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    Research Progresses of Basic Equipment Manufacturing and High-grade Integrated CNC Machine Tools
    HU Lai, ZHA Jun, ZHU Yongsheng, WEI Wenming, LI Dongya, LUO Ming, NIU Wentie, CHEN Yaolong
    China Mechanical Engineering    2021, 32 (16): 1891-1903.   DOI: 10.3969/j.issn.1004-132X.2021.16.001
    Abstract324)      PDF (26502KB)(436)       Save
    In order to solve the key problems faced by the aerospace manufacturing fields and improve the service capability for the industries,the machine tool industry proposed to build an innovative capability platform for high-grade CNC machine tools in the field of aerospace manufacturing. The research progresses in four aspects of basic assembly manufacturing and high-grade CNC machine tools were summarized about the innovation platform, including: motorized spindle unit technology(dynamic analysis of high-speed spindle—tool handle—tool system, digital simulation and prototype modal verification analysis); machine tool design(rigid-flexible coupling—electromechanical coupling dynamics of linear axis feed system, verification and analysis of electromechanical coupling dynamic model of multi-axis linkage and high-speed five-coordinate hybrid machining equipment and swing/rotary feed system, innovative structural design of MTC1000 boring, milling and grinding composite machining center); machine tool control(verification and analysis of high-speed start-stop residual vibration suppression technology) and machine tool verification(analysis of field data acquisition, mapping and storage technology for high-speed machining of aerospace structural parts). Finally, the future research trends were prospected.
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    Two-way Fluid-Solid Coupling Simulation and Experimental Research of Sealing Rings Based on MpCCI Method
    GONG Ran, ZHANG Zhenyu, CHENG Zhigao, XU Yi, ZHANG He
    China Mechanical Engineering    2021, 32 (14): 1639-1646.   DOI: 10.3969/j.issn.1004-132X.2021.14.001
    Abstract306)      PDF (5466KB)(344)       Save
    To predict the fluid-solid coupling characteristics of sealing systems in transmission of heavy-duty off-road vehicles, the stress state of sealing rings in small confined spaces and the flow characteristics in flow fields of rotating sealing gaps were taken into account, and then the numerical models of two-way fluid-solid coupling for sealing systems were established and the solving methods were presented. The multi physics code coupling tool MpCCI was combined with FLUENT and Abaqus to carry out the numerical calculations of two-way fluid-solid coupling of rotary sealing systems. According to the fluid-solid coupling calculations, the flow states of oil in flow fields of rotary sealing gaps were obtained. The effective characteristics of sealing ring deformations on the leakage of rotary sealing systems and the friction torques of sealing rings were studied. The influences of transmission system working conditions on sealing ring performances were explored by two-way fluid-solid coupling dynamic simulation. Experimental investigations were performed in sealing performance test rig for sealing rings of vehicle transmission systems. Comparisons of numerical and experimental results show a good consistency of their change rules, which verifies the correctness of sealing fluid-solid coupling numerical models and calculation results.
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    Tool Wear and Remaining Useful Life Estimation of Difficult-to-machine Aerospace Alloys:a Review
    LUO Huan, ZHANG Dinghua, LUO Ming
    China Mechanical Engineering    2021, 32 (22): 2647-2666.   DOI: 10.3969/j.issn.1004-132X.2021.22.001
    Abstract303)      PDF (2230KB)(306)       Save
     Due to the special application requirements, such as light weight designs, strength,in aeronautical manufacturing field, a large number of difficult-to-machine materials such as titanium alloy and nickel-based alloy were used, and the cutting tools wore fast. Excessive tool wear would affect product quality. Under the premise of ensuring product quality, it was urgent to monitor tool wear states and to predict tool remaining useful life in order to make full use of the cutting tools. The definition, classification and models of the cutting tool remaining useful life estimation were described herein. Meanwhile tool wear monitoring was the basis and prerequisite of tool life prediction, the main steps and common models were briefly described. The remaining useful life prediction models might be categorized into physics-based models, data-driven models and hybrid models. The advantages and disadvantages of different prediction methods and their application scenarios were summarized , and the future research directions were discussed.
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    Research Progresses of Robot Grinding and Polishing Force Compliance Controls
    GE Jimin, DENG Zhaohui, LI Wei, LI Chongyang, CHEN Xi, PENG Deping
    China Mechanical Engineering    2021, 32 (18): 2217-2230,2238.   DOI: 10.3969/j.issn.1004-132X.2021.18.011
    Abstract201)      PDF (6054KB)(329)       Save
    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.
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    Research Status and Prospect of CMG Technology
    REN Yinghui, ZHOU Jiaheng, LI Wei, ZHOU Zhixiong, LI Chenfang
    China Mechanical Engineering    2021, 32 (18): 2143-2152.   DOI: 10.3969/j.issn.1004-132X.2021.18.001
    Abstract200)      PDF (6455KB)(261)       Save
    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. 
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    A Review of Force Sensing Technology in Robot-assisted Laparoscopic Surgery
    ZHANG Jianxun, YAO Bin, DAI Yu, XIA Guangming,
    China Mechanical Engineering    2021, 32 (21): 2521-2531.   DOI: 10.3969/j.issn.1004-132X.2021.21.001
    Abstract198)      PDF (4488KB)(303)       Save
    In order to promote the further research and clinical applications of force sensing technology in robot-assisted laparoscopic surgery, the research progresses were reviewed. Sensor force sensing was divided into two categories:electrical signal-based sensing and optical signal-based sensing. Some key indicators were analyzed, such as sensor position distribution on surgical instruments, mechanical structure, measurement range, measurement accuracy and electromagnetic compatibility. Sensors advantages and disadvantages were discussed. Sensorless force sensing was divided into two categories:vision-based sensing and dynamic model-based sensing. And the realization method, technical obstacle and error sources were analyzed. Finally, the development trend of force sensing technology in robot-assisted laparoscopic surgery was prospected. 
