A virtual factory based approach to on-line simulation and scheduling for an FMS and a case study

The recent years have witnessed a revolution in computing capabilities. At the same time, modern manufacturing systems are becoming increasingly complex and capital-intensive. Here, we propose a virtual factory wherein an efficient prototyping testbed will be provided. It will be possible to develop detailed models to support system design and operation, to test different system configurations. Besides, It will be possible to manipulate all system features which impact performance, and to see the results of these manipulations, all without disrupting the actual system. This paper is one among very few that tries to represent the virtual factory in an analytic form so that many existing mathematical analyses can be applied. New pseudo resources can be added to form a new virtual environment, and control policy designed by engineers will be evaluated before being issued. Since a state-transition sequence of the virtual factory from the initial state to the final state can be seen as a schedule of the modeled system. An effective schedule of the processing can be obtained by using an A* based search algorithm, namely, Limited-Expansion A algorithm.     

信息驱动的制造系统构架

分析了信息化社会给制造业带来的变化，信息在制造中所起的作用越来越大，成为制造发展的主要驱动因素，高度信息化带来了网络化制造的发展，研究了制造信息的定义，表示、传输和存储等标准化的问题，认为信息的数字化是标准化的基础，网络化制造的制造信息采用STEP标准进行数据定义，XML进行数据的表示，以Internet/CORBA为信息交换的平台，最后给出了制造企业实现信息化的构架。     

Bond formation and fiber embedment during ultrasonic consolidation

The quality of ultrasonically consolidated parts critically depends on the bond quality between individual metal foils. This necessitates a detailed understanding of interface microstructures and ultrasonic bond formation mechanisms. In this work, the interface microstructures of a variety of ultrasonically consolidated similar and dissimilar metal samples were investigated. Samples with embedded SiC fibers were also investigated. Based on detailed microstructural studies, the mechanisms of foil bonding and fiber embedment in ultrasonic consolidation have been discussed.     

A three-dimensional finite element analysis of the temperature field during laser melting of metal powders in additive layer manufacturing

Simulating the transient temperature field in additive layer manufacturing (ALM) processes has presented a challenge to many researchers in the field. The transient temperature history is vital for determining the thermal stress distribution and residual stress states in ALM-processed parts that utilise a moving laser heat source. The modelling of the problem involving multiple layers is equally of great importance because the thermal interactions of successive layers affect the temperature gradients, which govern the heat transfer and thermal stress development mechanisms. This paper uses an innovative simulation technique known as element birth and death, in modelling the three-dimensional temperature field in multiple layers in a powder bed. The results indicate that the heated regions undergo rapid thermal cycles that could be associated with commensurate thermal stress cycles. Deposition of successive layers and subsequent laser scanning produces temperature spikes in previous layers. The resultant effect is a steady temperature build-up in the lower layers as the number of layers increases.     

Moore Automata for the Supervisory Control of Robotic Manufacturing Workcells

The potential of flexible-manufacturing workcells (FMCs) to produce a family of parts in many possible orders of operations and choices of different machines is advantageous. Despite intensive research on the theoretical control of discrete-event systems (DESs), however, current techniques can still only be used for the supervisory control of simple cells. In this paper, a novel modeling and control synthesis technique is presented for FMCs that allow part-routing flexibility. Our proposed methodology combines Extended Moore Automata (EMA) and Controlled-Automata theories to synthesize supervisors for such FMCs.     

Ingersoll-Rand压缩机中间冷却器的国产化及性能提升改造

150m^3／min三级压缩的Ingersoll-Rand空气压缩机组冷却器设计最高值仅32℃，不能满足现场运行条件，对冷却器结构进行了性能提升改造，实施后取得了很好的检验效果。     

冰模快速成形及其在铸造中应用的研究

采用FDM方法，离散式喷射实现了冰模快速成形。介绍了试验用快速成形硬件系统及工艺参数，分析了用冰模代替陶瓷型模和熔模铸造出蜡模的工艺流程。造型工艺。根据由冰模所翻制铸件的尺寸对铸件收缩率进行了研究。     

Petri网理论在柔性制造系统（FMS）性能分析中的应用

本文用 Petri 网的一个子类——时间事件图对流水车间型和作业车间型的柔性制造系统(FMS)建模并进行理论分析,给出了可行排序的判定条件及系统中托盘数量配置与系统生产率的关系,对系统的主要性能指标,如生产周期、工件驻留时间、在制品库存等给出了定量描述.这些结果为系统的设计和运行提供了理论依据.     

Bicharacteristic quality control in manufacturing

In this paper, the importance of bicharacteristic quality control has been discussed, when it is desired to exercise process control on manufacturing products that present two measurable characteristics which can suffer variations and on the other hand are considered significant for the functioning or the acceptance of the product. The verification that the process is in control or not is made by examining periodically the items of the samples drawn and plotting the points representing the mean of the characteristic in analysis on the corresponding charts. Using the computational program developed, a practical application is carried out for a mechanical manufacturing component that presents two critical characteristics. Also, a programmable mathematical model has been developed, aiming to computationally determine the sample size, and the interval between successive samples, which minimize the expected total cost. Idealized numerical application illustrates the use of the cost model that optimizes these parameters.     

Learning-based algorithms in scheduling

The aim of the paper is to present a conception of intelligent learning-based algorithms for scheduling. A general knowledge based model of a vast class of discrete deterministic processes is given. The model is a basis for the method of the synthesis of intelligent, learning-based algorithms, that is described in the paper. The designing simulation experiments that use learning is also described. To illustrate the presented ideas, the scheduling algorithm for a special NP-hard problem is given. The significant feature of the problem is that the retooling time depends not only on a pair of jobs to be processed directly one after the other, but also on the subset of jobs already performed. The proof of the NP-hardness of the problem is also given in the paper.