability and safty. Animal's fore-aft force can counterweight its bodyweight and push body upward, the lateral and normal forces make the body stably adhere on the vertical substrate. It is confirmed that the performace of gecko climbing and adhering vertically varies with surface energy of substrates.

    Tool Axis Control Method Based on Machine Rotation Angle for Impeller Tunnel Milling
    Han Feiyan, Zhang Dinghua, Dang Chuangfeng
    2014, 25(4):  439-443,450. 
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    To mill an impeller channel with different shape blades using nonorthogonal 4-axis machine, a tool axis control method based on linear interpolation of machine corner was proposed. Firstly, according to post-processing relationship of nonorthogonal 4-axis machine, the mathematical mapping of the machine rotation angle and the machine translation coordinates was established. After post-processing the clean-up CL data, a linear interpolation method was adopted to calculate the machine rotation angle of the whole impeller channel. And through the interference checking and correction, the interference-free machine rotation angle was obtained. Then the machine coordinates was solved by the
    mathematical mapping. Finally, simulation results show that the method can maintain the geometric information of CL data and mill the impeller channel precisely.

    Security Control for CAD Models in Collaborative Design
    Ye Jianhua, Gao Chenghui, Jiang Jibin
    2014, 25(4):  444-450. 
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    A multi-level and fine-grained access control method was presented herein for CAD models to meet the complexity of collaborative design environments and particularity of collaborative design process. This method realized life cycle protection for CAD models.Based on role-based access control(RBAC) and multi-level models, a multi-level security access control was developed to provide fine-grained access control. Multi-resolution models were created based on feature removal, tessellations and mesh simplification. Different resolution models included  different levels of detail to those who have appropriate access privileges, so the sensitive information can be protected. The key issues of control client software features were discussed, and they were insurance against information leak out. Transparent encryption technique was present to lift cycle protect the models in collaborative environment. A prototype system was developed and the results were reported. Based on practices, these methods can protection the information of CAD models effectively during collaborative design.

    Parameter Optimization on Precision Grinding of Ceramic Sphere Using Orthogonal Experiment and Genetic Neural Network
    Liu Wei, Deng Zhaohui, Wan Linlin, Wu Qiaoping
    2014, 25(4):  451-455. 
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    According to the requirements and characteristics of ceramics difficult-to-machine materials' precision processing, and traditional processing mode about spherical grinding, the grinding wheel normal tracking was analyzed for the silicon nitride material's spherical profile workpiece of precision grinding. The orthogonal test method was applied for the design of experiment, and the range method and variance method were used to analyse the influence of related grinding parameters on the machining quality and efficiency comprehensively. Considering the difficulties of current grinding scheme's selection and optimization, a nonlinear mapping relationship was established between the machining quality and efficiency and related grinding parameters, with the use of genetic neural network algorithm. Based on the analyses of the orthogonal test method, the genetic neural network algorithm was improved. With the genetic neural network algorithm, the related grinding parameter optimization was realized, thus to shorten the process formulation and operation time of silicon nitride ceramic material's spherical profile workpiece CNC grinding, and to improve grinding quality and efficiency.

    Optimization of Temperature Measuring Points for Machine Tools Based on Grey Correlation and Fuzzy Clustering Analysis
    Zhang Wei, Ye Wenhua
    2014, 25(4):  456-460. 
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    A method combining grey correlation analysis and fuzzy clustering analysis was used to optimize the temperature measuring points of thermal error compensation for machine tools. Grey correlation coefficient between thermal errors and the temperature measuring points was computed by grey correlation analysis. The selected temperature measuring points optimized by grey correlation coefficient were classified by fuzzy clustering analysis to determine the key temperature variables. Linear regression model of thermal error was established with the key temperature variables. The method was tested in precision horizontal machining center MCH63. The results show that the number of temperature measuring points reduces from 29 to 6, the axial thermal error reduces from 41.3μm to 7.6μm.

