China Mechanical Engineering

Research on Effects of Vapor Core on Fuel Supply Characteristics of Vapor Core Pump

GUAN Huasheng, WANG Bin, DENG Weihua, YE Zhifeng

2017, 28(04): 279-385.

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To find the influences of vapor core on fuel supply characteristic, a VCP with radial straight blades was studied by unsteady vapor-liquid two-phase numerical simulation. Vapor core configuration varied from opening of inlet throttle valve and outlet load. The effect laws of vapor core on fuel supply characteristics were analyzed based on the fluctuations of fuel supply. Response of fuel supply to the steps of outlet pressures was simulated to discuss the influence of vapor core on dynamic performance for fuel supply. Results show that vapor core will not cause considerable fuel supply ripple. When the valve opening is in the range of 4~8mm, vapor core may weaken the influences of pressure steps on the steady-states of fuel supply, but prolong the stabilization of fuel supply. When valve opening is as 2mm, the vapor core is close to impeller outlet, and larger step amplitudes on supply pressures bring larger ripple on fuel supply rates after self-regulation of the vapor core.

Research on Operator Pupil Localization Method in Micro Operations

CHEN Guoliang, MA Hui, ZHANG Chuanchuan

2017, 28(04): 385-390.

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According to the small deflections of the operator's eyeball and the small variations of the eye image grayscale, a fast pupil extraction and localization algorithm was proposed. Firstly, in order to extract high quality pupil areas, the specific interesting areas were extracted. Then, the semi-precise positioning method was adopted to narrow the pupil areas and increase the proportion of the pupil areas in the eye images. Finally, Hough transform was used to locate pupil center. The experimental results show that the new algorithm extracts high quality pupil areas, locates the pupil center and is suitable for pupil image captured by head-mounted devices.

Adaptive Fuzzy Sliding Mode Control of 3-UPS/PU Parallel Mechanisms Including Joint Frictions

ZHANG Da, YUAN Daning, LIU Hongzhao

2017, 28(04): 391-397,403.

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In order to overcome the tracking aberration caused by joint friction mutations of a 3-UPS/PU parallel mechanism, a fuzzy adaptive sliding mode control was proposed. Firstly, dynamics model of the mechanisms with respect to platform workspaces was constructed. Considering the traditional sliding mode control(SMC) had deficiency that driving force chattering and adaptive SMC(ASMC) was sensitive to friction mutations, a fuzzy ASMC(FASMC) was proposed, which might estimate and compensate the model uncertainty including joint friction based on adaptive theory. And the adaptive gains were adjusted dynamically by means of fuzzy logic system. Consequently, FASMC may estimate the frictions more accurately and restrain friction mutations more efficiently compared with ASMC, and the system robustness was improved. This control method did not need to rely on the friction model and had a simple structure, therefore it was suitable for complicated and uncertain systems such as parallel mechanisms. The simulation results show that the proposed control method may estimate and overcome the friction disturbances efficiently and improve the control precision, the chattering problems from driving torque are also resolved.

Non-Hertz Contact Characteristics Anslysis of Three-row Roller Slewing Bearings

FENG Jianyou, QI Xiaoli, TONG Jinyu

2017, 28(04): 398-403.

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The traditional contact analysis methods of the rolls and raceways of three row roller slewing bearings were based on Hertz contact theory, but the actual contact behaviors of rollers and raceways were beyond the scope of the Hertz contact theory. Aiming at this problem, focusing on the non-Hertz roller and raceway contact characteristics, the variation laws of contact deformation and contact stress along the axial direction of the rollers were found. Combined with McEwen theory on the cylinder normal contact, the analytical formula of stress components in contact filed of rollers and raceways was deduced, and the relationship among the raceway failures and stresses were discussed. Finally, the roller and raceway contact finite element model was built. The simulation results show that the contact stress distribution and the analytical solution are consistent with each other, the results may be used to provide a reference for designing and manufacturing of three-row roller slewing bearings.

Double Cylinder Synchronous Control Method of Advanced Support of Roadway Support

XIE Miao, LIU Zhixiang, XIE Chunxue, MAO Jun

2017, 28(04): 404-409.

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Taking into account the low synchronization performance of advanced support's hydraulic cylinder for moving forward, a double cylinder electro-hydraulic servo system was designed and the equality state cross coupling fuzzy dual cylinder synchronous control method was proposed. This method was a nonlinear synchronization control strategy which combined the fuzzy control strategy with the cross coupling control. The main errors of the master-slave cross coupling control method were avoided, because the signal fluctuation of the system was affected by the fluctuation of the system. Finally, the performance of the two kinds of synchronization control methods were studied by experimental analyses. The results show that the proposed method has better synchronization performance.

