Jonghun Park

Deadlock avoidance in sequential resource allocation systems with multiple resource acquisitions and flexible routings

The main purpose of this correspondence is to establish that, contrary to the claims that are made in the paper by D. Y. Chao in it, the results of the paper by Park and S. A. Reveliotis concerning the liveness characterization of the S3PGR2 nets by means of the structural object of deadly marked siphon, are correct and complete.

Algebraic synthesis of efficient deadlock avoidance policies for sequential resource allocation systems

Deadlock avoidance in sequential resource allocation systems is a well-defined problem in discrete event system literature, as it underlies the operation of many contemporary technological systems. In the past, the problem has been studied by means of a number of formal frameworks, including the finite-state automata (FSA) and Petri nets (PNs). In this paper, it is shown that a significant class of deadlock avoidance policies (DAPs), known as algebraic polynomial kernel (PK)-DAPs, originally developed in the FSA paradigm, can be analyzed using recent results from PN structural analysis. Furthermore, the approach to DAP analysis and design taken in this paper has led to the effective generalization of the currently available algebraic PK-DAPs, and to their enrichment with new and more flexible policy implementations.

A distributed, event-driven control architecture for flexibly automated manufacturing systems

This paper presents a new distributed real-time control architecture for flexibly automated production systems. The modelling assumptions underlying the design are driven by, and abstract, the structure and operations of the emerging 300 mm semiconductor manufacturing fab, one of the most extensively automated environments in contemporary manufacturing. The key element of the controller design itself, which differentiates it from past efforts, is the distribution of the control function to the constituent components of the system shop-floor architecture, while maintaining both the logical correctness and the efficiency of the system behaviour. The architecture was designed to be easily implementable in the actual system shop-floor, and therefore is aligned with, and augments, current practices in these environments. From a theoretical perspective, the proposed design has employed, integrated and extended a series of theoretical results from the field of Discrete Event Dynamical Systems. It is our expectation that the proposed architecture will also provide a formal framework for further analytical studies on the performance evaluation and performance-oriented control/scheduling of the considered class of manufacturing systems.

A high-fidelity, web-based simulator for 300 mm wafer fabs

Semiconductor fabs are capital intensive. The rate of capital return heavily depends on their productivity. Accordingly, simulation has been adopted in many cases as a viable design and analysis tool to achieve better productivity. However, the gap between the simplistic simulation models and real complex systems has limited the confidence to apply simulation results directly to real systems. Ideally, the simulator should support the rapid modeling and fast execution of high-fidelity fab models in order to be able to provide more realistic simulation results. In this paper, we present our current research effort to develop a high-fidelity web-based simulator for the 300 mm wafer fabs. We take a model-view-control approach that allows us to develop modular and reusable fab simulation objects. The proposed approach is implemented as a distributed system that uses a message-based event synchronization mechanism to coordinate the simulation objects as well as to support distributed simulation execution. The presented simulator also provides a high quality VRML animation for visualization of real time paced simulation execution.

A polynomial-complexity deadlock avoidance policy for sequential resource allocation systems with multiple resource acquisitions and flexible routings

The need for effective and efficient deadlock avoidance policies (DAPs) is ever increasing due to the higher demand for system automation. This paper considers the deadlock avoidance problem for the class of conjunctive/disjunctive (sequential) resource allocation systems (C/D-RAS), in which multiple resource acquisitions and flexible routings are allowed. A new siphon-based characterization of deadlocks arising in C/D-RAS is developed, and subsequently, this characterization facilitates the development of a polynomial complexity deadlock avoidance policy for the considered RAS class. The developed policy can be perceived as a generalization of RUN DAP, originally developed for sequential RAS with unit resource allocations and no routing flexibility. The proposed approach is demonstrated by an example.

