Table of Content

25 August 2020, Volume 31 Issue 16

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Lubrication Characteristics of Spiral Groove Mechanical Seals during Transient Start-up

XU Lushuai1;WANG Yunlei1;ZHANG Fan1;HAO Muming2;YUAN Xiaoyang1

2020, 31(16):  1891-1900.  DOI: 10.3969/j.issn.1004-132X.2020.16.001

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A mathematical model of lubrication characteristics and sealing performance in spiral groove mechanical seals during transient start-up was established，which included the average Reynolds equation with flow factors, contact factor and JFO(Jakobsson-Floberg-Olsson) (mass conserving) cavitation boundary, elastic-plastic asperity peak contact equation as well as the equations of axial dynamics model. Furthermore, the influences of different working conditions and structural parameters on lubricate regime transformation were compared. Results show that fluid bearing capacity and film thickness increase while the asperity peak contact force gradually decreases to zero during acceleration periods. Mixed lubrication regimes have larger film stiffness and more obvious oscillation amplitude compared with hydrodynamic lubrication regimes. A distinct mutation of axial speed appears when reaching separation speed. The smaller accelerated speed may achieve hydrodynamic lubrication regime at low speed affected by squeezing effect. Both higher outer pressure and lower inner pressure are beneficial to the transformation of lubrication regimes. The separation speed ascends at first and then descends with the increment of groove number. The decrease of spiral angle, groove depth and the increase of groove width ratio play an effective role in the ability of lubrication regime transformation.

Applications of Improved Time-frequency Analysis and Feature Fusion in Fault Diagnosis of IC Engines

CAI Yanping;FAN Yu;CHEN Wan;ZHANG Jinming

2020, 31(16):  1901-1911.  DOI: 10.3969/j.issn.1004-132X.2020.16.002

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Aiming at the problems of fault identification and diagnosis based on the IC engine vibration signals, a time-frequency analysis method was proposed based on variational mode decomposition(VMD) threshold filtering，Margenau-Hill time-frequency distribution(MHD). The method aimed at the problems of cross-interference terms of the Cohen time-frequency distribution, determining decomposition level of the VMD algorithm by the threshold filtering method, the IC engine vibration signals were decomposed into a series of single-component modal signals; then the MHD time-frequency characterization and linear superposition were applied to the single-component signals to get the time-frequency images of the vibration signals with good time-frequency clustering and clear physical meaning.Then，the local non-negative matrix factorization(LNMF) was used to extract features of time-frequency images，and the extracted features were combined with the time domain parameters of the vibration signals to obtain the fused feature vectors. The improved particle swarm optimization algorithm was used to optimize the parameters of the support vector machine(SVM)，and then the feature vectors were trained and tested by SVM to realize the fault identification and diagnosis of the IC engines. The method was applied to the identification and diagnosis tests of the cylinder cover vibration signals under 8 working conditions of valve clearances. The results show that the method may effectively identify and classify the vibration signals of different working conditions. Through parameter optimization, the highest recognition rate reaches 99.17%，and compared the classification results of the traditional nearest neighbor classifier，the superiority of the method is proved.

Automatic Overlap Detection Method for Weld Seam Images of X-ray Inspection

ZHANG Fan1,2;ZHANG Boyan3;SHI Xiaowan1;ZHANG Xinhong4

2020, 31(16):  1912-1916,1930.  DOI: 10.3969/j.issn.1004-132X.2020.16.003

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In view of the phenomenon of false weld inspection images was very common in engineering, at present, it was mainly checked by manual reading, which was low efficiency and easy to miss the inspections, based on image processing a method was proposed to automatically locate, segment and compare the overlapping areas of the weld seams. An automatic detection system of weld seam flaw detection image overlap was established to detect whether the weld images were false. Based on the Radon transform, the overlap position marks were found, the overlap areas were cut from the weld images, and the overlap matching were performed using the SIFT algorithm to calculate the structural similarity of the two lap areas. Finally, according to the number of matching points of SIFT key points and structural similarity, they were judged whether the two overlap areas were matched. The experimental results show that the detection accuracy of automatic overlap detection method achieves 87.3%.

