Table of Content

10 July 2019, Volume 30 Issue 13

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Fractional Integral Sliding Mode Control for Trajectory Tracking of Underwater Manipulators

HUANG Daomin1,2；HAN Lijun1；TANG Guoyuan1；ZHOU Zengcheng1；XU Guohua1

2019, 30(13):  1513-1518. 

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A fractional integral sliding mode control scheme was proposed to solve the trajectory tracking problems of underwater manipulators with unknown and bounded external disturbances. The proposed method was made with the adoption of the exponential reaching law that was based on a fractional integral sliding mode surface and with one term added as the approximate estimate for the external disturbances, which made it possible to achieve fast convergence and have strong capacity of resisting disturbances for the systems. Moreover, the stability of the closed-loop system could be guaranteed by the Lyapunov theory. Numerical simulations of the six degree-of-freedom (DOF) underwater manipulators shows promising results that validate the high-precision tracking performance and the better robustness of the proposed control systems against external disturbances.

Effects of Structure Parameters of MEWs on Vehicle Rollover Stability

LI Haiqing；ZHAO Youqun

2019, 30(13):  1519-1527. 

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Aiming to analyse the influences of the structure parameters of MEWs on rollover stability of an off-road vehicle, a corrected steady-state cornering model of MEWs was set up with the brush tire model. According to the theoretical, experimental and simulation results, the specific impacts of structure parameters(including geometric and material parameters) on cornering characteristics of MEWs were analyzed. Then, a nonlinear 3-DOF vehicle model for rollover prediction with MEWs was built up, which utilized a predictive load transfer ratio(PLTR) as the rollover index. The cornering properties of MEWs to rollover stability were analyzed. The results show that the influences of structure parameters of hinge-group on lateral stiffness properties are not obvious. And as cornering stiffness and peak value of lateral forces increase by increasing the vertical distribution of snap ring and decreasing the aspect ratio and shear modulus of flexible tire body, the vehicle may achieve a better rollover stability.

Review on Ultra-precision Machining Technology of Precision Balls

ZHOU Fenfen1；YUAN Julong2；YAO Weifeng3；LYU Binghai2；NGUYEN Duc-Nam4

2019, 30(13):  1528-1539. 

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For improving the precision and efficiency of precision ball machining, understanding of the distribution characteristics of the spherical machining trajectory and the influences of each process parameters on the machining results were essential prerequisites. Historical progresses of the ultra-precision machining technology of precision balls and evaluation of lapping uniformity were plotted, and based on the development of precision ball machining methods，the present advanced ultra-precision machining methods of precision balls were described with emphasis on the processing mechanism and examples. The different ultra-precision machining methods of precision balls were compared in terms of material removal rate, machining accuracy and batch consistency. And aiming to high machining accuracy and high efficiency, the probable further trends of ultra-precision machining technology of precision balls were forecasted．

A Geometric Nonlinear Method of Truss Booms Considering Second Order Effect

WANG Xin；YU Haojie；GU Zhenhua；HU Weinan

2019, 30(13):  1540-1544. 

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Based on the second-order effect, a differential equation of the compressing bars bearing laterally uniformly distributed loads was established under the deformation positions using the differential equation method. Then the differential equation was decomposed into the superposition of sinusoidal and quadratic parabolic curves, which were both under axial pressures. The equation was expressed in the form of undetermined geometric parameters, the deformation equation was obtained by analyzing the boundary conditions and equilibrium conditions. The deformations of the equal cross section space truss booms were analyzed by using this method, comparisons with the results of nonlinear analysis of ANSYS and ABAQUS indicate the proposed method's feasibility and practicability.

Robust Design of Interval Uncertainty Based on Sensitivity Analysis

XU Huanwei；LI Mufeng；WANG Xin；HU Cong；ZHANG Suichuan

2019, 30(13):  1545-1551. 

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In order to solve the uncertain factors in the design optimization of mechanical and electrical products, a robust design method for interval uncertainty was proposed based on sensitivity analysis. Firstly， discussed the Sobol' method of the sensitivity analysis theory, the factors which had great influences on the system were selected. Secondly, by using the characteristics of interval uncertainty factors and the effects of uncertain factors on the whole system were analyzed in a certain interval. Finally, a robust design optimization model for interval uncertainty was given based on sensitivity analysis. The effectiveness of the proposed method was proved by an engineering examples.