    Static Analysis Method and Application Research of Line Array Deployable Structures Based on SLE
    Liu Guolin, Wang Sanmin, Shang Peng
    2014, 25(4):  461-466. 
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    A new method was proposed to carry out deployable structure static analysis, which overcome the FEM disadvantages that computation was of large amount and time-consuming. Firstly, the paper established the stiffness matrix of the SLE, which was assembled to obtain the global stiffness matrix and the equilibrium equations. Secondly, the global stiffness matrix was transformed equally to be a circulant matrix and the equilibrium equations were expressed in the form of discrete convolution. Lastly, a new method was applied to solve the equilibrium equations, which could be extended to any other kind of deployable structures, and the displacements and constraint forces on each joint were obtained, which increases the computational efficiency significantly.

    Study on a New Structure of Main Valve Sleeve Through-hole for Proportional Throttle Cartridge
    Yao Jing, Yu Bin, Li Yaxing, Kong Xiangdong,
    2014, 25(4):  466-470. 
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    Based on traditional round through-hole structure of main valve sleeve of cartridge proportional throttle, an optimized kidney-shaped through-hole structure was proposed herein. The computational fluid dynamics(CFD) technology was used to analyze flow characteristics of these through-hole forms mentioned above and the force of main valve spool. Then, visualization experimental study which was based on the similarity theory was completed. The research results show that compared to traditional round through-hole structure,kidney-shaped through-hole structure can increase flow capacity and improve radial unbalanced force of the main spool. This research can provide theory basis for structure optimization design of cartridge proportional throttle.

    Dynamics Modeling and Simulation of FROG-LEG Vacuum Manipulator
    Huang Yuchuan, Qu Daokui, Xu Fang,
    2014, 25(4):  471-475,490. 
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    According to characteristic structure of a FROG-LEG vacuum manipulator, this paper presented the kinematics model of the vacuum manipulator's equivalent series structure, then solved the forward and inverse kinematics. After that the dynamics in the direction of level and upright was discussed respectively, using Newton-Euler method to give dynamics equation in two directions. Lastly,robot tool of MATLAB was utilized to simulate the kinematics and dynamics of FROG-LEG vacuum manipulator.

    Numerical Simulation of Time-dependent EHL Line Contact Problems
    Sun Ang, Liu Deliang, Xu Jiujun
    2014, 25(4):  476-479. 
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    Time-dependent EHL is a common state in engineering. EHL line contact problems with periodic loads were solved by the indirect iteration method to research the equipment performance of this state. The common engineering example with cosine periodic loads was studied to reveal the dynamic load, load amplitude and frequency variation effects on the oil film and the EHL characteristics. The calculation results show that, with the increase of the load, the export necking phenomenon abate; with the frequency and amplitude of the dynamic load increases, the pressure curve shape changes, squeezing effects are more obvious.

    Analysis of Influences of End Position Mass and Joint Rotary Inertia on Motion Stability of a Flexible Manipulator Arm
    Liu Guangrui, Wu Xiaoling, Chen Yuan, Yu Zhengping
    2014, 25(4):  480-485. 
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    The influences of end position mass and joint rotary inertia of a flexible manipulator on the elastic motion stability of the flexible manipulator was studied herein using the analysis method of control system. Dynamics mode of the flexible manipulator arm having end position addition mass was deduced in the first place, and transfer function was obtained using drive moment as input and the elastic vibration of end position as output. Then the stability criterion of the elastic motion of end position was deduced. The elastic motion stability of flexible manipulator under different end position masses and joint rotary inertia was evaluated and compared, the effect extents of two parameters on the elastic motion stability of flexible manipulator arm were verified quantitatively.

    Surgical Guidance of Second Reconstruction Surgery of Defective Mandible Based on Rapid Prototyping Technique
    Chen Yadong, Li Hu, Shang Dehao, Wang Wanshan
    2014, 25(4):  486-490. 
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    Mandibular tumor resection or mandibular trauma can cause mandibular defects, resulting in the language and chewing dysfunction. Free fibula flap mandible surgery is the most mainstream and the most advanced mandibular defect repair method, which can maximize recovery of the mandible shape and function, but the procedure is very complicated. In order to improve the individual matching of free fibula flap for mandible defect reconstruction, a custom-made titanium plate design and manufacture was presented. Visualization and CAD were adopted to design the repair model with biomimetic shape by CT data. RP was employed to build the resin mold, which could gain the surgery time and improve success rate. A failed back surgery patient using routine treatment was performed second surgery successfully using rapid prototyping.