Review of Docking Interface Technology for Orbital Replacement Units

ZHUANG Yuan1;KONG Ning2;REN Jie2;LIU Yuqiang1;WANG Yaobing1;ZHANG Jie2;WANG Wenlong1;MA Shuai2

2020, 31(16):  1917-1930.  DOI: 10.3969/j.issn.1004-132X.2020.16.004

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According to the requirements of on-orbit service and maintenance technology for module replacement of spacecrafts in space engineering, the research progresses and achievements of docking interface technology of ORUs at home and abroad were reviewed. The technical requirements, functional principles and performance indexes were summarized on the basis of the action characteristics for the robotic arms and docking interfaces. The gaps of docking interface technology of ORUs were compared and analyzed between China and foreign countries. The main development directions were proposed for the key technologies of the ORU docking interfaces in China.

SOC-based Active Equalization Control for Lithium-ion Battery Packs

ZHANG Kai1;ZHAO Peng2;WANG Youren1;XU Zhitong1;CHEN Zewang1

2020, 31(16):  1931-1939.  DOI: 10.3969/j.issn.1004-132X.2020.16.005

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The differences between single cells in the lithium-ion battery packs seriously affected the capacity utilization and remaining useful life of the battery packs. Therefore, an inductive active equalization circuit was designed. Based on recursive least square extended Kalman filter(RLS-EKF) algorithm, the SOC of lithium-ion batteries would be estimated online. And SOC was used as the equalization criterion to realize a novel strategy based on RLS-EKF algorithm of active equalization control. A test platform for energy balance management system of lithium-ion battery packs was designed and developed. Experimental results show that the SOC estimation errors of RLS-EKF algorithm are within 3.5%, the proposed active equalization control method may effectively improve the inconsistency among individual cells and the capacity utilization of the batteries.

Hybrid Teaching-learning-based Optimization Algorithms for Integrated Scheduling of Multi-workshop Collaborations

LIAO Bufan1;LEI Qi1;WU Wenlie2;SONG Yuchuan1;GUO Weifei1

2020, 31(16):  1940-1949.  DOI: 10.3969/j.issn.1004-132X.2020.16.006

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Aiming at the current integrated scheduling problems of multi-workshop collaborations with similar processing properties, where almost using the scheduling rules, relying too heavily on the processing structures of the products, reducing the algorithm adaptability to different instances on the same type of problems, and the poor results of solving large instances, a hybrid teaching-learning-based optimization algorithm was proposed. A self-learning phase was added, the mutation operators were executed in the individual self-learning phase to improve the local search ability. In the three phases of teaching, mutual-learning and self-learning, the probability calculated by the Metropolis procedure in the simulated annealing algorithm was adopted to accept randomly a bad individual as a new one, further improving the ability of running away from local optima. The transformation operations designed in the three phases taken into account the sequential constraint relations among the virtual processes in the integrated scheduling problems and ensure that the solutions generated were all feasible solutions. The feasibility and validity of the proposed algorithm were verified by testing the previous examples.

Kinematics Analysis and Simulation of Eight-degree-of-freedom Continuum Manipulators

LI Fenggang;ZHAO Lei;HE Guangping;YANG Miao

2020, 31(16):  1950-1959.  DOI: 10.3969/j.issn.1004-132X.2020.16.007

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From the perspective of flexibility and safety of endoscopic services, an eight-degree-of-freedom continuum manipulator with flexible skeletons driven by casing cables was developed. Based on the assumption of piecewise constant curvature and screw theory, the analytical solutions of forward and inverse kinematic model of the manipulators were obtained. In order to realize automatic endoscopic detection of the inner surfaces of small-inlet cavities such as gas cylinder, oil tank and mouth, a dual-space coordinated motion planning method was proposed to coordinate the workspace and the joint space. Finally, the forward and inverse kinematic model and the motion planning method were validated by numerical simulations.