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    Similarities Detection and Analysis of Tire Patterns Based on Similarity Theory
    LI Hongling, DONG Yude, HUANG Zhihao, GAO Haoyu, TAO Senwang
    China Mechanical Engineering    2021, 32 (14): 1646-1652.   DOI: 10.3969/j.issn.1004-132X.2021.14.002
    Abstract194)      PDF (4852KB)(173)       Save
    Based on the similarity theory, the characteristics of tire pattern structures were analyzed. Using image processing method such as gray histogram, aHash algorithm and co-occurrence matrix method, a 2D similarity detection system for tire patterns was built in MATLAB software. The similarities of the existing tire patterns were detected by the system, and the similarities of the specified patterns with local change and the original patterns were detected. Results show the stability and the reliability of the system. It may provide a basis for similarity quantization of different tire patterns.
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    Design and Adsorption Performance Optimization of Non-contact Variable Magnetic Gap Type Permanent Magnet Absorption Mechanisms of Pipe Climbing Robots
    GUO Denghui, CHEN Yuan
    China Mechanical Engineering    2021, 32 (14): 1659-1668.   DOI: 10.3969/j.issn.1004-132X.2021.14.004
    Abstract194)      PDF (3267KB)(169)       Save
    A non-contact variable magnetic gap type climbing robot was designed, which was adaptive adsorb tubes with different diameters. A magnetic field distribution model and magnetic adsorption force model of adsorption mechanisms were established by vector magnetic position method and finite element method. Based on equilibrium equation of space force system, the mechanics model of the robot was established and the minimum magnetic adsorption force was obtained. Based on the theoretical model of magnetic field and magnetic adsorption force and Maxwell simulation, the optimal magnet width and magnetic adsorption force were obtained by discrete combination method. After comparing different magnetic fields and magnetic adsorption forces, when the optimal magnet width is as 80 mm, the magnetic attraction force per unit volume of approximate circular arc mechanisms is as 0.0078 N/mm3, which is larger than 0.0047 N/mm3 of rectangular magnet. The magnetic adsorption force satisfies the load requirements of the minimum magnetic adsorption force of 2100 N. Finally, the magnetic adsorption force characteristics of the magnetic adsorption mechanisms were obtained by experiments. The results prove the feasibility of the optimization design of magnetic adsorption mechanisms.
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    A Fault Diagnosis Method of Rotating Machinery Based on LBDP
    SHI Mingkuan, ZHAO Rongzhen
    China Mechanical Engineering    2021, 32 (14): 1653-1658,1668.   DOI: 10.3969/j.issn.1004-132X.2021.14.003
    Abstract191)      PDF (2566KB)(159)       Save
    Aiming at the problems of classification difficulty caused by multi-class and high-dimensional complex characteristics of rotor fault data, a LBDP dimensionality reduction algorithm was proposed. First of all,the mixed features of the rotor vibration signals were extracted from multiple angles in time domain, frequency domain and time-frequency domain,and the high-dimensional feature sets were constructed. The original feature sets were fused by LBDP algorithm, and the low-dimensional sensitive feature subsets which might best reflect the intrinsic information of the faults were selected. Then the low-dimensional feature subsets were input into K-nearest neighbor(KNN) classifier for training and fault classification. The effectiveness of the proposed method was verified by the vibration signal sets of a double-span rotor systems, and it is proved that the method may extract the local discriminant information comprehensively and make the difference among fault categories clearer. 
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    China Mechanical Engineering    2021, 32 (23): 1-.  
    Abstract189)      PDF (140286KB)(332)       Save
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    Investigation of Influences of Stator Can Deformations on Axial Flow Resistance in Annular Gap Flow
    WANG Shengde, YAO Zhenqiang, SHEN Hong
    China Mechanical Engineering    2021, 32 (17): 2017-2024.   DOI: 10.3969/j.issn.1004-132X.2021.17.001
    Abstract187)      PDF (7775KB)(283)       Save
    In order to predict the flow distribution between the upper and lower branches of the internal cooling circuit within a canned motor reactor coolant pump(RCP), the stator can deformations and the influences on axial resistance of the annular gap flow were studied. The deformed profile of stator cans under the high pressure was calculated with the finite element method and verified by experiments. The influences of stator can deformations on annular gap flow were studied by using computational fluid dynamics and a modified model for axial flow resistance evaluation was established by variable parameter analysis and mathematical fitting. Calculation result from the established model shows that, compared to ideal cylindrical state, 11% boundary deformation of the stator can under the rated working state of the RCP, will lead to 83% decrease of the axial flow pressure drop in the rotor and stator clearance.
