Table of Content

25 October 2017, Volume 28 Issue 20

Previous Issue    Next Issue

Static Stiffness Modeling and Experiments of Polishing Manipulator Arm

QU Mengke1,2,3;WANG Hongbo1,3;RONG Yu2

2017, 28(20):  2395-2401. 

Asbtract ( )   PDF (608KB) ( )  

References | Related Articles | Metrics

A new type of 3-DOF manipulator arm was proposed, which was based on (U+UPS)P+UPS parallel mechanism. Using the idea of sub structure decomposition and superposition, deformation factors of manipulator arm's wrists were divided into 3 main factors: only considering branches' tension/compression deformations, only considering UP branch's torsion deformations, only considering UP branch's bending deformations. Also, 3 main factors affecting to stiffness model were established by virtual work principle and structure matrix based on vector loops. Deformation coefficients of each components in the branches were defined according to the structural characteristics of each branches. Then, the stiffness model of each influencing factors was integrated into the whole stiffness model of the manipulator arm by superposition principle. Finally, experimental prototype of the manipulator arm was developed. Using high precision robot calibration system, the stiffness calibration experiments of manipulator arms were done. Experimental results indicate that the deviation between measured position deformations and theoretical position deformations are less than 3μm, the deviation between measured attitude deformations and theoretical attitude deformations are less than 0.05 °. The deformations of the manipulator arm's experimental prototype are within a reasonable range.

A New Determination Method of Overconstraints for Mechanisms

LU Wenjuan1,2;ZHANG Lijie1,2;XIE Ping3;ZENG Daxing1,2;ZHANG Yitong1,2

2017, 28(20):  2402-2407,2413. 

Asbtract ( )   PDF (644KB) ( )  

References | Related Articles | Metrics

A method of overconstraint determination presented by pre-researches based on link group parameter matrix and list intersections, its range of pre-research needed to further extend to general spatial overconstraint mechanisms. Based on the engendered natures of overconstraints, usual closing forms and corresponding overconstraints were discussed, including rigid closure, closure by kinematic chain, and closure by single joints. Meanwhile, two criteria for judging the overconstraints in a single loop mechanism were obtained. Furthermore, an idea with the aid of “structural flow diagram” to determine the overconstraints for a complex mechanism was put forward. According to the closing form, the overconstraint might be checked in each closed processes by the corresponding link group parameter matrix. Finally, two typical mechanisms from the literatures were taken as instances. The results coincide with the prototype data, which shows the convenience and practicality of the proposed theory.

Development of In-process Trueing Devices for Metal-bonded Arc Grinding Wheels Used in Large-aperture SiC Reflection Mirror Grinding

RAO Xiaoshuang1;ZHANG Feihu1;LI Yingjie2;LI Chen1;LIU Zhongde1

2017, 28(20):  2408-2413. 

Asbtract ( )   PDF (631KB) ( )  

References | Related Articles | Metrics

In respect to metal-bonded arc grinding wheels for the aspherical grinding of large-aperture SiC reflection mirrors in space optical system, the formation mechanism of the arc with pulsed discharge under double rotating axes was proposed and deduced. Based on the analysis of the aspherical grinding of 4m large-aperture SiC reflection mirrors in CIOMP（Changchun institute of optics, fine mechanics and physics）, the effective grinding arcs and their radius and the dimensions of cup-shaped electrode were determined. An in-process trueing device for the metal-bonded arc grinding wheels was designed according to the 5-axis CNC grinding machine in CIOMP. The device was verified by the arc trueing experiments. The results show that the designed in-process trueing device of metal-bonded arc grinding wheels may well trim the target arc and meet the requirements of the aspherical grinding for 4m large aperture SiC reflection mirrors.

Improved Wavelet Packet Multi Threshold Denoising Method and Its Engineering Applications

CHEN Shiping;WANG Zhenzhong;YU Hui;WANG Quanjin

2017, 28(20):  2414-2419. 