In-process Tool Wear Monitoring Model Based on LSTM-CNN

HE Yan1;LING Junjie1;WANG Yulin2;LI Yufeng1;WU Pengcheng1;XIAO Zhen1

2020, 31(16):  1959-1967.  DOI: 10.3969/j.issn.1004-132X.2020.16.008

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To improve the accuracy of in-process tool wear monitoring in machining processes, an in-process tool wear monitoring model was proposed based on LSTM-CNN. In the monitoring model, the vibration, force and acoustic emission signals during the cutting processes of the tool was collected respectively by vibration, force and acoustic emission sensors, the collected datum were essentially time series datum. Considering the sequence and multidimensional characteristics of the collected datum, the LSTM-CNN performed sequence and multidimensional feature extraction on the collected datum, and used linear regression to map the features to the tool wear values. The validity and feasibility of the model were verified by experiments. Compared with other methods, the accuracy of the model is greatly improved.

Design and Analysis of Soft Manipulator Teleoperation Systems

YAO Jiantao;CHEN Xinbo;CHEN Juntao;WEI Chunjie;ZHANG Shuai;LI Haili;ZHAO Yongsheng

2020, 31(16):  1968-1977.  DOI: 10.3969/j.issn.1004-132X.2020.16.009

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Aiming at the requirements of pneumatic soft manipulators working in remote unstructured environments, a teleoperation system of pneumatic soft manipulators was built. Based on the principle of “fast pneumatic network” and modular disassembly, a flexible bending actuator was designed and manufactured. A hand-like flexible manipulator was assembled according to the experimental requirements. The mechanics model of the soft actuator was established based on Yeoh model, and was revised by simulation analysis, which provided a theoretical basis for the control of the soft actuator. The architecture of the teleoperation system was designed, the driving mode and control strategy of the pneumatic soft manipulators were put forward. The client software interface was created in the C# windows application. Based on skinning technology, the soft actuator was modeled in 3D Max software, and a virtual working scene was built in Unity3D. The motion control of the soft manipulators and the collision and picking of the target objects were realized by remote feedback information through script programming. Experiments for finding the relationship between the bending angle of the soft actuator and pressure were carried out to verify the accuracy of the analytics mechanics model. And the teleoperation gesture mapping experiments were carried out to analyze the feasibility of the teleoperation systems, and the further research and applications were discussed.

#br# Wafer Acceptance Test Key Parameter Identification Based on Hybrid Feature Selection Method

LYU Youlong;XU Hongwei;ZHENG Cheng;ZHANG Jie;ZHENG Peng

2020, 31(16):  1978-1984,1997.  DOI: 10.3969/j.issn.1004-132X.2020.16.010

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Wafer acceptance test was a key process of the semiconductor manufacturing systems. The identification of key testing parameters enabled accurate prediction of wafer yield and in-time detection of product defects. With the consideration of high dimensions, strong redundancy and insignificant key parameters of testing data, a hybrid feature selection method composed of filter and wrapper was proposed to minimize the number of key parameters as well as the prediction errors of wafer yield. The relevance between each testing parameter and wafer yield and the redundancy of testing parameters were measured at the filter stage based on mutual informations. Additionally, the pre-screening of testing parameters with the goal of maximum relevance and minimum redundancy was realized.The encoding and combination optimization of testing parameters were realized by using a genetic algorithm to output key testing parameters at the wrapper stage, of which the fitness of each combination case was evaluated based on prediction errors of wafer yield provided by a backpropagation neural network. Finally, the effectiveness of this method was validated through a set of reference data as well as practical data collected from a wafer fabrication shops.

Research and Application of Variable Speed Cooperative Transfer Control Strategy of Dual Manipulators

WANG Liang1;AN Xingyun2;ZHANG Xueqin2;WANG Yilin1;ZHANG Yisheng1

2020, 31(16):  1985-1990.  DOI: 10.3969/j.issn.1004-132X.2020.16.011

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Based on the intelligent and advanced, efficient and stable manufacturing concepts, aiming at the problems of synchronous sheet transfer of multiple robots, a fast transfer and delivery method of efficient cooperative work of dual manipulators under a limited distance was proposed. Through the kinematic analysis, an experimental platform of cooperative transfer for dual manipulators was designed and built. The main factors that affected the fast synchronization in several feasible solutions were studied, and the realization of several methods for cooperative transfer was given. Considering speed and stability comprehensively, the needs of minimum cooperation distance, using a two-stage variable speed control synchronization method, the sheet transfer cycle was shortened by more than 11%.