Optimization of Looper Control Systems for Hot Strip Mills

JI Yafeng, TIAN Min, GUO Pengcheng, HU Xiao, LIU Guangming

2017, 28(04): 410-414,431.

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Aiming at the problems that traditional looper control systems could not meet the requirements of practical productions, the calculation method of looper motor torques and the detection methods of tension were given according to looper currents, the optimal control strategies of loopers were put forward based on the soft touch method, no whip control method and flow compensation method. The optimized looper control system was applied in a hot strip mill, and the practical application results show that with the specification of 3.0mm×520mm, the angles of loopers may be controlled within the target tolerances of ±2°, the currents of loopers may be controlled within the target tolerances of ±5%. The thickness may be controlled within the allowable thickness deviation of ±40μm over 98.7%, and the strip width deviation may be controlled within the target tolerances of 0～4mm over 96.9% of the strip steels and the precision of strip head and tail is enhanced.

SODF-SPH Method and Its Applications in Heat Conduction Problems

2017, 28(04): 415-420.

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Based on the principles of SPH method, a SODF-SPH method to compute second order derivatives was constructed through Taylor series expansion. Equal particle distance and same smoothed length were chosen to compute and simulate 1D heat conduction problems. After compared with conventional SPH method, results show that the accuracy, convergence rate and stability of the new method are better. To compute and simulate 2D and 3D heat conduction problems and compared with analytical solutions, the numerical results are in accord with analytical solutions. The derivatives may avoid calculating differential coefficients of kernel function. Therefore, the demands of kernel function are reduced, more kernel functions may be used and the calculation amounts are decreased. The new method may be widely used in engineering fields and numerical calculations.

Wireless Fiber Sensing Online-monitoring Mechanism for Crosshead Bearings of Reciprocating Compressor

CAO Chi, TONG Xinglin, CHEN Liang, DENG Chengwei, GUO Qian, ZHOU Chaoran, ZHANG Baolin

2017, 28(04): 420-424.

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According to the technical problems of the moving crosshead bearing temperature monitoring problems of a reciprocating compressor in petrochemical industry, combined with the characteristics of reciprocating compressor crosshead reciprocating motions, an wireless optical fiber sensing online-monitoring method for crosshead bearings of reciprocating compressors was presented. The wireless mechanism, monitoring method and the characteristics of wireless fiber sensing output were studied. The results show that the method may still monitor temperature with the 20% energy transfer efficiency, which shows the feasibity of the wireless fiber sensing online-monitoring method.

Fault Diagnosis of Bearings Based on Extreme-point Symmetric Mode Decomposition and Probabilistic Neural Network

ZHANG Shuqing, XU Jiantao, JIANG Anqi, LI Junfeng, SU Xinshuang, JIANG Wanlu

2017, 28(04): 425-431.

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Aimed at the complex non-linear rolling bearing systems, a new method combining ESMD and PNN was introduced for bearing fault diagnosis. ESMD expanded the definition of the intrinsic mode function, and changed the external envelope interpolation to internal pole symmetric interpolation. An idea of adaptive global mean(AGM) was used to optimize the last remaining modal, thus to determine the optimal number of decomposition. PNN was a neural network classifier based on kernel function approximation. The exponential functions were introduced to the neural network to replace the S type activation functions and to reconstruct the functions, representing the notion of gradient steepest descent method prominently, and reducing the errors between the actual and predicted output functions. Through the decomposing comparison to the simulation signals among empirical mode decomposition(EMD), making empirical mode decomposition(MEMD） and ESMD, and the diagnosis to the bearing vibration data by ESMD and PNN shows that the new method introduced may diagnose the bearing faults more effectively.

Contour-parallel Tool Path Generation Method Based on Pair-wise Offset

PAN Haihong, , GAN Lin, YU Zongyi, CHEN Lin,

2017, 28(04): 432-437,450.

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A contour-parallel tool path generation method was proposed based on pair-wise offset to solve the problems of generating contour-parallel tool paths, which were composed of lines and arcs. The convex vertex and interfering concave vertex of closed contour were used as a start point respectively, and the local and global invalid areas of contour including lines and arcs were identified respectively with the method combining pair-wise-interference-detection(PWID) procedures and arc segmentation processing. Non-interference contour-parallel tool path was generated by offsetting the closed contour without invalid area. The proposed method was realized in the self-developed CAD/CAM software. The simulation results show that the tool path without interference area may be generated accurately and effectively with the proposed method, and may be applied to closed contours with islands as well.

