Dec 2006, Volume 1 Issue 4

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  • CHU Hong-yan, CAO Quan-jun, FEI Ren-yuan
    The task of production scheduling is to determine the detailed machining path, time, machine tool, etc., for every work piece, according to the production objective and constraints. It is also an important part of the manufacturing system. In this paper, the manufacturing cell-based workshop is described and its scheduling system structure is established based on MAS (multi-agent system) technology. Through the negotiation and communication of each agent, the machining path is determined and the machining sequence and start time are calculated by GA (genetics algorithm). The communication among agents uses the CORBA (common object request broker architecture) technology of the OMG (Object Management Group). The CORBA-based architecture of the communication is designed and some interfaces for the communication are listed. For the genetics algorithm, chromosome coding, fitness function, parameters selection, and the basic genetics operation including selection, crossover and aberrance, are described. The scheduling system also can deal with some abnormal conditions, such as machine tool failure and urgent tasks. Finally, two scheduling examples are given.
  • WANG Qing-chun, FAN Zi-jie, GUI Liang-jin, WANG Zheng-hong, FU Zi-lai
    Drop hammer tests were carried out to study the axial crash behavior of aluminum foam-filled hat sections. First, the axial crash tests of the empty hat sections, aluminum foam and the aluminum foam-filled hat sections were carried out; then, based upon the test results, the axial crash behavior of the aluminum foam-filled hat sections were analyzed. It was found that aluminum foam filling can increase the energy absorption capacities of the hat sections. Compared with the non-filled structures, aluminum foamfilled structures were much more stable and needed less mass to absorb the specified energy.
  • LIU Jian-hua, NING Ru-xin, YAO Jun, WAN Bi-le
    VA (virtual assembly) provides a more efficient, intuitive and convenient method for assembly process modeling, simulation and analysis. Previous researches about VA are almost isolated and dispersive, and have not established the understanding and definition of VA from a macroscopical and integrated view. Based on the analysis of the connotations of VA, a PLO-VATA (product lifecycle-oriented virtual assembly technology architecture) is proposed, in this architecture, VA is decomposed into four basic elements: principles and methodology of DFA (design for assembly), assembly analysis and evaluation, virtual assembly model and virtual assembly toolkits. Immersion, concurrence, integration and collaboration are the four main characteristics of VA being put forward. The key techniques of VA including virtual assembly model, virtual assembly analysis and evaluation, and virtual assembly process planning are discussed. Finally, a prototype system is built to validate the feasibility of the proposed method.
  • LU Zhen-li, MA Shu-gen, LI Bin, WANG Yue-chao
    The rhythmic locomotion of a creature is a self-excitation behavior of the CPG (central pattern generator), which makes it supremely adapted for environment. Based on this fact, firstly, a snake-ike robot controller with cyclic inhibitory CPG model was designed, and then the stability of a single neuron, CPG model and the NON ( neuron oscillator network) was analyzed. By implementing this control architecture to a simulator based on the mechanical dynamics of a real snake-like robot named Perambulator-I, we presented preliminary rules for parameter setting of the CPG controller to modulate the number of S shapes, the curve of the body shape, locomotion velocity, and the curve of the locomotion trajectory for serpentine locomotion. Moreover, we demonstrated that Perambulator-I can successfully exhibit serpentine locomotion by using the output of the proposed CPG controller. The results of this paper provide a realistic approach for designing an artificial CPG controller.
  • LIANG Hong-bin, WANG Yong-zhang, LI Xia
    NURBS (non-uniform rational B-spline) interpolation algorithms have been provided in modern CNC (computer numerical control) systems. However, most of them focus on a constant feed speed without considering the contour accuracy. In order to deal with this problem, an adaptive feed speed interpolation algorithm for 3D NURBS parametric curves with confined chord errors is proposed. When the instantaneous radius of the curvature is small enough, the proposed interpolation algorithm automatically reduces the feed speed to meet the specified chord error. In the other situation it uses the second-order Taylor s expansions approximation interpolation algorithm to obtain a constant feed speed so that the contour accuracy in the CNC system is guaranteed. Experimental results were provided to verify the feasibility and precision of the proposed interpolation algorithm.