Asbtract ( )   PDF (826KB) ( )  

References | Related Articles | Metrics

Aiming at the problems of denoising in mechine vibration signal extrations, based on the wavelet packet multi-threshold criterion denoising method, an improved wavelet packet denoising method to multi threshold standards was proposed herein, referred to improved FMC denoising method. This method was applied to pre-process original vibration signals of machine tools by pseudo point elimination technique to eliminate interferences of external noise signals to vibration signal extractions. Then the method of determining decomposition level was optimized by the method of determining maximum decomposition level with minimum frequency components of useful signals, and optimal wavelet packet basis was determined by minimum cost principle. Finally, vibration signals were reconstructed by wavelet packet multi threshold denoising criterion. Simulation experiments were implemented, and the results show that the method has good noise reduction effect, especially in strong noise background with a mutation of noise signal recovery. Experimental results show that the improved FMC denoising method may effectively eliminate band noises and improve separability of signal characteristics. Experiments were carried out to analyze the vibration signals of air bag dressing machine using this method, and experimental results show that the improved FMC denoising method may effectively eliminate the band noise and improve signal feature separability.

Degradation Trend Prediction of Rolling Bearings Based on Two-element Multiscale Entropy

LI Hongru1;YU He1;TIAN Zaike1;LI Baochen2

2017, 28(20):  2420-2425,2433. 

Asbtract ( )   PDF (659KB) ( )  

References | Related Articles | Metrics

Aiming at the problems that vibration signals of rolling bearings were greatly disturbed by random noises and representation errors of multi-scale entropy(MSE) for bearing degradation trend were relatively large. A degradation trend prediction method was proposed to solve the problems based on two-element multi-scale entropy(TMSE). Firstly, local characteristics-scale decomposition(LCD) was conducted to decompose the bearing vibration signals into several orders, and multi-element multi-scale theory was applied to compute the first two orders. In this way, TMSE was extracted to characterize bearing degradation trend. And then, mutual information method and false nearest neighbor method were used to optimize embedding dimensions and delay vectors. Lastly, ELM was applied as predictive model to predict the degradation trend which was represented by TMSE, and the prediction performance of different activation functions was compared. The results show that representation errors of TMSE are smaller than that of MSE, and the prediction performance of ELM is better when its activation function is sigmoid.

Research on Overloading Capacity of Bus Bars in Battery Module and Influence Factors of Current Balance

YU Jianwu1,2;FAN Guanghui1,2;LEI Jiping2;LI Xin2;ZHANG Yafei1

2017, 28(20):  2426-2433. 

Asbtract ( )   PDF (905KB) ( )  

References | Related Articles | Metrics

The bus bar connection of power battery pack of a electric-driven vehicle was studied, and the thermo-electric coupling effects were numerically calculated based on bus bars with different structures and thicknesses. The influences of bus bars structure, current I/O mode, welding width, location on the temperature rise of the bus bars and the balance of the cell were researched. Especially, taking the standard bus bar as the research object, the influences of the bus bar on the current balance was analyzed under the 2-in and 2-out current distribution mode. The standard aluminum bus bar was developed, and temperature rising of aluminum bus bar was inspected under various currents by using temperature tester, the errors between the experimentally measured rising temperature and the numerical simulation results are within 5%. The analysis results show that metal sheet bending has little effects on the overloading capacity of bus bars. However, the overloading capacity was significantly reduced with opening structures in the bus bar. Increasing of the bus bars thickness to some extent may significantly improve the overloading capacity. The width and location of the bus bar welding have some impacts on the capacity, and the influences of the welding locations are greater than that of welding widths. Finally, the mechanism of the bus bar temperature rising and the current unbalanced distribution was analyzed.

Tooth Surface Error Equivalent Correction Method of Spiral Bevel Gears Based on Ease off Topology

NIE Shaowu1;DENG Jing2;DENG Xiaozhong2;YANG Jianjun1;LI Jubo1

2017, 28(20):  2434-2440. 