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    Key Technologies of Design and Performance Improvement of Heavy-duty and High Precision Machining Robot Bodies for Large-scale Components
    FENG Fei, YANG Haitao, TANG Lina, DING Han,
    China Mechanical Engineering    2021, 32 (19): 2269-2287.   DOI: 10.3969/j.issn.1004-132X.2021.19.001
    Abstract187)      PDF (16780KB)(255)       Save
    According to the summary and analysis of the application background and development status of mobile robot machining for the typical large-scale components, the basic performance requirements of large-scale component processing robot bodies such as the large workspace, high rigidity, high precision, heavy-duty, light-weight, high dynamic response and high load-to-weight ratio were proposed. Furthermore, focusing on the basic performance requirements, the optimization design and robot performance improvement method of heavy-duty and high-precision machining robot bodies were demonstrated, from the aspect of the optimization design of robot body configurations and mechanisms, the development of the high-performance dedicated and professional controller and the open source operating system of machining robots, dynamic calibration of kinematic parameters and real-time prediction and dynamic compensation of pose errors, dynamics modeling of rigid-flexible coupling multibody system, as well as the robot dynamics control and active vibration suppression control. And then, the conceptual design of the configurations and mechanisms of the machining robot bodies utilized on the large-scale components was completed. The innovative design and development of the robot bodies for the large-scale component processing robots may provide high-performance and super flexible robot machining system for the typical large-scale components in aerospace and other fields, and help to promote the improvement of key performance of domestic industrial robots. 
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    Electromechanical Coupling Modeling and Dynamic Characteristic Analysis of Wind Power Transmission Systems under Operation Conditions
    QIN Datong, LYU Xuehui, CHEN Ruibo, YANG Zhanbin
    China Mechanical Engineering    2022, 33 (03): 253-260.   DOI: 10.3969/j.issn.1004-132X.2022.03.001
    Abstract181)      PDF (5566KB)(191)       Save
    To reveal the electromechanical coupling dynamic characteristics of the wind power transmission systems under the variable speeds and variable load operation conditions, the electromechanical coupling model of the wind power transmission systems including the gear system dynamics model, the finite element model of permanent magnet synchronous generator and the operation control model of wind turbine was established, taking into consideration of the nonlinear factors such as gears time-varying meshing stiffness, cogging effect and magnetic saturation of generators. The dynamic responses of the systems under the starting and power generation operation conditions and the electromechanical coupling dynamic characteristics of the system were analyzed. The results show that the dynamic responses of the wind power transmission systems are stable under the starting condition; under the power generation operation condition, the wind power transmission systems are under a variable speed and variable load state, and low-frequency torsional vibrations are vulnerable to be excited and dynamic responses are complicated. Under the effects of generator cogging, magnetic saturation and other factors, the currents and electromagnetic torques may produce main harmonic frequency fluctuations caused by time harmonics and space harmonics. Because of the electromechanical coupling effects, the gear vibration characteristics and the electromagnetic characteristics may affect each other. The currents and electromagnetic torques contain more mechanical vibration frequency components related to gear meshing. At the same time, the electromagnetic torques react to the gear systems, which excites rich structural frequency components of the gear systems. 
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    Review on Development of Legged Robots for Deep Space Landing Exploration#br#
    SUN Junkai, SUN Zezhou, XIN Pengfei, LIU Bin, WEI Qingqing, YAN Chuliang
    China Mechanical Engineering    2021, 32 (15): 1765-1775.   DOI: 10.3969/j.issn.1004-132X.2021.15.001
    Abstract167)      PDF (9048KB)(314)       Save
    The research status of deep space landing exploration legged robots was introduced in the major aerospace powers, such as the United States, Europe and China. Moreover, advantages and disadvantages of legged robots for deep space landing exploration were analyzed, and the issues that caused the legged robots not to be used in engineering yet were discussed from the hardware and software design aspects. Then, the key technologies of legged robots for deep space landing exploration were proposed, including sensory fusion technology, intelligent control technology, reconfigurable structure technology and multi-robot cooperation technology, which offer references for the development of legged robots that may be actually applied in the deep space landing exploration. 
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    Hydrodynamic Force Calculation Method of Tracked Equipment Based on Artificial Lateral Line#br#
    WU Jiaxiong, SHEN Yanhua , YANG Shudi, FENG Zhipeng
    China Mechanical Engineering    2022, 33 (10): 1135-1141.   DOI: 10.3969/j.issn.1004-132X.2022.10.001
    Abstract164)      PDF (7590KB)(275)       Save
     Aiming at the challenge that the hydrodynamic forces of underwater equipment could not be measured in real time, a method for calculating the hydrodynamic forces of track equipment was proposed based on ALL. Through the ALL system of the track equipment, the pressure values of different incoming flow speeds and angles were extracted, and the distribution law of pressure values was used to perceive the local flow field information of the track equipment. Through the hydrodynamic force restraint experiments of the track equipment combined with the computational fluid dynamics(CFD)simulation method, the functional relationship between the front surface shapes of the track equipment and the viscous coefficient was established. Based on the flow field perception results of the ALL, the hydrodynamic force empirical model of the track equipment was derived. The verification results show that the pressure distribution characteristics of the ALL may effectively identify the incoming flow velocity and angle. The hydrodynamic force empirical model combined with the results of ALL perception may be used to estimate the hydrodynamic force of underwater track equipment in real time, the water resistance calculation error of underwater track equipment model is within the acceptable range of the engineering application. 
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    Programming by Demonstration with Virtual Fixture Assistance for Robotic Machining of Complex Surfaces
    GE Kedi, ZHAO Huan, CHEN Pengfei, DING Han
    China Mechanical Engineering    2021, 32 (14): 1716-1725.   DOI: 10.3969/j.issn.1004-132X.2021.14.010
    Abstract158)      PDF (7051KB)(109)       Save
     In order to solve the difficulties of virtual fixture construction and adaptive adjustment according to the operators intention in robot programming by demonstration for complex surface machining,a Programming by Demonstration (PbD) strategy for virtual fixture generation and iterative updating was proposed. A prior virtual fixture was constructed offline by demonstrating surface manifold. If the prior virtual fixture matched the surfaces to be machined, the spring-damping system was used to online compensate the path deviations of demonstration. Otherwise, the iterative correction was realized by adaptive adjustment of virtual fixture stiffness and flexibility. The results show that the construction of virtual fixture based on surface manifold is simple and has generalization characteristics, which improves the construction efficiency of complex surface virtual fixtures; in the auxiliary demonstrating processes of the virtual fixtures by using the sinusoidal and fan track , the position and orientation errors of auxiliary demonstrated path may be decreased at least by 84% and 81% respectively, and the virtual fixture may be adjusted adaptively according to the operators intention to better match the target surfaces.
