Modeling the control of a flexible manufacturing cell for automatic verification and control program generation

Richardsson, Johan; Fabian, Martin

doi:10.1007/s10696-006-9004-2

Cited by 17 publications

(8 citation statements)

References 14 publications

(21 reference statements)

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“…Such systems are common, e.g., in the automotive industry [15]. The method enables offline generation of machine paths used for restart, which greatly facilitates the work of the maintenance personnel, while a restart is to be performed.…”

Section: B Main Contributionsmentioning

confidence: 99%

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Restarting Manufacturing Systems; Restart States and Restartability

Andersson

Lennartson

Fabian

2010

IEEE Trans. Automat. Sci. Eng.

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A method for restart after an error in a manufacturing system is introduced. The method is able to restart systems even after nonforeseen errors that cannot be planned for, and the online part of the restart method does not require use of more powerful computers than a standard Programmable Logic Controller.It is shown what properties the control function must have to ensure that there is at least one restart state for each controller state. Sufficient conditions to guarantee the possibility to restart a system regardless of where an error occurs are given, along with indications on how the system could otherwise be rebuilt to be restartable.Note to Practitioners-The motivation for this work has been the difficulties of resuming normal production in a manufacturing system after the (often manual) correction of an error. These difficulties are especially pronounced for systems where errors cannot be foreseen, a common situation, e.g., in the automotive industry. Existing restart methods often assume extensive knowledge of the possible errors and/or require more computational resources than are typically available on the shop floor. Therefore, the impact on industrial practice has to date been limited.We propose a restart method where the above mentioned problems are avoided. The control program is analyzed offline to find the states from where a restart is possible. If paths to these states are offline synthesized and stored in the controller, a simple online method executable by any industrial control system can then restart the system. This facilitates the work of the maintenance personnel who no longer need to check online the safety of each path used in the restart.The offline analysis also tells if the system can be restarted by the proposed method from all possible states or if certain situations require special treatment. If all situations cannot be handled by our method, indications of suitable modifications of the system are given. In future research, we will address the task of restarting a number of machines that have simultaneously broken down. We will also study how to model the system and structure the work to facilitate restart.

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Section: B Main Contributionsmentioning

confidence: 99%

“…In [15], [26], and [27], an approach for structuring and generation of control programs for flexible manufacturing systems is presented. The work of the present paper is related to and within the context of this approach.…”

Section: Preliminariesmentioning

confidence: 99%

Restarting Manufacturing Systems; Restart States and Restartability

Andersson

Lennartson

Fabian

2010

IEEE Trans. Automat. Sci. Eng.

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“…undoubtedly represents a great part of the code. In (Lucas and Tilbury, 2003;Richardsson and Fabian, 2006) it is reported that according to their experience at Lamb Technion and Volvo Car Corporation respectively, the part of the code representing automatic control is about 10 % of the total. However, no data supporting this was shown in the two papers.…”

Section: Classification and Statistics Of Function Blocksmentioning

confidence: 99%

Practice of Industrial Control Logic Programming using Library Components

Ljungkrantz¹,

Åkesson²,

Fabian³

2010

Programmable Logic Controller

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“…The restart method of the present paper is related to and within the context of the approach presented in [18] and [19], concerning the structure and representation of control functions for manufacturing cells. The work of the cell is divided into operations, e.g.…”

Section: Proposed Conceptmentioning

confidence: 99%

Generation of restart states for manufacturing systems with discarded workpieces

Andersson

Lennartson

Falkman

et al. 2009

2009 IEEE International Conference on Automation Science and Engineering

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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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Modeling the control of a flexible manufacturing cell for automatic verification and control program generation

Cited by 17 publications

References 14 publications

Restarting Manufacturing Systems; Restart States and Restartability

Restarting Manufacturing Systems; Restart States and Restartability

Practice of Industrial Control Logic Programming using Library Components

Generation of restart states for manufacturing systems with discarded workpieces

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