Table of Content

25 July 2019, Volume 30 Issue 14

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Fast Measurement of Abrasive Grains on a Single Layer Brazed Diamond Grinding Wheel Surface

CUI Changcai;WANG Kexian;HUANG Guoqin;HUANG Hui

2019, 30(14):  1639-1645. 

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In order to quickly obtain the two-dimensional distributions of full-field abrasive grains on grinding wheel, a rapid inspection system was established based on a linear array camera.The principles of the inspection system, the acquisition of clear picture without motion distortion and key algorithms of the image processing were studied.First, the hardware structure and the working principles of the inspection system were analyzed.Then, the Sobel operator of the eight-direction template and standard parts were used to complete the camera focusing and motion distortion image rectification.Then, the image was pretreated and the image after pretreatment was segmented by improved Otsu operator.Finally，the real coordinates and equivalent area of each abrasive grain was extracted.The experiments for a grain distributed single layer brazed diamond grinding wheel (grain number 35/40) show that totally 77.4 seconds are needed for full-field pictures capturing and grain coordinates and areas extracting, which meets the fast inspection requirements of single layer brazed diamond grinding wheel.

Analysis of Dynamic Responses of Collisions between Three Types of Offshore Wind Turbine Foundations and Ship

LIU Yuhang;LI Chun;ZHOU Hongjie;HAN Zhiwei

2019, 30(14):  1653-1657. 

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A model of 5 MW offshore wind turbine and ship collision was established, and the nonlinear dynamics theory was used to compare the impact resistances of the three kinds of offshore wind turbine supporting foundations under the impact of different speed ships and the response characteristics of the wind turbines on the tops of the tower. The results show that the displacement and acceleration responses of the single-column foundation offshore wind turbines are more obvious than that of others. In the processes of collision,the collision area is deformed, and the casing pipe and X-Joints have obvious strains. These parts should be reinforced during the design proceses. From the impact depths and contact forces of the offshore wind turbine supports, the impact resistance of the jacket foundation is the best.

On|line Temperature Detection Method in Core Area of Friction Stir Welding

ZHANG Yucun1;CUI Yan1;FU Xianbin2;SUN Shixuan3

2019, 30(14):  1658-1664,1672. 

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A method for measuring the temperature in the core areas of FSW was proposed based on thermal image herein. The relation between radiance and voltage of the welding consumables on the shoulder edge, and the mapping relationship between gray value and voltage of the thermal image were established. The relationship between surface temperature of the welding consumables at the shoulder and the gray value of the thermal image was deduced. The relationship between the surface temperature of the welding consumables at the shoulder and the temperature in the core area was deduced combining with the radiation heat exchange principle, and the temperature in the core areas was obtained. Finally, the correctness and feasibility of the method for measuring the temperature in the core  areas were verified by experiments.

Design and Analysis of Magnetorheological Fluid Dampers Based on Ultrasonic Effects

QIANG Lusheng;WANG Junshan;CHEN Chao;WANG Fufei

2019, 30(14):  1665-1672. 

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In order to reduce the angular momentum losses of MRDs under no magnetic field, a MRD was designed based on the effects of ultrasonic field. The damper had a built-in plate-type ultrasonic vibrator for the generation of ultrasonic fields, which might reduce the damping moments of the damper under no magnetic field. The dynamic characteristics of the ultrasonic vibrators and the magnetic circuits of the damper were analyzed by the FEM, and the output performances of the ultrasonic vibrators were verified by the experiments. Based on the Bingham model, the theoretical moment model of the dampers was derived. The output performance measurements of the dampers and the damping adjustment experiments of ultrasonic field under no magnetic field were conducted on the high-speed ground load test system. The experimental results show that the ultrasonic field has a significantly reduction effect on the damping of the dampers under no magnetic field.

Mechanics Properties of Cross-groove Equi-speed Output Mechanisms for Cycloid Ball Planetary Transmissions

ZHANG Yue;AN Zijun;YANG Ronggang;JIANG Wei;LIU Ziqiang

2019, 30(14):  1665-1672. 