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    State-of-the-art on MQL Synergistic Technologies and Their Applications
    YANG Jianzhang, WANG Chengyong, YUAN Yaohui, YUAN Songmei, WANG Xibin, LIANG Cile, LI Weiqiu
    China Mechanical Engineering    2022, 33 (05): 506-528.   DOI: 10.3969/j.issn.1004-132X.2022.05.001
    Abstract156)      PDF (22261KB)(303)       Save
    MQL technology had the advantages of low cutting fluid consumption and high lubrication efficiency. However, there were more problems such as inadequate lubrication and low cooling performance under the specific conditions. MQL synergistic technology, such as cryogenic air or liquid carbon dioxide which combines the advantages of cooling and lubrication, might effectively solve the machining problems of difficult-to-cut materials. The latest research of principle, key devices and technology applications of various types of MQL synergistic technology were summarized. The performance of various devices and their parameter regulation characteristics were analyzed in details. Combining with the applications and the mechanism of MQL synergistic technology, the machinability in titanium alloy, nickel alloy, stainless steel and other difficult-to-cutting materials were analyzed. In addition, a sustainable analysis of various types of MQL synergistic technology was provided. The purpose is to provide technical support and reference for the engineering applications of clean cutting technologies.
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    Collaborative Design Optimization of Damping Layers and Stiffener Layout of Thin-walled Stiffened Plate Structures for Dynamics Performances
    NIU Bin, YAN Jiaming, MAO Yuming, LIU Haiyang
    China Mechanical Engineering    2021, 32 (16): 1912-1920.   DOI: 10.3969/j.issn.1004-132X.2021.16.003
    Abstract155)      PDF (5637KB)(115)       Save
    In order to reduce the vibrations of thin-walled stiffened plate structures in dynamic environment, a topology optimization method was proposed for designing the layout of reinforced ribs and damping layers. The penalization model of damping material and the ground structure approach were combined in the optimization. The density of stiffened rib and element density of the damping material were introduced as the independent design variables. Two constraints on the material used in the stiffened ribs and the damping layers were considered. The collaborative design optimization of damping layers and stiffening ribs was established with dynamic compliance as the objective function. The optimized topological design of stiffeners and damping materials was realized simultaneously. Several numerical examples of stiffened plate with different damping properties and various excitation frequencies were given to verify the effectiveness of the proposed method.
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    Kinematic Parameter Optimization of Workspace-based Generalized Spherical Parallel Robots for Ankle Joint Rehabilitation
    LIU Xiuying, ZHANG Jianjun, LIU Chenglei, NIU Jianye, QI Kaicheng, GUO Shijie
    China Mechanical Engineering    2021, 32 (16): 1921-1929.   DOI: 10.3969/j.issn.1004-132X.2021.16.004
    Abstract149)      PDF (3703KB)(151)       Save
    In order to solve the difficult problems for the existing ankle joint rehabilitation robots to completely fit the motion of the human ankle joints, a high-matching ankle joint motion series fitting model was developed based on bionics, and a new type of three degree of freedom generalized spherical parallel robot was proposed. In order to study the fitting ability of the parallel robots, the degree of freedom characteristics was analyzed based on the spiral theory. The kinematics model of the mechanisms was established, it was clarified that had partial decoupling characteristics based on inverse kinematics. According to the characteristics of the dual spherical centers of the robots, the moving sphere center and the working space of the moving platform were solved. Finally, taking the degree of matching between the working space of the ankle joint motion fitting model and the working space of the robots as the objective function, the genetic algorithm was used to optimize the kinematic parameters. The working space scatter plots of the robots and the model were compared and the effective working space ratios were obtained as 0.79 and 0.86 respectively. The results show that the optimized working space of the generalized spherical parallel robots may meet the motion requirements of the ankle joints. 
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    Vehicle Tracking of Information Fusion for Millimeter-wave Radar and Vision Sensor
    HU Yanping, LIU Fei, WEI Zhenya, ZHAO Linfeng
    China Mechanical Engineering    2021, 32 (18): 2181-2188.   DOI: 10.3969/j.issn.1004-132X.2021.18.006
    Abstract147)      PDF (4596KB)(227)       Save
    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.
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    Fatigue Crack Growth Prediction Based on NPF Algorithm
    GU Zhenhua, LI Ke, GU Jiefei, , SU Lei, SU Wensheng
    China Mechanical Engineering    2021, 32 (14): 1709-1715.   DOI: 10.3969/j.issn.1004-132X.2021.14.009
    Abstract147)      PDF (4332KB)(134)       Save
    A fatigue crack growth prediction method was proposed based on NPF algorithm, aiming at solving the problems that traditional Paris fatigue crack growth model had low accuracy and could not take the influences of various uncertain factors in the crack growth processes into consideration. State space equations were used to characterize crack growth processes based on Paris formula. Observation space equations were established using monitoring technology based on Lamb waves.The real-time observation information was used to modify the predicted values of the model. Finally, the effectiveness of the method herein was verified by the fatigue crack growth experiments of Q235 steel specimens. Experimental results show that the NPF algorithm may effectively correct prediction errors of Paris formula in fatigue crack growth prediction. The prediction accuracy is better than that of the extended Kalman filter and particle filter(PF) algorithms, and the algorithm efficiency is significantly better than that of PF algorithm.
