Recognizing finite repetitive scheduling patterns in manufacturing systems

Optimization of timing behaviour of manufacturing systems can be regardedas a scheduling problem in which tasks model the various productionprocesses. Typical for many manufacturing systems is that (collectionsof) tasks can be associated with manufacturing entities, which canbe structured hierarchically. Execution of production processes for severalinstances of these entities results in nested finite repetitions, whichblows up the size of the task graph that is needed for the specification ofthe scheduling problem, and, in an even worse way, the number of possibleschedules. We present a subclass of UML activity diagrams whichis generic for the number of repetitions, and therefore suitable for thecompact specification of task graphs for these manufacturing systems.The approach to reduce the complexity of the scheduling problem exploitsthe repetitive patterns. It reduces the original problem to a problemcontaining the minimum amount of identical repetitions, and afterscheduling of this much smaller problem the schedule is expanded tothe original size. We demonstrate our technique on a real-life examplefrom the semiconductor industry

Model Checker Aided Design of a Controller for a Wafer Scanner

Contains fulltext : 60427.pdf (preprint version ) (Open Access

Model Checker Aided Design of a Controller for a Wafer Scanner

Contains fulltext : 35654.pdf (preprint version ) (Open Access

Recognizing finite repetitive scheduling patterns in manufacturing systems

Optimization of timing behaviour of manufacturing systems can be regardedas a scheduling problem in which tasks model the various productionprocesses. Typical for many manufacturing systems is that (collectionsof) tasks can be associated with manufacturing entities, which canbe structured hierarchically. Execution of production processes for severalinstances of these entities results in nested finite repetitions, whichblows up the size of the task graph that is needed for the specification ofthe scheduling problem, and, in an even worse way, the number of possibleschedules. We present a subclass of UML activity diagrams whichis generic for the number of repetitions, and therefore suitable for thecompact specification of task graphs for these manufacturing systems.The approach to reduce the complexity of the scheduling problem exploitsthe repetitive patterns. It reduces the original problem to a problemcontaining the minimum amount of identical repetitions, and afterscheduling of this much smaller problem the schedule is expanded tothe original size. We demonstrate our technique on a real-life examplefrom the semiconductor industry

Model Checker Aided Design of a Controller for a Wafer Scanner

For a case-study of a wafer scanner from the semiconductor industry it is shown how model checking techniques can be used to compute (1) a simple yet optimal deadlock avoidance policy, and (2) an infinite schedule that optimizes throughput. in the absence of errors. Deadlock avoidance is studied based on a simple finite state model using Smv, and for throughput analysis a more detailed timed automaton model has been constructed and analyzed using the Uppaal tool. The Smv and Uppaal models are formally related through the notion of a stuttering bisimulation. The results were obtained within 2 weeks, which confirms once more that model checking techniques may help to improve the design process of realistic, industrial systems. Methodologically, the case study is interesting since two models were used to obtain results that could not have been obtained using only a single model

Specification of a Flexible Manufacturing System Using Concurrent Programming

Because of the growing complexity, the design of and reasoning about modern industrial systems becomes increasingly difficult. In order to understand and estimate the dynamic system behaviour, appropriate models have to be used. In many cases, existing mathematical models like queuing networks, Markov chain models, or perturbation analysis cannot be applied. In such cases, usually a model is constructed that can be validated by means of computer simulation. Since industrial systems exhibit concurrency, formalisms developed to reason about concurrent systems are also well suited for developing models in this specific application area. Models of systems can be expressed, for instance, in terms of Petri nets or in terms of programs written in a concurrent programming language, like Timed CSP. Both approaches, originating from computer science, are increasingly often applied in modelling of manufacturing systems. In this paper, we present a simple modular approach to the specification of (..

Cooperative Multi-robot synchronization via estimated state feedback

Optimization of timing behaviour of manufacturing systems can be regardedas a scheduling problem in which tasks model the various productionprocesses. Typical for many manufacturing systems is that (collectionsof) tasks can be associated with manufacturing entities, which canbe structured hierarchically. Execution of production processes for severalinstances of these entities results in nested finite repetitions, whichblows up the size of the task graph that is needed for the specification ofthe scheduling problem, and, in an even worse way, the number of possibleschedules. We present a subclass of UML activity diagrams whichis generic for the number of repetitions, and therefore suitable for thecompact specification of task graphs for these manufacturing systems.The approach to reduce the complexity of the scheduling problem exploitsthe repetitive patterns. It reduces the original problem to a problemcontaining the minimum amount of identical repetitions, and afterscheduling of this much smaller problem the schedule is expanded tothe original size. We demonstrate our technique on a real-life examplefrom the semiconductor industry