| 1. |
- Andersson, Kristin, 1976, et al.
(författare)
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Generation of restart states for manufacturing systems with discarded workpieces
- 2009
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Ingår i: 2009 IEEE Conference on Automation Science and Engineering, CASE 2009, Bangalore, India. - 9781424445783 ; , s. 191-196
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Konferensbidrag (refereegranskat)abstract
- In earlier work we presented a method for restart of manufacturing systems. After correction of an error, the system resumes normal production by returning to a certain restart state in the control function, and from there reexecutes parts of the work schedule. In the present paper the method is extended to handle also systems where some, but not necessarily all, workpieces are discarded during the error correction preceding the restart. The restart process must then replace the discarded workpieces with new ones. The workpieces that remain in the cell may limit the possibilities of executing certain operations needed to process the new workpieces correctly, thus complicating the restart. Properties of the restart states that guarantee a correct restart are defined, typical situations that make the system impossible to restart are presented, and some suggestions are given for modifications that make the system restartable.
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| 2. |
- Bengtsson, Kristofer, 1979, et al.
(författare)
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Operation-Oriented Specification for Integrated Control Logic Development
- 2009
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Ingår i: 2009 IEEE Conference on Automation Science and Engineering, CASE 2009, Bangalore, India. - 9781424445783 ; , s. 183-90
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Konferensbidrag (refereegranskat)abstract
- In order to develop a manufacturing automation system, it is necessary to understand the manufacturing operations and their relationship, the sequence of operations, which is the basis for control logic design. The operations have preconditions that define when they are allowed to start executing, which also defines the sequence relations among them. Requirements and demands throughout the development will add and change these conditions, which also changes the sequence of operations. This paper studies how an operation-oriented development approach better can handle the operations and manufacturing sequences from early product design to detailed control engineering. An operation is defined by an extended finite automaton, with an initial, executes and finished location. The start event is enabled by a precondition, the stop event is enabled by a postcondition and the reset event is enabled by a reset condition. This representation together with a resource and product description enables the possibility to integrate control logic in the complete development process.
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| 3. |
- Falkman, Petter, 1972, et al.
(författare)
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Generation of STEP AP214 models from discrete event systems for process planning and control
- 2008
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Ingår i: IEEE Transactions on Automation Science and Engineering. - 1545-5955 .- 1558-3783. ; 5:1, s. 113-126
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to show how the international standard STEP-AP214 can be used for communication and storing of process specifications. Even though there are several software tools available for the generation of both product and resource information systems, there is still a lack of tools related to the STEP standard for producing process information, e.g., sequence of operations and system capabilities for resource allocation. Therefore, such a tool is suggested, which makes use of a high-level language for discrete-event systems based on process algebra and Petri nets. This language, called process algebra Petri net), has been developed in accordance with the process relations defined in STEP-AP214. More specifically, it is shown how process specifications created with the PPN tool can be mapped to the STEP AP-214 format. Note to Practioners-Rapidly changing market needs is making demands on flexibility and ability to shorten lead times. Standards for exchanging information, as well as formal methods for automatic development of programmable controller code have been important research topics for many years. There are a lot of software tools available for the generation of both product- and resource information, but there is still a lack of tools for producing process information. Moreover, the connection between information exchange standards and such tools is absent, which makes the development of programmable controller code an isolated activity. This activity is often time consuming and performed in an ad hoc manner resulting in unnecessary production delay. The aim of this paper is to show how the international standard STEP-AP214 (a standard for exchange of product-, process-, and resource related information) can be used for communicating and storing process specifications. In order to achieve this, a tool which makes use of a formal high-level language is suggested. This tool can be used for automatic control generation and has been developed in accordance with the process relations defined in STEP-AP214. A further aim is to shown how the mentioned tool can be used to specify complex systems in a compact, yet highly readable manner, which is a crucial incentive for industry to use formal methods. The presented method will guarantee-that expected information is delivered quickly and without errors caused by the human factor, something that is very important in our ambition to achieve shortened lead times. The quick information exchange also makes it possible to perform simulation, supervisor synthesis, and verification early in the development phase. This is a first attempt at using a formal language for creating a tool that can automatically generate specifications in accordance with the international STEP-standard.
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| 4. |
- Falkman, Petter, 1972, et al.
(författare)
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Specification of a batch plant using process algebra and petri nets
- 2009
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Ingår i: Control Engineering Practice. - : Pergamon. - 0967-0661 .- 1873-6939. ; 17:9, s. 1004-1015
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Tidskriftsartikel (refereegranskat)abstract
- The focus of the present paper is on the specification of routing and resource allocation systems. Such systems can be described as a set of shared resources and a set of products. The products utilize the resources in order to be manipulated according to a certain specification. This product specification consists of a set of operations that are to be executed in a certain order by specific resources. This results in a desired product route through the resource system, and hence the product specification is also called a routing specification. The process algebra petri net (PPN) formalism, i.e. a combination of petri nets and process algebra, implies efficient and less complex models for routing specifications compared to PNs and automata descriptions. The aim of this paper is to show how the PPN language can be used in order to simplify the specification of desired routes of the chemical batch process.
