| 1. |
- Yuan, Chengyin, et al.
(author)
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Surface Potential Decay on Material Samples Taken From In-service Aged HVDC Silicone Rubber Composite
- 2017
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In: IEEE Transactions on Dielectrics and Electrical Insulation. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-4135 .- 1070-9878. ; 24:1, s. 592-600
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Journal article (peer-reviewed)abstract
- Surface potential decay characteristics of specimens extracted from in-service aged and reference HVDC composite insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity.
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| 2. |
- Bengtsson, Kristofer, 1979, et al.
(author)
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Aspect-Oriented Programming for Manufacturing Automation Control Systems
- 2009
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In: 13th IFAC Symposium on Information Control Problems in Manufacturing Technology, INCOM’09, Moscow, Russia. - 1474-6670. - 9783902661432 ; 13:PART 1, s. 668-673
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Conference paper (peer-reviewed)abstract
- The languages defined by the standard IEC 6-1131 for Programm\-able Logic Controllers (PLCs), have both benefits and drawbacks compared to object-oriented programming languages. For example, the current programming approach is good for maintaining the system, since it is easy to program and comprehend for a plant floor personal with limited programming experience. The main drawbacks are reusability, code dependability and flexibility. This paper proposes an aspect-oriented programming (AOP) approach as an alternative solution, which can keep the benefits and eliminate the drawbacks. AOP is an emerging programming methodology in computer science, which helps the programmer by separating different crosscutting concerns in the program. These crosscutting concerns and tangled behavior are especially important issues in PLC programming, which makes AOP a suitable approach. The paper describes how to adapt the AOP methodology into PLC program development and how it can benefit the control design process.
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| 3. |
- Bengtsson, Kristofer, 1979, et al.
(author)
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Developing control logic using aspect-oriented programming and sequence planning
- 2013
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In: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 21:1, s. 12-22
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Journal article (peer-reviewed)abstract
- A fundamental functionality of a Programmable Logic Controller (PLC) is to control and execute a set of operations. But a large part of the program code is more involved in supporting the user with concerns like alarm, HMI, communication, safety and manual control. Code related to these supporting concerns is often tangled with operation execution code, the core concerns, which makes it hard to reuse.This paper describes a method to reuse code and functionality when developing PLC programs and code libraries. The method proposes that core concerns are planned with a software tool called Sequence Planner, and the supporting concerns are integrated into the core concerns with a tool based on aspect-oriented programming.
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| 4. |
- Bengtsson, Kristofer, 1979, et al.
(author)
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Operation-Oriented Specification for Integrated Control Logic Development
- 2009
-
In: 2009 IEEE Conference on Automation Science and Engineering, CASE 2009, Bangalore, India. - 9781424445783 ; , s. 183-90
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Conference paper (peer-reviewed)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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| 5. |
- Bengtsson, Kristofer, 1979, et al.
(author)
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Relations Identification and Visualization for Sequence Planning and Automation Design
- 2010
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In: In Proc. IEEE Conference on Automation Science and Engineering, Toronto. - 9781424454471 ; , s. 841 - 848
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Conference paper (peer-reviewed)abstract
- The sequential behavior of a manufacturing system results from a number of constraints introduced both in product, manufacturing and control logic development. Sequence planning is therefore an important activity throughout the complete development process. This paper proposes a sequence planning approach using self-contained manufacturing operations that model actions and relevant execution conditions. These operations can have temporal relations with each other, due to execution constraints expressed by operation pre- post- and reset conditions. The operation relations can for example be parallel, sequence, arbitrary order, alternative or hierarchy. Based on a formal operation model, the relations among operations are identified and visualized with a graphical language called Sequences of Operations, SOP.
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| 6. |
- Bengtsson, Kristofer, 1979, et al.