Analysis of CVT Safe Operation Areas under Slip Control Mode Based on Elasto-hydrodynamic Lubrication Theory

2019, 30(13):  1552-1557. 

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For the problems of increasing the failure probability of transmission under CVT slip mode, the oil film pressure, thickness and shear stress of a secondary pulley friction pair were analyzed with elasto-hydrodynamic lubrication under different transfer torques and relative slipping speeds. The safety margin model was established, the safety margin of the friction pairs under the slip state of the metal strip was calculated based on the ultimate shear stress and maximum shear stress of the oil films. The safety margin model might be used to determine the safe working areas of the CVT slip control, which provided a basis for the formulation and optimization of slip control strategy. The results show that with the secondary pulley transfer torques, relative slipping speed increases, the friction pair of the safety margin decreased gradually； when the transmission torque is less than 130 N·m, the oil film of the friction pair is guaranteed to be in a safe state in all relative slip speed ranges; when the transmission torque is greater than 130 N·m, the failure probability of oil film increases with the increase of relative velocity.

Tolerance Conversion of Aircraft Component Intersection Axes Based on T-Map

XIAO Huan1，2；ZHU Yongguo1；LIU Chunfeng3；ZHOU Jiehua4

2019, 30(13):  1558-1567. 

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To solve geometric tolerance changes caused by the datum transformations after the assembly processes were changed, a tolerance conversion method was proposed based on T-Map for the intersection axes of aircraft components. The T-Map tolerance models of the intersection axis were established according to the variation of intersection axis. The datum transformation model of the intersection axes were constructed by the geometric dimension and tolerance(GD&T) relationships before and after datum transformation, the T-Map of the intersection axes after the datum transformation was reconstructed based on the datum transformation model. Then, a stacking tolerance-map(ST-Map) was constructed from the transformed T-Map accumulation. The relationship between the two-dimensional spatial domain of ST-Map and T-Map before datum transformation was analyzed to obtain the minimum constraints of ST-Map, and the maximum tolerance value of the constraints with different degrees of freedom was determined to obtain the tolerance conversion relationships based on the intersection axes of T-Map. Finally, an example was introduced to solve the tolerance conversion and compared with the traditional tolerance conversion method based on size chain with feature tolerance.

Fractal Contact Model for Cycloid Tooth and Pin Tooth Considering Friction Factors

HAN Ju1,2；LI Wei1；DONG Wei2

2019, 30(13):  1568-1576. 

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In order to comprehensively reflect the influences of macroscopic and microscopic characteristics of cycloid teeth and pin teeth, the surface topography model of cycloid teeth and pin teeth was established by Weierstrass-Mandelbrot function and vector function. The section plots of pin tooth and cycloid tooth with obvious fractal characteristics were described using MATLAB. In order to confirm the contact area between rough surfaces, the parameter called contact proportionality coefficient was proposed and the relations among the coefficient and fractal dimension, characteristic scale, center distance, radius of pin tooth, number of pin wheel were analyzed. The analyses indicate that the coefficient is less than 1 in any case and the values of inner contacts are larger than that of outer contacts. The fractal contact model with friction was set up. The model shows that the relationship between the contact load and area is affected by gross characteristics, and by the microscopic characteristics of the contact surfaces. It may be indicated by the analyses of the contact characteristics of the model, that the contact area in the same load increases with the increases of friction factors, increases at first and then decrease with the creases of surface roughness, decreases with the decreases of radius of pin teeth, decreases with the decreases of center distance, increases with the decreases of radius of pin wheel and decreases with the decreases of number of pin teeth.

Rearch on Depth Estimation in Unmanned Vehicle Using Fisheye Binocular Lens

YUWEN Xuan1；ZHAO Mingming2；CHEN Long2

2019, 30(13):  1577-1584. 