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    Influences of Service Conditions on Fatigue Properties of Stainless Steel Spot Welding and Cracking Analysis
    JIANG Yunlu, YANG Liang, HAN Xiaohui, XU Ye, CHEN Huaining, CAI Guixi
    China Mechanical Engineering    2021, 32 (14): 1726-1731.   DOI: 10.3969/j.issn.1004-132X.2021.14.011
    Abstract146)      PDF (13128KB)(261)       Save
    Joints of resistance spot welding on stainless steel body frame was used as research objects to find out the influences of temperature (-40 ℃, room temperature, 70 ℃), stress ratio(0.1,0.5) and 3.5% NaCl environmental medium on joint fatigue lifes. The electron back-scattered diffraction(EBSD) technology, scanning electron microscopy(SEM), instrumented ball indentation system(IBIS) and tensile-shear experiment were used to analyze the grain orientation, residual stress distribution, appearance of fatigue fractures and the mechanics properties. Results show that the fatigue property is better due to the increasing of material strength under low temperature conditions. And the high-cycle fatigue property is better due to the improvement of plastic property under 70 ℃. The fatigue property of stress ratio of 0.1 is better than that of 0.5. Corrosion medium and tensile stress may accelerate the strress corrosion, cracking and rapid dissolution of anode regions of crack top ends, accelerate the initiation and extension of the cracks,and may significantly reduce fatigue life of spot welding joints. The fatigue cracks are nucleated on the stress concentration interfaces, the cracks grow up along the softening zones and extend to the plate surfaces until fracture failure.
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    2DOF Internal Model Control for Steer-by-wire Systems with Time Delay
    DU Wenlong, CHEN Li, LIU Wentong, CHEN Jun,
    China Mechanical Engineering    2021, 32 (16): 1904-1911,1920.   DOI: 10.3969/j.issn.1004-132X.2021.16.002
    Abstract144)      PDF (4593KB)(125)       Save
    Aiming at the response time delay problems caused by signal transmission, mechanical clearance and friction of the SBW systems, a 2DOF IMC was designed to improve the angle tracking accuracy. The time delay model and the SBW model were established and combined as the nominal model. In order to avoid non-minimum phase terms, an all-pole approximation method was adopted to linearize the time delay model, so the tracking controller and the anti-interference controller might be solved. Compared with the 2DOF IMC without using a nominal model with time delay and the classical PID control, MATLAB/Simulink simulation results show the influences of time delay on the tracking performance of the three methods. The effects of time delay on the tracking performance of the 2DOF IMC using the all-pole, Taylor and Padé approximation methods were compared respectively. Finally, the bench test results of the SBW systems show that the 2DOF IMC based on the all-pole approximation has higher tracking accuracy and better adaptability to time delay.
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    Generation Mechanism of Grinding Marks Based on Grinding Trace Simulations
    CHEN Bing, LUO Liang, JIAO Haowen, DENG Zhaohui, YAO Honghui
    China Mechanical Engineering    2021, 32 (14): 1677-1685.   DOI: 10.3969/j.issn.1004-132X.2021.14.006
    Abstract144)      PDF (11755KB)(300)       Save
    Because grinding marks would remain on spherical and aspherical surfaces in cross grinding, so generating mechanism of grinding marks was investigated based on grinding trace simulations. Distribution equation of grinding traces was established. Generation and distribution mechanism of grinding traces on ground surfaces was analyzed in cross grinding, and the generation mechanism of grinding marks caused by alteration of grinding parameters was revealed. From the results of simulations, it may be found that the distribution of grinding traces is dense at central areas and sparse at outer areas of ground surfaces, and the distributions are periodic and radial. Length regularity, shape regularity, and distribution regularity of all the grinding traces remained on the ground surfaces were similar, except a certain phase angle is varied among grinding traces. When ratio of grinding wheel rotary speed to workpiece rotary speed is as integer, the worst grinding traces of two adjacent periods are connected together end-to-end, which leads to coupling and propagation of cracks at the junction. And then, breakage situation of ground surfaces is aggravated. Finally, the broken grinding traces are connected together, and the grinding marks are generated.
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    Meta-action-oriented Reliability Allocation Method of Mechanical Transmission Systems
    CHEN Yifan, ZHANG Genbao, RAN Yan, LI Yulong, YU Hui,
    China Mechanical Engineering    2021, 32 (17): 2032-2039.   DOI: 10.3969/j.issn.1004-132X.2021.17.003
    Abstract144)      PDF (2132KB)(166)       Save
    A reliability allocation method for mechanical transmission systems was proposed to quantify the uncertainty, aimed at the uncertainty in the reliability allocation of mechanical transmission systems. The minimum granularity of reliability allocation (i.e. meta-action) in transmission systems was extracted by the decomposition method of “function-motion-action (FMA)”. A method for calculating the sensitivity of the transmission systems was proposed based on the Sobol of LRA according to the reliability mathematical model of meta-action, which quantified the reliability sensitivity of meta-actions in the transmission systems, and the key meta-actions that affected the reliability of transmission systems were identified. The mapping relationship between the meta-action and the system reliability was established, and the mapping results were solved. The application results show that the method has high calculation accuracy and provides guidance for the reliability allocation of mechanical transmission systems.
