Table of Content

25 May 2017, Volume 28 Issue 10

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Research on Flow Field and Pressure Drop Characteristics of Main Valve Inlet Throttle of a Dual Spool Electro-Hydraulic Proportional Multi-way Valve

ZHANG Jin, ZHU Hanyin, YAO Jing, LI Jianbin, LI Yanpeng, KONG Xiangdong,

2017, 28(10):  1135-1143. 

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Taking a dual spool electro-hydraulic proportional multi-way valve as the research object, the flow field of main valve along the inlet flow channel, the orifice and valve cavity under different valve opening conditions and flow rate were studied by simulations and experiments using CFD simulation and PIV technology. The flow field, the main valve inlet throttle and the pressure drop characteristics were obtained and the results of flow field analysis were verified by means of PIV test. 2D-PIV technology was used to obtain the flow field distribution on a cross section of the main valve cavity, and the valve port pressure drop characteristics were calculated by similar theory. The results show that a larger vortex may be formed along the main valve outlet ring cavity, and the valve opening conditions and flow rate have important influences on both inlet throttle internal flow structure of the main valve and valve pressure drop characteristics. It has great practical significance for qualitative analysis of energy loss, noise, design and optimization of structures as well as flow channels of the main valve. It also provides a reference for the applications of CFD simulation and PIV technology in the field of dual spool multi-way valves.

Convergence Analysis of Stress Intensity Factor at Crack Tips for TBM Cutterheads

LING Jingxiu, SUN Wei, YANG Xiaojing, TONG Xin

2017, 28(10):  1143-1148. 

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Aiming at the engineering problems such as crack damage and life prediction of TBM cutterheads, a solution method of stress intensity factors was proposed based on the sub-model technique, and it was validated by a rectangular steel plate with a crack. Then the convergence effects of crack mesh parameters on stress intensity factors at the crack tips of cutterheads were analyzed. The analysis results show that the maximum relative errors of numerical and theoretical results are as 3.6%. Besides, the crack element mesh parameters were obtained that ensured both of the accuracy and efficiency for cutterhead stress intensity factors solutions, which may provide a reference for the crack growth life prediction of structures.

Axial Dynamic Stiffness Identification and Analysis of Ball Screw

HUANG Jun, WANG Zhenhua, YUAN Juntang, BIAN Wei

2017, 28(10):  1149-1155. 

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In order to get the axial dynamic characteristic parameters of ball screw, a ball screw axial dynamic parameter identification model was established and a test platform was developed. By test the axial dynamic parameters of different screws, the effects of structure parameters on axial dynamic stiffness of ball screws were analyzed herein. The experimental results show that, the increases of screw diameter, lead, helix angle, and effective circle may improve the axial dynamic stiffness. The increases of axial strains which caused by pretensions will reduce the axial dynamic stiffness. Finally, a prediction model of ball screw axial dynamic parameters was established. And the relative errors between predictive stiffness and experimental results are less than 8%.

Research on Compensation Strategy for Induced Forces of Force Feedback Master Manipulators

YUN Jintian, LIU Yangyang, YANG Quanli, SANG Hongqiang,

2017, 28(10):  1156-1162. 

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Aiming at the problems that the connecting rod gravity, joint frictions and inertia forces of force feedback master manipulator affected doctors real perception of feedback force informations, a complete dynamics model was established. Based on the dynamics model of force feedback master manipulator, gravity compensation model, friction compensation model, and inertia force compensation model were established respectively. Force compensation strategies were used to eliminate the interferences to feedback forces from gravity, joint friction and inertia force of force feedback master manipulator in joint movements. Thus the doctors real force perception is realized and the accuracy of minimally invasive surgery is improved.

Topological Design for a Class of Novel 3T1R Parallel Mechanisms with Low Coupling Degree Based on Coupling-Reducing

SHEN Huiping, QIANG Hengcun, ZENG Qingfei, MENG Qingmei, YANG Tingli

2017, 28(10):  1163-1171. 

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Comparing to the 3-DOF Delta mechanism, the 4-DOF parallel mechanisms which might achieve selective compliance assembly robot arm(SCARA ) motion (i.e., three translations and one rotation) had their own complex topological structures, which resulted in the complexity of solutions for forward kinematics and dynamics. Therefore, the researches and developments of novel SCARA parallel mechanisms were still open issues. Reducing coupling degrees of these mechanisms might directly reduce the difficulties of solutions for forward kinematics and dynamics of the mechanisms. Based on the methods for structure coupling-reducing proposed by the authors, the structure coupling-reducing optimization design for five novel practical SCARA mechanisms whose coupling degree κ were 2 proposed by authors was performed. Ten novel SCARA mechanisms with coupling degree κ=1 were obtained, both their degrees of freedom and the output motion type of the moving platform kept to be constant. Thus, the solutions for forward kinematics and dynamics of these ten novel mechanisms with coupling degree κ=1 might be easily obtained by using one dimensional search method, or by solving a one-variable polynomial equation derived. This paper provides a theoretical basis for topological optimization, design and applications for these novel SCARA mechanisms.