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The model of the binocular environmental perception system of the unmanned vehicle fisheye was studied. The conversion relationship between the fisheye binocular model and the pinhole binocular model was analyzed. Aiming at the large deformations of the fisheye images, a method was proposed for the conversion, a cosine similar interpolation algorithm was developed for the image correction of fisheye cameras. The algorithm resembled cosine similarity to measure the similarity between the interpolation point and the surrounding gray-scale known points. The pixel missing due to re-projection was effectively interpolated. Finally, the scene depth extraction experiments were performed. The model and algorithm presented herein were verified by experiments. The results show that compared with the traditional binocular model, the fisheye binocular model may obtain a greater range of depth informations; for the interpolation in the fisheye binocular model, the algorithm may better handle the interpolation details and thus extract the depth informations of the scene more effectively.

Reliability Analysis of EMUs Braking Systems with Fuzzy Dynamic Fault Tree

GUO Jiming1,2；QI Jinping1,2；LI Xingyun1

2019, 30(13):  1585-1589,1599. 

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According to the fuzzy uncertainty of the failure incidence rates and the dynamic characteristics of the fault occurrence under the actual working environments of the EMUs braking systems, Markov model and fault tree model were combined to present a dynamic fault tree analysis method based on fuzzy Markov model. The bottom event failure rates and ambiguity of different state transition rates in Markov models were expressed by triangular fuzzy number and extension principle. The membership function of the fuzzy fault rate of the system fault tree top event was obtained by using the dynamic fault tree model. This research solves the reliability analysis problems of dynamic systems under uncertain conditions. The braking systems of EMUs on the Lanzhou-Wulumuqi high-speed railway dedicated line were analyzed, and the reliability of the braking system curves were obtained. It provides a theoretical basis for making the corresponding maintenance and repair plans for the braking systems of the trains running on this route according to the fault characteristics.

Plug-in Diesel-electric Hybrid Vechicle Rule Control Strategy and Processor-in-loop Tests

WEI Hanbing；REN Peilin

2019, 30(13):  1590-1599. 

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Taking a plug-in diesel-electric hybrid vehicle as the research object, the vehicle dynamic model was established based on the quasi-static assumption, which including engine-ISG motor, battery， selective catalytic reduction(SCR) system and transmission system. The linear function was used to approximate the engine fuel consumption MAP to improve the calculation speed. The weighted sum of engine fuel consumption, the catalyst outlet discharge and their corresponding weighting coefficient products were selected to solve the objective function. The typical characteristics including the mode switch and energy distribution were extracted with the constraints of national Ⅴ emission regulations according to the results of the optimal control solution. The CD-CS strategy was improved based on DP algorithm optimization results, and the simulation verifications and processor-in-loop tests were implemented. The research results show that compared with the original CD-CS strategy, the improved CD-CS strategy reduces the fuel consumption by 4.95%, reduces the emission indicators such as the NOx and particulate matter（PM） by 20.8% and 6.06% respectively. The effectiveness and instantaneity of the proposed rule control strategy are validated.

Modeling and Experimental Study on Freeze-form Extrusion Fabrication of FGMs

MA Weidong；LI Shujian；YANG Leipeng；WANG Xinyi；GU Zhonghao

2019, 30(13):  1600-1606. 

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In the making processes of the FGMs by the FEF methods, the extrusion processes were difficult to control due to the presence of bubbles, agglomeration and a certain degree of liquid phases migration in the paste materials. The differential model of the forming processes of FGM was established by using the method of system identification. The variance analysis methods were used to estimate the order of the system model. The parameters were identified by recursive least squares methods to obtain FGM molding control model. And the design of adaptive controllers were finished to achieve the FGM molding processes for real-time control. The validity of the control model and the effectiveness of the control method were verified by experiments.

Influences of Cladding Materials on Cracks and Hardnesses of Laser Cladding Chip Breakers on High Speed Steel Cutting Tools

WU Maochao；YU Aibing；WEI Jinlong；CHEN Qiujie；SUN Lei；YUAN Jiandong

2019, 30(13):  1607-1612,1620. 

