Table of Content

10 September 2014, Volume 25 Issue 17

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Adjustment for the Machining Errors of Machine Tool Based on Grey Bootstrap Maximum Entropy Method

Xia Xintao, Qin Yuanyuan, Qiu Ming

2014, 25(17):  2273-2277. 

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According to grey bootstrap maximum entropy method, the distribution of output errors and the adjustment for the machining errors of machine tool was studied in mechanical manufacturing process. This method included bootstrap methodology, the grey system theory, and the maximum entropy theory. In order to analyze the error distribution, the bootstrap methodology was applied to get a large number of sample data by bootstrap resampling from the current information vector of small size, and then the grey system theory was used to establish a grey bootstrap model (GBM) of dynamic prediction. The probability distribution of output errors could be obtained by using the maximum entropy method. Based on the probability distribution of output errors, the machining errors of machine tool was adjusted so that the machining errors of products could satisfy the requirements. Computer imitation and actual cases show that the machining errors of machine tool can be adjusted accurately by using grey bootstrap maximum entropy method, and the forecasting accuracy is high.

Flow and Heat Transfer of Cu-Water Nanofluids in Grooved Microchannels

Chen Wei, Li Yuanyuan, Lin Jun

2014, 25(17):  2277-2282. 

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This paper analyzed the fluid flow and heat transfer of Cu-water nanofluids in grooved microchanel.The velocity and temperature distribution of Cu-water nanofluids in grooved-microchannels with depth to width ratio of 0.3 and 0.5 were conducted. Besides, the heat transfer coefficients of Cu-water nanofluids and the fluid transport power factor in the arc-grooved microchannels were also investigated. The grooves strengthen convective heat  transfer in the microchannels. Compared with the plate microchannels, the heat transfer of Cu-water nanofluids in arc-grooved microchannels displays different characteristics. Nanofluid concentration, fluid transport power factor and the depth to width ratio influence the heat transfer in the grooved microchannels greatly. The results herein accord with experimental data.

Research on Application of GOM Formula-a Novel Mobility Formula

Lu Wenjuan, Zhang Lijie, Zeng Daxing, Zhang Yitong

2014, 25(17):  2283-2289. 

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Based on a new method-GOM formula referred to before, which was expressed with “DOF of general link-group”, steps of calculating DOF with this idea were established firstly. Meanwhile, displacement parameters of basic link-groups commonly used were listed and a method of determining the rank of link-group was introduced. Secondly, a theory which could quickly determine the DOF and motion characteristics of output part was determined. Finally several typical examples from the literature were performed to illustrate the accuracy and validity of the new theory mentioned above. The results show that this new formula can avoid calculating virtual constraints, and without the aid of sophisticated mathematical tool, the DOFs of mechanisms including hybrid mechanisms can be calculated quickly and availably. In short, its accuracy and versatility get a test in a certain extent.

Geometric Error Decoupling for Multi-axis CNC Machines Based on Differential Transformation

Chen Jianxiong, Lin Shuwen

2014, 25(17):  2290-2294. 

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A new modeling method for multi-axis CNC machines was proposed based on differential transformation theory,where the geometric errors were equivalent to the differential movement relative to its ideal position.Meanwhile, the Jacobian matrix was adopted to describe the mapping relation between tool pose error vectors and compensation error vectors, and all elements in the matrix could be solved by differential transformation. Thus the compensation error vectors were calculated by computing the generalized inverse of Jacobian martix. And then, an automatic error decoupling procedure was developed herein. Finally, an experiment was conducted on a five-axis CNC machine to test and verify this method. The results show that the overall position accuracy of the test path is improved dramatically.

Parameter Vibration Response of Electromechanical Integrated Electromagnetic Worm Drive

Hao Xiuhong, Zhu Xuejun, Liu Shuang

2014, 25(17):  2295-2299,2304. 

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Considering the periodic change of meshing pole numbers in an electromechanical integrated electromagnetic worm drive (EIEWD), expression of the electromagnetic meshing stiffness was deduced in form of Fourier series. On the basis of that, the parameter vibration model and the linear time-varying differential equation of EIEWD system were founded. Approximate analytic solution of the free vibration for the drive system was got by multi-scale method. Time domain and frequency domain responses of the free vibration and main resonance were studied, where there were the natural frequency, combination frequency between natural frequency and combination resonance meshing frequency. The results show that the dominant frequency of the combination resonance is the natural frequency of the EIEWD system. Resonance amplitude of combination resonance will decrease with harmonic order increase.

