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Globalization and advanced technology have defined twenty-first century manufacturing, creating a hyper-competitive environment where continuous growth in productivity has become imperative--not just for the success of firms, but for their [...]

Since the early 1980's, when Japanese manufacturing firms in a number of industries - including auto, electronics, and machinery - achieved high levels of international competitiveness, Japanese manufacturing practices - particularly those associated with just-in-time manufacturing (JIT) - have attracted considerable attention in North America. Transfer to the United States of JIT is characterized by special production management practices involving inventory and quality control, industrial relations, and supplier-manufacturer relationships. Because so many different aspects of plant operation are involved, the transfer of JIT requires a substantial effort on the part of U.S. manufacturers. Despite this barrier, anecdotal evidence suggests that substantial transfer of Japanese production methods has taken place and that this transfer has had a significant impact on the performance of U.S. manufacturing plants. However, there is little empirical evidence of this process that is based on broad samples of plants and workers from various manufacturing industries. The purpose of this paper is to help fill this gap in the literature. Using a sample of U.S.- and Japanese-owned manufacturing plants in the United States in three different industries, we show that the implementation of JIT has improved many of the performance measures for these U.S. manufacturing plants. Index Terms - Just-in-time manufacturing, manufacturing performance, production management practices.

Considering the code division multiple access (CDMA) radio communication schemes, this paper proposes a wireless access infrastructure and a protocol for factory automation with several mobile terminals. A factory manufacturing floor usually forms several islands of automation with each having multiple mobile terminals. Each island of automation can be covered by a base station that then connects to a supervisory computer (command center). The base station can then serve as a bridge between the wireless network and the MAP backbone. Adding wireless access capability to a MAP-based network can release the problem of rewiring the moving devices in floor planning and restructuring. Considering a priority structure, we propose a Handshake-Aloha protocol suitable for such wireless factory environment. The numerical results show that it performs much better than the random access schemes such as Aloha protocol in terms of the throughput and delay performance. Index Terms - CDMA, delay, Handshake-Aloha protocol, MAP, throughput.

The planning method adopted in the visual programming system for sequence-control program specification design (VIPS/S-SFCD) is described. VIPS/S-SFCD is based on two unique features: 1) an example-based programming technique in which designers specify the initial states and goal conditions of equipment blocks using visual representations and 2) a planning method that infers machine actions and generates control program specifications. The planning method is based on a state-space model and uses scope to make the searches more efficient. To investigate the effectiveness of the method, VIPS/S-SFCD was used to experimentally generate control program specifications for an existing steel plant. The results showed that the quality of the control program specifications generated by the planner was equal to that achieved by a design specialist, and the time required for designing control programs was much shorter. Using VIPS/S-SFCD, errors in writing specifications are reduced because designers can easily understand the initial and goal state of an equipment block and the sequence of state transitions. The reliability of the specifications is improved because VIPS/S-SFCD generates valid segments of the specifications. The design time is also reduced because designers can use high-level instructions that closely reflect their thought processes. Index Terms - Dijkstra algorithm, planning, scope, sequence-control program, state-space model, visual programming.

Continuous-state plants place specific demands on the structure and operation of multi-agent, multi-paradigm distributed intelligent controllers. An investigation of the use of distributed artificial intelligence techniques for continuous-state control is presented. The choice of agents and how they interact to control a continuous-state plant is discussed. A distinction between a priori and operational knowledge is introduced to simplify and aid the design of distributed intelligent controllers. A simulation study of a controller designed for a deep-shaft mine winder serves to demonstrate the application of distributed intelligent control to a continuous-state plant. Index Terms - Continuous-state plants, distributed intelligent control, real-time.

This paper presents the use of neural networks for process scheduling in the area of factory automation, where bus-based communication systems, called FieldBuses, are widely used to connect sensors and actuators to the control systems. The need to respect the strong time constraints typical of the applications supported in these systems requires suitable scheduling strategies in order to devise an appropriate sequence for transmission of the information produced by the processes using the communication system. The most widely used strategy consists of drawing up off-line scheduling tables containing this transmission sequence. As the size of a table may be considerable, thus creating serious problems for memorization, the authors previously developed an innovative method which allows the size of the table to be reduced greatly but complicates the problem of scheduling as it requires the use of computationally complex algorithms. In this paper, they present an alternative approach to scheduling based on a Hopfield-type neural-network model and show how it overcomes the problem of the computational complexity of the algorithmic solution. The neural model proposed allows several processes to be scheduled simultaneously; the time required is polynomial with respect to the number of processes being scheduled. This feature allows real-time process scheduling and makes it possible for the scheduling table to adapt to changes in process control features. The paper presents the neural model for process scheduling and assesses its computational complexity, pointing out the drastic reduction in the time needed to generate a schedule as compared with the algorithmic scheduling solution. Finally the authors propose an on-line scheduling strategy based on the neural model which can achieve real-time adaptation of the scheduling table to changes in the manufacturing environment.