Review on Science Fund Management of Mechanical Engineering Discipline of NSFC in 2016

LAI Yinan, SONG Jianli, HE Baiyan, LIU Lei

2017, 28(04): 438-445.

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The applications, evaluations and fundings of projects in the mechanical engineering discipline of National Natural Science Foundation of China(NSFC) in 2016 were reviewed. The research progresses of undertaking programs and the achievements of finished programs in 2015 were summarized, problems occurred in the program implementation were indicated. The management measures on academic exchange and cooperation, talent cultivation, academic team construction, and project arrangement were introduced. The latest progresses and typical achievements obtained in the fields of mechanical engineering supported by the discipline in 2016 were listed, and the future work in 2017 was also proposed.

Analysis of Abrasion for Stator Bushings of Equal Thickness Screw Pump in High Temperature and Sand Crude Oil

HAN Chuanjun, REN Xuyun, ZHENG Jipeng

2017, 28(04): 446-450.

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In order to study the abrasion characteristics for stator bushings of screw pump under boiling drilling conditions, the tribological experiments of stator rubbers were carried out in hot and sand oil, and the friction coefficients of rubbers were measured. The nonlinear contact computation of equal thickness stator rubber bushings was implemented by using the FEM, and the influences of working pressure, interference, and frictional coefficients as well as other factors on the abrasion of stator bushings were studied. The results show that at temperature of 60℃ and pressure of 0.5MPa，the maximum equivalent stress and strain of the rubber bushings appear on the outside of the stator bushings, which increases with the increase of interference and frictional coefficients. The influences of frictional coefficients on the abrasion of the stator rubber bushings are relatively small. Appropriate amount of interference helps to reduce abrasion and improve efficiency.

Research on Characteristics of Bourdon Tube 2D Pressure Servo-valve Feedback Equipment

ZUO Xiqing, RUAN Jian, LI Sheng, LIU Guowen, SUN Jian

2017, 28(04): 451-455.

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A prototype of 2D pressure servo-valve was designed by using Bourdon tube for servo feedback equipment to keep output pressure constant. Aiming at Bourdon tube, which was linearly changed with pressure variations in a particular range, based on the analysis of its deformation mechanism, a mathematical model was established and its deformation processes were simulated, the influences of its structural parameters on linear deformation were presented. The linear deformation experiments of Bourdon tube and its test stand were designed and built, experimental results show that the deformation has nearly linear relationship with pressure risings, the linear deformation range is as 0.7mm when system pressure is of 16MPa. In dynamic experiments of Bourdon tube, it took about 0.9ms from impacts to basic stabilizing. Experimental results and simulated analysis are basically consistent, the research lays the foundation for the applications in a 2D pressure servo-valve.

Effects of Grinding Fluid Supply Parameters on Workpiece Surface Integrity

ZHANG Xiuming, JIANG Ang, SHI Xiaoliang, XIU Shichao

2017, 28(04): 456-461.

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According to the different parameters of grinding fluid supplyies, gas and liquid phase of jet flow model of grinding zone in the grinding processes was established by using CFD software. And the jet parameters of grinding machine nozzle were simulated and calculated. Through the comparison of the effects of jet speeds, jet directions and jet angles on mass flow rate of grinding fluid flow field and the volume fraction of jet flow process in the grinding zone, the most reasonable nozzle jet would be determined. At last, the experimental studies of workpiece surface integrity were used to provide experimental basis to determine the most suitable nozzle positions and verify the rationality of the grinding flow supply parameter selection in the grinding processes.

Experimental Study on Energy Consumption Characteristics of Fast Hydraulic Forging Press with Open Variable Pump-controlled System

YAO Jing, REN Xuhui, CAO Xiaoming, ZHAO Jingsong, KONG Xiangdong,

2017, 28(04): 462-470.

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Aiming at the problems of low power recovery and large heat release of the conventional pump-controlled system free forging hydraulic press, a fast hydraulic forging press with open variable pump-controlled system was proposed, and its energy consumption model was analyzed according to the energy flow. Based on 0.6 MN pump-controlled system free forging hydraulic press experimental platform, laws of energy consumption distribution on regular and fast forging conditions were obtained. The results show that the active power remains 50% of system energy consumption under regular forging conditions, and the ratio of active power increases with load power increasing. The active power remains above 40% of system energy consumption under fast forging conditions, and the ratio of active power increases with the forging frequency increasing. The results verify that the fast hydraulic forging press with open variable pump-controlled system has a great energy-saving advantage.