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    Research on Thermally Induced Preload of Machine Tool Spindle Bearings Based on FBG Sensor
    LU Tuanliang, QIU Ming, DONG Yanfang, ZHANG Yatao, DU Hui
    China Mechanical Engineering    2021, 32 (17): 2025-2031,2039.   DOI: 10.3969/j.issn.1004-132X.2021.17.002
    Abstract143)      PDF (4918KB)(114)       Save
    Aiming at the difficult and inaccurate testing of the machine tool spindle bearing preloads, an online monitoring method was proposed herein based on FBG sensor. Firstly, the thermal analysis model of the spindle unit was established considering the heat generated by the spinning friction of the rolling elements, the contact thermal resistance between the inner/outer ring of the bearings and the spindle/housing. Secondly, a thermally induced preload test system for the spindle bearings was built. Through simulation and experimental comparison, the temperature distribution and thermally induced preloads of the key components of the spindle unit were analyzed at different speeds. The results show that the temperature measured by FBG sensor and thermal sensor is consistent with the simulation temperature prediction, which verifies the accuracy and reliability of the method proposed.
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    Study on Thermal Coupling Durability of Mechanical Elastic Wheels under Random Loads
    ZHANG Chen, ZHAO Youqun, ZHENG Xin, DU Yiyan
    China Mechanical Engineering    2021, 32 (14): 1669-1676.   DOI: 10.3969/j.issn.1004-132X.2021.14.005
    Abstract141)      PDF (5279KB)(137)       Save
    In order to predict the maximum driving range of mechanical elastic wheels under random loads caused by uneven road surfaces under straight driving conditions, the durability of mechanical elastic wheels was studied. A finite element model for durability research was established based on structure characteristics of the wheels. Considering uneven roads, the relationships of speeds, dynamic loads and dynamic load coefficients of the wheels were determined, and the equivalent cyclic loads were applied to the wheels. Based on fatigue damage theory and fatigue test methods, the FE-safe software was used to predict the durability of wheels, and the maximum driving range is as 8787 km. The thermal coupling durability of the clasps was analyzed, and the minimum life position is the middle pin ear, and the maximum driving range is as 5258 km.
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    Research on Safety Performance of Lane Keeping Assist Systems Based on Human-machine Cooperative Control
    SUI Xin, LIU Chunyang, ZHAN Kun, WANG Zhangfei, ZHANG Yihui,
    China Mechanical Engineering    2021, 32 (16): 1994-2001.   DOI: 10.3969/j.issn.1004-132X.2021.16.012
    Abstract136)      PDF (3458KB)(134)       Save
    The overlook of interference of drivers' behavior and environmental factors might cause human-computer conflicts during the transition from drive mode to assistance mode. A human-machine cooperative based lane keeping assist(LKA) control system was proposed to aid the issue, where a two degrees-of-freedom vehicle dynamics model was established and linear quadratic regulation lateral control algorithm was employed to determine vehicle's optimal front wheel angle. Vehicle deviation safety assessment model, torque control and safety exit strategy were implemented in the proposed LKA system to realize human-computer interaction and co-driving. A collaborative simulation was fulfilled in CarSim and  Simulink to validate the feasibility of LKA. As the feasibility was demonstrated, the LKA control system was further implemented on the JAC light truck to test the system safety performances. Both of the simulation and experimental results shows that better lane keeping and security performances are achieved with the proposed LKA system.
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    Structural Optimization Design and Research of Direct-drive Quadruped Robots
    LIU Mingyuan, CHEN Ping, MA Jianshe
    China Mechanical Engineering    2021, 32 (18): 2246-2253.   DOI: 10.3969/j.issn.1004-132X.2021.18.014
    Abstract136)      PDF (8229KB)(134)       Save
    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. 
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    Online Monitoring Method for NC Milling Tool Wear by Digital Twin-drivenLI Congbo
    SUN Xin, HOU Xiaobo, ZHAO Xikun, WU Shaoqing
    China Mechanical Engineering    2022, 33 (01): 78-87.   DOI: 10.3969/j.issn.1004-132X.2022.01.009
    Abstract135)      PDF (11516KB)(122)       Save
    In order to solve the problems of large errors of tool wear prediction model caused by continuous aging of CNC milling machines and difficulties of on-line acquisition of dynamic data during machining, a digital twin-driven online tool wear monitoring method was proposed. Firstly, a neural network was used to extract features from multi-source data in the machining processes, and a quantitative model of tool wear time varying deviation was established considering machine aging. Based on this, an on-line prediction method of tool wear in CNC milling was proposed. Then, a numerical control milling digital twin system for tool wear was developed to online sense the dynamic data and simulate the tool wear processes in real time. Finally, this method was applied to actual machining and compared with other prediction methods. The results show that this method may reduce the prediction errors and realize the accurate prediction of tool wear value.
