China Mechanical Engineering

Research Status and Prospect of CMG Technology

REN Yinghui, ZHOU Jiaheng, LI Wei, ZHOU Zhixiong, LI Chenfang

2021, 32(18): 2143-2152. DOI: 10.3969/j.issn.1004-132X.2021.18.001

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At present, the CMG technology was widely applied in fields of optics and semiconductors manufacturing, because it might achieve ultra-precision, high quality and low damage processing for hard-brittle materials such as monocrystalline silicon and quartz glass through chemo-mechanical synergistic processes. Current CMG research status around material removal mechanism, grinding processes and compound processes was reviewed, and these existing problems for related researches were summarized. Factors affecting the quality and processing efficiency of CMG were discussed furtherly. The analyses show that revealing the mechanism of CMG from the perspective of solid-solid phase chemical reaction and chemo-mechanical synergistic effect is helpful to innovate feasible methods to improve the processing efficiency of this technology from the perspectives of material removal mechanism, grinding tool structure design and compound processing development. Furthermore, the probable development trend of CMG technology in the direction of diversified processing materials, more complicated structure processing, multi-energy field compound processing, and related intelligent machining databases were forecasted.

Ensemble Variable Predictive Model Based on Optimal Features and Its Applications

LIU Xiaofeng, TAN Qi, YE Rongting

2021, 32(18): 2153-2158，2164. DOI: 10.3969/j.issn.1004-132X.2021.18.002

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Aiming to the problems of low recognition accuracy of conventional variable predictive model resulting in case of small samples, an integrated variable predictive model was proposed based on the optimal selection of recurrence quantification features. Some feature subsets with high weight and low redundancy optimally were formed and then the best feature subsets were selected using the embedded rater. The Gauss function, radial basis function and generalized regression functions were introduced to establish the complex nonlinear interaction relationships among the selected features. The newly established models and conventional models were integrated based on the fitting errors of each model. The experimental results show that the proposed method has higher accuracy and better stability in the bearing fault diagnosis compared with the conventional methods, especially in case of small samples.

Preparation of Electroplated Grinding Wheels with Abrasive Ordering Configuration and Study on Pullout Strength

HE Qingshan, YANG Tianbiao, LIU Tianli, ZHAO Yanjun, CUI Zhongming

2021, 32(18): 2159-2164. DOI: 10.3969/j.issn.1004-132X.2021.18.003

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To solve the problems of insufficient storage chip spaces in grinding processes for electroplated grinding wheels, a new electroplated grinding wheel with abrasives ordering configuration was developed by the method of dispensing and adhesion for abrasives. Effectiveness of adhesive for abrasives and mechanics properties for coating were analyzed. Bonding interface characteristics among abrasives, coating, and conductive glue were described by SEM. Dry grinding experiments were carried out. Research results show that glue spots whose diameter accounts for about 40% of abrasive diameter may effectively bond abrasives, and keep abrasive overlap rate of single glue spot less than 6%. Micro hardness of the coating prepared by double pulse electroplating processes is higher than 500HV, and residual stress of surface layer is lower than 100MPa, while the bonding interfaces among the abrasives, the coating, and the conductive glue may integrate close with no obvious defects. There is no fall off of abrasives in dry grinding experiments.

Characteristics of High Compact Power Transmission Mechanisms of Crossed Swash-plates

ZHANG Lei, XU Haijun, ZHANG Xiang, XU Xiaojun, ZOU Teng'an

2021, 32(18): 2165-2174. DOI: 10.3969/j.issn.1004-132X.2021.18.004

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As a way to increase power density and sealing performance of expander used in Rankine cycle, a crossed swash-plate mechanism which could eliminate lateral forces between piston and cylinder was proposed. A mathematical model was established to analyze the theory of linear driving and high-power density. Then a thermodynamics model was built to analyze the pressure curves in cylinder varying with rotated angle of shaft, numerical experiments and corresponding simulation were carried out. By the means of investigating friction loss in transmission of crossed swash-plates, power transmission characteristics were studied. The experiments which power prototype by gas and motor were completed. Experimental results correspond to the simulation ones well.

