PhD Oral Exam - Andrew Kingsley Jeyaraj, Mechanical Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

To reduce the environmental impact of aviation, aircraft manufacturers develop novel aircraft configurations and investigate advanced systems technologies. These new technologies are complex and characterized by electrical or hybrid-electric propulsion systems. Ensuring that these complex architectures are safe is paramount to enabling the certification and entry into service of new aircraft concepts. Emerging techniques in systems architecting, such as using model-based systems engineering (MBSE), help deal with such complexity. However, MBSE techniques are currently not integrated with the overall aircraft conceptual design using automated multidisciplinary design analysis and optimization (MDAO) techniques. Current MDAO frameworks do not incorporate the various aspects of system safety assessment. The industry is increasingly interested in Model-Based Safety Assessment (MBSA) to improve the safety assessment process and give the safety engineer detailed insight into the failure characteristics of system components early in the design process. This thesis presents a comprehensive framework to introduce various aspects of the SAE ARP4761 safety assessment process in conceptual design while also considering downstream compatibility of the system architecting and safety assessment processes. A generic element architecture description approach, implemented using a graph-based system architecture descriptor, is introduced to model and transfer system architecture information between each stage of the systems architecting process while also supporting safety assessment activities at multiple levels of architecture granularity. The proposed framework introduces a safety-based filtering approach for large system architecture design spaces and integrates quantitative safety assessment methods compatible with early-stage system architecture specifications. Furthermore, the generic element descriptor links early system architecture specification with formal architecture specification in an MBSE environment. The framework also enables both simple and formal system architecture specification models to be used as inputs to safety assessment as well as a source of system-level sizing parameters for MDAO workflows featuring system sizing tools. The framework’s effectiveness is illustrated with examples from applications in recent collaborative research projects with industry and academia, which feature safety-focused system architecting studies for both conventional and novel aircraft concepts. The work presented in this thesis contributes to increasing maturity in conceptual design studies and enables more innovation by opening the design space while considering safety upfront.