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In view of the influences of cross sections with cone or sphere on the mechanics properties of the engagement points of the cross-groove equi-speed output mechanisms, a cross-groove structure of the cross section with a double arc of equal radius of curvature was proposed. The accurate formulas of the axial micro displacement was obtained according to the Hertzian contact theory by the geometrical relationship between normal deformation at the engagement points and the axial micro displacement. A four-point-contact mechanics model of the cross-groove was established, and the engagement normal forces of the cross-groove were obtained by the axial force balance equation and torque balance equation. The influences of parameters on the engagement normal forces and the stress of contact zone were analyzed. The results show that engagement normal forces of the cross-groove are changed periodically. The most important factor affecting the engagement normal forces is the quantity of steel balls, and the least important factor affecting the engagement normal forces is the input shaft eccentricity. The normal stresses and the peak values of the shear stresses in the contact zones may be reduced by increasing the radius of steel ball, and may be reduced by the radius coefficients.

A Hybrid Reliability Analysis Method with Mixture of Random and Dependent Interval Variables

XIE Shaojun;PAN Baisong;LUO Luping;XIANG Yongyong

2019, 30(14):  1673-1678,1683. 

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Considering the dependence between interval variables, an efficient hybrid reliability analysis method with the mixture of random and dependent interval variables was proposed based on the multi-ellipsoid model. To resolve the inefficiency of the hybrid reliability analysis due to dependent interval variables, a sequentially iterative strategy was adopted for decoupling the double-nest loop of the hybrid reliability analysis into the probability analysis and interval analysis. And an efficient interval analysis algorithm was developed by using polynomial interpolation, which was capable of efficiently handling the cases where the limit-state functions were monotonic or non-monotonic with respect to dependent interval variables.The results of numerical examples show that the proposed hybrid reliability analysis method has good accuracy and efficiency.

A Method for Feature Extraction of Environments of Laser Radars Based on Slope Difference

LIU Peng;REN Gongchang;YANG Lipeng;HU Xiaolong

2019, 30(14):  1679-1683. 

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The most existing methods for feature extraction of the data obtained from laser radars were based on iterative calculation, which were sensitive to the thresholds and had high computational complexity.To overcome these drawbacks, a new algorithm was proposed to split the lines and extract the feature points by calculating the slope difference of adjacent scanning points.Experimental results show that the developed algorithm may obtain the same results as manual segmentation and is insensitive to the thresholds.Comparing with the results of measurement, the method may obtain higher accuracy in both of length and slope of the feature line segments.

Effects of Cross-section Shapes on Filtering Characteristics of Expansion Chamber Hydraulic Pulsation Attenuators

YANG Fan;DENG Bin

2019, 30(14):  1684-1687,1695. 

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The Green's function method in the design theory of gas muffler was extended to calculate and analyze the filtering characteristics of the expansion chamber hydraulic pulsation attenuators with rectangular and square cross sections. In the range of plane wave cut-off frequency, the theoretical results of the insertion loss (IL) of these two types of pulsation attenuators might be well matched with the experimental measurements, which proved that this method might also be used to calculate the filtering characteristics of expansion chamber pressure dampers with rectangular and square sections. Besides, for the expansion chamber hydraulic attenuators with circular sections, in order to avoid the troubles caused by the coordinate system transformation, the one-dimensional analytical method was introduced, which was the most commonly used in the study of the acoustic characteristics of the muffles, and the calculation results were also in good agreement with the experimental measurements. By comparing the ID of these three different cross-section expansion chamber pulsation attenuators, it could be concluded that under the premise of controlling the circumference of the cavity of the expansion chambers, the circular section has the best filtering characteristics in the 2 kHz test band, the square section is the second, and the rectangular section has the worst pulsation attenuation performance.

Energy Recovery and Control of Forging Manipulators Based on Matrix Circuit

ZHAI Fugang1;ZHAO Guichun1;WEI Lizhong1;YAO Jing1,2;LI Dongming3

2019, 30(14):  1688-1695. 

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Aiming at the problems of high energy consumption and low energy efficiency of the valve-controlled forging manipulator hydraulic systems, based on the hydraulic matrix circuit, a hydraulic system of energy recovery was designed by the flexible combination of the pump/motor energy transfer units and matrix valve groups. Using servo control method of constant pressure difference, energy recovery was performed for the two operations of the forging manipulator's walking and clamp dropping. In order to verify the characteristics of energy saving, simulation and experiments were conducted. The results show that the accumulator recovers 39.2% of the gravitational potential energy during the dropping motions of the clamps, the accumulator recovers 37.1% of the inertial potential energy while the walking motions of the cart, and the pump output energy that with the energy recovery system is reduced by approximately 13% compared to the original systems. The energy recovery hydraulic system and the constant pressure difference servo control method realize the energy recovery of the two motions of the forging manipulators, which provides guidance for the energy saving development of the multi actuator systems.

