Table of Content

10 June 2020, Volume 31 Issue 11

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Dynamics Modelling and Analysis of Elasto-plastic Contact-impact of a Rod-like Structure with a Oblique Flat Surface

WANG Yao1;ZHANG Tiefeng2;SHI Weiyi2;FU Zhuang1;CHEN Guangbiao1

2020, 31(11):  1261-1269. 

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For the elasto-plastic contact-impact problems of a vertical rod-like structure impacting the fixed oblique flat surface, the dynamics equations of the rod-like structure and the formulations of instantaneous contact forces in each phase during contact-impact events were established, and the various laws of the motion parameters and the contact forces were systematically studied in detail. Using ODE45 function, the time-variation laws such as the kinetic energy of the rod-like structure, position and velocity of the contact point, angle and angular velocity of the rod-like structure were analyzed. Besides, the relationships between the coefficient of restitution and the initial impact velocity, and the permanent deformations depending on initial impact velocity, as well as the contact forces with the contact deflection, were also achieved by the numerical analyses. The results show that the higher the initial drop height, the shorter the contact-impact time and the more obvious the rebounding phenomenon. And the contact force vs. contact deflection curves show similar trends with increasing initial drop height, but the permanent deformations are closer to the maximum deformation. Contact-impact tests were performed by dropping the vertical rounded ended rod-like structure from different initial drop heights on the fixed oblique flat surface with the inclination angle of 45°, and then, combined with testing data for the coefficient of restitution and permanent deformation in normal impact events reported in literatures, the comparative analysis results show that the simulation results are basically match with the testing results, which is verified the accuracy of the established model.

Precision Grinding of Micro-structured Mould Cores and Its Application in Micro Injection Molding

LU Yanjun;CHEN Fumin;WU Xiaoyu;ZHOU Chaolan

2020, 31(11):  1270-1276,1284. 

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For low efficient mass production and manufacture of the micro-structured polymer components, a precision trued V-tip diamond grinding wheel was used to grind V-groove array structures with controllable form accuracy on the surfaces of titanium silicon carbide(Ti3SiC2) ceramic mould cores with good self-lubricity and demoulding, then the micro injection molding technology was employed to replicate micro-ground V-groove array structures on mould core surfaces to efficiently injection mold the polymer workpieces with inverted V-shaped array structures. The surface machining quality and form accuracy of the micro-structured mould cores were analyzed. The influences of micro injection molding parameters, including melt temperature, injection speed, holding pressure and holding time on injection molding angle deviation and filling rate of micro-structured polymers were investigated. The experimental results show that the micro injection molded parts with regular and integrated micro-array structures may be high efficiently and precisely fabricated through micro grinding processes and micro injection molding technology. The injection speed has the greatest influence on the micro-molding angle deviation and the holding pressure has the greatest impact on micro-molding filling rate. The micro-ground form accuracy value of micro-structured mould cores is as 4.05 μm. The smallest angle deviation and the highest filling rate of micro-molding are as 1.47° and 99.30%, respectively.

Path Tracking Control of Vehicles Based on Variable Prediction Horizon and Velocity

BAI Guoxing1;MENG Yu1,2;LIU Li1;GU Qing1;LUO Weidong1;GAN Xin1

2020, 31(11):  1277-1284. 

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NMPC was widely applied to the path tracking control of vehicles. However, the impacts of prediction horizon and velocity on the performances of path tracking control were not considered in reported researches. Thus, the relationship among prediction horizon, velocity and the performances of path tracking control was analyzed. Through the cubic polynomial fitting, the control laws of the optimal prediction horizon and reference velocity were obtained, which may guarantee the lateral error of path tracking less than 0.1 m. Then, the NMPC controller for path tracking control was improved, and the performances of the NMPC controller were vertified by simulation. The simulation results show that, for the improved NMPC controller, the lateral error is within 0.092 8 m and the heading error is within 0.072 4 rad. Compared with the traditional NMPC controller, the improved NMPC controller reduces the maximum lateral error by more than 4.267 1 m and reduces the maximum heading error by more than 0.392 7 rad, and the performances of path tracking control are improved.

