Table of Content

    25 October 2021, Volume 32 Issue 20
    Integral Double-layer Disc Permanent Magnet Eddy Current Coupling and Its Torque Characteristic Analysis
    ZHENG Hongmei, ZHENG Mingrui, CHEN Ke, SHI Hongyang, YIN Lei,
    2021, 32(20):  2395-2402.  DOI: 10.3969/j.issn.1004-132X.2021.20.001
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    Based on the magnetic circuit analysis of the traditional single-layer disc permanent magnet eddy current coupling, an integral double-layer disc permanent magnet eddy current coupling was designed. The coupling installed the permanent magnets of two single-layer disc permanent magnet eddy current couplings on the front and back of a piece of back iron in a N-S corresponding manner, thus, reducing the loss caused by the back iron reluctance in the magnetic circuit, improving the magnetic energy utilization rate of the permanent magnet and increasing the torque. Through the equivalent magnetic circuit method, a mathematical model of the structure was established, and combined with the finite element method simulation model, the torque characteristics were comprehensively analyzed. A prototype of the permanent magnet eddy current coupling was built, and the reliability of the above analysis was verified through experiments. The results show that the mathematical model built is accurate; and the torque of the coupling is greatly improved compared to the torque of the traditional permanent magnet eddy current coupling.
    Topology Optimization of Sandwich Damping Composite Structure with Connective Constraint
    ZHANG Heng, DING Xiaohong, SHEN Lei, XU Shipeng
    2021, 32(20):  2403-2410.  DOI: 10.3969/j.issn.1004-132X.2021.20.002
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    The structural performance of the sandwich damping composite structures was depended on the material property of the damping layers. A topology optimization method for the microstructure design of damping layers of the sandwich structures with connective stiffness phase material was proposed under considering the structural damping property and manufacture constraints. The design objective was to maximize the structural modal loss factor with considering the manufacture constraints. An optimization mathematical model for the design of sandwich structures with connective stiffness phase material was presented by combining kinematical connective constraints method and nonlinear diffusion method. The optimized sandwich structures might be manufactured by 3D printing technology. Typical sandwich structures were designed by the proposed method. The optimal sandwich structures with a connective stiffness phase are obtained, which have a high structural damping and low frequency response. The proposed method realizes the integrated “material-structure-design-manufacture” optimization of the sandwich damping composite structures. Both of the simulation and experiment results show that there is an optimal volume fraction of the damping material in the microstructures to make the sandwich structures has a minimum frequency response. 
    Cutting Performance and Lubrication Mechanism of Cutting 45 Steel with Tool Continuously Lubricated at the Tool-chip Interface
    CAO Tongkun, XU Yingtao, TAN Qingyao
    2021, 32(20):  2411-2417,.  DOI: 10.3969/j.issn.1004-132X.2021.20.003
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    In order to improve the tool lubrication performance and reduce the use of cutting fluid as much as possible, a new type of tool with continuous lubrication at tool-chip interface has been fabricated. The tool can deliver the cutting fluid directly to the tool-chip contact interface through the inner microchannel. The new cutting tool and conventional cutting tools under the condition of dry cutting and pouring cutting fluid were used to cut 45 steel. The three-dimensional cutting force was measured. The wear surface of the rake face was analyzed by SEM micro morphology and element detection. The friction and wear characteristics and lubrication mechanism of the tool were analyzed. The results show that, compared with the conventional tools in dry cutting and pouring cutting fluid, the tool with continuous lubrication at too-chip interface may effectively reduce the friction and wear during the cutting process, while the amount of cutting fluid is only 1/120 of that in traditional pouring cutting. Through the element analysis of the rake face, it maybe seen that the cutting fluid can arrive at the area closer to the main cutting edge, and maysupply continuously. This is the main reason that the tool has better antifriction and anti-wear effect. Although the adhesion of new tools is greatly reduced, the main wear mechanism of tools is still adhesive wear and oxidation wear. 