Elastic Deformations of Surface under EHL Point Contact

SHEN Jinlong1;XUE Zhengtang2;HENG Chuanfu2;LIU Xiaojun1

2019, 30(14):  1696-1702,1712. 

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In order to investigate the surface deformations and the effects on surface properties under EHL point-contacting mode, a series of raceway surface samples for rolling bearings with different surface topographies were fabricated by laser texture processes and the elastic deformation values under different operational conditions were calculated based on spectrum analysis and fast EHL method called Amplitue Reduction. Three-dimensional topography parameters from ISO25178 were used to characterize surfaces before and after elastic deformations. The relationships among elastic deformations under EHL point-contacting mode and loading force/rotational speed was studied. The results show that obvious elastic deformations occur during EHL contacting processes and the operational parameters have significant influences on deformation values. Surface elastic deformations will obviously change surface topographies.

Quality Control Method of VC Processes for Intelligent Manufacturing

ZHANG Zhuangya;LI Yuesong;DUAN Mingde

2019, 30(14):  1703-1712. 

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According to the problems that the VC product quality was difficult to be controlled,low automation of VC equipment and poor flexible processing,depended on the experience of process designers,a quality control model for VC processes was established based on the computer graphics and artificial intelligence.By constructing the voxel model,the geometric parameters of the cavity,such as wall thickness,uniformity and volume,were approximated.On the basis of this,case-based reasoning and network-based reasoning technology were used to establish the relationship model between cavity geometrical parameters and forming processes,which made full use of the historical processing cases to achieve intelligent recommendation of initial processing parameters; then technicians' experiences were excavated to correct product defects by fuzzy inference after trial mode.The examples show that the quality control model based on the above thought method and reasoning mechanism has better reasoning and quality control ability.

Fault Diagnosis Method of Rolling Bearings Based on Refined Composite Multiscale Dispersion Entropy and Support Vector Machine

LI Congzhi;ZHENG Jinde;PAN Haiyang;LIU Qingyun

2019, 30(14):  1713-1719,1726. 

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In order to overcome the shortcomings of MSE and extract the nonlinear fault features of rolling bearings more accurately, a new nonlinear dynamic analysis method called RCMDE was introduced to the fault feature extraction of rolling bearings. Based on the feature extraction method via RCMDE and support vector machine (SVM), a new method of rolling bearing fault diagnosis was proposed. Through the analysis of rolling bearing experimental data, the proposed method was compared with the multiscale dispersion entropy and MSE based fault diagnosis methods and the results show that the fault diagnosis method may accurately identify the fault locations and severities of rolling bearings, and has a higher fault recognition rate than that of the two methods mentioned.

Mapping Rules between Geometric Errors in Six-axis Stages and Alignment Accuracy of Fiber Array

TANG Hao;TANG Guoning

2019, 30(14):  1720-1726. 

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Aiming at positions and poses of fiber array which was fixed on six-axis stage, geometric error model was established by homogeneous transformation matrix. A variance sensitivity analysis was adopted to identify important error terms on alignment accuracy according to stage configuration. Based on the results, mapping rules between geometric errors in multi-axis motion stage and alignment accuracy of fiber array were established. This analyzing procedure is reliable from the simulation results, and also may develop the mapping rules easily and conveniently, which will be as the theoretical basis for increasing packaging efficiency and alignment efficiency.

Dynamics Modeling and Analysis for a Kind of Half Outside LET Compliant Joint

LI Pengfei;CAO Boyu;WANG Zhenyu;ZHAO Chen;ZHAO Rongchang

2019, 30(14):  1727-1733. 

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A model of a kind of half outside lamina emergent torsional（LET）compliant joints was set up and the dynamics characteristic analyses were carried out herein. The ANCF method with the slope discontinuity was used to derive the system dynamics equation of the LET compliant joints. Motion deformation of the center line and contour of the LET compliant joints applied external forces were simulated. Comparing experimental results with that of simulations, the effectiveness using ANCF to model a half outside LET compliant joints was proved. Furthermore, influence laws of contour dimensions to deformation of the compliant joints were analyzed.