Product Innovation Design Based on QFD, TRIZ and Bionics

CHEN Liang;DOU Hao;WEI Huang;LIU Xiaomin;CHEN Bowen

2020, 31(11):  1285-1295. 

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In order to improve the efficiency of product innovation design, a product innovation design process model was proposed based on QFD、TRIZ and bionics. First of all, according to the customer demands, the product quality house was constructed by using QFD theory, and the negative correlation technical characteristics were mapped to the corresponding invention principles by combining the contradiction and conflict theory of TRIZ. Considering the three major criteria of invention principles, the suitable invention principles were screened out. Next, based on the invention principles by searching the biological case base, several biological examples were obtained. Then, the functional flow similarity among the biological examples and the design targets was calculated, and the bionic prototype with the highest flow similarity value was used as the bionic prototype. Finally, based on the established biological system database, product system database and collaborative middleware database, the product bionic design scheme was obtained by using collaborative middleware to carry out cross-domain and multi-level collaborative mapping. The above-mentioned process model was used to innovatively improve the fan blade, and the numerical simulation was carried out with FLUENT software. The results show that the air flow rate is improved and the noise of fan blade is reduced at a certain extent. The feasibility and effectiveness of the proposed design model are verified.

Kinematics，Stiffness and Dynamics Analysis of a Type of Planar Tensegrity Mechanisms

ZHU Wei;LI Hanbing;SHEN Huiping;LIU Jiahong;MA Zhiyuan

2020, 31(11):  1296-1305. 

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A topological structure synthesis method of a class of planar tensegrity mechanisms was proposed. A new type of planar tensegrity mechanisms composed of rigid rods and  flexible components was designed and analyzed. Compared with the traditional parallel mechanisms, this type of mechanisms had the characteristics of light weight, small inertia and foldable, etc. The inverse solutions of the mechanisms in equilibrium states were solved by using the absolute instantaneous center method, and the forward solutions were analyzed and numerically verified based on the minimum potential energy method. The velocity Jacobian matrix was derived, and the singular solution configurations were analyzed. Through numerical calculation and programming, the actuator workspaces and output workspaces of the mechanisms were obtained, and the numerical results by the minimum potential energy method and the absolute instantaneous center method were turned out to be identical. After that, the stiffnesses of the mechanisms were analyzed based on the energy formula, and the contour maps were obtained to reveal the stiffness distribution of the mechanisms in equilibrium states. Finally, the dynamics model of the mechanisms was established according to Lagrange method, the calculation results were confirmed by emulation in ADAMS. 

Isogeometric Optimization Method for Structural Shapes Based on Analysis of Weight Sensitivity

CHEN Long;ZHU Ying;XU Li;ZHANG Gaopeng

2020, 31(11):  1306-1314. 

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An isogeometric optimization method was proposed based on weight sensitivity analysis. Based on the derivation of weight sensitivity, two shape optimization methods were proposed, one was the global shape optimization with NURBS control points and weights as design variables simultaneously, the other was local shape optimization based on size optimization results and weight optimization step by step. And the feasibilty of the two shape optimization methods were verified by examples, the results show that when the structures need the conic curves to express the shapes, the proposed method may obtain more accurate optimization results.

Q-precentile Life Prediction Based on Bivariate Wiener Process for Gear Pumps with Small Sample Sizes

LIU Xiaoping1,2;GUO Bin1,2;CUI Dejun1,2;WU Zhenyu1,2;ZHANG Lijie1,2

2020, 31(11):  1315-1322. 

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One kind of Q-precentile life prediction method for gear pumps with small sample sizes was proposed based on bivariate Wiener process.The degradation processes of volume efficiency and total efficiency for gear pumps were modeled by Wiener process with random effects, and the fluctuation of gear pump performance characteristics with time and individual differences were characterized.The appropriate Copula function was selected to describe the correlation between the two degradation performance characteristics based on Akaike information criterion(AIC). A bivariate degradation model was established and the unknown parameters of the model were estimated by Markov chain Monte Carlo(MCMC) method. The Bootstrap sampling method was used to re-sample the parameters representing individual differences by considering the facts that the performance degradation test of gear pumps was usually a small sample size. Finally, through gear pump performance degradation tests, the Q-precentile life prediction was realized, and the validity and accuracy of the proposed method were verified.The testing results show that there is a non-linear correlation between the two characteristics in the degradation processes. Q-precentile life prediction considering correlation is more conservative than single feature prediction, and is more affected by the performance characteristics that first reach the failure threshold.