    Dimensional Synthesis of a Novel Asymmetric 5-DOF Hybrid Robot
    DONG Chenglin, LIU Haitao, YANG Junhao
    2021, 32(20):  2418-2426.  DOI: 10.3969/j.issn.1004-132X.2021.20.004
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    A novel asymmetric 5-DOF hybrid robot was proposed, which composed of a 3-DOF 1T2R parallel mechanism and a 2-DOF A/C wrist. In order to achieve a nearly plane symmetric kinematic performance, the dimensional synthesis approach of the 3-DOF parallel mechanism was subsequently investigated. Firstly an approach to extract the dimensional parameters was presented by the definition of the reference configuration. Then a set of kinematic indices were proposed for evaluating the workspace, motion/force transmissibility and level of plane symmetry. Finally the optimal dimensional synthesis was theoretically formulated as a multi-objective optimization problem with constrains, leading to a set of homogeneous dimensionless parameters that were enable to achieve both of large ratio of workspace volume over footprint and good motion/force transmissibility with a nearly plane symmetric and even axisymmetric distribution. A comparison study shows the novel hybrid robot has a very similar global kinematic performance to that of the Exechon and TriMule provided that they both have same dimensions.
    Research on Basic Working Characteristics of a New Type Mechanical Continuously Transmission with Planetary Centrifugal Structure
    ZHAO Huipeng, ZHOU Junjie, LI Jin, FAN Shurui, QIAN Changxian
    2021, 32(20):  2427-2435.  DOI: 10.3969/j.issn.1004-132X.2021.20.005
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    Continuously variable transmission technology might improve the power and economy of the vehicles through continuous changes in the transmission ratio. At present, the metal belt type continuously variable transmission was the mainstream form. The continuously variable transmission device was innovatively designed, a new type of planetary centrifugal mechanical stepless transmission scheme was proposed, the structure and working principle of the transmission scheme was introduced, a dynamics model was established, and then a new planetary centrifugal type continuously variable transmission basic working characteristics was obtained. At the same time, the influences of different track curves on the working characteristics were compared and analyzed. The research results provide a basis for the structural design of the planetary centrifugal mechanical transmission, and verify that the planetary centrifugal mechanical transmission has the characteristics of stepless speed regulation and self-adaptive output torques.
    Review and Prospect of Grinding Wheel Dressing Technique
    JIAO Feng, LI Chenglong, NIU Ying, MA Xiaosan
    2021, 32(20):  2435-2448.  DOI: 10.3969/j.issn.1004-132X.2021.20.006
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    Grinding wheel dressing performsed a vital role in the processes of high-speed and high-efficiency grinding, precision and ultra-precision grinding, and form grinding. Since the grinding processes were mainly the interaction between the grinding wheel and the surfaces of the workpieces, and as grinding progresses, the grinding wheel was gradually dulled, and it was difficult to grind effectively. To ensure grinding quality and grinding accuracy, the grinding wheel needed to be regularly dressed. In order to promote the development of grinding wheel dressing techniques, scholars at home and abroad had continuously improved and innovated grinding wheel dressing methods and achieved a lot of pioneering and groundbreaking research results. However, the increasing requirements of high precision, high efficiency, high performance products had posed challenges to grinding wheel dressing techniques. Aiming to drive the continuous development and progresses of grinding wheel dressing techniques, the current development status, basic principles, main features, and development bottlenecks of grinding wheel dressing methods were summarized and analyzed in detail. The problems needed to be solved urgently for grinding wheel dressing were also briefly discussed, and the direction of grinding wheel dressing investigation was prospected.
    Monitoring and Visual Analysis of Processing Data Based on Time-Position Mapping
    ZHANG Ying, ZHANG Yang, XIA Weihong, WU Baohai, ZHANG Dinghua,
    2021, 32(20):  2449-2457.  DOI: 10.3969/j.issn.1004-132X.2021.20.007
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    The data acquisition method of the machining processes was studied. The processing conditions were discretized in time domain and space, and the voxel model was introduced to subdivide and mark the part space and machining process signals. The short-time domain processing method was used to characterize the machining process signals as corresponding short-time domain signal characteristics. Thus, the knowledge association between the unit voxel working condition and the processing signals was established, and the time-position mapping model of the processing data and the part processing position was established. Finally, taking blade rough milling as an example, the spindle power was visualized and analyzed through the time-position mapping model based on processing signals. The power cloud map was generated, which clearly located the power out-of-tolerance area in blade machining, evaluated the machining state, and provided a basis for processing parameter optimization.