Asbtract ( )   PDF (689KB) ( )  

References | Related Articles | Metrics

In order to improve modify efficiency of spiral bevel gears, a kind of tooth surface error equivalent correction method which only modified pinion was proposed. By means of comparing the differences between real tooth surface and design tooth surface Ease off, the pinion tooth surface equivalent errors were calculated. By means of establishing the modification mathematical model between the pinion tooth surface equivalent errors and processing parameters, the pinion processing parameters meeting theoretical mismatch requirements were calculated. Experimental results demonstrate that the differences between real tooth surface mismatch values and design values are within 5μm after modifying the pinion tooth surfaces, and the differences between the real transmission errors and theoretic values are as 0.5″, so the real tooth meshing performance is in accordance with the theoretic results.

Analyses of Amplitude Catastrophe Bifurcation Sets for a Rotor System with Nonlinear Stiffness Considering Stability

PAN Yong1;WANG Xianggeng1;CHENG Min2,3; LIU Baoguo2

2017, 28(20):  2441-2447. 

Asbtract ( )   PDF (623KB) ( )  

References | Related Articles | Metrics

With help of averaging method, a main resonance frequency response equation of a nonlinear stiffness rotor system was derived. Expressions of bifurcation set and its cusp were obtained based on catastrophe theory, which were represented by frequency coordination factor and excitation force amplitude. Stability conditions of a rotor system were derived based on stability theory of singular points, and expressions of critical unstable regions and its bifurcation points were also given by frequency coordination factor and amplitude. Influences of nonlinear stiffness on bifurcation catastrophe areas, unstable regions and amplitude characteristic curves were discussed though numerical examples. The results show that reducing nonlinear stiffness values is the best method to control amplitude catastrophe of the rotor systems.

Multi-level Pressure Switching Displacement Servo Control Systems

CAO Xiaoming3;GUO Baofeng2,3;WANG Pei3;LI Yao3;YAO Jing1,2,3

2017, 28(20):  2447-2454. 

Asbtract ( )   PDF (886KB) ( )  

References | Related Articles | Metrics

For conventional valve-controlled servo control system in huge throttling loss, a multi-level pressure hydraulic switching system presented a possible solution to this challenge. Firstly, composition, working principles, definitions of multi-stage output forces and realization of energy-saving mechanism of this new hydraulic system were given, and the mathematical model were established. Secondly, taking a three-level pressure power supply for a displacement control system as example, a hybrid switching control strategy was designed. Finally, an experimental rig was established, and the control and energy saving characteristics of multi-level pressure hydraulic switching system were validated. The results prove that displacement and velocity jitter are existed during pressure switching, it has a significant energy saving effectiveness compared to the conventional hydraulic displacement control systems with the similar useful working energy.

Anti-fatigue and Lightweight Design for Frame Structures of Electric Wheel Dump Trucks

MI Chengji1,2,3;GU Zhengqi1,3;JIAN Haigen3;ZHANG Yong1,3;LI Guang3;XIONG Yonggang3;JIANG Chao1

2017, 28(20):  2455-2462. 

Asbtract ( )   PDF (734KB) ( )  

References | Related Articles | Metrics

In consideration of insufficient stiffness, weld cracking, weight redundancy, and possibility of resonance for frame's natural frequency closing to non-sprung mass's excitation frequency by traditionally experiential design, multi-objective optimization design for frame structure performances of electric dump trucks was studied. The multi-objective topology optimization design was conducted on initial frames based on variable density method and SIMP interpolation model, considering fatigue life as constraints during optimization processes. A new frame topology structure was obtained, which might meet minimum compliance under static multi-conditions and maximum multi-low-order natural frequencies. The anti-fatigue and lightweight co-optimization designs were conducted on the new frames based on Kriging approximation model. Utilizing the non-dominated sorting genetic algorithm to find the optimal solution in global variables, the weight of optimized frame structures were reduced by 4.3%, compared with the masses of original frame structures. The final frames have more uniform stress distributions under the same loading, and better strength, stiffness, dynamic characteristics and longer fatigue life.