A Calculation Method of Mesh Stiffness for Face Gear Transmission System

Lei Duncai, Tang Jinyuan

2014, 25(17):  2300-2304. 

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A new method for calculating the mesh stiffness of gear transmission system which was the foundation of gear dynamics analysis was proposed based on finite element method. To validate the calculation method, a spur gear pair was adopted to calculate the mesh stiffness. The results show that the mesh stiffness is identical with that from ISO 6336 method. Subsequently, the proposed method was used to calculate the mesh stiffness of face gear transmission system, and the change law of the meshing stiffness for the face gear transmission system was researched. The research results provide the basic condition for dynamics analysis and design of face gear transmission.

A New Magnetic Circuit Structure for an Electronic Fuel Injector

Lu Jinhe, Zhang Zhendong, Cheng Qiang, Yin Congbo

2014, 25(17):  2305-2309. 

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With an electronic fuel injector as the object, a new magnetic circuit structure was developed by adding a ring made by non-magnetic material between the core and guide pipe in order to improve its dynamic response performance. Both of the original and improved injector's electromagnetic performances were analyzed and the influence of the yoke's thickness on its electromagnetic performance was also studied by using the electromagnetic field simulation. The results show that adding a non-magnetic shell can speed up the rate of electromagnetic force's rise, reduce the opening response time effectively but it will cause longer closing response time due to the increase of saturated electromagnetic force. Reduction of the thickness of yoke has little effect appropriately on the rate of the electromagnetic force's rise and since it increases the reluctance, it can decrease the saturated electromagnetic force and reduce the closing response time. Based on the analyses, an optimization of the injector was developed and experiences were conducted to verify its effectiveness. Experimental data indicates that the improved injector can reduce the opening response time by 0.25ms and closing response time by 0.3ms.  

Kinematics and Dynamics Analysis of Ring Array Deployable Structures Based on SLE

2014, 25(17):  2309-2313. 

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Firstly, by analysing the geometric parameter relationship of SLE, the relationship among the element size, element number and the radius of the ring deployable structures was obtained in deployed and folded configurations. Secondly, according to the characteristics of the ring array deployable structure, a method was adopted, which was the combination of unit mechanism method and influence coefficient method, and the kinematics analysis method of the structure was established. Thirdly, the influence coefficient method and the principle of virtual work were combined to form the dynamatics analysis of the structure.At last, the effectiveness of the kinamatics and dynamics methods was confirmed by an example.

Configuration and Optimization of Agile Supply Chains Based on Interactive Two-level Fuzzy Programming

Peng Anhua, Xiao Xingming, Yue Rui

2014, 25(17):  2314-2319,2350. 

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The source of uncertainties existing in agile supply chains was analyzed and expressed as trapezoidal fuzzy numbers, which were then defuzzificated with graded mean integration representation. On the basis of analyzing the various methods for selecting partners or configuring agile supply chains, an interactive two-level fuzzy programming was proposed, the solution method of which used the LINGO13 software. Since the method gave consideration to both upper level and lower level interests, an optimal compromise solution could be obtained through repeated negotiation among the decision makers. The decision making procedure was illustrated with an example, and compared with the other methods, and showed the advantages. Something to be desired  as well as the further research directions were pointed out.

Rescheduling Algorithm Based on Uncertain Processing Time of Operations for a Flexible Job-shop

Peng Jiangang, Liu Mingzhou, Zhang Xi, Zhang Mingxin, Ge Maogen

2014, 25(17):  2320-2326. 

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A flexible job-shop rescheduling of operations with uncertain processing time was studied, and the target was to minimize both the makespan and the total workload of machines. The interval number was utilized to describe the processing time uncertainty and the universal grey number was employed to implement scheduling. Event-driven based on queue size(EDQS) rescheduling triggering mechanism and the rolling horizon optimization were introduced. The conformation method of critical operation set was designed. The complete operation set scheduling was implemented by means of the optimization of critical operation set applied modified NSGA-Ⅱ and heuristic method of non-critical operation set based on shortest processing time. In order to obtain good performance in both convergence and distribution, the hypervolume indicator was introduced to maintain evolutionary population. The order relation of universal grey number was used to ascertain the most optimal scheduling scheme. As demonstrated by simulation, the proposed algorithm which comprises both feasibility and validity is agilely responded the uncertain factors. 