    Research on Intelligent Workshop Disturbance Processing Decision by Improved Case-based Reasoning
    YUAN Minghai, LI Yadong, PEI Fengque, ZHANG Lizhi, GU Wenbin
    2021, 32(20):  2458-2467,2491.  DOI: 10.3969/j.issn.1004-132X.2021.20.008
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    In view of the facts that once the workshop disturbance occured, it would seriously affect the production operations of the workshop, in order to deal with disturbances quickly and efficiently, and to restore normal operations of the workshop, a method on intelligent workshop disturbance processing decision was proposed by improved case-based reasoning. The discrete manufacturing workshop disturbance processing under the intelligent manufacturing environment was taken as the research object, the ternary method was used to model the workshop disturbance case, the hierarchical attributes of the case problem domain were analyzed. A multi-dimensional similarity matching algorithm of case feature attributes was proposed, and the corresponding similarity matching formula was designed. Combined with index contribution rate and kernel density estimation, the order relation analysis method was improved to determine the attribute weight values, the accuracy of case matching was improved, the fast and efficient matching of disturbance cases and historical cases was realized, and the specific solutions was provided. The effectiveness and feasibility of the proposed method were verified by a disturbance case of a mold intelligent manufacturing workshop.
    A Frequency Domain Feature Extraction Auto-encoder and Its Applications on Fault Diagnosis
    ZHAO Zhihong, LI Lehao, YANG Shaopu, LI Qing
    2021, 32(20):  2468-2474.  DOI: 10.3969/j.issn.1004-132X.2021.20.009
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    An asymmetric frequency domain auto-encoder method was proposed to extract spectrum characteristics of vibration signals. Unlike traditional auto-encoder, which took reconstructed vibration signals as the target output, the frequency domain auto-encoder used the frequency spectrum of vibration signals as the target output. This asymmetric auto-encoder might learn the mapping between vibration signals and the frequency spectrum, so that the encoder might output frequency domain features. In order to illustrate the feature extraction effectiveness of the proposed frequency domain auto-encoder, feature extraction and fault diagnosis experiments were carried out on bearing data sets. Without introducing label information, the features extracted by the frequency domain auto-encoder show better clustering effectiveness and may distinguish different fault types of the bearings. In the further generalization experiment, using 1% labeled samples in training classifier may achieve more than 90% of fault classification accuracy. The experimental results show that the frequency domain auto-encoder may extract fault feature information from vibration signals better than that of the traditional auto-encoder and has certain practical value.
    Fault Diagnosis Method of Wind Turbine Gearboxes Mixed with Attention Prototype Networks under Small Samples
    YU Haoshuai, TANG Baoping, ZHANG Kai, TAN Qian, WEI Jing
    2021, 32(20):  2475-2481.  DOI: 10.3969/j.issn.1004-132X.2021.20.010
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    The scarcity of labeled fault sample data of wind turbine gearboxes in some wind farms seriously reduced the accuracy of fault diagnosis. To solve this issue, a fault diagnosis method based on mixed self-attention prototype networks under small samples was proposed. First, the vibration signals were mapped to the fault feature measurement space through the prototype networks. Then, the position self-attention mechanism and channel self-attention mechanism were used for matrix fusion to construct a mixed self-attention module, which established the global dependence of the original vibration signals and obtained more discriminative characteristic information to learn the measurement prototypes of wind power gearboxes in various health states. Finally, the trained metric classifier was adopted to identify the faults of the wind turbine gearbox under the condition of small samples. Experimental results show that the fault diagnosis method of the mixed self-attention prototype networks may achieve high-precision fault diagnosis of wind turbine gearboxes on different scales of small sample datasets.
    Tool Wear Online Recognition Method Based on Multi-source Synchronous Signals and Deep Learning
    YIN Chen, ZHOU Shichao, HE Jianliang, SUN Yuxin, WANG Yulin
    2021, 32(20):  2482-2491.  DOI: 10.3969/j.issn.1004-132X.2021.20.011
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    To improve the practicability of the tool condition monitoring systems and avoid signal interference caused by operation changes in the actual machining processes, a tool wear online recognition method was proposed based on multi-source synchronous signals and deep learning. The proposed method leveraged the automatic triggering to achieve the synchronous online collection of multi-source signals, i.e., tool vibration, spindle power, and CNC system parameters while the machine tool was running in a specific process. The synchronization of the collected signals might be ensured and the signal fluctuation interference caused by operation changes might be also avoided. Moreover, high-frequency vibration characteristics were employed to achieve the accurate division of samples collected during the “cutting process” and the “cutting interval”, and the Pearson correlation coefficient was utilized to extract the highly correlated features, guaranteeing the availability of the multi-source signal fusion samples. Finally, a tool wear online recognition model was established based on the one-dimensional convolutional neural network. The experimental results indicate that the proposed method fulfills the requirements of online recognition of tool wear in the actual machining processes in terms of recognition accuracy and diagnostic efficiency.