Design and Analysis of a Novel RR-RURU Ankle Rehabilitation Robot Mechanism

ZHANG Yanbin1，2，3;JING Xianling1;HAN Jianhai1，2;CHEN Zihao1

2019, 30(14):  1734-1741. 

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A novel ankle rehabilitation robot was designed based on the uncoupled RR-RURU rotational parallel mechanism.The kinematic output characteristics mechanism was analyzed and the degree of freedom was calculated in terms of the screw theory.Mathematical models of the posture and the angular velocity of the platform were established.Structural conditions of the fully-isotropic performance for the mechanisms were discussed in detail.Singularity was analyzed based on the linear dependence of the kinematic screw system of the first limb and the singular configurations were given as well.Workspace was investigated and the three-dimensional graphic was also described.Finally, CAD model of the novel ankle rehabilitation robot were given.The output angular displacement curves of the robot were obtained by means of the clinical gait analysis data (CGA).In addition, the dynamics of the ankle rehabilitation robot was simulated by using the virtual prototype.The results provide the theoretical basis to develop the physical prototype of the ankle rehabilitation robots.

A Design Method of Processing Parameters of Rotary Friction Welding for a Plastic Clutch Pump

SHENG Jing1,2;XIE Ruoyu1

2019, 30(14):  1742-1747. 

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Aiming at the problems that the welding parameters of the upper and lower pump bodies of a plastic clutch general pump were difficult to be determined in the rotary friction welding processes, a welding parameter design method was proposed based on the rotating friction welding temperatures. Based on quadratic orthogonal regression design and response surface method, a prediction model of friction surface temperatures was established by three welding parameters of spindle speed, welding pressure and number of turns during rotating welding. The melting points of clutch pump materials were obtained by different scanning calorimetry. Based on the analysis of the friction surface temperatures and the two-order response surface diagram of three welding parameters, a coupling model of welding parameters was established based on the prediction model, and reasonable welding process parameters might be designed according to the model. Through the evaluation of welding strengths, the rationality of the design method of welding parameters was verified. With the aid of a numerical control welding system, the mass production of clutch pump welding was realized, which shows that the welding parameter design method is feasible.

Application of 2RPU-UPR Parallel Mechanism in Antenna Support

2019, 30(14):  1748-1755. 

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In order to solve the problems that the existing antenna support mechanisms could not meet the requirements of high load-bearing capacity and large working space simultaneously, a two-rotation and one-translation PM 2RPU-UPR with few joints was proposed to be used as the antenna supporting mechanisms. Firstly, the degrees of freedom of 2RPU-UPR PM with few joints were analyzed and the kinematics model was established. Two optimization indexes, i.e,the maximum load-bearing capacity and motion range of driving branch, were proposed, based on which the key dimensions of the supporting mechanisms were optimized. As a result, a set of structural dimensions that provided excellent performances were obtained. Furthermore，the experimental prototype of the antenna support mechanisms was developed and experimental investisgations were performed. The experimental results show that the proposed antenna supporting mechanisms may withstand large loads, and meet the large working space requirements of ±90° rolling and ±90° pitching, thus it has a good application prospect.

Image Binarization Method of Equal-thickness Butt Welds Based on Regional Optimization

WANG Xingdong1;YANG Yalun1;KONG Jianyi1;SHI Yi2

2019, 30(14):  1756-1763. 

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Due to the reflected surfaces of the grooves，complicated appearances of multi-layer and multi-pass welding grooves，and splatters，the images had the problems of excessive gray levels，uneven distribution of the gray level，and random noises.The image binarization method of equal-thickness butt welds was proposed based on regional optimization.An adaptive method for ROI definition was established to shrink the original images.Based on the distribution characteristics of neighborhood gray difference，an algorithm was proposed to divide the ROI images into two regions-flatness and intensity.With high-quality binary images as the target，the optimal model for the judgment of laser stripe regions was established to determine the regions with the optimal results.Binary processing was completed by using the gray mean values of the regions and was taken as threshold.The experimental results have good evaluation from subjectivity and objectivity.The method is satisfied the real-time requirements of various thickness plates and multi-layer and multi-pass welding.