Maintenance and continuous improvement of complex systems linking stakeholder requirements to the use of built-in test systems

Abstract: The failure of a technical system represents two different kinds of change. One change is the degradation of system functions, while the other change is the increase in stakeholder requirements. Hence, information about both stakeholder requirements and system health are necessary in order to properly manage system failures. This management includes a combination of maintenance and improvement efforts. The combination is especially crucial when dealing with complex and critical systems, where a change may result in unwanted consequences with extensive losses. In this situation, maintenance and improvements can be supported by the use of Built-in Test systems, which aim at enhanced testability and maintainability performance of the technical system. The purpose of this research is to explore and describe the linking of changing stakeholder requirements to the use of Built-in Test systems, in order to facilitate maintenance and continuous improvement of complex and critical systems. To fulfil the stated purposetwo case studies and one pilot study, supported by a continuous literature study have been made. The main case study and the pilot study focused on a modern combat aircraft, which is considered as a highly complex and safety critical system with stringent requirements on low life cycle cost. The second case study focused on maintenance-related requirements and risks during maintenance execution within a paper-mill, which is a complex system with stringent requirements for uninterrupted production. The research is presented in this thesis, which consists of an extended summary of five journal papers that are appended in full. The thesis includes examinations of important stakeholders and their requirements of critical system health information. Furthermore, the thesis includes studies and analyses of hazards related to health information retrieved through Built-in Test systems and combined with information from external test systems. The thesis also provides suggestions for how stakeholder requirements can belinked to the use of Built-in Test systems, so that they together with external test systems provide required health information and reduce related hazards.