    Energy Consumption Data Collection and Supervision Systems of Forging Workshops with OPC Unified Architecture
    JIAO Yuyang, LI Li, NIE Hua, ZHOU Li, CHEN Xingzheng, LI Tao
    2021, 32(20):  2492-2500.  DOI: 10.3969/j.issn.1004-132X.2021.20.012
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    Aiming at the characteristics of multi-source heterogeneous data in forging workshops, and current situation of information silos and difficulties in interconnection among equipment, a set of energy consumption data and monitoring systems for forging workshops was proposed. Combined with specific requirements of the systems in combination with data characteristics of the workshops, network architecture of data perception and transmission according to field layout was designed, and an information interaction model was established with OPC UA. Finally, taking a forging workshop as application object, a collection of consumption data and statistical supervision of information in the entire processes of forging actual productions was realized.
    Key words: forging shop; object linking and embedding(OLE) for process control unified 
    Design of Inner Cone Roller Swaging Tool for Aviation Self-lubricating Spherical Plain Bearings
    WANG Qiang, CHEN Jigang, ZHAO Jianhua, LI Xue, HU Zhanqi,
    2021, 32(20):  2501-2507,2519.  DOI: 10.3969/j.issn.1004-132X.2021.20.013
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     Based on the requirements of aviation standards, a new type of roller swaging tool was studied to achieve pure rolling of the rollers, good surface quality, and to reduce the influences on the starting torque of the bearings. Based on the theorem for the composition of velocities, the conditions for the roller to achieve pure rolling were studied, and a roller with an inner cone roller was designed. The swaging of MS14101-9 bearing was taken as an example, the effects of two kinds of rollers on the fit between the outer ring and the housing, the equivalent stress of the inner and outer rings of the bearing, the push-out load, and the surface quality of the swaging groove were studied. Finally, with the constraints of the range of the starting torque of the bearings specified in aviation standard, the parameters of swaging load and roller revolution speed were optimized by virtual orthogonal tests with the displacement changes of the outer spherical surface of the inner ring as an optimization index. The results show that a good process quality may be achieved with tools with inner cone rollers, when the swaging load is as 4000 N and the roller revolution speed is as 200 r/min, which may ensure that the process quality index and the starting torque of the bearing after the swaging are within the standard requirements.
    Development of Structure Monitoring Systems and Digital Twin Technology of Active Jacket Platforms
    YAN Tianhong, WANG Weigang, ZHAO Haifeng, ZHOU Guoqing
    2021, 32(20):  2508-2513.  DOI: 10.3969/j.issn.1004-132X.2021.20.014
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    Abstract: At present, nearly one-third of Chinas offshore jacket platforms had exceeded or were about to reach the design life, and the maintenance or repair of the platform structures were more urgent than ever. The traditional underwater structure damage detection of jackets had fewer measuring points, and was difficult, expensive, and might not predict the states of the platform structures. A jacket platform structure monitoring system was developed in the South China Sea. The system mainly included marine wind and wave environmental monitoring and platform structural vibrations and strain response monitoring. According to the monitoring data, a digital twin of the active jacket platform structures was proposed based on the dual finite element model modification. The safety assessment and life prediction models of the platform structures were modified through the digital twin technology to grasp the structural behaviors of the offshore jacket platform structures during the entire service cycle. Scientific prediction and preventive maintenance were used to extend the life of the platforms.
    Shape Change Mechanism and Prediction Model of Cross Cutting Units during Straightening Processes
    BAI Zhenhua, CUI Xiying, WANG Wei, JING Qunping, ZHANG Ligeng, LIU Yaxing, ZHANG Yanyan
    2021, 32(20):  2514-2519.  DOI: 10.3969/j.issn.1004-132X.2021.20.015
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    Taking fully into account the equipment and process characteristics of the cutting straightening units, the change mechanism of the finished flatness of the straightening units was analyzed, and then, the test study was carried out to explore the influences of the straightening roll systems on the flatness. It is concluded that the straightening processes of the straightening units are realized by multiple bending and straightening of the strip steels. After the test data were analyzed and processed, the pressure stress and friction of the straightening rolls on the strip steel were solved, and the mathematical model of flatness changes in the straightening processes was obtained, so a complete flatness prediction model suitable for the straightening processes of the cross cutting units was established. Thus, the corresponding shape prediction software for the straightening processes of the cross cutting units was compiled, which may quickly calculate the shape distribution of the straightened strips. By applying the software to the production practices of a 1220 cross cutting unit, it may be clearly seen that the calculated values and the measured values of the strip shapes after straightening are almost equal. Therefore, the shape prediction results are in line with the field production practices.