(author)
-
Sequence Planning Using Multiple and Coordinated Sequences of Operations
- 2012
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In: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 9:2, s. 308-319
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Journal article (peer-reviewed)abstract
- The sequential behavior of a manufacturing system results from several constraints introduced during the product, manufacturing, and control logic development. This paper proposes methods and algorithms for automatically representing and visualizing this behavior from various perspectives throughout the development process. A new sequence planning approach is introduced that uses self-contained operations to model the activities and execution constraints. These operations can be represented and visualized from multiple perspectives using a graphical and formal language called Sequences of Operations (SOPs). The operations in a manufacturing system are related to each other in various ways, due to execution constraints expressed by operation pre- and post-conditions. These operation relations include parallel, sequence, arbitrary order, alternative, and hierarchy relations. Based on the SOP language, these relations are identified and visualized in various SOPs and sequences. A software tool, Sequence Planner, has been developed, for organizing the operations into SOPs that visualize only relevant operations and relations. Note to Practitioners-This paper proposes methods and algorithms for a new sequence planning approach in which sequences are automatically created based on the relations among operations instead of having to be manually constructed. Using various views, the sequences of operations related to, for example, part flow, robot operations, and operator tasks, can be visualized. The use of various views helps the user better understand the relations between cell control and mechanical design, and between product design and total system behavior.
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| 7. |
- Bengtsson, Kristofer, 1979, et al.
(author)
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The Origin of Operations: Interactions Between the Product and the Manufacturing Automation Control System
- 2009
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In: 13th IFAC Symposium on Information Control Problems in Manufacturing Technology, INCOM’09, Moscow, Russia. ; , s. 40-5
-
Conference paper (peer-reviewed)abstract
- This paper investigates the interaction and relationship between the product design and the control logic design for manufacturing automation system. One important challenge during the development of a manufacturing automation system, is to handle the information related to the manufacturing control system (i.e PLC), since it influences almost every part of the manufacturing design and process. Therefore it is crucial to know when and how this information is created, to be able to increase the development quality and efficiency. This is especially true for the product related information that impacts the design of the control system. This paper studies the liaisons, the interfaces among parts and features in the product design, and its relationship with operations and resources in the manufacturing system. These liaisons must be considered in both product and manufacturing development since the inter-relation between liaisons and operations establishes the direct mapping of constraints and demands between the two domains. This paper further proposes how the manufacturing operations can be described during the development and how they are realized by resources in the manufacturing system. An example from automotive industry is included in this paper, to demonstrate the proposed concept.
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| 8. |
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| 9. |
- Elmegreen, B.G., et al.
(author)
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Dust Spirals and Acoustic Noise in the Nucleus of the Galaxy NGC 2207
- 1998
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In: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 503:2, s. L119-L122
-
Journal article (peer-reviewed)abstract
- Observations with the Hubble Space Telescope reveal an irregular network of dust spiral arms in the nuclear region of the interacting disk galaxy NGC 2207. The spirals extend from ~50 to ~300 pc in galactocentric radius, with a projected width of ~20 pc. Radiative transfer calculations determine the gas properties of the spirals and the inner disk and imply a factor of ~4 local gas compression in the spirals. The gas is not strongly self-gravitating, nor is there a nuclear bar, so the spirals could not have formed by the usual mechanisms applied to main galaxy disks. Instead, they may result from acoustic instabilities that amplify at small galactic radii. Such instabilities may promote gas accretion into the nucleus.
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| 10. |
- Lennartson, Bengt, 1956, et al.
(author)
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Sequence Planning for Integrated Product, Process and Automation Design
- 2010
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In: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 7:4, s. 791-802
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Journal article (peer-reviewed)abstract
- In order to obtain a unified information flow from early product design to final production, an integrated framework for product, process and automation design is presented. The framework is based on sequences of operations and includes a formal relation between product properties and process operations. This relation includes liaisons (interfaces) and precedence relations, where the precedence relations generate preconditions for the related process operations. From this information a set of sequences of operations (SOPs) is generated. A formal graphical language for hierarchical operations and SOPs is then introduced and defined based on automata extended with variables. Since the operations are self-contained they can be grouped and viewed from different angles, e. g., from a product or a resource perspective. These multiple views increase the interoperability between different engineering disciplines. A case study is performed on a car manufacturing cell, where the suggested modeling framework is shown to give comprehensible SOPs. Note to Practitioners-When designing an automation system, an important challenge is to specify in what sequence the different tasks, or operations, should be executed. This has become a problematic bottleneck in the automotive industry, especially for body-in-white manufacturing. The rising needs on manufacturing flexibility increases the complexity of the entire manufacturing system, as well as its control function, the sequence of operations. This paper proposes a new sequence planning approach, where sequences are viewed based on the relations among operations instead of manually constructing the sequence. By the use of different views the sequence of operations related to, e. g., the part flow, robot operations or operator tasks can be visualized. Different views help the user to easier understand the relation between different parts and components, as well as the total system behavior.