Kinetic Simulation on ADAMS and Experimental Study of Wear Failure of Cylindrical Roller Bearings

Yao Jianxiong, Tan Jianping, Yang Bin

2014, 25(17):  2327-2330,2343. 

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The wear failure of cylindrical roller bearings can easily cause deterioration of the system. A model of bearings-shaft-base was made on the basis of bearing NJ204. The simulation of varying degrees of wear failure was analysized to reveal the failure process. The failure eigenvalue was obtained finally and verified experimentally.The results of simulations and experiments show that the spectrum concentration of the vibration signals can reflect the degree of bearing wear failure.

Process Energy Consumption Modeling of Sand Casting Based on Petri Net

Zheng Jun, Zhu Bangwen

2014, 25(17):  2331-2336. 

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To calculate the process energy consumption of sand casting, a model for energy consumption was built based on Petri net.The process of sand casting energy consumption was huge,and had a large potential for energy saving. A process activity model was proposed with analyzing the characteristics of energy consumption. The relationship between process activity and resource consumption was described by graphical description based on Petri net. The consumption model of sand casting process activity was realized. The proposed method was verified through the sand molding workshop.

Control Algorithm of Successive Iteration of Vector Field for Physical Human-Robot Interaction

Xie Guanghui, Yang Zhiping, Wang Guangjian

2014, 25(17):  2337-2343. 

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In order to synchronize motions between robot and human, a control method for physical human-robot interaction was proposed by using successive iteration of vector field. The attractor corresponding with target trace of robot was introduced in 3 dimensional space. The vector field system with any target trajectory was designed by successive iteration for the 3D space, so that it could realize the synchronization between joint torque information as an input signal and desired trajectory of each robot joint as an output signal, and the strength of the synchronization could be varied by adjusting some internal parameters value in the vector field system. It was analyzed that the mutual interactions for two dynamics had different vector fields. Finally, the presented dynamics was applied to the control simulation of lower limb power-assisted robot, and it was analyzed that the joint torque components influenced synchronous movement. Simulation results prove the validity of the proposed control method.

Two Degree of Freedom Vertical Vibration Characteristics of Cold Rolling Mill Based on Dynamic Rolling Force

Liu Bin, Zhao Hongxu, Zhu Yue, Liu Haoran, Hou Dongxiao

2014, 25(17):  2344-2350. 

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The Establishment of dynamic force model was based on the consideration of the dynamic changes of vibration displacement of cold rolling mill roller in vertical direction. The vibration influences of rolling mill's of the mechanical structure were considered, which formed the two-degree-of-freedom nonlinear vertical vibration equation. In addition, by using the multi-scale method, it was able to solve out the primary resonance and internal resonance amplitude-frequency characteristic equation of system. Lastly, parameters of the actual mill were used to conduct a simulation research and parameters such as equivalent nonlinear stiffness of a mill system, damping, and extraneous force were analyzed how to affect the primary and internal resonance. The study of the characteristics of work roll and back up roll was carried out and found that as the changes of the external disturbance force, the rolling mill will cause periodic, period-doubling, chaotic motion and a series of complex movements. The conditions where different kinds of motions occurred are also found. As a results it provides an effective theory reference for the research of inhibition of rolling mill vibration problems.

Adaptive Impendence Control of Two-links Flexible Manipulator under Unknown Environments

Jin Yinglian, Wang Binrui, Fang Shuiguang

2014, 25(17):  2351-2355. 

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For the operation contacting with objects, a rigid-flexible coupling dynamics model was established based on the assumed mode approach for two-link flexible manipulators. An adaptive impendence scheme was designed to compensate the environment uncertainties and the stability condition was analyzed. The control simulation platform was established using MATLAB/Simulink. The tip motion and deformation mode were computed under manipulator sliding on the surface with the triangular crack. Performances of position and force control were compared between the flexible and rigid manipulator, and performances of adaptive impedance control were analyzed. The physical experiment was conducted on Staubli robot. The results show the flexible deformation decreases the position and force control precision, and the adaptive impedance proposed can increase the response time. Adaptive impedance is robust to the environment position uncertainties and can realize the flexible manipulator stably contacting and moving on the not-flat surface.

PML Absorbing Boundary Conditions for Computational Aeroacoustics

Chen Zhifu, Wen Guilin, Qing Hongjun, Wang Ming, Wang Yanguang

2014, 25(17):  2356-2360. 