    Application of Improved VPMCD Approach in Roller Bearing Fault Diagnosis
    Yang Yu, Li Jie, Pan Haiyang, Cheng Junsheng
    2014, 25(4):  491-496. 
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    According to the drawbacks in the parameter estimation process of a new pattern recognition approach—VPMCD, the VPMCD approach was improved, its parameter estimation approach,least square method, was replaced by principal component estimation. The principal component estimation can eliminate the influences of the multiple linear correlations among the predictive variables. As a result, it can get more stable model parameters and improve the precision of pattern recognition. LCD approach was first adopted herein to decompose the roller bearing vibration
    signals into several mono-component signals. Then the approximate entropies were abstracted from the mono-component signals and formed into fault feature vector which will act as input in the improved VPMCD. Finally, the improved VPMCD was used as a classifier to distinguish the different working conditions and failures of roller bearing. The analysis results from vibration signals of the four roller bearing states i.e. normal, outer faults, inner faults and roller faults demonstrate the effectiveness of the proposed method.

    Research on Self-adapting Sampling along “Slide” Direction of ICP Algorithm
    Jiang Xiaotong, Dai Ning, Zhang Changdong, Cui Haihua, Yan Guodong, Sun Yuchun
    2014, 25(4):  497-502. 
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    On the basis of existing related theory, this paper placed emphasis on sampling strategy and determination of the matching point set of ICP algorithm. Firstly, the overlap area was determined and the point on the boundary was recognized. Secondly, sampling in the overlap area,and took different sampling strategies in different stages of the iteration of ICP algorithm. At the same time, this paper presented a new way to determine the match point set to guarantee the precision and increase the speed of the fine registration. Finally, experiments based on the point data verified the effectiveness and practicability of the algorithm.

    Maintenance Visualization of Flexible Tube Based on Kirchhoff Dynamics Analogy Theory
    Jiao Yumin, Wang Qiang, Xu Ting, Xie Qinghua
    2014, 25(4):  502-507. 
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    To deal with visualization of motional flexible tube in the virtual environment, a tube model was presented based on cross-section hypothesis. In this model, deformation process was transformed into force feedback process of section centre. According to its physical characteristics, loading analysis at equilibrium state and Kirchhoff kinetics equation were provided. For easy solution, Euler quaternions were employed to build kinetics differential equation of section. And then, finite difference method was used to solve this equation. Based on cross-section hypothesis, this paper presented collision detection method by minimum distance between nodes. Finally, taking natural rubber for example, numerical simulation was carried out with geometric and physical characteristics. The simulated results show that this theory can exactly display the transformation of deformable body in the virtual environment.

    Wear Forms and Mechanism of Carbide Alloy Disc Cutter in Disc Slitting Process for Silicon Steel Sheet
    Yan Qiusheng, Zhao Xueming, Lu Jiabin, Li Zhongrong, Huang Shengwei
    2014, 25(4):  508-512. 
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    The force of disc cutter was analyzed in the disc slitting process, and the slitting experiments of silicon steel sheet using carbide alloy disc cutter were conducted to study the wear process of the disc cutter.The surface topography, microstructure and percentage variation of Co-content before and after  wear of the carbide alloy disc cutter were compared, and the wear mechanism of the disc cutter was investigated.Experimental results indicate that the wear of carbide alloy disc cutter mainly occurs on the side of the cutting edge. The fillet radius of the cutting edge becomes bigger and the cutting edge of the disc cutter becomes blunt with the wear of the disc cutting tool. The wear mechanism of the disc cutter is mainly the loss of bonded phase cobalt, fatigue wear causing the desquamation of WC grain and adhesive wear.

    Research on Swing Type Sizing Technology for Ceramic Blank Balls
    Ye Cheng, Lü Binghai, Deng Qianfa, Yuan Julong
    2014, 25(4):  512-516. 
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    In order to improve the processing efficiency of ceramic balls, a swing type sizing technology for pre-sintered ceramic blank balls was proposed. In this method, the ceramic blank balls were driven by rotation of the lower plate and swing of the upper plate to achieve uniform lapping. It was aimed to eliminate roundness error of the pre-sintered blank balls rapidly, improve the precision of the full sintered blank balls, and reduce the machining allowance of the full sintered blank balls. The kinematic analysis and simulation results show that each point on the surface of pre-sintered blank balls can be lapped uniformly and has good ‘lapping probability'. The results of the processing experiments on Si3N4 pre-sintered blank balls show that the roundness error is modified from 196μm to less than 6μm (best to 2μm) after one hour's lapping by this method, and a good diameter and roundness consistency are obtained, the errors are less than 19μm and 4μm respectively.