Quasi-Hertz Loaded Tooth Contact Analysis of Gears Based on Ease-off Surface Topology

2021, 32(18): 2174-2180. DOI: 10.3969/j.issn.1004-132X.2021.18.005

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Numerical tooth surface and ease-off surface model of gears were established based on polynomial rack surfaces and theory of rack-gear common-tangential conjugate generating. By map of ease-off surface, characteristic information of tooth surface meshing, such as tooth surface contact path, transmission error, and contact line, was analyzed. Load calculation of tooth surfaces and contact stress of edge areas were solved by potential energy approach, deformation compatibility equation, and quasi-Hertz contact analysis. Time-varying history characteristics of tooth surfaces such as gear tooth meshing stiffness, transmission errors, load sharing between teeth, load distribution, contact stress and so on were obtained. Calculation results are in good agreement with third-party software.

Vehicle Tracking of Information Fusion for Millimeter-wave Radar and Vision Sensor

HU Yanping, LIU Fei, WEI Zhenya, ZHAO Linfeng

2021, 32(18): 2181-2188. DOI: 10.3969/j.issn.1004-132X.2021.18.006

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In order to improve accuracy of vehicle forward collision prevention warning system on road environment perception, a vehicle tracking method of information fusion for millimeter-wave radar and vision sensor was proposed. An algorithm to eliminate radar jamming targets was proposed to reduce processing time of jamming targets. A symmetric detection algorithm was proposed to detect radar target ROI (region of interest) symmetrically and reduce lateral position errors of radar target ROI. In order to improve the tracking accuracy, a KCF-KF combined filtering algorithm was proposed to track and fuse vehicles. Actual vehicle tests show that the method may effectively track vehicle position information, and the tracking accuracy of X and Y coordinates in pixel coordinate system is more than 97.34% and 95.19% respectively.

Double-drive Coordinated Control Systems of Fine Stamping Machines Based on Adaptive Sliding Mode Variable Structure Control

LIU Yanxiong, WANG Genju, HUA Lin, ZHAO Xinhao,

2021, 32(18): 2189-2196. DOI: 10.3969/j.issn.1004-132X.2021.18.007

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Aiming at the problems of uncoordinated motions for mechanical servo high-speed fine stamping machines in dual-motor combined driving processes, a dual-motor coordinated motion control strategy was proposed based on adaptive sliding mode variable structure control. The sliding mode variable structure control was introduced into servo motor motion control, and the fuzzy algorithm was used to optimize sliding mode control parameters to reduce chattering while improving the robustness of the systems. Different from the simplified structure of the transmission systems as a rigid body in traditional dynamics analysis, a rigid-flexible coupling transmission system dynamics model of the fine stamping machines was established. The simulation results show that the proposed control strategy may make the main motor provide punching forces in stamping stages, and make the auxiliary motor connecting toggle link realize rapid return of sliding block in idle stages, which fulfil the requirements of design and usage for the fine punchs.

Influences of Nozzle Structure on Air Curtain Effect in Oil-air Lubrication of Angular Contact Ball Bearings

WANG Baomin, BAI Chen, NAN Yang, WU Yan

2021, 32(18): 2197-2202. DOI: 10.3969/j.issn.1004-132X.2021.18.008

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Aiming at air curtain effect in oil-air lubrication of high-speed angular contact ball bearings, a numerical analysis model of oil-air two-phase flow in bearing cavity was constructed, which was based on the theory of air-liquid two-phase flow. Formation mechanism and influencing factors of the air-curtain effect in bearing cavities were analyzed. Influences of 5 types of nozzles on the air curtain effect and oil-air two-phase flow were compared and analyzed. The results show that, under high-speed working conditions, air curtain effect occurs near the contact areas between inner ring and rolling elements, which prevents lubricating oil from reaching lubrication point. The air curtain effect will be intensified with the increase of bearing rotation speed. When the D type oil-air nozzles is used, the effects of air curtain on oil-air two-phase flow are minimal, volume fraction of oil phase is the biggest near the contact zones of inner ring and rolling elements, bearing lubrication is also the best.