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    Research on Traveling Wave Resonance Characteristics of Spiral Bevel Gears and Its Influence Laws under Parameter Adjustment
    LUAN Xiaochi, ZHAO Yu, SHA Yundong, LIU Gongmin, ZHAO Qian,
    China Mechanical Engineering    2021, 32 (24): 2899-2908,2914.   DOI: 10.3969/j.issn.1004-132X.2021.24.001
    Abstract134)      PDF (7272KB)(93)       Save
    Aiming at the driven bevel gear fracture failure of a certain type of aero-engine central drive bevel gear due to traveling wave resonance in actual processes, combination of simulation analysis and test verification was used to study the traveling wave resonance characteristics and influence laws of spiral bevel gears under parameter adjustment. The modal analysis of the driven gears was carried out based on finite element method, and the relationship between the thickness of the spoke plate and the working temperature with the gear traveling wave resonance characteristics was discussed. Transient dynamic analysis of meshing gears was carried out based on Hertz contact theory, and the influences of load power, operating temperature and damping factor on the stress distribution of driven bevel gears under traveling wave resonance were discussed. The comparison of simulation and test results shows that the errors of simulation results of modal calculation and dynamic analysis are within a reasonable range. Under the premise of meeting the relevant requirements of gear design, the resonance speed or resonance frequency may be avoided by adjusting the thickness of the spoke plate. In terms of the sensitivity of the resonance parameters of the vibration stress distribution, the analysis shows that when the gear is working in the third or fourth nodal diameter traveling wave resonance states, the stress values at the tooth roots are the largest, and the stress values on the front surfaces of the spoke plate are the smallest; when the temperature and damping factor changing, the change of stress values at front of the driven bevel gear spoke plate is small, and the change of stress values at the back of the spoke plate and tooth root is big. Therefore, in improvement and optimization designs of the gears, it is necessary to deal with the third or fourth nodal diameter traveling wave resonance.
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    Intelligent Connected Vehicle PnP Networking Model and Decision Fusion Algorithm
    ZHOU Xiaochun, LIANG Jun, CHEN Long, WANG Yafei, GONG Jinfeng
    China Mechanical Engineering    2021, 32 (16): 1983-1993.   DOI: 10.3969/j.issn.1004-132X.2021.16.011
    Abstract134)      PDF (9498KB)(72)       Save
    To simplify the networking processes of ICVs before multi-sensor fusion, a networking model of self-search—self-identification—self-calibration(S-SIC) was proposed for a PnP environmental sensing sensor. The PnP sensors were searched and connected to ADAS domain by using the depth-first search planning algorithm. The PnP sensors were identified and initialized by using the broadcast messages. The PnP sensors were calibrated by the coordinate transformation matrix of the vehicle body coordinate system and compensation algorithm. Aiming at the incompatibility of ICV multi-sensor data-level and feature-level fusion, a K-m.AW decision-level fusion algorithm was proposed. The experimental results show that the S-SIC model search success rate reaches 92%, and the average search time is as 1.79 s. In the trajectory estimation of the preceding vehicle, the multi-scene fusion estimation based on K-m.AW algorithm is increased by 7.6% and 11.8% respectively compared with contrast algorithms.
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    Body Design of a Storage Tank Wall-climbing Robot Based on Magnetic Adsorption
    QIU Shicheng, WU Jianbo, ZHAO Hengzhong, WANG Shen, HU Qifan, YAN Rong
    China Mechanical Engineering    2022, 33 (03): 270-278.   DOI: 10.3969/j.issn.1004-132X.2022.03.003
    Abstract133)      PDF (11924KB)(165)       Save
     For the automatic detection of weld defects in large storage tanks, a wall-climbing robot needed to complete automatic omni-directional scanning. Firstly, according to the force state of the wall-climbing robot under different operating conditions, a mechanics model of the wall-climbing robot was established to analyze and obtain the four unstable hazards of non-sliding, non-longitudinal rollover, non-lateral rollover and compound motion state. The force state of the permanent magnet adsorption wheel was simulated and optimized by Maxwell software to meet the adsorption requirements. At the same time, the coding wheel with auxiliary adsorption function was designed to supplement the margin of safe adsorption force while feeding back the position information to increase the obstacle crossing and anti-instability abilities. Finally, according to the design model, the wall-climbing robot body was manufactured and tested. The test results prove that the robot designed herein may realize the omnidirectional driving operations with load stability at various ustable hazards.
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    Research on Virtual Grinding Wheel  Modeling Based on Convex Polyhedron Collision Detection
    CHEN Hao, ZHAO Ji, XU Xiuling, YU Tianbiao
    China Mechanical Engineering    2022, 33 (02): 127-133.   DOI: 10.3969/j.issn.1004-132X.2022.02.001
    Abstract132)      PDF (9130KB)(178)       Save
     The bounding sphere was usually used to detect the collision of grinding grains in the virtual grinding wheel modeling methods. When the bounding spheres were in contact, there was still a large gap between the abrasive grains, which resulted in a big difference between the virtual and actual grinding wheel surfaces. To solve this problem, a virtual grinding wheel modeling method was proposed based on convex polyhedron collision detection. The mathematical model of the random positions of abrasive grains on the grinding wheel surface was derived in detail. The interferences of grains were judged based on the convex polyhedron collision detection method, and the virtual grinding wheel was finally generated. The virtual grinding wheel surfaces generated by convex polyhedron and bounding sphere collision detections were compared. The improved method may generate virtual grinding wheel with 60% volume fraction of abrasive grains, while the original method may not generate virtual grinding wheel with more than 50% volume fraction of abrasive grains. The results indicate that the improved method may generate a virtual grinding wheel with a higher abrasive volume fraction and more randomness surface. Finally, the virtual grinding wheel surfaces were compared with the actual grinding wheel surfaces, and results show that the virtual grinding wheel surface has the characteristics of actual grinding wheel surface. 
