Model-Based Reliability Engineering

Abstract

This thesis work proposes an approach to integrate design and reliability assessment, based on a single modeling environment by deployment of Systems Modeling Language (SysML). The main purpose of the developed approach is to help enhance reliability assessment in student-based CubeSat projects. Considering the limited project resources, that CubeSat university design teams typically have to cope with, an attempt is made to create a methodology, that allows adoption of single modeling environment for both system design and reliability analysis, thereby focusing on the main principles and advantages offered by the Model-Based Systems Engineering (MBSE) practice. To develop the considered methodology and to demonstrate its practical application the following steps were taken: A SysML design model is built, consisting of both functional and physical architectures, based on a hypothetical simplified spacecraft subsystem. Thereby an assessment is made to what detail a system needs to be modeled and which characteristics it should at least comprise to provide a sufficient basis for a risk model, as a choice of a certain risk assessment methodology may influence the extent to which a system must be modeled, while certain system design model characteristics influence the selection of the appropriate risk assessment methods to be implemented. To determine how risk analysis can be performed in SysML for a given hypothetical design problem, various risk assessment methods were considered for the sake of risk assessment methodology development, based on specific criteria. After it became clear how the implementation of both qualitative and quantitative parts of risk assessment had to be realized in SysML, the actual risk analysis was initiated; the design model was extended by a reliability model. The evaluation on the obtained results was finally performed, and general observations from integrating risk analysis in MBSE were presented, based on the comparison with traditional methods, considering the major risk assessment aspects.