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For nonlinear Euler equations in primitive variables，a pseudo mean flow was introduced in the derivation of the time-dependent fluctuation equations. Then a hypothesis for changed frequency was employed, a proper space-time transformation was presented for deriving the time-dependent fluctuation equations in transformed coordinates. A complex change was applied to the new equations and a damping parameter was introduced. Several nonlinear PML absorbing boundary condition in primitive variables for x layer, y layer and corner layer were derived. Finally, the stability and effectiveness of nonlinear PML absorbing boundary conditions were validated by computing the CAA benchmark problems. The results prove that: the maximum reflection error is less than 0.5% and 0.1% with PML width of 10 and 40 layers grid points, respectively, and the reflection error reduces with the increase of PML width; for actual CAA problems in the case of oblique mean flow, the proposed PML absorbing boundary conditions can absorb the vortex and acoustic wave with little or no reflection.

Modeling of CNC Machine Tool Thermal Errors Based on LS-SVM within Bayesian Evidence Framework

Yu Wenli, Yao Xinhua, Fu Jianzhong, Sun Lei

2014, 25(17):  2361-2368. 

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LS-SVM is an effective tool for machine error modeling. The traditional methods to set the parameters of LS-SVM which determined the modeling accuracy included ten-fold cross validation and grid method. However, using these methods, parameter calculation was complex and prone to low accuracy. Moreover, the LS-SVM model with only one set of parameters was hard to precisely describe the thermal error behaviors under the different work conditions. In order to solve these problems, based on Bayesian evidence framework a novel method was proposed to identify and optimize LS-SVM parameters under multiple working conditions. Three inferring levels of Bayesian evidence framework were used to derive the optimal model parameters corresponding to the different operating conditions. A series of experiments for thermal error modeling verified the validity of this method. LS-SVM model based on Bayesian evidence framework has good generalization ability, accurate prediction, and rapid calculation speed, so it can describe the actual thermal error characteristics more accurately under multiple work conditions.

Study on Flow Program Compensation Technology for Dead Zone of 2D Digital Valves

Zuo Qiang, Li Sheng, Ruan Jian

2014, 25(17):  2369-2374. 

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The structure and working principle of a 2D digital valve were described firstly, then the causes of 2D digital valve dead zone were analyzed. In view of the problems existing in the traditional dither compensation technology, a new  compensation method of flow program was proposed, and the technology of flow program superposing dither compensation was  studied. The experimental results show that, after flow program compensation, the dead zone almost disappears, but hysteresis still exists; the dead zone can be completely eliminated and the hysteresis significantly reduced after applying the technology of flow program superposing dither compensation. Finally the nonlinearity is less than 0.5%, which achieves the requirements of the servo system. Its frequency response is as 141Hz at -3dB of 25%  maximum spool displacement after compensating the dead.

Experimental Research on Hardware-in-the-Loop of Novel Hybrid Electric System

Liu Yonggang, Qin Datong, Peng Zhiyuan, Ye Ming

2014, 25(17):  2374-2380. 

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A novel hybrid electric system was proposed based on planetary gears and the HIL bench of the system was designed. The whole structural and control principles of the bench were analyzed. The control strategies of bench system were proposed based on driving and braking conditions. Finally, the HIL experimental bench of the novel hybrid electric system was developed by using tools based on MATLAB/Simulink and dSPACE real-time simulation platform and the performances of the system were verified. Test results show that different operating modes are achieved.

Design and Property of Multi-chamber Cascaded Electrorheological Valve

Hua Shunming, Li Xin, Liu Jianfang, Pang Liang

2014, 25(17):  2381-2385,2390. 

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A kind of multi-chamber cascaded electrorheological valve was proposed. Some parallel plate electrodes with distributing axial-flow holes were set in it. The valve could meet requirement of wide range speed regulation because its flow gap and number were adjustable conviniently. The fomula of pressure difference was deduced, so the inherent laws among pressure difference, field intensity, flow rate and chamber height were discovered. The fluid pressure distribution and flow condition in the valve were simulated by using Fluent software. At last, the validation and contrast tests were made on series prototype electrorheological valves. The results show that the disc-type valve runs well while the height of chamber is within 1.0mm. Cascaded structure is also proved helpful to improve the performance of electrorheological valve.

