Browsing by Subject "Production control"
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Item A conceptual model and prototype of an adaptive production control system(Texas Tech University, 1995-12) Ottaway, Thomas A.The literature suggests two divergent approaches to the structure of intelligent production control systems. The National Institute for Standards and Technology (NIST), through its Advanced Manufacturing Research Facility (AMRF), and the European Community, tlirougli the European Specific Research and Technological Development Programme in the field of Information Technology (ESPRIT), advocate a centralized coordination structure for intelligent production control systems (Jones and McLean, 1986: ESPRIT Consortium AMICE, 1993). Advocates of the centralized coordination structure note the requirement for a global view of the factory in order to facilitate global optimization of the production system (Joshi and Smith, 1992). The centralized coordination structure of the NIST AMRF is shown in Figure 1.1. All existing commercial production control systems are based on a centralized coordination structure (Veeramani, Bhargava, and Barash, 1993). Many researchers in the field question the efficacy of the centralized coordination structure and have proposed intelhgent production control systems based on a decentralized coordination stnicture (Hatvany, 1985; Duffie and Piper, 1987; Duffie, 1990, Veeramani, Bhargava, and Barash, 1993). The expected benefits of the decentralized coordination structure are reduced complexity, reduced software development costs, higli modularity, high flexibihty, and improved fault tolerance (Duffie and Piper, 1987).Item A heuristic algorithm for sequencing n technologically ordered jobs through m machines with passing permitted(1967-06) Calvert, David Darwin; Dudek, Richard A.; Anderson, Ronald M.; Burford, Charles L.Not AvailableItem A heuristic solution technique for near optimal production schedules(1966-05) Campbell, Herbert George; Dudek, Richard A.; Ghare, P.M.; Ayoub, M.M.; Halcomb, Charles G.Not AvailableItem An analysis of the effects of unbalancing in a just-in-time production system with variable operation times(Texas Tech University, 1985-08) Villeda Rodriguez, RamiroA significant amount of research has been conducted aimed at providing industrial engineers and production managers with effective flow-line design, inventory control, and work design principles that are applicable to production systems operating under a push type production order system. However, the validity of some of these principles under a pull type production order system has not been fully verified. One of these principles is related to the line-balancing problem. There was no information about the allocation of work elements to work stations of Just-in-Time (JIT) production systems , when these elements have a great variability or when equal allocation of work to stations may be prevented by precedence and/or technological constraints. A perfectly balanced production system was used in this research as a control in order to analyze and evaluate the effects of unbalancing on this type of production system. This system (control) was compared with systems that were unbalanced with different strategies (high-low-high, low-medium-high, high-low-low and high-medium-low). The JIT production system studied (three lines with three work stations each, and a final assembly) was simulated with GPSS/H and executed under the effect of four independent variables: buffer stock allowed between each pair of work stations (three levels); line variability (three levels), and degree of imbalance (sixteen levels). The statistical analysis of the results showed that the output of all the configurations unbalanced with the high-medium-low strategy (at the two lower levels of buffer stock) was significantly higher than that of its balanced counterparts. The increase in production was in the 0.25% to 8.72% range. Furthermore, the analysis showed that there is a statistically significant reduction in work-i-process (WIP) for those configurations (between 2.65% and 15.1%. Additional experimentation confirmed that inequality of variability of operation times have the same general effect on output rate as inequality of operation times but little effect on the number of units (WIP) in the system.Item An investigation of the graph theoretic properties of the sequencing problem(Texas Tech University, 1968-06) Zurla, Charles FrancisNot availableItem An investigation of the job-type performance of priority scheduling in manufacturing cells(Texas Tech University, 1991-12) Gunal, Ali KamilIn traditional job-shop studies, it is usually assumed that jobs arrive randomly, they have random processing requirements, and measures of performance are taken over all jobs completed within a time period. There are many instances in practice, however, where a group of machines is formed to process a certain set of similar job types. A number of flexible manufacturing systems and group technology cells are examples of such manufacturing environments. In these types of manufacturing environments, the performance by job type is as important as the performance over all jobs. Problems may arise when jobs of a certain type are delayed more than the other job types. Such a situation is more likely to be seen when priorities are assigned based on information that is dependent on the type of a job. This study is an investigation of such variation in the job-type performance of the scheduling rules. It may be looked upon as an exploratory study since there is a lack of published results in this field of scheduling literature. Some fundamental questions regarding the job-type performance of a typical manufacturing cell are answered through a large-scale simulation experiment.Item Characterization and integration of control structures for hierarchical process control in production systems(Texas Tech University, 1999-08) Gherasoiu, IulianThe main objective of the research is to construct a generic framework for the design of control structures for production systems. The research deliverables are embedded in the control design framework methodology. The deliverable components of the design framework include the motivation of hierarchical control structure selection, general principles for process characterization, control element definition guidelines, formulation of control enabling principles, and definition of elementary control methods. The integration of control structures is presented from the perspective of goal and temporal coordination. Finally, procedures for conflict resolution and continuous improvement are presented in the context of control structures. The validity of the theoretical construct is based on the scientific rigor of the reference domain—control theory—and on the logical development of argumentation.Item Investigation of workload smoothing in the performance of a dual resource constrained job shop(Texas Tech University, 1992-08) Murray, Mary Ann SumstadThis study examined the effect of workload smoothing on the performance of a dual resource constrained (DRC) job shop utilizing an integrated system. A simulation study was conducted in two stages. The primary experiments evaluated the effect of four smoothing rules, three order review/release (ORR) rules, and six dispatching rules at a 90% shop utilization level on six performance measures. The second set of experiments provided a sensitivity analysis using the four smoothing rules, three ORR rules, and the four best-performing dispatching rules from the primary experiments at the 85% shop utilization level. Analysis of Variance, ranked data, and interaction plots were examined to determine which policies provided the best results for both sets of experiments. Results of this research indicate the following. (1) Workload smoothing had no significant effect on the performance of the DRC job shop. At the 90% shop utilization level, the ORR provided the necessary control using the Maximum Shopload (MSL) release mechanism, except for the performance measures of standard deviation of flowtime and percent jobs tardy where the Immediate Release (IMR) rule performed better. At the 85% shop utilization level, IMR performed better and the primary decision became the dispatching rule to select, except for the performance measure of standard deviation of flowtime. With standard deviation of flowtime, extreme smoothing and MSL performed better with either the Earliest Due Date (EDD) or Modified Due Date (MDD) dispatching rules. It appears more control is required at the lower utilization level to reduce the variation of individual jobs about the mean flowtime. (2) The Maximum Jobload (MJL) release rule designed for this study performed as well as, but no better than, the MSL rule. (3) The "crossover phenomenon" was not an issue as those rules that did exhibit evidence of crossing over were either rules which were not candidates for consideration in policy decisions, or members of a group of rules that were not significantly different from each other and were considered as a group.Item Item Steady state flowship sequencing to meet due date with bonus and penalty functions(Texas Tech University, 1969-08) Ramaswamy, Kizhanatham V.Not availableItem The bidirectional-ordered flow shop scheduling problem(Texas Tech University, 1992-08) Latorraca, DomingoNot available