Planning transport sequences for flexible manufacturing systems*

IEEE Trans. Contr. Syst. Technol.

Åkesson

2012

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Abstract-In this paper, we settle some problems that are encountered when modeling and synthesizing complex industrial systems by the supervisory control theory. First, modeling such huge systems with explicit state-transition models typically results in an intractable model. An alternative modeling approach is to use extended finite automata (EFAs), which is an augmentation of ordinary automata with variables. The main advantage of utilizing EFAs for modeling is that more compact models are obtained. The second problem concerns the ease to understand and implement the supervisor. To handle this problem, we represent the supervisor in a modular manner by extending the original EFAs by compact conditional expressions. This will provide a framework for the users where they can both model their system and obtain the supervisor in form of EFAs. In order to be able to handle complex systems efficiently, the models are symbolically represented by binary decision diagrams (BDDs). All computations that are performed in this framework are based on BDD operations. The framework has been implemented in a supervisory control tool and applied to industrially relevant benchmark problems.Index Terms-Binary decision diagrams (BDDs), extended finite automata (EFA), supervisor representation, supervisory control theory (SCT), symbolic representation.

“…This benchmark concerns a fabrication production system that can build different products [35]. There exist two product families, each one consisting of two product types.…”

Section: ) Fabrication Production System (Fbs)mentioning

confidence: 99%

A BDD-Based Approach for Modeling Plant and Supervisor by Extended Finite Automata

Miremadi

IEEE Trans. Contr. Syst. Technol.

Åkesson

2012

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“…different resources or products can be displayed by using a projection of operations that somehow relates to that resource or product. Recently, it has been shown that transport operations can be automatically generated from simulation software [8]. The next step is to also generate process operations based on the product recipe from external CAD software.…”

Section: Operation Relationsmentioning

confidence: 99%

Event- and time-based design of operation sequences with uncertainties in execution times

Sundström

2013 IEEE 18th Conference on Emerging Technologies &Amp; Factory Automation (ETFA)

2013

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In this paper, we introduce a complete framework for integrating the design of the manufacturing process and control system. We show how operation sequences can be designed in a modeling tool, Sequence Planner (SP), and how relations between operations may be expressed using logical conditions. An approach to convert the SP model into a constraint programming model for optimization is presented. The time-based solution is transformed to an event-based description. Due to uncertainties in execution times, some logical restrictions based on the optimal schedule are relaxed to avoid unnecessary delays. The control logics to achieve the desired operation sequences are added to the SP model. Hence, the process designer can revise the sequences if necessary, and the control designer retrieves a logical description of the optimized process that can be automatically converted to control code.

“…This tool provides a bridge between other simulation languages, formal language verification tools and PLC code generation. Magnusson et al (2011) proposes a method for generating the sequences of operation in SPL directly from a virtual environment.…”

Section: Sequence Planner Languagementioning

confidence: 99%

“…Comparing the methodologies of SysML and SPL, clarifies the representation of the specification of the model in each respective language. The methodology for modeling a system in SPL begins by obtaining the information from a simulation tool or a design tool, continues by forming the sequences of operations of the process, see Magnusson et al (2011). The specification, or requirement is also defined as a model in the Sequence Planner tool, either by defining a resource and its particulars, or by defining the specification of other necessities.…”

Section: Formal Verificationmentioning

confidence: 99%

System Modeling Specification in SysML and Sequence Planner Language - Comparison Study

Kanthabhabhajeya

Falkman

IFAC Proceedings Volumes

2012

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This paper compares two languages, Systems Modeling Language(SysML) based on Unified Modeling Language and Sequence Planner Language, where both are used for systems engineering applications. As the modern manufacturing industries pass through a challenging period in storing and exchanging huge amounts of information/data, a common platform that is helpful in putting different parts together is of major interest. This paper presents an analysis of these two languages focusing on their behavioral constructs and details their advantages and disadvantages. This paper concludes by mentioning the points that are lacking in SysML, which could be solved by combining it with Sequence Planner Language and using the combined approach for system engineering applications.