Schedule execution in autonomic manufacturing execution systems

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Journal of Manufacturing Systems 26 (2007) 75–84

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Technical paper

Schedule execution in autonomic manufacturing execution systems
Paul Valckenaers ∗ , Hendrik Van Brussel, Paul Verstraete, Bart Saint Germain, Hadeli
Mechanical Engineering Department, K.U.Leuven, Belgium



a b s t r a c t
This paper discusses a manufacturing execution system (MES) that prefers and attempts to follow a given schedule. The MES performs this task in an autonomic manner, filling in missing details, providing alternatives for unfeasible assignments, handling auxiliary tasks, and so on. The paper presents the research challenge, depicts the MES design,and gives experimental results. The research contribution resides in the novel architecture in which the MES cooperates with schedulers without inheriting the limitations of the world model employed by the scheduler. The research forms a first development, and a list of further research is given. © 2008 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.Article history: Received 31 August 2006 Received in revised form 17 April 2007 Accepted 14 December 2007

1. Introduction Decentralized manufacturing control systems have been successfully demonstrating robustness and reconfigurability [1–5]. However, regarding system-wide overall optimization there remains significant margin for improvement. A key issue is the (in)ability of such systems to planahead in time: decision myopia [6]. A first step in this regard is the ability to predict the nearfuture behavior of the system [7]. Alternatively, a market-based decentralized control system may use learning and adaptation to remedy its decision myopia within sufficiently stable manufacturing environments [8]. But even when the decentralized control system anticipates the consequences of itsdecisions (and may reconsider them), centralized scheduling technology retains superior abilities to optimize the overall system. In contrast, centralized scheduling has failed to provide robust, detailed, and complete solutions (see further). The above situation has prompted the design of manufacturing execution systems (MES) that account for a given schedule but retain their robustness andflexibility. Actually, a team of skilled human operators and shop floor managers – using a given schedule as an initial guideline but handling all details and contingencies – is the most common MES in industrial practice. This already is an MES belonging to the class of systems envisaged by the research in this paper. The research in this paper discusses the first developments aimed at providing the samefunctionality in an autonomic holonic MES. In this context, autonomic implies that the MES keeps functioning

∗ Corresponding address: Mechanical Engineering Department, Room - 04.72, Afd. CIB, Celestijnenlaan 300A - Bus 2422, 3001, Heverlee, Belgium. Tel.: +32 16322 483. E-mail address: (P. Valckenaers).

regardless of the availability and quality of the givenschedule (cf. The paper first discusses the research challenge: cooperating scheduling and manufacturing execution systems. Next, the holonic MES is presented concisely. This control system has been adapted and extended to prefer executing a given schedule. Subsequently, the experiments – testing these adaptations against various schedules – andtheir results are presented and discussed. Finally, conclusions are given and future research is discussed. Importantly, note that the contribution of this paper resides in the novelty of the overall architecture: a cooperating MES that provides MES functionality while accounting for an externally supplied schedule. This architecture allows an MES developer to add whatever MES functionality...