Research On The Improved Bi-level Integrated System Synthesis Collaborative Optimization Method Based On Variable Fidelity Approximation

Multidisciplinary Design and Optimization method is the new trend of complex coupled engineering product design. It changed the traditional method of splitting coupled relationship and relying on the experts' experience to coordinate the differences between sub-disciplines. Moreover, it can improve the design quality, shorten the design cycle, reduce the design cost and so on. MDO has gradually attracted the attention of domestic and foreign scientific research institutions, companies and the government. The research areas of MDO are very broad and the architecture, treated as the core content of MDO, can effectively reduce the organizational complexity and the coordination difficulty between sub-disciplines. Though the optimization strategies now have a variety of expressions through constant development, from single-level to multi-level, they can hardly simultaneously meet the requirements of operating easily and being solved efficiently. What is more, the approximate model technology can greatly decrease the high cost of repeated calls of accurate computer simulation model during the subsystem analysis process, and it has become the essential tool to decrease the computational cost of the complex engineering MDO design problem.In this paper, BLISCO architecture with relative good comprehensive performance in both organization structure and coordination capability, combined with Variable Fidelity Modeling(VFM) later, is studied and then applied to engineering project case.Firstly, domestic and foreign research on the MDO architectures and Variable Fidelity Approximations are reviewed in this paper and the characteristics of BLISCO, CO and BLISS2000 method are systematic researched and compared. To solve the problem of possibly mutually coupled again in the subsystem objectives and avoid the complex derivation process, the improved BLISCO method based on the quasi-separable MDO form is proposed. One mathematical example and one engineering problem are tested to verify the feasibility of the proposed method.Secondly, in view of the improved BLISCO method requiring calling repeated high computational accurate simulation models in the subsystem analysis, this paper introduced VFM technology and proposed a new improved BLISCO method based on Variable Fidelity Approximation. The solving procedure of the new method, further improved and optimized with the VFM technology, is given in details.Finally, the design task of Small Waterplane Area Twin Hull(SWATH) is described in details, and through an application of the parameter design optimization of SWATH, the improved BLISCO Method based on Variable Fidelity Approximation proposed in this thesis is verified. Results show that the proposed method can not only achieve the target of design optimization, reduce the computational cost but also meet the requirement of concurrent design of sub-disciplines.