The student Miriam Ugarte Querejeta obtained an OUTSTANDING CUM LAUDE qualification with 'INTERNATIONAL DOCTORATE' mention

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The student Miriam Ugarte Querejeta obtained an OUTSTANDING CUM LAUDE qualification with 'INTERNATIONAL DOCTORATE' mention

THESIS

The student Miriam Ugarte Querejeta obtained an OUTSTANDING CUM LAUDE qualification with 'INTERNATIONAL DOCTORATE' mention

2023·07·11

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Thesis title: Methodology and Toolset for Testing Highly Reconfigurable Programmable Logic Controllers

Court:

  • Chairmanship: Eunkyoung Jee (Korea Advaced Institute of Science & Tchnology)
  • Vocal: David Sanderson (University of Nottingham)
  • Vocal: Itziar Ricondo Iriondo (IDEKO)
  • Vocal: Maider Azanza Sesé (UPV/EHU)
  • Secretary: Aitor Arrieta Marcos (Mondragon Unibertsitatea)

Abstract:

The manufacturing industry has entered a new era of highly changeable customer requirements and tailor-made products. To meet market demands, manufacturing systems need to be redefined to be able to cost-effectively produce a wide variety of products. Sustainability is key in this endeavour, maximizing the utilisation of all available resources to address new bills of processes. To achieve this, however, the development of new capabilities are imperative to seamlessly adapt the manufacturing sector to the new paradigm.

At the core of the production system, the Programmable Logic Controller (PLC) orchestrates all necessary resources to initiate new processes, including modifications to the PLC program. For this reason, PLC software must be thoroughly tested after each adaptation, to ensure operational safety. At present, testing is conducted during commissioning, which typically takes place at the end of the development process, resulting in a significant impact in time and cost. In addition, the manual nature of testing practices requires considerable manual effort, and leaves the PLC open to errors. All these issues are further compounded in frequently changing and adaptive environments, hence the need to adopt new practices.

In this research project, therefore, we present an automated and cost-effective methodology to test highly reconfigurable PLC programs in industry. The presented approach is industry oriented, and thus we focus on the transfer of best-practices in software engineering, to the manufacturing environment. To this end, we introduced a theoretical digital-twin framework to enhance commissioning practices. Moreover, our approach was based on testing the logic of FBD programs, one of the most widely employed PLC programming languages in Europe. Our methodology comprised the generation of the test cases based on the IEC 61131-3 standard, cost-effective test selection of the test cases, and simulation-based testing in commercially used automation solutions (the Siemens TIA portal) with the use of test oracles.

The proposal was validated with two real industrial case studies: 1) Omnifactory, which is the future automated aerospace assembly demonstrator under development at the University of Nottingham, and 2) the machine tool manufacturing industry at Danobat Group. The results demonstrate that by automating conventional practices our methodology can effectively test real industrial PLC programs, which ultimately reduces costs and time, and ensures the reuse of available resources.