We address the problem of systematically constructing diagnostic systems for large industrial plants. Toward this end, we propose an environment based on methods, languages, and tools allowing systematic construction of diagnostic systems for units of large industrial plants. This environment is based on a skillful articulation of methods, languages, and tools. The process of construction proceeds in three stages as follows. Using methods, the first stage aims at structuring the unit into a set of hierarchies and graphs pointing out several views. The second stage makes use of languages to give a precise specification of the different components embedded in the unit. Finally, tools map the specifications of the unit to derive the diagnostic system. Index Terms - Artificial intelligence, diagnostic methods, fault diagnosis, large industrial plants, methodology, specification, software engineering, system engineering

This paper presents an overview of research at Stanford University on the development of concepts of a programmable factory, based on a new generation of flexible multi-functional equipment implemented in a smaller flexible factory. This approach is demonstrated through the development of a novel single wafer Rapid Thermal Multiprocessing (RTM) reactor with extensive integration of sensors, computers and related technology for specification, communication, execution, monitoring, control, and diagnosis to demonstrate the programmable nature of the RTM. The RTM combines rapid thermal processing and several other process environments in a single chamber, with applications for multilayer in-situ growth and deposition of dielectrics, semiconductors and metals. Because it is highly instrumented, the RTM is very flexible for in-situ multiprocessing, allowing rapid cycling of ambient gases, temperature, pressure, etc. It allows several processing steps to be executed sequentially in-situ, while providing sufficient flexibility to allow optimization of each processing step. This flexibility is partially the result of a new lamp system with three concentric rings each of which is independently and dynamically controlled to provide for better control over the spatial and temporal optical flux profile resulting in excellent temperature uniformity over a wide range of process conditions namely temperatures, pressures and gas flow rates. The lamp system has been optimally designed through the use of a newly developed thermal simulator. For equipment and process control, a variety of sensors for real-time measurements and a model based control system have been developed. The acoustic sensors noninvasively allow a complete wafer temperature tomography under all process conditions - a critically important measurement never obtained before. In an exemplary demonstration of multiprocessing, we have integrated three different processes with disparate process conditions - cleaning, thermal oxidation and CVD of silicon - sequentially in-situ. This technology integrates an entire MOS capacitor stack into one process chamber as opposed to three stand alone pieces of equipment needed in conventional technology. This will result in reduced cost of the factory, reduction in cycle time and may provide better device characteristics, since the interfaces between the semiconductor, gate dielectric and gate electrode are free of contamination from the room ambient. In general, adaptable manufacturing systems (AMS) based on this approach may offer more economical small or large scale production, higher flexibility to accommodate many products on several processes, and faster turnaround to hasten product innovation.

In an elegant and yet easily comprehensible and applicable way, it is shown how the outputs of n identical plants (Mathematical Expression Omitted) with different output initial conditions can be made to perfectly track a reference, or command, input r(t) through the commissioning of only one central controller H(s). Two simulations support the theoretical results. The proposed technique has wide applications in industrial plants and research centers: it drastically reduces the effort and cost of controllers dictated by the orthodox one-plant/one-controller philosophy.

Recent debates on the 'factory of the future' refer almost exclusively to computer integrated manufacturing (CIM); but there is still a long way to go towards the realization of fully automated and computer integrated production. The current dynamic diffusion of CIM components creates new problems for the organization of future factory and work structures. Our findings from the German capital goods industry illustrate that there is presently no uniform structural paradigm emerging from these computer-based innovation processes. Efforts to make traditional Tayloristic forms of work organization more efficient is the path still taken by many companies, while others are seeking ways of maintaining or revitalizing forms of skilled production work on the shopfloor. The restructuring of industrial labour seems more than ever a political question. Concepts of technology, the system of education and vocational training, as well as the management of innovation on the company level, have important influences in determining the direction of further development. (Reprinted by permission of the publisher.)

The work design philosophy embodied in the human-centred computer integrated manufacturing (CIM) approach provides a radical alternative to traditional technology-oriented and Taylorist approaches to CIM. In order to extend the work that has been done on redesigning factory production and planning tools and systems, this approach can usefully be enhanced by drawing on research on 'simultaneous engineering' and the technical and organizational redesign of the design/manufacturing interface. The vision of the 'informated' factory of the future embodied in this human-centred CIM vision provides a much needed challenge to traditional guiding images of the ideal automated factory. (Reprinted by permission of the publisher.)