Tests and Optimization of Structural Vibration Characteristics for Truck Steering Systems

CHEN Jian;RONG Fangming

2017, 28(20):  2463-2466,2492. 

Asbtract ( )   PDF (557KB) ( )  

References | Related Articles | Metrics

Dynamic analyses of steering systems were carried out for a certain type of vehicles, and experimental studies were carried out. Vibration responses of the steering systems were measured by transient excitations, and the frequency response function curves of accelerations were obtained. Constraint modal parameters of steering wheels, steering column assembly and tube beam of cross car beam were obtained by hammering method. Modal vibration mode and dynamic stiffness of mounting point were combined into an integrated analysis, and the structure that needed to be optimized was determined. Effectiveness of the optimization scheme was verified by the vibration sensitivity tests of control points of the steering wheels.

Topology Optimization Designs of Large and Complex Structures Based on Super Element Technique

LI Ang;LIU Chusheng

2017, 28(20):  2467-2474. 

Asbtract ( )   PDF (799KB) ( )  

References | Related Articles | Metrics

The SE technique was utilized to deal with the connection parts to the crane frames and crawlers, and the crane frame structures were redesigned with the topology optimization method. Compared to the traditional methods, using the SE measure has the same solution accuracy, and the calculation time is only one third, which achieve the purposes of saving calculation time and keeping the accuracy of calculation. Finally, the finite element analysis (FEA) and fatigue test were performed to validate the rationality of SE technique to deal with complex models.

Process-based Evolution Process Information Integrated Modeling

WANG Qingwen;QIN Shichao;LI Jing

2017, 28(20):  2474-2482. 

Asbtract ( )   PDF (963KB) ( )  

References | Related Articles | Metrics

Process informations used and produced during the process evolution were dynamic, diversified and interrelated. An integrated model of process information was constructed by taking the process as a carrier. Firstly, a fountain-type model of the process evolution was designed to discuss different evolutionary modes of the process and their evolutionary relationships on macro-level. A process-based modeling method was presented by analyzing the forms and relevance of process evolutionary informations. In this method, resources, experiential knowledges and management informations were marked on the process planning using a “Tag-Object” mapping mode, in order to build the extensible associations between the process and other kinds of information. Finally, a process information example was given to illustrate the applications of the proposed method in information modeling and prototype system development.

Product Comprehensive Scheduling Problems Solved by Genetic Algorithm Based on Operation Constraint Chain Coding

SHI Fei;ZHAO Shikui

2017, 28(20):  2483-2492. 

Asbtract ( )   PDF (890KB) ( )  

References | Related Articles | Metrics

A genetic algorithm based on operation constraint chain coding was proposed to solve product comprehensive scheduling problems. The coding method designed in the algorithm might accurately reflect the operation constraint relations in product operation trees, and did not impose new constraints to ensure feasibility and completeness of initial solution spaces. At the same time, the problems of imposition constraints and omission of solution spaces were avoided in division coding methods. For the infeasible solution generated by crossover and mutation operations, a repair method was designed based on adjacency matrix. Experimental results verify effectiveness of the proposed algorithm.

Fault Diagnosis of Rolling Bearings Based on Path Graph Laplacian Norm and Mahalanobis Distance

YANG Hanjian1, 2;YU Dejie1;GAO Yiyuan1

2017, 28(20):  2493-2499,2519. 

