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ABSTRACT: This paper addresses the problem of real-time deadlock-free scheduling for a semiconductor track system. The system is required
to process wafers continuously, cassette by cassette. The process is not necessarily a repeated one. In addition, the system
is deadlock-prone and its modules are failure-prone. Thus, real-time scheduling approaches are required to achieve high-performance.
The problem can be solved in a hierarchical way. A deadlock avoidance policy is developed for the system as a lower-layer
controller. With the support of the deadlock avoidance policy, heuristic rules are proposed to schedule the system in real-time.
An effective modeling tool, colored–timed resource-oriented Petri net, is presented. It is shown that with this model we can
schedule a system to achieve satisfactory results in real-time. This method is tolerant to module failures.
Operations Research-Spektrum 04/2012; 29(3):421-443. · 1.23 Impact Factor
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IEEE T. Automation Science and Engineering. 01/2012; 9:203-209.
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IEEE International Conference on Robotics and Automation, ICRA 2011, Shanghai, China, 9-13 May 2011; 01/2011
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IEEE T. Automation Science and Engineering. 01/2011; 8:190-204.
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IEEE Transactions on Intelligent Transportation Systems. 01/2011; 12:977-989.
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IEEE Conference on Automation Science and Engineering, CASE 2011, Trieste, Italy, Aug. 24-27, 2011; 01/2011
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Proceedings of the IEEE International Conference on Networking, Sensing and Control, ICNSC 2011, Delft, The Netherlands, 11-13 April 2011; 01/2011
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IEEE T. Automation Science and Engineering. 01/2011; 8:42-55.
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Proceedings of the IEEE International Conference on Networking, Sensing and Control, ICNSC 2011, Delft, The Netherlands, 11-13 April 2011; 01/2011
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ABSTRACT: In the context of automated manufacturing systems (AMS), Petri nets are widely adopted to solve the modeling, analysis, and control problems. So far, nearly all well-known Petri net approaches study AMS with either flexible routes or assembly operations, whereas few work investigates their combination. In this paper, we propose a novel class of nets, which can well deal with both features. We also derive a supervisory controller for on-line ratio enforcement among all processes. Using structural analysis, we show that liveness of such systems can be attributed to the absence of undermarked siphons. We also reveal the design separability between ratio-enforcing and liveness-enforcing supervisors.
Automation Science and Engineering (CASE), 2010 IEEE Conference on; 09/2010
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ABSTRACT: Because of wafer residency time constraints for cluster tools, it is very difficult to schedule them. This paper addresses their scheduling issues and conducts their schedulability and scheduling analysis. A Petri net (PN) model is developed to model them. With this model, to schedule a dual-arm cluster tool with wafer residency time constraints is to determine when and how long the robot should wait for. Based on the model, necessary and sufficient conditions under which the system is schedulable are presented. The conditions can be checked analytically. Meanwhile, an algorithm is developed for the optimal scheduling of dual-arm cluster tools. The algorithm finds an optimal periodic schedule with closed form expressions if it is schedulable. A method is also presented for the implementation of the obtained cyclic schedule by appropriately controlling the initial transient process. Examples are presented to show the application and power of the theory and algorithm.