Research on Shear Characteristics of LHP Flow Fields

WEN Donghui, XU Xinqi, ZHENG Zijun

2021, 32(18): 2203-2210，2216. DOI: 10.3969/j.issn.1004-132X.2021.18.009

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Based on the dynamic pressure lubrication theory, a mathematical model of the flow field shear forces of LHP was derived. With the help of FLUENT software, the shear force distribution on the bottom of flow fields was studied, and the influences of each parameters on shear force was explored through a single-factor control variable test. The sensitivity sequence from high to low is as follows: polishing gap, polishing fluid viscosity, polishing roller speed and polishing roller radius. Using orthogonal test results as training set, a shear characteristic prediction model was established based on support vector regression(SVR), and the correlation coefficient is as 98.35% and the mean squared error is as 3.44×10-3. Finally, the theoretical values of shear forces were calculated. Comparison results show that the errors between numerical simulations and theoretical calculations are within 15%. Shear force distribution trends are the same under different parameter combinations. SVR prediction model has a high credibility.

Parametrization Design of Arc-star-shaped Structures with Tunable Poisson's Ratio

LIU Haitao, , WANG Yanbin, ZHANG Zhengyan,

2021, 32(18): 2211-2216. DOI: 10.3969/j.issn.1004-132X.2021.18.010

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A novel arc-star-shaped structure with tunable Poissons ratio was proposed, which was composed of arc rods and traditional star structure. Stress concentration problems were solved, and the manufacturability of the structure was improved. Poissons ratios of the structure with different parameters were obtained by energy method. Finite-element simulations and experiments of 3D printing specimens verified the correctness of theorical calculations. Effects of geometric parameters on the Poissons ratios of the structure were discussed in detail. Different geometric parameters may be selected according to the required performance to meet the engineering needs.

Research Progresses of Robot Grinding and Polishing Force Compliance Controls

GE Jimin, DENG Zhaohui, LI Wei, LI Chongyang, CHEN Xi, PENG Deping

2021, 32(18): 2217-2230,2238. DOI: 10.3969/j.issn.1004-132X.2021.18.011

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Low-cost and high-dexterity robots were used in field of grinding and polishing more and more widely. Compliance control of grinding and polishing forces for robots were the key to reduce surface roughness of workpieces and obtain high shape accuracy and surface integrity. Main research results of at home and abroad scholars in robots grinding and polishing force active compliance control strategies, passive compliance control devices, active-passive compliance control methods were summarized. Principles and implementation processes of various typical control methods were analyzed, and the advantages and disadvantages of each method were compared. Problems existing in current researches were pointed out. Finally, the key technical difficulties were summarized, and development trend was looked forward.

Compressed Sensing Method for Cutting Force Signals Based on Improved Gauss Random Measurement Matrix

WU Fenghe, ZHANG Ning, LI Yuanxiang, ZHANG Huilong, GUO Baosu,

2021, 32(18): 2231-2238. DOI: 10.3969/j.issn.1004-132X.2021.18.012

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In high-speed cutting processes, traditional Nyquist-Shannon sampling theorem was used for data collection which confront difficult problems of storage, transmission and processing for large amount of cutting force signals. A novel method of cutting force signal acquisition was proposed to realize the compression acquisition of signals based on the ompressed sensing theory. Gauss random matrix was selected as the basic measurement matrix and was redesigned by combining the approximate orthogonal upper triangular decomposition and the minimum correlation coefficient method to improve the compression measurement performance. Then the original cutting force signals were reconstructed from the measurement values by using the efficient compressive sampling matching pursuit algorithm. The experimental results show that the improved Gauss random measurement matrix has higher reconstruction accuracy and stability, and the proposed method greatly reduce the amount of data while ensuring the reconstruction efficiency and accuracy of cutting forces.

