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Applications of Optimization Methods in Industrial Maintenance Scheduling and Software Testing
Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. (IS (Embedded Systems))ORCID iD: 0000-0003-2234-1255
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

As the world is getting more and more competitive, efficiency has become a bigger concern than ever for many businesses. Certain efficiency concerns can naturally be expressed as optimization problems, which is a well studied field in the academia. However, optimization algorithms are not as widely employed in industrial practice as they could. There are various reasons for the lack of widespread adoption. For example, it can be difficult or even impossible for non-experts to formulate a detailed mathematical model of the problem. On the other hand, a scientist usually does not have a deep enough understanding of critical business details, and may fail to capture enough details of the real- world phenomenon of concern. While a model at an arbitrary abstraction level is often good enough to demonstrate the optimization approach, ignoring relevant aspects can easily render the solution impractical for the industry. This is an important problem, because applicability concerns hinder the possible gains that can be achieved by using the academic knowledge in industrial practice. In this thesis, we study the challenges of industrial optimization problems in the form of four case studies at four different companies, in the domains of maintenance schedule optimization and search-based software testing. Working with multiple case studies in different domains allows us to better understand the possible gains and practical challenges in applying optimization methods in an industrial setting. Often there is a need to trade precision for applicability, which is typically very context dependent. Therefore, we compare our results against base values, e.g., results from simpler algorithms or the state of the practice in the given context, where applicable. Even though we cannot claim that optimization methods are applicable in all situations, our work serves as an empirical evidence for the usability of optimization methods for improvements in different industrial contexts. We hope that our work can encourage the adoption of optimization techniques by more industrial practitioners.

Place, publisher, year, edition, pages
Västerås: Mälardalen University , 2014.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 180
National Category
Computer Science
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:mdh:diva-25944ISBN: 978-91-7485-163-2 (print)OAI: oai:DiVA.org:mdh-25944DiVA: diva2:746643
Presentation
2014-10-14, R3-131, Mälardalens högskola, Västerås, 13:30 (English)
Opponent
Supervisors
Available from: 2014-09-15 Created: 2014-09-14 Last updated: 2014-10-08Bibliographically approved
List of papers
1. A Tool for Gas Turbine Maintenance Scheduling
Open this publication in new window or tab >>A Tool for Gas Turbine Maintenance Scheduling
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2009 (English)In: Proceedings of the 21st Innovative Applications of Artificial Intelligence Conference, IAAI-09, 2009, 9-16 p.Conference paper, (Refereed)
Abstract [en]

We describe the implementation and deployment of a software decision support tool for the maintenance planning of gas turbines. The tool is used to plan the maintenance for turbines manufactured and maintained by Siemens Industrial Turbomachinery AB (SIT AB) with the goal to reduce the direct maintenance costs and the often very costly production losses during maintenance downtime. The optimization problem is formally defined, and we argue that feasibility in it is NP-complete. We outline a heuristic algorithm that can quickly solve the problem for practical purposes, and validate the approach on a real-world scenario based on an oil production facility. We also compare the performance of our algorithm with results from using mixed integer linear programming, and discuss the deployment of the application. The experimental results indicate that downtime reductions up to 65% can be achieved, compared to traditional preventive maintenance. In addition, using our tool is expected to improve availability with up to 1% and reduce the number of planned maintenance days with 12%. Compared to a mixed integer programming approach, our algorithm not optimal, but is orders of magnitude faster and produces results which are useful in practice. Our test results and SIT AB's estimates based on operational use both indicate that significant savings can be achieved by using our software tool, compared to maintenance plans with fixed intervals

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-7374 (URN)9781577354239 (ISBN)
Conference
21st Innovative Applications of Artificial Intelligence Conference, IAAI-09; Pasadena, CA; United States; 14 July 2009 through 16 July 2009
Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2014-09-15Bibliographically approved
2. Maintenance plan optimization for a train fleet
Open this publication in new window or tab >>Maintenance plan optimization for a train fleet
2010 (English)In: WIT Transactions on the Built Environment Volume 114, 2010, 349-358 p.Conference paper, (Refereed)
Abstract [sv]

Maintenance planning is an important problem for railways, as well as other application domains that employ machinerywith expensive replacements and high downtime costs. In a previous paper, we have developed methods for efficiently finding optimized maintenance schedules for a single unit, and proposed that the maintenance plan should be continuously re-optimized based on the condition of components. However, fleet-level resources, such as the availability of expensive spare parts, have largely been ignored. In this paper, we extend our previous approach by proposing a solution for the fleet level maintenance scheduling problem with spare parts optimization. The new solution is based on a mixed integer linear programming formulation of the problem. We demonstrate the merits of our approach by optimizing instances of maintenance schedules based on maintenancedata from railway companies operating in Sweden.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-21314 (URN)10.2495/CR100331 (DOI)9781845644680 (ISBN)
Conference
12th International Conference on Computer System Design and Operation in the Railways and other Transit Systems, COMPRAIL 2010; Beijing; China; 31 August 2010 through 2 September 2010
Available from: 2013-09-20 Created: 2013-09-11 Last updated: 2014-09-15Bibliographically approved
3. An Integrated Adaptive Maintenance Concept
Open this publication in new window or tab >>An Integrated Adaptive Maintenance Concept
2010 (English)Conference paper, (Refereed)
Abstract [en]

In this paper, we present a novel maintenance concept based on condition monitoring and dynamic maintenance packaging, by showing how to connect the information flow from low-level sensors to high-level operations and planning under uncertainty. Today, condition-based maintenance systems are focused on data collection and custom-made rule based systems for data analysis. In many cases, the focus is on measuring "everything" without considering how to use the measurements. In addition, the measurements are often noisy and the future is unpredictable which adds a lot of uncertainty. As a consequence, maintenance is often planned in advance and not replanned when new condition data is available. This often reduces the benefits of condition monitoring. The concept is based on the combination of robust, dynamically adapted maintenance optimization and statistical data analysis where the uncertainty is considered. This approach ties together low-level data acquisition and high-level planning and optimization. The concept has been illustrated in a context of rail vehicle maintenance, where measurements of brake pad and pantograph contact strip wear is used to predict the near future condition, and plan the maintenance activities.