Optimal Design and Experiments for Structural Parameters of Engine Intake Systems

LI Qiang, YU Xiaoli

2017, 28(10):  1172-1177,1182. 

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To find out the influences of structural parameters of intake systems on engine power performances, the airflow field distributions and dynamic characteristics were simulated under full load conditions by using the multiphysics coupling software. The effect laws of restrictor valves on average flow velocities and pressures were analyzed by inlet cone angles and diffusion cone angles according to the total length limitation. An orthogonal optimizing scheme was designed for structural parameters of cavity resonance and conducted to study the influences of these factors on uniformity of average flow velocities for concerning individual cylinders. The results indicate that the diameter of cavity resonance has the most important effects on uniformity of average flow velocities, whereas the length of body has the least effects. The restrictor valves make less effects on volumetric efficiency with low speed operations, and a great effects on the changing tendency with medium speeds and high speeds. The original injection control strategy was modified by MOTEC ECU in order to improve the power performances effectively by engine test bed based on the optimized intake system.

Analysis of Whole Contact Stresses of Tapered Roller Bearings under Radial Forces，Axial Forces and Moment Loads

CHEN Qiang, LAN Jian, HUA Lin,

2017, 28(10):  1178-1182. 

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Firstly, the equilibrium equations of a single tapered roller bearing under radial, axial and bending moment loads were derived, according to the conditions of deformation compatibility and force balance, a mathematical model of the whole contact analyses was established, the whole balance equation of the tapered roller bearings was finally formulated to solve a set of nonlinear equations. Then the numerical solution procedure was programmed by MATLAB, through the iterative method, the solutions to the whole balance equation were obtained. Finally, an example was given to verify the analyses.

Perturbation Sensitivity Analysis and Dynamic Topology Optimization for Heat Transfer Structures

ZOU Zhongfei, HE Lin, LI Jiachun, CHEN Yuewei

2017, 28(10):  1183-1190. 

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Aimed at the effects of the generated new hole boundaries on the topology optimization in the processes of heat transfer enhancement topology optimization, a topological derivative analysis with respect to the new holes was studied , and an adaptive dynamic boundary treatment method was proposed for the new boundaries in the optimization processes. By using Lebesgue differential theory, based on the domain perturbation technique and local limit law, the topological derivative formulas with different objective functions subjected to three kinds of boundary conditions were derived for the control system of Poisson equation. Finally, a number of numerical examples were presented to demonstrate the feasibility and effectiveness of the proposed method for designing the efficient heat exchangers.

Optimization Design and Performance Analysis of High Performance TLPs

CHEN Bo, YU Zhiyong, LI Xiaojian, LYU Yong

2017, 28(10):  1190-1194. 

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According to the deficiency of the existing TLP drilling platforms, A TLP with excellent performance was designed to provide reference for the design and selection of TLPs. Based on structure design method of sixth generation semi-submersible drilling platform, combining the advantages and disadvantages of heave plates and TLPs for analysis and design, a comprehensive evaluation was presented by hydrodynamics analysis software. Under the action of unit wave height, heave responses of TLPs were greatly influenced by incident wave frequencies and less influenced by wave directions. The new platform may effectively restrain the maximum heave responses. The natural periods of platforms heave response were reduced by heave plate structures. The vertical resistance of new type platform is about 1.769 times larger than that of the original platform. The time history responses of the new platform are decline of 7.247m, the heave responses reduce 60.74%. Results show that the optimization design of TLPs is reasonable. Compared with original platform, the new platform has an excellent hydrodynamic performance and good application prospects.

Fabrication and Corrosion Resistance of Copper Electroforming Layers on Tube Electrodes in EDM Processes for Turbine Blade Cooling Holes

LI Zhiyong, LI Li, ZHENG Guangming

2017, 28(10):  1195-1201,1214. 