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    Contact States of Workpiece-Abrasive Particles-Polishing Pad in Cemented Carbide CMP Processes
    MAO Meijiao, XU Qing, LIU Jingli, YUAN Julong, LI Min, HU Zihua
    China Mechanical Engineering    2021, 32 (17): 2074-2081.   DOI: 10.3969/j.issn.1004-132X.2021.17.008
    Abstract132)      PDF (6792KB)(260)       Save
    Theoretical analysis of the contact states among workpiece, abrasive particles and polishing pads was carried out based on the theory of elastoplastic mechanics, the depth of the abrasive particles pressed into the workpieces under each contact states was calculated, and the mathematical model of the critical conditions of the contact states was established, and the verification experiments were conducted. The research results show that in the cemented carbide CMP processes, there are three forms of non-contact state, partial contact state, and full contact state among workpiece, abrasive particles and polishing pads. The depth of the abrasive particles pressed into the cemented carbide workpieces in the three contact states is mainly affected by the polishing load, the size of the abrasive particles and the hardness of soft layer of workpiece, and the critical conditions of each contact states are determined by the characteristics of the polishing pad, the mass fraction of abrasive particles, and the polishing load. The experimental results show that the established mathematical model is credible. 
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    Optimization of Gear Grinding Parameters with Worm Grinding Wheel
    WANG Liting, ZHAO Xiuxu, LI Jiao
    China Mechanical Engineering    2021, 32 (17): 2136-2141.   DOI: 10.3969/j.issn.1004-132X.2021.17.015
    Abstract131)      PDF (1083KB)(97)       Save
    Taking the 20CrMnTi gear grinding processes with worm grinding wheels as the research object, the uniform design test method was selected to study influences of the grinding parameters(i. e. grinding wheel linear speed vs, grinding wheel along the gear axial feed speed vw, grinding thickness ap)on the tooth surface roughness. The regression model of grinding parameters and tooth surface roughness was established by using two-level stepwise regression method, and the optimization model with multiple goals was established with the machining efficiency and tooth surface roughness as the optimization objectives. The particle swarm optimization algorithm was used to optimize the grinding parameters. The experimental results show that the optimized grinding parameters may improve the machining efficiency and reduce the tooth surface roughness. 
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    Ensemble Variable Predictive Model Based on Optimal Features and Its Applications
    LIU Xiaofeng, TAN Qi, YE Rongting
    China Mechanical Engineering    2021, 32 (18): 2153-2158,2164.   DOI: 10.3969/j.issn.1004-132X.2021.18.002
    Abstract130)      PDF (2073KB)(186)       Save
    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. 
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    Research on Forming Manufacturing Technology and Equipment of Composite Preforms
    SHAN Zhongde, LIU Yang, FAN Congze, WANG Jun
    China Mechanical Engineering    2021, 32 (23): 2774-2784,2931.   DOI: 10.3969/j.issn.1004-132X.2021.23.001
    Abstract130)      PDF (13069KB)(119)       Save
    The revolutionary history of composite preforms forming technique was summarized from the standpoints of manufacturing technology and equipment development.The technical characteristics of the composite preform forming manufacturing technology were analyzed.The status of typical technology and equipment of composite preform forming manufacturing at home and abroad as well as existing challenges and gaps were listed.Finally,the future development directions and trends of composite preform forming technique were discussed prospectively.The development of digital precision forming manufacturing technology and equipment for high-performance composite components may promote the technical progresses of composites in China better,and achieve more extensive promotions and applications.
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    Multi-scene Motion Planning of Manipulators Based on Improved RRT*FN Algorithm
    FANG Lijin, WU Zhenghan, WANG Huaizhen
    China Mechanical Engineering    2021, 32 (21): 2590-2597.   DOI: 10.3969/j.issn.1004-132X.2021.21.008
    Abstract128)      PDF (7704KB)(85)       Save
    Aiming at the problems of low precision, poor environmental adaptability of RRT*FN algorithm, an improved RRT*FN motion planning algorithm for manipulators was proposed. Firstly, in the iteration processes, combining the advantages of target biased random sampling and ellipsoid subset sampling, a new heuristic method was constructed to constrain the sampling areas, so as to ensure better search paths. Then, in expanding node processes, the preset values of total number of nodes in the tree were configured, and the leaf nodes in the tree were deleted by weighting method, which avoided the infinite growth of tree sizes. Finally, under the dynamic environment, a heuristic replanning method of node pruning and connection was adopted to effectively improve the adaptability of dynamic environment. Experimental results show that the algorithm herein has faster convergence speed and higher efficiency in planning processes, and has strong environmental adaptability.
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    Model-driven Software-physical Parallel Conceptual Design for Complex Mechatronics Systems
    CAO Yue, WU Lingjiu, QIN Xujia, CHEN Jiazhou, LIU Yusheng
    China Mechanical Engineering    2021, 32 (21): 2532-2541.   DOI: 10.3969/j.issn.1004-132X.2021.21.002
    Abstract126)      PDF (10251KB)(68)       Save
     Parallel design was an important trend in the conceptual design of mechatronics systems. However, as an indispensable constituent of complex mechatronics systems, software was normally designed after that the design of physical subsystems was frozen. Such sequential design approached restrict the design space of software subsystems and might cause severe design defects in early design. In order to realize the parallel design of software and physical subsystems in the conceptual design stages of complex electromechanical systems, a model-driven software-physical parallel conceptual design approach was proposed based on SysML. A hybrid functional model was defined by combining the physical-oriented flow-based functional representation and the data/control flow diagram for software functional representation. From this model, two subsystems might be designed in parallel. For the physical design, working principles might be retrieved and filtered considering implicit temporal constraints by leveraging the functional effectiveness matching techniques and a temporal rule template. For the software design, an algorithm for automatically generating the software components and their behavior models was proposed based on the distributed control application design pattern. A mobile robot system was used as a case study to illustrate the parallel conceptual design processes.
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