Policy mixtures: a novel approach for enhancing the operational flexibility of resource allocation systems with alternate routings

Liveness-enforcing supervisors (LESs) guarantee deadlock-free operations in resource allocation systems (RASs). Given the growing emphasis on higher resource utilization and operational flexibility, it is greatly desirable to obtain the optimal LES that can provide the maximum behavioral latitude. In general, however, computation of the maximally permissive LES is computationally intractable and, accordingly, the class of algebraic LESs has been proposed in the literature as a viable suboptimal alternative for various RAS classes. The objective of this work is to further enhance the permissiveness of algebraic LESs by taking advantage of the routing flexibility inherent in contemporary RASs. Specifically, we consider a class of algebraic LES that allows supervisor parameterizations based on the system routing flexibility, and propose a method to effectively mix the algebraic LESs obtained from the policy instantiation through a set of different parameter values. The resulting policy mixture, to be called dynamic algebraic LES, provides increased permissiveness as it allows flexible online switching among different resource reservation schemes, corresponding to different process routings. The proposed method for constructing the dynamic algebraic LES is presented in the context of the class of conjunctive/disjunctive RASs, which subsumes the major RAS classes currently studied in the literature.

A colored Petri net-based approach to the design of 300 mm wafer fab controllers

As the effective deployment of system production capacity and operational capability becomes critical for competitive semiconductor manufacturing, there is an increasing interest toward the development of a control framework which allows effective and efficient operation of the emerging 300 mm wafer fabs. In the paper, a colored Petri net-based approach is taken to develop such a distributed event-driven 300 mm fab controller. The key element of the proposed controller design is the distribution of control function, to the constituent components of the 300 mm fab, while maintaining the logical correctness and efficiency of the fab behavior. Furthermore, in order to achieve the viability of the resulting control scheme, the proposed approach seeks to incorporate detailed operational characteristics of the 300 mm fabs, including batching, setups, reworks, maintenance, machine failures, and complex resource allocation dynamics due to the routing flexibility and auxiliary resource sharing. The proposed approach is demonstrated through a small-scale example, modeling the operation of a 300 mm fab bay.

Enhancing the flexibility of algebraic deadlock avoidance policies through Petri net structural analysis

Deadlock avoidance in sequential resource allocation systems is a well-defined problem in discrete event system literature, as it underlies the operation of many contemporary technological systems. In the past, the problem has been studied by means of a number of formal frameworks, including the finite state automata (FSA) and Petri nets (PN). In this paper, it is shown that a significant class of deadlock avoidance policies (DAP), known as algebraic PK-DAP, originally developed in the FSA paradigm, can be analyzed using recent results from PN structural analysis. Furthermore, the approach to DAP analysis and design taken in this paper has led to the effective generalization of the currently available algebraic PK-DAP, and to their enrichment with new and more flexible policy implementations.

Algebraic deadlock avoidance policies for conjunctive/disjunctive resource allocation systems

Operational flexibility of deadlock avoidance policies (DAPs) is an essential requirement for achieving high resource utilization of the underlying deadlock-prone resource allocation system. The paper presents computational methods for synthesizing highly flexible DAPs for the class of conjunctive/disjunctive resource allocation systems (CD-RAS), which generalizes the resource allocation model that has been typically studied in the past, by allowing multiple resource acquisitions and flexible routings. Specifically, a linear programming method to compute DAPs for CD-RAS is developed, and subsequently a series of computational tools are provided to enhance the policy permissiveness/flexibility. These methods are based on: (i) the pertinent exploitation of the policy parameterization, (ii) the observation that the considered class of policies is closed under policy disjunctions, and (iii) the systematic relaxation of the policy-imposed constraints through Petri net structural analysis. The presented results are demonstrated through an example modeling an agile automation system.

Correction to the RUN DAP for conjunctive RAS presented in "Polynomial-complexity deadlock avoidance policies for sequential resource allocation systems"

This note first identifies a problem with the correctness of the RUN DAP for conjunctive RAS, presented in the above paper by Reveliotis et al. (1997), and subsequently proceeds to the problem correction through an appropriate policy modification.