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MAS-based production scheduling system for manufacturing cell-based workshop
CHU Hong-yan, CAO Quan-jun, FEI Ren-yuan
Front. Mech. Eng.. 2006, 1 (4): 375-380.
https://doi.org/10.1007/s11465-006-0043-x
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.
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Experimental studies on the axial crash behavior of aluminum foam-filled hat sections
WANG Qing-chun, FAN Zi-jie, GUI Liang-jin, WANG Zheng-hong, FU Zi-lai
Front. Mech. Eng.. 2006, 1 (4): 381-387.
https://doi.org/10.1007/s11465-006-0044-9
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.
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Product lifecycle-oriented virtual assembly technology
LIU Jian-hua, NING Ru-xin, YAO Jun, WAN Bi-le
Front. Mech. Eng.. 2006, 1 (4): 388-395.
https://doi.org/10.1007/s11465-006-0045-8
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.
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Design of a cyclic inhibitory CPG controller for the locomotion of a snakelike robot
LU Zhen-li, MA Shu-gen, LI Bin, WANG Yue-chao
Front. Mech. Eng.. 2006, 1 (4): 396-402.
https://doi.org/10.1007/s11465-006-0046-7
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.
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Design and characteristics of electric supercharger for diesel engine acceleration by additional rapid air injection
YAO Chun-de, ZHOU Hong-xiu
Front. Mech. Eng.. 2006, 1 (4): 409-412.
https://doi.org/10.1007/s11465-006-0048-5
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.
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Porosity model for flows in CMP
ZHANG Chao-hui, YE Wei, LUO Jian-bin, WEN Shi-zhu
Front. Mech. Eng.. 2006, 1 (4): 418-423.
https://doi.org/10.1007/s11465-006-0050-y
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.
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Research on the method of cavitations resistance in a piezoelectric pump with 3-dimensional mesh structure
ZHANG Jian-hui, Bai Heng-jun, XIA Qi-xiao, NING Hong-gang, ONUKI Akiyoshi
Front. Mech. Eng.. 2006, 1 (4): 429-433.
https://doi.org/10.1007/s11465-006-0052-9
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.
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Digitalization optical open loop test system for fiber optic gyroscope
ZHANG Deng-wei, SHU Xiao-wu, MU Xu-dong, LIU Cheng
Front. Mech. Eng.. 2006, 1 (4): 434-438.
https://doi.org/10.1007/s11465-006-0053-8
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.
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Analysis and experiment on deformation of sheet metal by laser shock wave
YANG Chao-jun, ZHANG Yong-kang, ZHOU Jian-zhong, DU Jian-jun, HUANG Shu, FENG Ai-xin, ZHANG Lei-hong, NI Ming-xiong
Front. Mech. Eng.. 2006, 1 (4): 448-451.
https://doi.org/10.1007/s11465-006-0056-5
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.
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22 articles
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