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| 5. |
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| 6. |
- Falkman, Petter, 1972, et al.
(författare)
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Specification of Production Systems Using PPN and Sequential Operation Charts
- 2007
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Ingår i: 3rd IEEE International Conference on Automation Science and Engineering, IEEE CASE 2007; Scottsdale, AZ; United States; 22 September 2007 through 25 September 2007. - 1424411548 ; , s. 20-25
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Konferensbidrag (refereegranskat)abstract
- In this paper specification of discrete event systems, more specifically flexible production systems, is performed using two high level specification languages. The first language, called process algebra Petri net (PPN), is a mathematically well defined language that combines Petri nets and process algebra in order to achieve compact and concise specifications of complex systems. The second language, sequential operation charts (SOC), is a language specifically developed to meet expectations from industry concerning both programming style and information handling. SOC is based on the PPN language, but presents constructs that enable the language to be used not only for specifying process descriptions but also product and preparation related information. This makes it possible to use the SOC language all the way from the concept phase until final production. This paper has three aims. The first is to show the advantages of the PPN language compared to ordinary Petri nets. The second aim is to show how the SOC language is defined with respect to the PPN, language and the third aim finally is to show how SOCs can be used for the specification of a real industry case.
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| 7. |
- Falkman, Petter, 1972
(författare)
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Specification of Resource Allocation Systems; a STEP towards a unified framework
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years growing demands on flexibility and ability to decrease time to market has made it increasingly important for engineering companies to find ways of making information exchange between product design and manufacturing systems design more efficient. A much shortened iteration cycle could be obtained ifinformation about product design solutions could be made instantly available for engineers involved in manufacturing systems design. Due to the high costs associated with modifying and changing system implementations, the ability to model and simulate systemsbefore they are implemented is becoming more and more essential. Consequently it is vital that the system specifications used are as clear and concise as possible. The present thesis deals with the specification of discrete event systems, especially resource allocation systems. A combination of process algebra and Petri nets is presented. This combination results in a powerful language, called process algebra Petri nets (PPN), for specifyingresource allocation systems, delivering both concise andeasy-to-read specifications of large complex systems. The fact that both Petri net constructs and algebra expressions can be used in order to decrease specification complexity also makes it a flexible language. A method is also presented that formally converts the PPN models into finite state automata, which means that existing formal evaluation techniques for simulation, verification, and controller synthesis can be easily applied.The presented language defines an algebra where the processoperators express the same process relations that are possible in the international standard STEP-AP214. To the best of our knowledge, the PPN language constitutes a first attempt at using a formal language in order to create a tool that can automatically generate specifications according to the STEP standard.So far little has been investigated concerning the connection between information modelling and discrete event systems. The present work, however,researches this connection. The presented mapping defines the relationship between the information and theDES specification.Finally, it can be said that the introduced method guarantees that the expected information is delivered fast and without the errors potentially induced by manual handling, something which is crucial when short lead times are required. Due to the fast information exchange it also enables simulation, automatic controller synthesis and verification, to be conducted early in the development chain.
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| 8. |
- Falkman, Petter, 1972, et al.
(författare)
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Verification of Operation Sequences in Process Simulate by Connecting a Formal Verification Tool
- 2009
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Ingår i: 2009 IEEE INTERNATIONAL CONFERENCE ON CONTROL AND AUTOMATION, Christchurch, NEW ZEALAND, DEC 09-11, 2009. - 9781424447060 ; 1-3, s. 1207-1212
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Konferensbidrag (refereegranskat)abstract
- It is very advantages to use virtual techniques for testing and developing new hardware and software systems. It is cost effective since no real machine or manufactory system is needed. It is safe since there are no real components that can be damaged. Simulation is a fast design method since the time can go faster then real time and the machine can be set to desired machine states without time consumption. Novel concepts can be tested prior to manufacturing. However, it is of greatest importance that the virtual model can be trusted so that the results of the development and tests can be directly transferred to a real system without any manual last minute changes. Testing all possible scenarios within a system by simulation is an ambiguous task and is impossible to do with todays complex systems. The present paper introduces a method for combining virtual development and simulation techniques with tools for formal verification methods. The aim is to enable the use of formal verification techniques and by doing that guaranteeing a correct system behavior.
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| 9. |
- Lennartson, Bengt, 1956, et al.
(författare)
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Control architecture for flexible production systems
- 2005
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Ingår i: 2005 IEEE Conference on Automation Science and Engineering, IEEE-CASE 2005; Edmonton; Canada; 1 August 2005 through 2 August 2005. - 9780780394261 ; , s. 307-312
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Konferensbidrag (refereegranskat)abstract
- An architecture for control of flexible production systems is presented, with focus on flexibility, generality, and reusability. The architecture is based on a framework which partitions the control system into the following main components: resources, product routes, control functions, the operator's interaction and the information system. The clear separation of the resources employed from the products' paths through the plant is important in order to simplify the handling of changes to the system, for instance when introducing new equipment or new product types. Compared to an earlier preliminary result [7] this paper introduces a new formalism based on process algebra. It means that high level user friendly but still formal specifications are achieved for resources as well as product routes. Both event and state based specifications are illustrated related to industrial applications.
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