  • YAO Chun-de, ZHOU Hong-xiu
    The ES (electric supercharger) driven by a high-speed brushless motor was developed to solve the problem of smoke caused by the turbocharger s sluggish response during acceleration. Its rotation speed was from 6 000 r/min to 24 000 r/min, and the maximum flux was 0.1 kg/s. The structural design of the electric supercharger is novel, which makes it easier to set the lubricating installation and to assemble. The velocity distribution at the outlet of the electric supercharger is determined by hot-wire anemometry under various rotation speeds in steady state. Furthermore, the trends of the flux and charge rate with various speeds were analyzed. In addition, the transient response was detected from the motor setup to smooth running within 10 s, 15 s, 20 s and 25 s respectively, and the characteristic of the transient flux is under pilot study. Research results indicate that the electric supercharger can respond rapidly with the great flux, and it is independent of the operating conditions of a diesel engine. Therefore, it is a feasible way to reduce smoke emission and improve the acceleration performance.
  • LIANG Lin, XU Guang-hua
    A novel attribute reduction approach of rough set based on immune clone selection is proposed. In this method, the approximation quality and attribute set were adopted as evolution object and antibody, respectively. On the basis of the inherent distribution within the immune response, the global optimization of the antibody was realized through parallel local optimization. Moreover, the diversity of the antibody population was maintained with the affinity maturation and renewal of the antibody. Thus, the stable multi-optimal solutions can be preserved. In addition, the machinery fault data were analyzed by this method, and the attribute reduction sets were obtained further to satisfy the demand of feature selection in machinery diagnosis.
  • ZHANG Chao-hui, YE Wei, LUO Jian-bin, WEN Shi-zhu
    In an effort to explore the contribution of the pad, which is usually full of pores, to the performance of CMP (chemical mechanical polishing), a three-dimensional flow model of CMP is presented by assuming that the fluids in the porous layer comply with Darcy s law, which states that the flow velocity is proportional to the pressure gradient and inverse proportional to the viscosity. The flow equation is deduced accordingly and, by taking advantage of the multilevel technique and line relaxation technique, numerical simulations are carried out to reveal the relationships between the load capacities and operational parameters (including pivot height, roll angle and pitch angle), under conditions with different porous parameters and different thicknesses of the porous layer. The little porous parameter will lead to a prominent increase of load capability (for instance, the load and the moment predicted), which is still augmented by the thicker layer parameter. This will result in a higher material removal ratio of CMP. A pad full of large pores will be used to deduce load capability, facilitating the free flow of the fluids through the pores. The research will add some insights on the mechanism of the CMP technique.
  • LIU Ke-ge, YAN Chu-liang, ZHANG Shu-ming
    Taking the main landing gears of fighter and transport airplanes as examples, the fatigue life was estimated by means of the Miner s rule and from the spectrum of the real measurements. The computed results show that the landing damage to the fighter and transport airplanes is 75% and 60% of the total damage, and the damage caused by the landing stroke is 40% of the landing-gear damage. The fatigue damage properties can provide important information for reliable designing and the structural optimization.
  • ZHANG Jian-hui, Bai Heng-jun, XIA Qi-xiao, NING Hong-gang, ONUKI Akiyoshi
    The volume valve piezoelectric pump has received increasing attention from many areas because of its different characteristics such as the absence of chemical pollution and electromagnetic pollution. However, when the pump is working, it produces cavitations and the air bubbles that originate from these will flow out of the pump. Cavitations occurring in the pump will bring out noise and shorten the life of the pump. Furthermore, air bubbles flowing out of the pump will hinder its application in areas such as medical treatment and health care where blood transfusion and infusion are concerned. As a solution to this disadvantage, the CR3DMS (cavitations resistance with 3-dimensional mesh structure) method is developed, which is tested and verified to be effective on not only reducing the occurrence of cavitations and eliminating cavitations  flowing out, but also restraining the emission of noise. In conclusion, the pump with CR3DMS, on the relationship between flow and driving frequency and the relationship between flow and the number of Resistant-Layers in both theory and test, are analyzed.