Asbtract ( )   PDF (661KB) ( )  

References | Related Articles | Metrics

In order to extract fault features of vibration signals of rolling bearings effectively, the graph signal processing technology was introduced into fault diagnosis of rolling bearings. Vibration signals of a rolling bearing was firstly transformed into path graph signal. Then, the path graph Laplacian norm was calculated as characteristic parameters, and the standard feature space was obtained. Finally, the Mahalanobis distance of test samples and the standard feature space were used to identify fault patterns of the rolling bearings. Analytic results of the practical vibration signals of rolling bearings demonstrate that the proposed method may be used to diagnose the rolling bearing faults effectively.

Workspace and Kinematics Analysis of a 3-CRCR /RPU Symmetrical Parallel Robot Mechanism

ZHOU Shaorui;LIU Hongzhao

2017, 28(20):  2500-2508. 

Asbtract ( )   PDF (737KB) ( )  

References | Related Articles | Metrics

A novel symmetrical 3-CRCR/RPU parallel mechanism was proposed. Based on the modified Kutzbach-Grübler formula and the screw theory, it is concluded that the mechanism has four degrees of freedom. The vector equation was established according to the conditions of geometric constraint. The kinematic positive and inverse solutions were gained in form of analytical solutions. The velocity and acceleration of the parallel mechanism were analysed, which was based on the kinematic inverse solution. The mechanism had no singularity and partially decoupled by analyzing Jacobian matrix. A simulation model was established by ADAMS software to verify the correctness of the kinematics model. The workspace was given according to the conditions of each joint constraint, and the conclusion was obtained, that α-β-z configuration space of the mechanism was similar to oblique hexahedron. Finally, the influences of the structural parameters on the workspace were studied. The overall performance distribution of the mechanism under different structural parameters was studied based on the improved global performance index ηJ, which provides the basis for the optimization of the mechanism's spatial trajectory planning and structural design.

Effects of Interface Characteristics on Compound Effectivenesses of Ultra Heavy Plate Clad Rolling

SUN Jianliang1;PENG Yan1;GU Shangwu2;DU Xingming1

2017, 28(20):  2508-2513. 

Asbtract ( )   PDF (664KB) ( )  

References | Related Articles | Metrics

Influences of vacuum degree, temperature and surface roughness on compound effectivenesses in ultra heavy plate clad rolling were studied herein. Experiments of vacuum degree and temperature's influences on the compound effectivenesses were conducted on a thermal simulation test machine, while experiments of surface roughness's influences on the compound effectivenesses were carried out on a 2-h mill based on equivalent deformation method. Research results show that the effects of vacuum degree and temperature on the compound effectivenesses of heavy plate rolling are obvious, it is beneficial to improve the compound effectivenesses by increasing the vacuum degree and temperature. The effects of surface roughness on the compound effectivenesses of heavy plate rolling are also obvious, and the smaller roughness enhances the compound effectsivenesses. Because the costs of production increase exponentially as the roughness levels up, in the actual production the roughness may be decrease properly.

Rheological Forming Ability of Zr55Cu30Al10Ni5 Bulk Metallic Glasses under Ultrasonic Vibration Fields

LI Hui1;ZHENG Zhizhen1;WU Xiao1,2;LI Jianjun1

2017, 28(20):  2514-2519. 

Asbtract ( )   PDF (606KB) ( )  

References | Related Articles | Metrics

Ultrasonic vibration field was introduced into rheological forming of amorphous supercooled fluid, and an ultrasonic vibration-assisted metal forming experimental apparatus was designed. Experiments of high temperature uniaxial compression of Zr55Cu30Al10Ni5  bulk metallic glasses were carried out, and the rheological behaviors of the Zr55Cu30Al10Ni5 in supercooled liquid state with ultrasonic vibrations were studied. The experimental results show that ultrasonic vibrations may reduce flow stress and viscosity of the bulk metallic glasses, and the greater the input power, the more conducive to the deformation of amorphous alloys. The mechanism of the improving of the rheological forming ability by ultrasonic vibrating fields is analyzed, and it is considered that the vibrations cause the periodic disappearance of the internal stress and friction in deformation, thus the macro performance is the reduction of deformation resistance and the improvement of friction conditions.