Date of Award
Master of Science
Christina L. Bloebaum
Large-scale complex engineered systems (LSCES) are naturally a part of different areas of aerospace engineering and are typically characterized by high cost, high risk and complex interactions at different levels. The design of such LSCES involves multiple organizations at different geographical locations with large number of individuals working at various levels of organizational hierarchy. System engineering processes, which is a traditional approach used in the design of such LSCES, uses requirements as a means of communicating the preferences of stakeholder. The use of requirements does not directly communicate the actual preference of the stakeholder and is actually an indirect way by communicating what the stakeholder does not want. Traditional System engineering is a pass/fail approach in which design is considered to be achieved once all the requirements are satisfied. All the designs, which satisfy the set of requirements, are equally weighed and there is no search for the best design within the accepted design sets. MDO paves way for finding the best design through optimization in which the requirements are translated as constraints. The inconsistency in preference communication still exists in traditional MDO due to presence of requirements in the form of constraints and in addition, the use of constraints restricts the design space exploration by creating a hyperspace called feasible region.
A Value Based System Engineering Framework (VBSE) as studied by the past researchers addresses this inconsistency in preference communication. In VBSE a decomposable value function that is singular in unit, is used to capture the stakeholder’s preference, representing the system level preference. The system level preference is communicated along the hierarchy, also allowing each of the lower levels to form their own objectives consistent with the system level objective. The approach ensures capturing the true preference of the stakeholder by directly communicating what the stakeholder wants. The main aim of the present work focuses on explaining the process of transitioning from traditional requirements based approach to value based approach and quantifying the impact of requirements based communication using value gap analysis. A commercial communication satellite is used as an example to demonstrate the process of transitioning to a value based system engineering framework. An attribute based DSM is used to explain the process of capturing the attribute relationships. The study on impact of requirements using value gap analysis shows there is a definite value loss, which exists due to use of requirements. Value gap between preference communication due to probabilistic representation of uncertainty and traditional tolerance representation is also studied. The results indicate the existence of significant value gap and hence the uncertainty needs to be captured adequate enough. Further uncertainty study indicates the requirement of knowledge on the risk preference of the stakeholder and utility theory.
Murugaiyan, Suresh, "Modeling requirements to value formulation in the design of large-scale complex engineered systems: A satellite system case study" (2017). Graduate Theses and Dissertations. 16523.