Forming Planning Method and Experimentation of Personalized Orthodontic Archwires

JIANG Jingang1;CHEN Houjun1;MA Xuefeng1;ZHANG Yongde1;LIU Yi2

2020, 31(11):  1323-1330,1336. 

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Traditional manual archwire bending was low efficiency and low bending precision，using the orthodontic archwire bending robots might overcome the shortcomings of manual bending method. The dental position was marked according to the clinical orthodontist's common dental position identification method. The shapes, positions and constraint relations of orthodontic archwires in three-dimensional space were expressed by the Bezier curve. In order to realize the bending of the space curves for the orthodontic archwires, the continuous state was expressed in the form of discrete motion by interpolation. The planning method of forming control points based on finite point extension method and the spatial angle planning method based on the synthesis of projection plane angle were proposed. The effectiveness of robotic bending method was proved by an experiment of maxillary three-dimensional node information of a clinical patient which was conducted by an orthodontic archwire bending robot.

Analysis of Micro Texture and Friction Properties of Friction Coupling Surfaces Produced by AS-EMM

TONG Wenjun;WANG Minghuan;QIU Guozhi;XU Xuefeng

2020, 31(11):  1331-1336. 

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An AS-EMM method was presented to process the micro-structures with different array shapes on planes and cylindrical metal surfaces. Comparisons were carried out between AS-EMM and EMM by analyzing the machining accuracy, surface quality and friction properties of the micro-texture. The results show that the eroded dimple aspect ratios of planes and cylinder pairs are increased by 45.6% and 25.8% respectively which may improve the dissolution localization and the machining precision by AS-EMM. Besides, the friction-wear test results express the 13.6% and 16.2% reduction respectively in average coefficient of friction values on different pairs by AS-EMM.

Lightweight Design Method Based on Combined Approximation Model

TONG Shuiguang1;HE Shun1;TONG Zheming1;FAN Huichu1;LI Yuansong2;LI Minghui2;TAN Dahui3;ZHONG Yuwei3

2020, 31(11):  1337-1343. 

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Aiming at the defects of low efficiency and large computational complexity of traditional structural optimization design methods, a lightweight design method was proposed based on combined approximation model. Taking the two-stage gantry structure of a certain type of internal combustion forklift as an example, the upper and lower flanges and web thicknesses that had the greatest influences on the performance of the gantry were selected as the lightweight design variables by TOPSIS method. 100 sample points including design variables and performance responses were obtained based on Opt-LHD method. Combined approximation model of outer gantry mass, maximum stress, and maximum deformation were constructed, combined with quadratic sequence programming algorithm， the lightweight design was developed. And the results show that the quality of the outer gantry is reduced by 13.36% and the maximum stress is reduced by 4.65%.

Research on Multi-objective Green Flexible Job-shop Scheduling Based on Improved ABC Algorithm

LI Yibing1,2;HUANG Weixing1;WU Rui1

2020, 31(11):  1344-1350,1385. 

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Aiming at the characteristics of multi-objective green flexible job-shop scheduling problem (MGFJSP), three indicators of carbon emissions, noises and wastes were proposed to evaluate the degree of environmental pollution comprehensively. A MGFJSP model was established with the optimization goals of minimizing the makespan and the degree of environmental pollution. And the improved ABC algorithm was proposed to solve this model. The specific improvements of algorithm included: a three-dimensional vector coding schemne and the corresponding decoding scheme were designed, an effective dynamic neighborhood search operation was introduced to improve the local search ability of the algorithm in the follow bee search stage, and a strategy for generating new food sources was proposed to increase the diversity of the population in the bee detection stage. Finally, the experimental study and algorithm comparison were carried out to verify the validity of the established model and the proposed algorithm.