Mechanism and Laws of Peel-off Demolding for Large-area Nanoimprint Lithography

LI Yanqiang, LAN Hongbo

2017, 28(04): 470-477.

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This paper investigated the mechanism and influencing factors of peel demolding for large-area nanoimprint lithography. A model estimating the air pressure-assisted peel-off demolding forces was established based on the interfacial adhesion energy. A model of predicting the critical speed of air pressure-assisted peel-off demolding was derived by the combination of the strain energy method and the conservation of energy in demolding stage. Furthermore, the influences and laws of the demolding process parameters(demolding force, demolding angle, demolding speed) were revealed by numerical simulation using ABAQUS software.

Modeling and Analyses of Heavy-duty Truck Dynamics Based on System Constraints

HUANG Kang, DUAN Songlin, ZHEN Shengchao, XU Rui, XUE Yongchang

2017, 28(04): 478-486.

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Aiming at difficulties of building vehicle model, a discrete dynamics model of heavy-duty truck was proposed based on system constraints, and dynamics analyses were made based on the model. Basic theory of the model was from Udwadia and Kalaba's multi-body dynamics system. The situations that four tires' loads generated by road were different during normal operations considered. The dynamics characteristics of z direction of the vehicle were mainly researched . Though simulations by MATLAB, the graphs of each particles under conditions of unload and load beyond level D were obtained. Compared with the graphs which was generated by Lagrange model, the correctness of the dynamics model was proved, and the simulation graphs of dynamic characteristics of key particles and the driver were analyzed.

CACC System Based on MPC

SUN Tao, XIA Wei, LI Daofei

2017, 28(04): 486-491.

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Driving behaviors of the vehicle had a great influence on the riding comfort and fuel consumption in urban traffic conditions. Therefore, CACC system was designed based on the traffic conditions containing the informations such as traffic lights to improve the performance by reducing unnecessary speed keeping or acceleration. The type of tracking target was judged by processing current traffic information data and preceding vehicle or string of preceding vehicles' future states were predicted, relevant weights to different targets were used to calculate the optimal control inputs by means of MPC. Multi-objective optimization was realized by controlling the vehicles to keep a safe distance and cruising under the optimized speeds. The simulation results of CarSim and Simulink show that the control system takes the initiative to adjust the speed and to switch the target guarantee driving safety, and reduces fuel consumption, the peak value of acceleration and jerks which improves the ride comfort and fuel economy.

Identification of Gas-liquid Two-phase Flow Patterns in Automobile Hydraulic Braking Systems

LI Xiaolu, LIANG Siwei, WANG Wenyue, ZHAO Jinhui, ZHU Junjiang, LI Yuntang

2017, 28(04): 492-496.

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A test rig was completed for gas-liquid two-phase flow pattern identification in automobile hydraulic braking system, where the gas-liquid two-phase flow patterns were identified by Hilbert-Huang transform(HHT) using the pressure differential signals, and the flow patterns of brake fluid were also acquired in the braking pipes by a high speed camera under the different conditions. Results show that as improving the braking speed, the amplitudes of pressure differential signals are higher, which are at the frequency distribution area of 0~50Hz. The flow patterns of brake fluid were identified as a bubble flow during braking. The photos also show that the brake fluid is a bubble flow in hydraulic braking pipelines, and the sizes of bubbles are smaller as the rotating speed increasing. This paper discloses the gas-liquid two-phase flow patterns in automobile braking system during braking, and also gives a method on identifying the flow patterns by HHT only using the pressure differential signals of brake liquid.

Vibration Test and Simulation of Traction Converters for Mining Dumper Trucks

DING Jie, ZHANG Ping

2017, 28(04): 497-503.

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Due to the status for mining dump truck without vibration test standard reference that led to problems difficult to assess the reliability of the structure for the core components of traction converters, the acceleration data for mining dump truck traction converter's installed parts were collected and validated. The power spectral density were calculated and then the data were summarized to give vibration acceleration spectral density curves of empty and full load two kinds working conditions in different directions. In order to solve the problems that the vibration test could not be long run in accordance with the product life times, the accelerated measured spectrum was calculated that the vibration level would be increased with the testing time was significantly shortened. According to the finite element modeling, modal analysis and random vibration analysis based on the accelerated measured spectrum for the traction converters, the characterization of structural stress level 1σ stress distribution was came out. Ultimately, the results determine that the structure fatigue lifes of traction converters may satisfy the application requirements. The method of vibration test and simulation may provide a reference for the development of similar products.

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