Simulation and Application of Anti-backlash Technique with Dual-motor in Tandem Manipulators

JIANG Yong;ZHANG Wei;LIU Xiaoyuan;JIN Bopi

2020, 31(16):  1991-1997.  DOI: 10.3969/j.issn.1004-132X.2020.16.012

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Typical nonlinear backlashes widely existed in the robot servo systems. In order to reduce the backlash's impacts on system performance, tandem manipulator adopted anti-backlash technology with dual-motor master-slave drives. Firstly, nonlinear elastic dead-zone model of the backlash was establish based on the basic principles and structure of dual-motor backlash system. Then, the Simulink model which used dual-motor bias torque control strategy for anti-backlash was establish,according to the dynamics formula based on the dual-motor system, and the algorithm framework and servo system hardware circuit schematic of the system were given at the same time.Finally, the principle of emulation was carried out, based on the engineering design actual parameters, the tandem manipulator system was verified, which used the dual-motor anti-backlash technology for accuracy test through laser tracker. Simulation and experimental results show that: the mathematical model reflects the basic characteristics of the actual systems, the end accuracy of the tandem manipulator whose workspace is 4.5 m reaches 1.2 mm, that meets performance requirements of the engineering applications.

Numerical Study on In-plane Impact Dynamics of Negative Poisson's Ratio Honeycomb Structures with Curved Concave Sides

SHEN Jianbang;XIAO Junhua;LIANG Xi;XU Yaoling

2020, 31(16):  1998-2004.  DOI: 10.3969/j.issn.1004-132X.2020.16.013

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The in-plane impact dynamics properties of the negative Poisson's ratio effect honeycomb structures with variable arc angle curved concave sides were studied by using numerical method. The effects of the impact velocities and arc angles on the deformation failure mode and the energy absorption capacity of the honeycomb structures with curved concave sides were discussed. The results show that changing the impact velocities and arc angles has effects on the deformation failure mode of the honeycomb structures with curved concave sides. When the impact velocity is high, the stress fluctuation ranges of the honeycomb structures are large and the energy absorption value per unit volume of the structures increases with the increasing of the arc angles. The above phenomenon does not exist when the impact velocity is low.When the arc angle is larger than 120°, the honeycomb structures with curved concave sides have negative Poisson's ratio effect, and the energy absorption capacity of the structures are higher than that with positive Poisson's ratio honeycomb structures corresponding to other arc angles, where the phenomenon is independent of the impact velocity.

Research on Thermal-mechanical Stamping Forming Considering Deformation Heat and Friction Heat Effects

NIE Xin1;XIAO Bingbing1;SHEN Danfeng2;GUO Wenfeng1

2020, 31(16):  2005-2015.  DOI: 10.3969/j.issn.1004-132X.2020.16.014

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The DP780 material was subjected to constant temperature tensile test in the temperature range of 20~140 ℃ and the strain rate range of 0.001~0.1s-1, and the true stress and strain change trends were analyzed. The constitutive equations of materials were established based on the Norton-Hoff model, which might better reflect the shaping constitutive relationship of DP780 during different cold forming processes. Combined with the Norton-Hoff constitutive model and friction model related to temperature and pressure，the combination of theoretical research and numerical simulation was used to study the mechanism and macroscopic characteristics of deformation heating and friction heating of DP780 steel plates. According to the theory of complete thermal coupling numerical simulation, considering the coupling analysis of temperature field, stress field and strain field, a research method of stamping was proposed considering deformation heat and friction heat effects. Through the stamping experiments, the forming results and springback characterization of DP780 steel plates applied to U-shaped parts were obtained. Comparing the simulation results of the traditional cold stamping and the new analytical method considering self-heating effects, it is found that the new stamping forming research method improves the accuracy by 10.1% on the sidewall and the accuracy by 23.2% at the flange.