  • ZHANG Deng-wei, SHU Xiao-wu, MU Xu-dong, LIU Cheng
    In order to receive and process the open loop signal from fiber optic gyroscopes speedily, stably and expediently, and to realize the amity interface between human and machine, a digital system that can convert GPIB (general purpose interface bus ) parallel bus into Universal Serial Bus is developed. All the interface functions of GPIB and the hardware system are realized through FPGA. With a digital sampling and processing system designed with VC++ in Windows platform, the real-time controlling procedure, high-speed receiving and sending data can be carried out, and the results can be displayed too. So the design of the system is flexible, the reliability and the stability are improved, error rate is no more than 10-11, the highest bit rate is 8 MB/s and the open loop detection system for optic fiber gyros achieves standardization and complete digitalization simultaneously.
  • BAO Bing-hao, ZHU Da-qi, DING Jian-ning, LI Chang-sheng
    An Fe73.5Cu1Nb3Si13.5B9 nanocrystalline toroidal core made by isothermal furnace annealing shows good thermal stability of magnetic properties and excellent soft magnetic properties due to the full release of the internal stresses of the core during the annealing process. Based on the feature of the magnetic core, a novel non-contact type weak current sensor adopting single nanocrystalline core and double-winding excited by multivibrator bridge is proposed. The measuring principles for static current are given in theory by an established mathematical model of the sensor. The theory is in good agreement with the experimental results and it indicated clearly the key factors affecting performance parameters for the sensor. The multivibrator bridge output signal was analyzed by Fourier transform. Furthermore, according to the theoretical results, the method to design the signal conditioning circuit was introduced.
  • DUAN Li-xiang, ZHANG Lai-bin, WANG Zhao-hui
    The vibration signals of diesel include excess noise that must be eliminated before extraction of characteristic parameters. Firstly, the effects of vibration-signal de-noising among Fourier transform, wavelet decomposition and wavelet packet decomposition are compared. Secondly, singular value decomposition is applied to de-noising vibration signals. Finally, a new de-noise method integrated with wavelet packet and singular value is presented. In this method, vibration signals are decomposed by wavelet packet, and the wavelet packet coefficient is de-noised by singular value decomposition again. The results indicate that the new de-noising method is the best. The SNR (signal-to-noise ratio) of the vibration signals of a diesel cylinder lid is the highest. The diesel vibration waveforms of combustion and valve become clear and the extracted characteristic parameters become more precise.
  • YANG Chao-jun, ZHANG Yong-kang, ZHOU Jian-zhong, DU Jian-jun, HUANG Shu, FENG Ai-xin, ZHANG Lei-hong, NI Ming-xiong
    The mechanism of laser shock deformation and the reason for the production of the shockwave are introduced. An evaluation formula of the detonation wave pressure in the system of laser, energy transferring-medium and sheet metal is built according to the theory of detonation wave and blasting gas-dynamics. The minimal energy of the laser pulse is evaluated on the basis of the formula of the laser shock pressure and evaluation of dynamic yielding strength. The experiment is also validated. The result shows that the quantity of sheet metal deforming is nonlinearly increased with laser energy, i.e., pressure of the laser shock wave. Under a laser-induced ultra-high pressure and high strain rate, structural steels and composite materials undergo plastic deformation.
  • ZHOU Yu-feng, CHEN Hua-ling
    To research the properties of a new kind of smart controllable MR (magnetorheological) fluid, in this paper, the rheological models are discussed. On the basis of analyzing the structural forms of MR dampers, an improved structure of the MR damper is introduced; the properties of the novel MR damper are then tested. The experimental results reveal that the Herschel-Bulkley model predicts the force-velocity well; the damping properties of the ameliorated structure of the MR damper have improved; when the excitation is a trigonal signal, the MR damper reveals a thinning effect at high velocity; and when the excitation is a sinusoidal signal, the MR damper reveals a nonlinear hysteretic property between the damping force and relative velocity. Finally, the main unsolved problems have been put forward.