    Experimental Research of Minor-loop Hysteretic Behaviors of Piezoelectric Actuator under Pure Electrical Loading
    Qin Haichen, Yin Zhouping
    2014, 25(4):  517-521,526. 
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    A typical piezoceramic stack actuator, as the research objective herein, the experimental investigation and analysis of the minor-loop hysteretic behaviors were studied. The Sawyer-Tower method was used to get the polarization and high precision capacitance sensor was used to measure the output displacement of piezoceramic actuator. Then combined with laboratory equipment, the polarization vs. voltage curve and strain vs. voltage curve of stack actuator were obtained when the input voltage changes frequently. From the domain switching of piezoelectric crystals, the generation mechanism of minor-loop hysteresis characteristics was analyzed. Finally, the optimum working zone of piezoceramic stack actuators is proposed.

    Calculation of Rotation Surface Form Errors by Least Square Based on Coordinate Transformation
    Chen Leilei, Huang Meifa, Xiao Mengmeng, Gong Wenfeng
    2014, 25(4):  522-526. 
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    This paper presented a common least square fitting method to improve the dependency on iteration initial value and reduce limit on the axial direction. This method translated nonlinear optimization model into a linear optimization model using coordinate transformation method. An example was presented to validate the method given herein. The results indicate that this method can evaluate the form errors of rotation surface quickly and accurately with no limit on the axial direction.

    Analysis of Motion and Deformation Characteristics of Ink Distributing System of Offset Printing Machine
    Chu Hongyan, Zhao Juntao, Yan Xiaofei, Cai Ligang
    2014, 25(4):  527-533. 
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    In order to analyze the movement and deformation of an ink distributing system, a model of ink distributing roller and ink vibrator was built using ANSYS, the characteristics and influence factors of the movement, deformation, shearing stress and normal stress of the ink distributing roller were analyzed. The results show that, the movement of ink distributing roller is influenced mainly by ink vibrator's rotating speed and oscillating amplitude, the normal stress of ink distributing roller is influenced mainly by its hardness, the shearing stress is influenced mainly by its hardness and the friction coefficient between two rollers, and the deformation of ink distributing roller is influenced mainly by its hardness and oscillating amplitude and rotating speed of the ink vibrator. The results are very important for the study of printing color quality control.

    Analysis of Tribology Properties in Sliding Model of Double Rough Surfaces under Adhesive Conditions
    Lai Lianfeng, Gao Chenghui, Huang Jianmeng
    2014, 25(4):  534-538. 
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    A two-dimensional sliding model of double rough surfaces was established, and the conditions for the fixed sliding speeds which considered adhesion factors in the process of contact. The friction and wear of sliding processes were analysed using the finite element analysis take into account elastic-plastic material properties with material failure. The wear rate and vibration were compared and analysed whether or not considering adhesive factors, the vibration power spectrum was obtained based on FFT arithmetic. The numerical results show that the average coefficient of friction is 0.48 when the interfacial shear strength τ=σy/3(where σy is the yield strength). In the case of considering adhesion, wear rate is larger, power spectrum low frequency component is more, vibration is relatively gentle, the corresponding energy also is larger. Compared with experimental results, it is concluded that the rationality of the simulation exists, these results also deepen understanding the physical image of the friction and wear processes.

    Weak Feature Extraction of Gear Faults Based on Stochastic Resonance Denoising
    Zhao Jun, Cui Ying, Lai Xinhuan, Kong Ming, Lin Min
    2014, 25(4):  539-546. 
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    Aimed at the feature extraction problem of weak gear faults under strong background noise, an early feature extraction method was proposed based on cascaed monostable stochastic resonance(CMSR) system and EMD with Teager energy operator demodulating. Firstly CMSRS was employed as the preprocessing to remove noise, and then the denoised signals were decomposed into a series of intrinsic mode functions(IMFs) of different scales by EMD. Finally, Teager energy operator demodulating was applied to get amplitudes and frequencies of each effective IMF so as to extract the faint gear fault features. The simulation and application results show that the proposed method can detect the characteristic frequency of gear faults of local damage effectively after the noise reduction by CMSR.

