Supporting multidisciplinary analysis using system architectures in SysML
Branscomb, Jaclyn Marie
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To develop competitive vehicles with ever increasing complexity, automotive designers need to improve their ability to explore a broad range of system architectures efficiently and effectively. Whereas traditional vehicle systems are based upon internal combustion (IC) engines, today’s environmentally conscious vehicle manufacturers must consider alternatives to the IC engine-only systems such as hybrid or electric systems. To help the engineers to model these multiple alternatives, it would be ideal to start from a base vehicle architecture. To design a good vehicle, it is necessary for each of these system architectures to be analyzed from a variety of attributes including performance, fuel economy, or even thermal behavior. Creating the necessary analysis models for each system architecture would be time-consuming, expensive, and could be error prone. To aid in overcoming such challenges, we have developed an approach for supporting the generation of subsystem model templates to support the integration of analysis models. The approach is based on formally modeling the system architecture in the Systems Modeling Language (OMG SysML) and then using model transformations to generate stubs for corresponding analysis models in Modelica and Simulink. In this manner, we assist designers in managing large systems with multiple analyses, ensuring that the systems remain consistent, and enabling the reuse of generic architectures through specialization and redefinition. The starting point is a reference architecture, called the Vehicle Model Architecture or VMA, in which all the key subsystems and interactions between subsystems are formally modeled. In addition, we have created a generic template that is a specialized version of the VMA. This specialized template can then be adapted by the systems engineer to represent a specific vehicle program. In addition, pre-defined, generic analysis templates can be redefined for the specific vehicle program under analysis. The SysML VMA system model is transformed through two model transformations, one that translates the physical portion of the system to Modelica, and one that transforms the logical controls portion of the system to Simulink. By automating these transformations and reusing a set of fixed templates for further specialized architectures, this approach helps to manage the complexity, reduces modeling time by enabling system model reuse. The entire approach taken in this thesis has been named the Vehicle Architecture Modeling Framework, VAMF, which includes the SysML VMA, the corresponding analysis templates, and the tools developed to support this approach. Throughout this thesis, the specific (fictitious) vehicle program “C100” and a 0-to-100 kph performance analysis test are used as examples for demonstration.