IEEE Transactions on Automation Science and Engineering 05/2010; · 1.46 Impact Factor
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ABSTRACT: Since the 1980s, Petri nets (PN) have been widely used to model automated manufacturing systems (AMS) for analysis, performance evaluation, simulation, and control. They are mostly based on process-oriented modeling methods and thus termed as process-oriented PN (POPN) in this paper. The recent study of deadlock avoidance problems in AMS led to another type of PN called resource-oriented PN (ROPN). This paper, for the first time, compares these two modeling methods and resultant models in terms of modeling power, model complexity for analysis and control, and some critical properties. POPN models the part production processes straightforwardly, while ROPN is more compact and effective for deadlock resolution. The relations between these two models are investigated. Several examples are used to illustrate them. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Asian Journal of Control 04/2010; 12(3):267 - 280. · 1.03 Impact Factor
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ABSTRACT: In this paper, a colored timed resource-oriented Petri net (CTROPN) is developed to model the cluster tools in semiconductor fabrication. It is structurally simple and concise, since each module in a cluster tool corresponds to a unique place in CTROPN. It is also powerful in modeling the qualitative and temporal behavior of the cluster tools with a single-blade or dual-blade robot. The initial transient behavior, steady-state behavior and the final transient behavior can all be investigated through a single model. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Asian Journal of Control 04/2010; 12(3):253 - 266. · 1.03 Impact Factor
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ABSTRACT: Since the 1980s, Petri nets (PN) have been widely used to model auto-mated manufacturing systems (AMS) for analysis, performance evaluation, simulation, and control. They are mostly based on process-oriented modeling methods and thus termed as process-oriented PN (POPN) in this paper. The recent study of deadlock avoidance problems in AMS led to another type of PN called resource-oriented PN (ROPN). This paper, for the first time, compares these two modeling methods and resultant models in terms of modeling power, model complexity for analysis and control, and some critical properties. POPN models the part production processes straightforwardly, while ROPN is more compact and effective for deadlock resolution. The relations between these two models are investigated. Several examples are used to illustrate them.
Asian Journal of Control 04/2010; 12(280). · 1.03 Impact Factor
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ABSTRACT: There are varieties of constraints for a short-term scheduling problem of crude oil operations in a refinery. These constraints are difficult to model and complicate the short-term scheduling problem. Among them, oil residency time and high fusion point crude oil transportation constraints are the challenging ones. With high setup cost for high fusion point oil transportation, it is desired that the volume of high fusion point oil can be transported as much as possible by a single setup. This may result in late transportation of other types of crude oil, leading to the violation of crude oil residency time constraint. These constraints are ignored by existing methods in the literature. To solve this problem, this paper studies the problem in a control theory perspective by viewing an operation decision in the schedule as a control. With this idea, the system is modeled by a hybrid Petri net. With this model and tank grouping strategy, schedulability analysis is carried out and schedulability conditions are presented with tank charging and discharging costs being taken into consideration. These conditions are necessary for determining a refining schedule and can be used to check whether a target-refining schedule is realizable or not. If so, a feasible detailed schedule for the refining schedule can be easily obtained by creating the operation decisions one by one.
IEEE Transactions on Systems Man and Cybernetics Part C (Applications and Reviews) 04/2010; · 2.01 Impact Factor
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ABSTRACT: When scheduling cluster tools under wafer residency time constraints, wafer sojourn time in a processing module should be carefully controlled such that it is in a permissive range. Activity time variation often results in wafer sojourn time fluctuation and makes an originally feasible schedule infeasible. Thus, it is very important to know how the wafer sojourn time changes when activity time varies. With bounded activity time variation considered, this paper conducts a detailed analysis of wafer sojourn time variation in dual-arm cluster tools. To do so, a Petri net (PN) model and a real-time control policy are presented. Based on the PN model, real-time operational architecture, and real-time control policy, this paper analyzes the effect of activity time variation on wafer sojourn time delay at a process module and presents its upper bounds. The upper bounds are given in an analytical form and can be easily evaluated. With the wafer sojourn time analysis, it is possible to develop an effective method for schedulability analysis and optimal steady-state scheduling. An example is used to show the applications of the proposed approach.
IEEE Transactions on Semiconductor Manufacturing 03/2010; · 0.72 Impact Factor
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IEEE T. Automation Science and Engineering. 01/2010; 7:303-315.
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Computers & Chemical Engineering. 01/2010; 34:529-543.
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IEEE Conference on Automation Science and Engineering, CASE 2010, Toronto, ON, Canada, 21-24 August, 2010; 01/2010
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IEEE Transactions on Systems, Man, and Cybernetics, Part C. 01/2010; 40:159-175.
