The scheduling problem forexiblemanufacturing systems (FMSs)has beenattempted inthis paper using the ant colony optimization (ACO) technique. Since the operation of a job in FMSs can be performed on more than one machine, the scheduling of the FMS is considered as a computationally hard problem. Ant algorithms are based on the foraging behaviour of real ants. The article deals with the ant algorithm with certain modi® cations that make it suitable for application to the required problem. The proposed solution procedure applies a graph-based representation technique with nodes and arcs representing operation and transfer from one stage of processing to the other. Individual ants move from the initial node to the ® nal node through all nodes desired to be visited. The solution of the algorithm is a collective outcome of the solution found by all the ants. The pheromone trail is updated after all the ants have found out their respective solutions. Various features like stagnation avoidance and prevention from quick convergence have been incorporated in the proposed algorithm so that the near-optimal solution is obtained for the FMS scheduling problem, which is considered as a non-polynomial (NP)-hard problem. The algorithm stabilizes to the solution in considerably lesser computational eA ort. Extensive computational experiments have been carried out to study the inuence of various parameters on the system performance.

http://www.et.byu.edu/~ered/ME482/Paper_Topics/TomAnt_ColonyOptimization.pdf

Scheduling of flexible manufacturing systems: An ant colony optimization approach

Integrated system for BIM-based collaborative design

Combined Petri net modelling and AI-based heuristic hybrid search for flexible manufacturing systems-part I: Petri net modelling and heuristic search

A distinguishing feature of a flexible manufacturing system (FMS) is the ability to perform multiple tasks in one machine or workstation (alternative machining) and the ability to process parts according to more than one sequence of operations (alternative sequencing). In this paper, we address the issue of deadlock avoidance in systems having these characteristics. A deadlock-free and maximally permissive control policy that incorporates this flexibility is developed based on finite automata models of part process plans and the FMS. The resulting supervisory controller is used for dynamic evaluation of deadlock avoidance based on the remaining processing requirements of the parts.

Deadlock avoidance in flexible manufacturing systems using finite automata

During the development of a production control system, an appropriate model of the production process is needed to evaluate the various control strategies. This paper describes how to apply timed Petri nets and existing production data to the modelling of production systems. Information concerning the structure of a production facility and the products that can be produced is usually given in production-data management systems. We describe a method for using these data to construct a Petri-net model algorithmically. The timed Petri-net simulator, which was constructed in Matlab, is also described. This simulator makes it possible to introduce heuristics, and, in this way, various production scenarios can be evaluated. To demonstrate the applicability of our approach, we applied it to a scheduling problem in the production of furniture fittings.

/pdf/production-process-modelling-based-on-production-management-momrpo3zcl.pdf

Production-process modelling based on production-management data: a Petri-net approach

This paper introduces a class of Petri nets which are reversible, live, and can be kept bounded. Furthermore, these Petri nets have output transitions that can be fired independently from each other. These properties are required when modeling manufacturing systems. Another important property is that the integration of models which belong to this class of Petri nets still belongs to the same class, assuming that the integration is performed following rules which reflect common manufacturing practice. As a result, the qualitative properties of the module models are preserved. The results obtained in this paper are expected to shed light on the design, management and control of large scale manufacturing systems since modular approach is a way to cope with complexity.

/pdf/a-class-of-petri-nets-for-manufacturing-system-integration-u9kfj89bt8.pdf

Liming Wang

Papers

A class of Petri nets for manufacturing system integration