Place, publisher, year, edition, pages
Tokyo, Japan: , 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-21313 (URN)
Conference
International Conference on Condition Monitoring and Diagnosis 2010, 6-11 September 2010, Tokyo, Japan.
Available from: 2013-09-20 Created: 2013-09-11 Last updated: 2014-09-15Bibliographically approved
4. Search Based Testing of Embedded Systems Implemented in IEC 61131-3: An Industrial Case Study
Open this publication in new window or tab >>Search Based Testing of Embedded Systems Implemented in IEC 61131-3: An Industrial Case Study
2013 (English)In: Proceedings - IEEE 6th International Conference on Software Testing, Verification and Validation Workshops, ICSTW 2013, 2013, 425-432 p.Conference paper, (Refereed)
Abstract [en]

This paper presents a case study of search-based test generation for embedded system software units developed using the Function Block Diagrams (FBDs), a graphical language in the IEC 61131-3 standard aimed at programmable logic controllers (PLCs). We consider 279 different components from the train control software developed by Bombardier Transportation, a major rail vehicle manufacturer. The software is compiled into C code with a particular structure. We use a modified hill climbing algorithm for generating test data to maximize MC/DC coverage for assignments with logical expressions in the C code, while retaining the semantics of the original FBD implementation. An experimental evaluation for comparing the effectiveness (coverage rate) and the efficiency (required number of executions) of hill climbing algorithm with random testing is presented. The results show that random testing performs well for most units under test, while around 30% of the artifacts significantly benefit from the hill climbing algorithm. Structural properties of the units that affect the performance of hill climbing and random testing are also discussed.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-21343 (URN)10.1109/ICSTW.2013.78 (DOI)2-s2.0-84883376015 (Scopus ID)978-1-4799-1324-4 (ISBN)
Conference
IEEE 6th International Conference on Software Testing, Verification and Validation Workshops, ICSTW 2013; Luxembourg; Luxembourg; 18 March 2013 through 20 March 2013
Projects
ATAC - Advanced Test Automation for Complex Software-Intensive System (ITEA2/Vinnova)
Available from: 2013-09-18 Created: 2013-09-11 Last updated: 2014-09-15Bibliographically approved
5. MOS: An Integrated Model-based and Search-based Testing Tool for Function Block Diagrams
Open this publication in new window or tab >>MOS: An Integrated Model-based and Search-based Testing Tool for Function Block Diagrams
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2013 (English)In: 2013 1st International Workshop on Combining Modelling and Search-Based Software Engineering, CMSBSE 2013 - Proceedings, 2013, 55-60 p.Conference paper, (Refereed)
Abstract [en]

In this paper we present a new testing tool for safety critical applications described in Function Block Diagram (FBD) language aimed to support both a model and a search-based approach. Many benefits emerge from this tool, including the ability to automatically generate test suites from an FBD program in order to comply to quality requirements such as component testing and specific coverage measurements. Search-based testing methods are used to generate test data based on executable code rather than the FBD program, alleviating any problems that may arise from the ambiguities that occur while creating FBD programs. Test cases generated by both approaches are executed and used as a way of cross validation. In the current work, we describe the architecture of the tool, its workflow process, and a case study in which the tool has been applied in a real industrial setting to test a train control management system.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:mdh:diva-21334 (URN)10.1109/CMSBSE.2013.6605711 (DOI)2-s2.0-84886543950 (Scopus ID)978-1-4673-6284-9 (ISBN)
Conference
First International Workshop on Combining Modelling and Search-Based Software Engineering, 20th May 2013. In conjunction with ICSE 2013, San Francisco, California, USA
Projects
ATAC - Advanced Test Automation for Complex Software-Intensive System (ITEA2/Vinnova)ITS-EASY Post Graduate School for Embedded Software and Systems
Available from: 2013-09-19 Created: 2013-09-11 Last updated: 2015-11-13Bibliographically approved
6. Search-based Testing for Embedded Telecommunication Software with Complex Input Structures: An Industrial Case Study
Open this publication in new window or tab >>Search-based Testing for Embedded Telecommunication Software with Complex Input Structures: An Industrial Case Study
2014 (English)Report (Other academic)
Abstract [en]

In this paper, we discuss the application of search-based software test-ing techniques for unit level testing of a real-world telecommunication middleware at Ericsson. Input data for the system under test consists of nested data structures, and includes non-trivial variables such as unini-tialized pointers. Our current implementation analyzes the existing test cases to discover how to handle pointers, set global system parameters, and any other setup code that needs to run before the actual test case. Hill climbing (HC) and (1+1) evolutionary algorithm (EA) metaheuristic search algorithms are used to generate input data for branch coverage. We compare HC, (1+1)EA, and random search as a baseline of performance with respect to e˙ectiveness, measured as branch coverage, and eÿciency, measured as number of executions needed. Diÿculties arising from the specialized execution environment and the adaptations for handling these problems are also discussed.

Place, publisher, year, edition, pages
SICS Swedish ICT, 2014
Series
SICS Technical Report, ISSN 1100-3154 ; T2014:03
National Category
Computer Science
Identifiers
urn:nbn:se:mdh:diva-25946 (URN)
Available from: 2014-09-14 Created: 2014-09-14 Last updated: 2015-02-03Bibliographically approved

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Output format
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