Visual Monitoring System for Small and Medium-sized Automatic Production Lines

WEI Dinghui;WANG Huifen;LIU Linyan

2020, 31(11):  1351-1359. 

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Aiming at the problems of difficulties in grasping of production process information in real-time and the low degree of visualization in automatic production lines, a visual monitoring system for small and medium-sized automatic production lines was studied. Based on the analyses of visual requirements of automated production lines, an overall technical framework of visual monitoring system was designed. The three key technologies of data acquisition and transmission for automated production lines based on OPC technology, construction of production line information model and visual monitoring were described based on production line layouts. Finally, a set of visual monitoring system was designed for an enterprise's automatic production line, which realized the functions of visual monitoring of production processes in automatic production lines and production line resource management. The feasibility and reliability of the system were verified in the practical applications of the enterprise.

Research on Mass Estimation Algorithm for Heavy Commercial Trucks

ZANG Zheng1;HUO Wei1;WANG Yuhai2;LI Xingkun3;ZHENG Xuguang3;LI Yuanyuan4

2020, 31(11):  1360-1367. 

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In order to accurately estimate the masses of heavy trucks in the PCC processes, based on the vehicle longitudinal dynamics model, a vehicle mass estimation algorithm was proposed. The Kalman filtering algorithm was used to estimate the engine output shaft torques which were used as inputs for the vehicle mass estimation algorithm. The vehicle mass was estimated based on the RLS method. C code was generated for the quality estimation control model built by MATLAB/Simulink and embedded in the development boards. And the proposed vehicle mass estimation algorithm was carried out under no-load, one-third load and full load road tests. The testing results show that the maximum errors of the proposed algorithm are 8.87% under full load, 7.43% under one-third load and 4.40% under the no-load, which may meet the mass estimation error requirement within 10% of the vehicle PCC processes and plays an important role in the stability and safety of the vehicle.

Design and Simulation of Electromagnetic Blanking Processes Based on Field Shaper

XU Jiahui1，2;HUANG Liang1，2;LI Jianjun1，2;HONG Xiudong1，2;SU Hongliang1，2

2020, 31(11):  1368-1377. 

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A finite element model of electromagnetic blanking forming processes with field shape was established based on LS-DYNA R8.0 software for diaphragms used in carrier rocket in aerospace field, and the variation rules of current, magnetic field, and sheet stress states under the field shape case were revealed. Furthermore, the processing parameters of the discharge voltage and the billet diameter were optimized. The results show that the section quality is optimized and the shear deformation is intensified with using the field shape. The sheets present a tearing fracture mode under the forming processes. With the increase of the discharge voltages, the deformation degree of the sheets increases, the fillet area of the fracture decreases and the diameter of the blanking part decreases firstly firstly increases. With the increase of the billet diameters, the deformation degree of the sheets increases firstly and then decreases, the fillet area of the fracture decreases firstly and then increases, and the diameter of the blanking part increases and then and then decreases. The optimum values of thedischarges voltages and the billet diameters are as 12 kV and 130 mm respectively.


Study on Deformation Control of Thin-walled Titanium Alloy Parts in Non-uniform Allowance Machining Based on Rayleigh-Ritz Method

LI Xi;YUAN Juntang;WANG Zhenhua;ZHANG Bo

2020, 31(11):  1378-1385. 

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A new design strategy of non-uniform allowance was presented to reduce the deformations of thin-walled titanium alloy parts in cutting processes. A mathematical model for predicting milling deformations of thin-walled parts was established based on Rayleigh-Ritz method. A design idea was put forward based on discretized volume elements of machining allowances and the non-uniform allowance design of workpieces was completed. Finally, the effects of different allowance design strategies on the milling deformations of thin-walled cantilever structure parts were analyzed and compared. The results show that the proposed non-uniform allowance design strategy of discrete allowance volume elements based on Rayleigh-Ritz solution has high utilization rate of the stiffness of workpiece itself and good consistency in distribution of surface machining errors, and it also has better effects to control the maximum surface machining errors.