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In order to reduce EDM electrode wear rate of turbine blade cooling holes of high temperature nickel base alloy, based on precision electroforming processes, the process parameters of fundamental electroforming solution were optimized, and some pure copper electroforming samples of copper tube electrode were prepared with different nano La₂O₃ addition quantities. These samples were used to compare with the copper electroforming samples prepared without La₂O₃. Blade cooling hole of Inconel 718 nickel base alloy was processed, and copper tube electrode was researched comparatively to verify the performance of electrical corrosion resistance. Experimental results show that copper electroforming layers with smallest grain size 15.9μm, microhardness 98.2HV, and roughness 0.140μm may be obtained with 1.2g/L La₂O₃. Its electrode wear rate decreases 13.29% and 7.26% than pure copper and copper electroforming layer without nano La₂O₃ addition respectively.

Natural Gas Pipeline Leakage Aperture Identification Based on ELMD and SRC

SUN Jiedi, PENG Zhitao, WEN Jiangtao, WANG Fei

2017, 28(10):  1202-1209. 

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Natural gas pipeline leakage was influenced by the aperture, the sensor distance, the pressures in the pipeline and many factors, so the feature extraction and recognition algorithm is relatively complicated. A novel leak aperture identification method which combined feature extraction based on ELMD-KL model with SRC was proposed. ELMD was applied to adaptively decompose leak signals, to obtain characteristic informations of different aperture leak signals, and to extract the principal product function(PF) components based on KL divergence which contained the main leakage informations. The method extracted multiple characteristic parameters in time domain and frequency domain as the feature vectors. For the classification of small sample complex signals, a SRC was put forward to realize the accurate classification of leak apertures. The classifier obtained the most sparse solutions of the test signals with overcomplete dictionary. The solutions were used as the sparse coefficient to reconstruct the test signals and obtain reconstruction signals in different classes of the test signals. Finally, classification of leak apertures was accomplished by judging the residual values between test signals and reconstruction signals. The experimental results show that the proposed algorithm has higher recognition accuracy compared with the traditional classification algorithm of SVM and BP.

An Aligning Method for 3D Measured Model with CAD Model of Integral Impeller Based on Geometric Features

XING Xiaohong, GUO Mingsen, HUANG Jinchang

2017, 28(10):  1210-1214. 

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A model alignment method was proposed based on geometric features, and applied to a 3D model of integral impellers. First, centroid of the measured models was extracted. According to the symmetry features of the integral impeller, the least square algorithm was utilized to estimate the rotational axis and was modified by the more accurate data of shaft part. Therefore, the centroids and rotational axes of the measured models were aligned with those of the CAD models. Then, the aligning of the blade parts of the measured models with the CAD models was realized by using weighted least squares method according to the characteristics of manufacture precision. The maximum alignment deviation caused by the proposed method is as 0.2mm.

Integrated VMD Denoising and KFCM Clustering Fault Identification Method of Rolling Bearings

JIANG Wanlu, WANG Haonan, ZHU Yong, WANG Zhenwei, DONG Keyan,

2017, 28(10):  1215-1220,1226. 

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A novel approach for fault identification of rolling bearings was proposed. The method integrated VMD denoising and KFCM clustering. Firstly, the measured vibration signals were processed to obtain VMD parameters. Secondly, the vibration signals were decomposed by VMD to obtain a series of band-limited intrinsic mode function(BIMF) components. And the effective BIMF components were screened out and superimposed into the reconstructed signals. Thirdly, the sample entropy and the root mean square value were calculated and coalesced as a feature vector, and the feature vector sets of test samples and that of training samples were obtained. Fourthly, the feature vector sets of training samples were analyzed by KFCM clustering method to obtain the clustering centers of the four types of signals. Lastly, depending on the principles that the Euclidean distance among feature vectors of test samples and cluster center of training samples was minimum, the fault types were recognized. In addition, the vibration signals were decomposed with the empirical mode decomposition(EMD) method and recognized by KFCM clustering method. Compared with the method based on the EMD denoising and KFCM clustering, the proposed approach may obtain better fault identification results.

Research on Improved BP-PID Steering Control Systems

YI Jun, CAI Heng, ZHANG Dong, ZHANG Daode

2017, 28(10):  1221-1226. 

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An electric linear motor loading test bench was designed to solve the problems existing in mechanical load simulator, such as big volume, high costs and pollutions, maintenance difficulties in electro-hydraulic load simulator. Then, the control effectivenesses of improved BP-PID and 2-DOF PID control systems were compared through Simulink simulation . Results show that the improved BP-PID control system does not depend on the parameter setting, the required parameters are self-setting through the neural network repeatedly training samples. Therefore, the BP-PID control system has greater stability and better tracking property, and may fully meet the requirements of the loading test system metrics.

