A ROBUST ADAPTIVE SCHEDULER FOR AN INTELLIGENT WORKSTATION CONTROLLER

A shop floor control system (SFCS) consisting of three hierarchical control levels (shop, workstation, and equipment) is described. Each controller plans, schedules, and executes the activities necessary to process an order. An intelligent workstation controller (IWC), which is a part of the SFCS, is described in detail. The IWC receives information such as part type and quantity, part routeing specifications, and process plans from the shop level controller and coordinates production activities. The IWC performs three main functions-planning, scheduling, and execution in real-time in order to ensure completion of jobs assigned by the shop controller. The focus of this paper is to develop a robust adaptive scheduler to support the IWC which fits within the functional SFCS architecture. The objectives of this paper are: (1) to develop a neural network model that generates several part dispatching strategies based on workstation status; (2) to develop a multi-pass simulator that evaluates the generated strategies and selects the best strategy to maximize system efficiency; and (3) to compare the efficiency of the scheduling function with other single-pass strategies with respect to several performance criteria.X1163sciescopu

GRAPH-THEORETIC DEADLOCK DETECTION AND RESOLUTION FOR FLEXIBLE MANUFACTURING SYSTEMS

Flexible manufacturing systems are capable of producing a broad variety of products and changing their characteristics quickly and frequently. This flexibility provides for more efficient use of resources, but makes control of these systems more difficult. Control problems previously unstudied now require practical resolution, like system deadlock. A system deadlock is a situation that arises due to resource sharing in manufacturing systems, when the flow of parts is permanently inhibited and/or operations on parts cannot be performed. This problem has been ignored by most scheduling and control studies, which usually assume infinite machine queue capacity and unlimited tooling resources. FMS's, however, have little or no queue capacity and Limited tooling resources. In this paper, graph-theoretic deadlock detection and resolution procedures are presented which are suitable for real-time control of manufacturing systems. These procedures determine whether part movement in the system causes system deadlock or not. To this end, a system status graph representing part routings is virtually updated for every part movement before parts move physically to the next destination. Two types of system deadlocks, part flow deadlock and impending part flow deadlock, are detected using the updated system status graph. If a deadlock detection and recovery method is used to recover from a deadlock using a storage buffer, only part flow deadlocks need to be detected. On the other hand, if no buffer is available, both types of existing as well as impending system deadlocks need to be detected to avoid a deadlock situation.X1188sciescopu

A FORMAL APPROACH TO INTEGRATING COMPUTER AIDED PROCESS PLANNING AND SHOP FLOOR CONTROL

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A STRUCTURED APPROACH TO DEADLOCK DETECTION, AVOIDANCE AND RESOLUTION IN FLEXIBLE MANUFACTURING SYSTEMS

Production scheduling models that determine part mix ratios and detailed schedules do not usually account for deadlocks that can be caused by part flow. Deadlocks must be prevented for operational control (especially in automated systems). The major thrust of this paper is in developing a structured model for deadlock detection, avoidance and resolution caused by part flow in manufacturing systems. A system status graph can be constructed for the parts currently in the system. Deadlock detection amounts to determining deadlocks in the system status graph. On the other hand, deadlock avoidance amounts to restricting parts movement so that deadlocks are completely avoided in the future. While deadlock detection is a one-step look ahead procedure, deadlock avoidance is a complete look ahead procedure. Deadlock resolution or recovery amounts to judiciously using a limited queue to recover from deadlocks. Deadlock detection and avoidance are absolutely crucial to uninterrupted operation of automated manufacturing systems. A model based in graph theory has been formulated to detect and avoid deadlocks in automated manufacturing systems.X11108sciescopu

PARTICULATE EMISSION ABATEMENT FOR KRAKOW BOILERHOUSES

A U.S./Polish Bilateral Steering Committee (BSC) and the Department of Energy (DOE) selected LSR Technologies, Inc. as a contractor to participate in the Krakow Clean Fuels and Energy Efficiency Program. The objective of this program was the formation of business ventures between U.S. and Polish firms to provide equipment and services to reduce air emissions in the city of Krakow. A cooperative agreement was entered into by DOE and LSR to begin work in April 1994 involving implementation of particulate control technology called a Core Separator{trademark} for coal-fueled boilerhouses in the city. The major work tasks included: (1) conducting a market analysis, (2) completion of a formal marketing plan, (3) obtaining patent protection within Poland, (4) selecting a manufacturing partner, and (5) completing a demonstration unit and commercial installations. In addition to work performed by LSR Technologies, key contributors to this project were (1) the Polish Foundation for Energy Efficiency (FEWE), a non-profit consulting organization specializing in energy and environmental-related technologies, and (2) EcoInstal, a privately held Polish company serving the air pollution control market. As the project concluded in late 1998, five (5) Core Separator{trademark} installations had been implemented in the city of Krakow, while about 40 others were completed in other regions of Poland

Defective IL-12 production in mitogen-activated protein (MAP) kinase kinase 3 (Mkk3)-deficient mice.

The p38 mitogen-activated protein kinase (MAPK) pathway, like the c-Jun N-terminal kinase (JNK) MAPK pathway, is activated in response to cellular stress and inflammation and is involved in many fundamental biological processes. To study the role of the p38 MAPK pathway in vivo, we have used homologous recombination in mice to inactivate the Mkk3 gene, one of the two specific MAPK kinases (MAPKKs) that activate p38 MAPK. Mkk3(-/-) mice were viable and fertile; however, they were defective in interleukin-12 (IL-12) production by macrophages and dendritic cells. Interferon-gamma production following immunization with protein antigens and in vitro differentiation of naive T cells is greatly reduced, suggesting an impaired type I cytokine immune response. The effect of the p38 MAPK pathway on IL-12 expression is at least partly transcriptional, since inhibition of this pathway blocks IL-12 p40 promoter activity in macrophage cell lines and IL-12 p40 mRNA is reduced in MKK3-deficient mice. We conclude that the p38 MAP kinase, activated through MKK3, is required for the production of inflammatory cytokines by both antigen-presenting cells and CD4(+) T cells