Profile Accuracy Control Method of Straight Bevel Gear by Near Net Shape Process Based on Numerical Calculation

Xu Hongbin, Hu Jianjun, Zhang Weiqing, Ling Wenkai

2014, 25(17):  2386-2390. 

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For the problem that tooth profile accuracy was not required high and modification was not full of consideration in straight bevel gear plastic forming process, a straight bevel gear tooth profile accuracy control method was proposed with near net forming based on the numerical calculation, then a detailed description of the process was carried out. The car differential planetary gear was studied by digital modeling, contact analysis, forming process finite element simulation and springback law calculation. The results display that the minimum rebound appears at drum and gradually increase to the tooth point or tooth root in the height of tooth direction. Maximum springback is up to maximum 0.14mm, and minimum 0.02mm closed to the tooth top. Twice modification was carried out to control accuracy of tooth profile and the maximum deviation value is up to -0.025mm while the minimum was close to zero. The results show that this method can use the near net shape process to obtain higher profile accuracy straight bevel gear products.

Dynamic Accuracy Measurement of High-speed Press

Wang Shangbin, Sun Yu, Zhang Xinzhou

2014, 25(17):  2391-2395. 

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Aimed at the difficulties of error elimination of horizontal direction dynamic accuracy measurement to press, a trigger measurement was proposed based on composite principle of displacement sensor and photoelectric sensor. The measurement as well as the existed defects of soft-triggerand hard-trigger were discussed, and an improved soft-trigger measurement was proposed. The feasibility of this measurement was validated by experiments, and the announcements in experiments were illustrated.Regarding to the larger noise of initial displacement signals in trigger measurement, two methods of noise reduction were provided using the filtering and themultiple-point averaging, and the results were compared.

Tensile Properties of Vacuum-assisted Scarf Repaired Laminates

Liu Weixian, Zhou Guangming, Wang Xinfeng, Qian Yuan

2014, 25(17):  2396-2401. 

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The tensile strength of the glass fiber composites using vacuum-assisted scarf repairs was first tested, and the final failure mode of repair structure was obtained. A three-dimensional finite element model of motherboard and patch in the repaired structure were established respectively, the material failure of unidirectional composites was simulated with continuum damage mechanics model, motherboard and patch contact with each other was assumed through the viscous force, and the contact analysis was defined for the secondary curing interface which was formulated by vacuum-assisted wet scarf repairs, the exponential softening cohesive model was used to simulate the properties of the interface contact. Test results and numerical simulation results agree well, so the model can be used to predict the tensile properties of the entire repaired structure. The damage and failure of the entire repaired structure were analyzed for the whole stretching process, the weak layer premature injury phenomenon is found, which caused by the stress concentration on the motherboard due to the additional patches. The influence of scarf angles on the strength of repaired structure in different sizes were discussed, the conclusion can guide technical staffs to make reasonable repair scheme.

Design of Steel-aluminum Hybrid Lightweight Frame by Multi-objective Optimization

Xin Yong, Ye Sheng

2014, 25(17):  2402-2407. 

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Taking an SUV frame as research subject, a finite element model was established, its bending, torsional stiffness and modal were analyzed, and the modal value was compared with test one to ensure the model effectiveness. Orthogonal test method was used to determine the lightweight components, and their steel materials were replaced by aluminum alloy, so a steel-aluminium hybrid lightweight frame was obtained. Then compromise programming multi-objective morphology optimization design method was adopted to improve its stiffness and modal property. Results of the design show that, using steel, aluminum and multi-objective optimization, the new steel-aluminum lightweight frame mass will be 6.7kg lighter than the original steel one with a well guarantee for the stiffness and modal performance.

Nonlinear Optimization of Mining Dump Truck's Cab Based on High Dimensional Model Representation

Li Weiping, Dou Xiandong, Zhang Baozhen, Wang Zhenxing

2014, 25(17):  2408-2413. 

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A nonlinear finite element analysis methodology was utilized to analyse the strength of ROPS of a safety cab herein. Additionally, some rectangular tube's thicknesses that influenced the structural strength and total weight considerably was selected as the design variables. An approximate model among design variables and objective function was established by high dimensional model representation(HDMR) based on thin plate spline interpolation（TPS-HDMR). Moreover, this paper adopted non-dominate sorting genetic algorithm(NSGA-Ⅱ) which was improved by adding elitist preserve strategy and removed duplicate individuals, for the sake of optimizing the deformation and weight simultaneously of the cab. The optimized results, the feasibility of the method proposed herein was verified.