Effects of Key Processing Parameters of Compression and Torsion Forming on Performances of Aluminum Cup Shells

DING Yonggen, XUE Kemin, WANG Jiulin, LI Ping, WANG Boxiaotian

2017, 28(10):  1221-1226. 

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Compression and torsion composite forming was used to process an aluminum cup shell. Optical microscope, tensile test and scanning electron microscope were used to study the effects of processing parameters on microstructure, mechanical properties and fracture modes of Al-Zn-Mg-Cu alloy cup shells. The results show that the optimum temperature for processing cup shells is as 400℃ and the microstructure is composed of fine equiaxed grains. Moreover, the tensile strength increases to 430MPa and the strength improves 49.8%. When the deformation temperature is over 300℃,the fracture mode of Al-Zn-Mg-Cu alloy deformed by compression and torsion is of ductile fracture. However, when the deformation temperature is below 300℃,the fracture mode is of brittle fracture. The torsion turns of Al-Zn-Mg-Cu cup shell forming may not be too large(less than 5 turns). When the torsion turn is less than 5 turns, the fracture mode of Al-Zn-Mg-Cu alloy is of ductile fracture. In addition, with the torsion turns increasing, the numbers of dimples on the microscopic fracture surface increase and the depths of dimples are larger. When the torsion turn is more than 5 turns, the fracture mode presents a certain degree of brittle fracture.

Influences of Mold Parameters on Mechanics Parameters in Closed-Open Type Cross Wedge Rolling of Automobile Oil Pump Shaft Part

WEI Yilun, SHU Xuedao, , WANG Yu , TIAN Duanyang, YIN Anmin, , JI Kaiyu

2017, 28(10):  1238-1244. 

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A 3D rigid-plastic finite element model of the closed-open type cross wedge rolling of automobile oil pump shaft part was established by DEFORM. Then, the influence rules of the mold parameters such as closed broadening angles, closed forming angles, open broadening angles and open forming angles on the mechanics parameters of automobile oil pump shaft part were analyzed. The increases of closed broadening angle accelerate the change rates of mechanics parameters. The increases of closed forming angles make the increases of mechanics parameters. The increases of open broadening angle makes the increase of radial forces. The increases of open molding angle make the increases of axial forces. For the relative errors range within 10% by comparing the rolling moments measured in 1∶1 ratio high-speed hollow shafts rolling experiments with the finite simulation results, the validity of the finite element model was verified.

A Closed-loop FMPC of Optimal Velocities for Connected Vehicles

QIU Lihong, QIAN Lijun, DU Zhiyuan, WANG Jinbo

2017, 28(10):  1245-1252. 

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In order to solve the optimal velocity prediction problems of multiple vehicles in the intelligent transportation system, improve fuel economy of the vehicles and execution efficiency of the control algorithm, a signal phase and timing based method was presented to calculate the ranges of the target velocity thus red light stoppage might be avoided. A modeling method of model predictive control was put forward based on the tracking of the optimal cruising velocities and optimal accelerations. A closed-loop velocity predictive control incorporating with efficiency feedback was formulated and FMPC was adopted to evaluate the optimal velocity profiles. The cloud-computing based software-in-the-loop simulation results indicate that, based on the proposed method, red light idling and collision may be avoided. Compared with baseline method 1 and 2, the average fuel economy improves 6.44% and 37.1% respectively. Compared with baseline method 1, the average propulsion efficiency improves 7.13%. The execution efficiency of FMPC is 13 times higher than that of MPC, and real time control may be achieved since the operation time of a single step is shorter than the step size.

Research on Dynamic Mode Transition of Hybrid Electric Vehicle Based on Continuously Variable Transmission(CVT)

WANG Jiande, ZHOU Yunshan, YANG Huiyong, JIA Jiefeng, LI Quan

2017, 28(10):  1253-236. 

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For a hybrid electric system based on continuously variable transmission(CVT), its structures and working modes were analyzed, and a kinetics model was established. A comprehensive control strategy combining fuzzy reasoning and optimal control theory was proposed for mode transition with engine starting. In the strategy, a clutch combination time was firstly obtained by fuzzy control based on driving intention. Then, an optimal clutch transmission torque and an optimal engine target torque were determined through the kinetics model with dynamic programming. Finally, the output torque of the motor was adjusted in real time according to the optimal clutch transmission torques by making use of the quick responsiveness of motor. Experiments were performed to verify the proposed control strategy. The experimental results show that the control strategy may optimize the clutch slip time based on driving intention, and achieve the smoothness of mode transition.