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Laser powder cladding technology was applied to fabricate laser cladding chip breakers on the rake faces of high speed steel(HSS) cutting tools. Through the cutting experiments, the chip breaking performances of common HSS cutting tools and cutting tools with laser cladding chip breakers were compared. The microstructures and morphologies of the laser cladding chip breakers were observed. Thermal expansion coefficient, phase composition and microhardness of laser cladding layers were measured. The experimental results show that HSS cutting tool with laser cladding chip breakers may reduce the curling radius of chips to break the chip more easily and realize an effective chip breaking during cutting processes. The laser cladding chip breakers made from M2/WC-12Co powder has metallurgical combined with HSS tool substrates. The laser cladding layers have no cracks and the hardness is similar to the substrates of HSS cutting tools. The M2/WC-12Co power is suitable for fabricating laser cladding chip breakers of HSS cutting tools.

Design and Analysis for Umbrella-type Deployable Mechanisms Based on Spider Web Structures

SUN Jianwei；ZHANG Shiliang；KONG Fanchen

2019, 30(13):  1613-1620. 

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A simplified structure mapping model of spider web was established according to the geometric characteristics of spider web structures.Then, a new type of umbrella-type deployable mechanism was proposed using a planar four-bar crank slider mechanism as a deployable unit.The static analysis and optimization of the model were performed using ANSYS Workbench, and the optimal ratio of the pitch of the silk thread in the spider circle net structure model was given;at the same time, the stiffness matrix of spider web rigid frame model was established, the optimal angle between the filaments was given by matrix displacement method.Based on the optimal ratio of the spacing of spiral thread and the optimal angle of spiral thread, the umbrella-type deployable mechanism with the best stress performance was proposed, and the static performances were simulated and analyzed.The results show that the strength performance of the umbrella-type deployable mechanisms optimized based on the spider web structure model is improved.Finally，the model of the expandable mechanism with a diameter of 1.2 m was designed and manufactured, and simulation of the exercise processes, verified the effectiveness of the model expansion and collapse processes.

Comprehensive Optimization of Heavy Machine Columns Using Structural Bionics

LI Yupeng1,2；BA Chunlai1；LIU Laichao3

2019, 30(13):  1621-1625,1637. 

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A heavy interal gear grinding machine with spherical worm shaped grinding wheel column was as research object. Topology optimization of the heavy column structures was carried out, with the minimum strain energy and the maximum first natural order frequency as the goals and the volume fraction as the constraint. The best distribution of materials under complex loads was obtained. The internal complex structure of the columns were optimized by structural bionics and size optimization. The comparison between before and after optimizations about static and dynamic performance indexes of columns shows that the static and dynamic performances of columns are significantly improved, and the bionic lightweight and the best sizes are achieved. The effectiveness of the comprehensive optimization were verified by the comparison results.

Applications of Profiled Groove Technology in Development of High Rigidity Solid Carbide End Mills

NI Gaoming；ZHANG Hai；ZHOU Lei；WANG Qiang；WANG Yuzhong

2019, 30(13):  1626-1631. 

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Targeted at problems that high-frequency vibration in milling hardened steels and the low durability caused by sharp wearing of cutting tools, a high rigidity end mill was developed at 0.7 ratio between web thickness diameter and end mill diameter based on profiled groove technology. The mathematical models with radial section shape of spiral flutes were derived, cutting simulations and statics simulations were carried out. The results show that compared with cutting tools, high rigidity end mill has relatively larger average cutting forces, but similar cutting temperature, chip tolerance and removal performance and also small deflection. According to results of cutting experiments compared with cutting tools, the surface roughness values of machined parts of high rigidity end mill decline from 0.30 to 0.16 μm, and relieving amount deflection from 0.18 mm to 0.08 mm and the durability of cutting tools increases from 35 minutes to 58 minutes that embodies performance advantages of high rigidity end mills.

Regenerative Braking Strategy Based on Dual-motor Hybrid Structure HEVs

ZHANG Yan1；YANG Yiyong1；LI Liang2；LI Weibing3；WU Qiong3

2019, 30(13):  1631-1637. 

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A dual-motor HEV equipped with an automatic manual transmission(AMT) was selected as the research platform. This platform might partially or even completely eliminate the power interruption problems caused by discontinuous transmission of AMT. A simplified dynamics model of the HEV system was established. The processes and advantages of AMT downshift were analyzed, and a rule-based downshift strategy was proposed. Finally, simulation tests were performed in the Simulink/MATLAB. The results show that the fuel consumption rate of the shift strategy is as 16.8% lower than that of the non-shift strategy.