Routing Planning for Assembly Line Material Distributions under Interval Uncertain Travel Time

ZHANG Jiahua, LI Aiping, LIU Xuemei

2021, 32(18): 2239-2246. DOI: 10.3969/j.issn.1004-132X.2021.18.013

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In order to solve the problems that the materials could not be delivered in time due to the uncertain travel time in assembly line material distributions, a vehicle routing planning method with interval uncertain travel time was proposed. The uncertain travel time was represented by interval data. By the robust optimization, the vehicle routing model for assembly lines was formulated based on a route-dependent uncertain parameter. In the model, the objective was to minimize the total travel distance of vehicles with three dimensional loading and time window constraints. A hybrid genetic algorithm was proposed to solve the model. In the algorithm, tournament selection was used to avoid the conversion of fitness values, and a discrete Levy flight was proposed to improve the algorithm search performance. The effectiveness of the proposed algorithm was verified after the comparisons of different algorithms. Finally, the routing planning problem of a gearbox assembly line material distributions was used as an example. The solutions with different degrees of uncertainty were obtained by the proposed method. And the abilities of different solutions to resist the uncertain travel time were analyzed by Monte Carlo method.

Structural Optimization Design and Research of Direct-drive Quadruped Robots

LIU Mingyuan, CHEN Ping, MA Jianshe

2021, 32(18): 2246-2253. DOI: 10.3969/j.issn.1004-132X.2021.18.014

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A direct-drive quadruped robot was proposed, and the leg stiffness characteristic model was established based on the spring inverted pendulum model, then the relationship among leg length ratio, attitude angle, and stiffness characteristics was analyzed. The influences of pole length ratio on energy utilization efficiency were discussed. Forward kinematics and inverse kinematics of the five-bar coaxial leg were analyzed, and the position control algorithm model was derived. The relationship between input current of leg drive motor and force on the foot was derived by Jacobian matrix. Running experiments and jumping experiments were carried out on the direct-drive quadruped robot, and the experiments verified the rationality of structural design for the robot.

Relationship of Raceway Center Distance Errors and Load-bearing Performance of Rolling Linear Guide Pairs

LIANG Yi, WANG Xudong, WANG Xiaoyi, FENG Jianwen, FENG Benzhe, OU Yi, FENG Hutian

2021, 32(18): 2254-2261,2267. DOI: 10.3969/j.issn.1004-132X.2021.18.015

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Static stiffness and friction, as the key load-bearing performance indicators of rolling linear guide pairs, affected the motion accuracy and operation performance directly. Based on Hertz contact theory, a model of raceway center distance errors, the friction forces and static stiffness of the guide rail pairs was established. The theoretical model and controlled variable tests were combined to analyze the influences of the center distance errors for guide rail raceway, slider raceway and ball interference on the bearing performance for the guide rail pairs. The friction forces and static stiffness under different errors of the raceway center distance were compared and analyzed. The results show that the relative errors of static stiffness are as 2.46%～8.20%, and the relative errors of friction are as 0.42%～11.33%. The theoretical simulation values and the experimental values are in good agreement.

Optimization of Train Crash Energy Allocation Scheme with Multi-objective Evolutionary Algorithm

LYU Tianyi, XIAO Shoune, ZHU Tao, ZHANG Jingke, WANG Xiaorui, LI Yuru, YANG Guangwu, YANG Bing

2021, 32(18): 2262-2267. DOI: 10.3969/j.issn.1004-132X.2021.18.016

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In order to study the effects of impedance forces of couplings on energy absorption in train crash, a dynamics model of train longitudinal crash was established. Taking maximum average acceleration, maximum instantaneous acceleration, and maximum plastic deformation of car body as optimization objectives, while taking the impedance forces of different couplings as optimization parameters, optimal solution set was obtained by NSGA-Ⅱ algorithm. And then, a comprehensive evaluation system for the optimization objectives was established, and the optimal solution was selected. Crash acceleration of the train after optimization is less than that of train before optimization, which is due to the smaller interfacial force difference between two ends of the vehicles.

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