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| 11. |
- Ljungkrantz, Oscar, 1978, et al.
(author)
-
A formal specification language for PLC-based control logic
- 2010
-
In: Proceedings of the 8th IEEE International Conference on Industrial Informatics, INDIN 2010; Osaka; 13 July 2010 through 16 July 2010. - 1935-4576. - 9781424473007 ; , s. 1067-1072
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Conference paper (peer-reviewed)abstract
- Formal verification, using model checking tools, is promising in developing (IEC 61131) industrial control logic. Formal verification requires a formal specification of the properties to be verified. Specifications in model checking tools are typically expressed using temporal logic. However, the standard temporal logic dialects are not well suited for control engineers who do rarely have a background within computer science. In this paper a new dialect of linear temporal logic, ST-LTL, is introduced that intends to be easier to use for control engineers than the existing dialects. The relation of ST-LTL compared to existing temporal logic dialects is analyzed. © 2010 IEEE.
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| 12. |
- Ljungkrantz, Oscar, 1978, et al.
(author)
-
Formal Specification and Verification of Industrial Control Logic Components
- 2010
-
In: IEEE Transactions on Automation Science and Engineering. - 1558-3783 .- 1545-5955. ; 7:3, s. 538-548
-
Journal article (peer-reviewed)abstract
- Component-based programming frameworks for industrial control logic development promise to shorten development and modification times, and to reduce programming errors. To get these benefits, it is, however, important that the components are specified and verified to work properly. This work introduces Reusable Automation Components (RACs), which contain not only the implementation details but also a formal specification defining the correct use and behaviour of the component. This formal specification uses temporal logic to describe time-related properties and has a special structure developed to meet industrial control needs. The RAC can be formally verified, to determine whether the implementation fulfils the specification or not. A RAC prototype development tool has been developed to demonstrate this capability. The main difference between the RAC and other frameworks for formal verification of control logic is the specification modeling. In RAC, not only the implementation but also the specification is based on the structure and languages of conventional control logic, aiming at being easy to comprehend for control logic engineers. Several industrial examples are discussed in this paper, showing the benefits and potential of the framework. Note to Practitioners-Today robots and machines in automated production are usually controlled by a special industrial computer called Programmable Logic Controller (PLC). Although PLC programs are widely used in manufacturing industry, current programs tend to be difficult and time-consuming to modify when needed. They are also often tested to work first on the real equipment, which may be expensive since the regular production is stopped for code testing and error resolving. In this work, we introduce Reusable Automation Components (RACs), to facilitate PLC program development. Reusing components may speed up the development and also reduce the number of errors, if the components are already verified to work properly before the reuse. To achieve this, the RACs can be richly specified, defining the correct use and behaviour of the components. The specification can then be used to verify, formally, whether the RAC works correctly or not, according to the specification. Formal verification uses math-based models and algorithms to automatically explore all possible behaviours of the component. The RAC can be automatically translated to a tool that performs the formal verification and shows counterexamples if the specification is not fulfilled. The specification and verification of RACs are intended to be useful for control logic engineers. Hence, the specification of the RAC is based on the structure and languages of conventional PLC programs. This paper discusses a number of industrial examples which show the applicability of the RACs. The RAC framework can be further improved, especially by developing guidelines and aid for writing the specifications.
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| 13. |
- Ljungkrantz, Oscar, 1978, et al.