  • ZHANG Kai, HU De-jin
    A revolving electromagnetic actuation mechanism composed of an electromagnetic stator and an electromagnetic rotor has been developed for boring non-circular holes. The main component of the rotor is a flexure-hinged based flexible body. There are four pole-pair coils in the stator supplying actuation currents. The micro-displacement between the stator and rotor can be controlled by changing the currents applied in the pole-pair coils. Through linearization of the actuation force near the static action point, a linear relationship between the control current and the actuation force was established, and the synchronizing control method of the electromagnetic actuation mechanism is presented here. With two-factor analysis of the linearization error of the actuation force, the influences of control current and micro-displacement to the linearization error of the actuation force were studied. Then, the principle for designing the basic parameters of the magnetic actuation mechanism is put forward. The calibration of the mechanism indicates that the relationship between the micro-displacement of the rotor and the control current has linear characteristics in the required micro-displacement range. Simulation tests show that the turning radius of the rotor changes with the control current. The proposed mechanism can feasibly supply a controllable micro displacement to the boring bar.
  • MA Yan-yan, CHENG Xian-hua
    The cavitation damage model was built using finite element analysis software MSC.Marc. This paper attempted to numerically analyze the action process based on damage mechanics when a jet created by bubble collapse acted on the bearing surface in the process of cavitation erosion. The numerical results show that the values of equivalent plastic strain and void volume fraction increase with time. The values of damage scalar are higher on the bearing surface and subsurface, and decrease when it approaches the interface of overlay and nickel layer. The strain history and damage evolvement of bearing material acted on by jet impact load can be calculated efficiently using the proposed method, which develops a new method of analyzing cavitation erosion failure of the bearing surface.
  • PAN Yong-ming, CHEN Shao-wei
    The development of new maraging steel overlaying welding rod, which contains Co, Mo, W and V alloy, solved the problems of poor homogeneity of hardness and mechanical process, prolonged the service life of wear-resistant components and increased the productive efficiency of repairing, greatly benefiting the national economy.
  • CHENG Ying, TU Hong-mao, FAN Hong-li
    To analyze structural reliability by the stochastic FE (finite element) method rapidly and efficiently, a method combined with the FE method and gradient optimum algorithm based on ANSYS was presented when referring to the geometric interpretation of structural reliability index. ANSYS-based development was adopted to implement it. Results of an example demonstrate that the method requires fewer FE calculations compared with the design point method and Monte-Carlo simulation, and achieves satisfactory accuracy.
  • WEN Xin-lin, CI Tie-jun, ZHANG Rong-ying, WEN Peng
    In this paper, the technical method of cooling quench medium with air-cooler in the process of bearing quenching is introduced. The exhausted hot air is directly used to dry bearing balls. It is a novel approach for full utilization of heat energy during heat treatment, which increased 30 % of the heat efficiency when compared with normal air-cooler methods that directly put exhaust air into atmosphere.
  • LIU Ming-tao, ZHANG Ce, YANG Yu-hu
    A new type of planetary indexing cam mechanism called type !c is presented. The transmission principle of type !c is discussed. Based on the principle of formation of conjugate tooth contour, the equations of the cam s pitch curve are derived. The continuity and symmetry of the cam s pitch curve are also analyzed. It can be concluded that: 1) This type has no output institution so the output precision can be improved; 2) The asymmetrical two-ring structure is used to overcome dead point and its phase angle is equal to (π - 2π/n); 3) The continuous condition of the cam s pitch curve is that the average transmission ratio is -n in an intermittent motion period.
  • LIU Fu-yun, QI Guo-ning, YANG Qing-hai
    Applying directed complex network to model the main structure of a product family, according to in-degree bi-logarithmic coordinate distribution curve and distribution rule of nodes of the network, in-degree evolving rule of nodes of the network is presented and analytic expression of in-degree probability density of nodes is derived. Through the analysis of the relation between existing kinds of components and existing product numbers, an expression of the relation between kinds of components and product numbers is derived. A forecast method for the increment of component numbers and parts based on the increment of products is presented. As an example, the component numbers of an industrial steam turbine product family is forecasted, forecast result verified and forecast error analyzed.