    Numerical Simulation of Casting Filling Process Based on Approximate Factorization Method
    Niu Xiaofeng, Wang Guanqian, Liang Wei, Hou Hua
    2014, 25(4):  546-549. 
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    To simulate  the flow patterns of casting filling,a SOLA method was used for calculating the pressure and the velocity fields.Because of  repeated iteration,the computational efficiency was low.Herein,an approximate factorization scheme   was applied in numerical solution of the pressure and the velocity fields.The finite difference program was established to calculate filling process.In order to demonstrate the correctness of  this new program,a benchmark filling experiment was simulated.The simulated results agree very well with the experimental results and this new program can be used to properly predicate the mold filling simulation in casting.

    Research on Springback Compensation Technology of U-shaped Parts Based on Equal Arc Length
    Gong Zhihui, Wang Richao, Yang Jitao, Zhou Shunfeng
    2014, 25(4):  550-554. 
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    Arc springback compensation of bottom surface was an effective method to eliminate stamping negative angle,which was from springback compensation of U-shaped parts. The radius of bottom arc and corner arcs, arc center coordinate values of the corner can be acquired based on equal arc length compensation rule, Consequently, the dimensional accuracy of U-shaped part's springback compensation was improved. The approximate model for the calculation of U-shaped part's springback angle was constructed based on experimental design and response surface methods(RSM), and furthermore, springback compensation angle and the maximum compensation angle of the U-shaped parts were worked out by theoretical analysis, the model of arc compensation of bottom surface for U-shaped part's springback compensation can be constructed rapidly, and the example herein shows its feasibility.

    Research on Influences of Axial Movement for Cross Wedge Rolled Asymmetric Shafts
    Peng Wenfei, Qi Yong, Shen Fa, Shu Xuedao, Zhang Kangsheng
    2014, 25(4):  555-558. 
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    Finite element model of asymmetric CWR was established, simulation conditions were designed by using quadratic orthogonal rotation combination,axial movement formula was regressed. Upon examination, the regression formula was highly significant, part of simulation conditions were validated experimentally, which indicated regression formula has good predictability. Based on the regression equation, the influences of the forming angle difference, the spreading angle difference and the area reduction difference on the axial movement were studied. The impact primary and secondary of axial movement, the selecting principle of process parameters of reducing axial movement were gained.

    Development of an Equipment System Used for Passenger Car Ergonomic Design and Evaluation
    Li Shihai, Ren Jindong, Gao Xiaoxian, Liu Yongqing Mi Mengdong, Du Jian, Du Xia
    2014, 25(4):  559-563. 
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    The traditional evaluation method of ergonomics adopted physical mockups or prototypes, which was very costly, and was inconvenient to modify, and usually caused prolonged development cycle-time. Herein, in conjunction with enterprise's requirements, an ergonomic validation equipment system, which had adjustable main parts, was developed.
    Firstly, requirements were analyzed, and target model cars ranges were determined, and ergonomic contents which could be validated using this equipment were clarified. The main functions and structural needs were confirmed. Based on above analysis, the overall concept, reference fiducial marks system, space requirement, positions and travels of adjustment devices were designed. According to the validated concepts, considering the standards of section bars and machines, the structure and adjustment devices of every part were designed and analyzed for their strength, stiffness and movement spaces. Finally, together with the manufacturer,the equipment systems were produced, assembled and tested. The test runs show that the system can simulate and present the cars defined in design target, and can evaluate, modify and reevaluate various ergonomic problems in their applications.

    Evaluation of Dynamic Characteristic of Vehicle Steering Control Based on Gray Correlation Method
    Zhao Youqun, Xu Jianxiong, Lin Yingjie, Wang Wei
    2014, 25(4):  563-567. 
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    In order to solve the problem of how to evaluate the dynamic characteristic of vehicle steering control, an integrated subjective evaluation method was presented. Because of the personal factors the subjective evaluation results of experts have both gray characteristics and fuzziness, gray correlation method was used to dispose the subjective evaluation results of experts. Then the final evaluation result of the dynamic characteristic of vehicle steering control was calculated through fuzzy mathematics. Finally, the correctness and feasibility of this method was verified through an example calculation.