(author)
-
Towards Industrial Formal Specification of Programmable Safety Systems
- 2012
-
In: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 20:6, s. 1567-1574
-
Journal article (peer-reviewed)abstract
- Formal methods for specification and verification are promising in developing PLC (Programmable Logic Controller) programs in manufacturing industry. Particularly this holds for safety PLCs, used to protect humans and equipment from injuries and damages. An important challenge though, is the development of formal specifications, typically a tough task for control engineers. This paper proposes a systematic work procedure that can be used as a first step of developing formal specifications of safety PLC programs in industry. The work procedure intends to facilitate the development of relevant formal properties for safety PLC program components. The formal specifications can be used for automatic formal verification of the components, using model checking techniques. The paper shows how the work procedure has been applied to industrial safety components, resulting in relevant and nontrivial specifications.
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| 14. |
- Skeoch, S., et al.
(author)
-
Imaging atherosclerosis in rheumatoid arthritis: evidence for increased prevalence, altered phenotype and a link between systemic and localised plaque inflammation
- 2017
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7:1
-
Journal article (peer-reviewed)abstract
- In rheumatoid arthritis (RA), chronic inflammation is thought to drive increased cardiovascular risk through accelerated atherosclerosis. It may also lead to a more high-risk plaque phenotype. We sought to investigate carotid plaque phenotype in RA patients using Dynamic Contrast-Enhanced MRI (DCEMRI) and Fludeoxyglucose Positron Emission Tomography(FDG-PET). In this pilot study, RA patients and age/sex-matched controls were evaluated for cardiovascular risk factors and carotid plaque on ultrasound. Subjects with plaque >2 mm thick underwent DCE-MRI, and a subgroup of patients had FDG-PET. Comparison of MRI findings between groups and correlation between clinical, serological markers and imaging findings was undertaken. 130 patients and 62 controls were recruited. Plaque was more prevalent in the RA group (53.1% vs 37.0%, p = 0.038) and was independently associated with IL6 levels (HR[95% CI]: 2.03 [1.26, 3.26] per quartile). DCE-MRI data were available in 15 patients and 5 controls. Higher prevalence of plaque calcification was noted in RA, despite similar plaque size (73.3% vs 20%, p = 0.04). FDG-PET detected plaque inflammation in 12/13 patients scanned and degree of inflammation correlated with hs-CRP (r = 0.58, p = 0.04). This study confirms increased prevalence of atherosclerosis in RA and provides data to support the hypothesis that patients have a high-risk plaque phenotype.
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| 15. |
- Vergnano, Alberto, et al.
(author)
-
Embedding detailed robot energy optimization into high-level scheduling
- 2010
-
In: 2010 IEEE International Conference on Automation Science and Engineering, CASE 2010. - 9781424454471 ; , s. 386-392
-
Conference paper (peer-reviewed)abstract
- Reduction of energy consumption is important for reaching a sustainable future. This paper presents a novel method for optimizing the energy consumption of robotic manufacturing systems. The method embeds detailed evaluations of robots' energy consumptions into a scheduling model of the overall system. The energy consumption for each operation is modelled and parameterized as function of the operation execution time, and the energy-optimal schedule is derived by solving a mixed-integer nonlinear programming problem. The objective function for the optimization problem is then the total energy consumption for the overall system. A case study of a sample robotic manufacturing system is presented. It shows that there exists a possibility for a significant reduction of the energy consumption, in comparison to state-of-the-art scheduling approaches. © 2010 IEEE.
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| 16. |
- Åkesson, Knut, 1972, et al.
(author)
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Hybrid Computer-Human Supervision of Discrete Event Systems
- 2002
-
In: proc. of 2002 IEEE International Conference on Robotics and Automation, Washington DC, MAY 11-15,, USA. ; , s. 2321-2326
-
Conference paper (peer-reviewed)abstract
- This paper presents a framework for accommodating human intervention in a computer supervised discrete-event system. The basic mechanism for allowing such hybrid supervision by a computer and a human operator is by switching priorities between events controlled by each according to some specified schedule. To synthesize a computer supervisor under such conditions, a transformation that maps the problem to one that satisfies the model stipulations of the Supervisory Control Theory is presented. The aforementioned framework introduces a parameter that can be tuned to provide for different levels of co-operation between the human and computer supervisors. Several important properties of the resulting supervisors are presented.
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