Design Automation for Multidisciplinary Optimization A High Level CAD Template Approach

University dissertation from Linköping : Linköping University Electronic Press

Abstract: In the design of complex engineering products it is essential to handle cross-couplings and synergies between subsystems. An emerging technique, which has the potential to considerably improve the design process, is multidisciplinary design optimization (MDO).MDO requires a concurrent and parametric design framework. Powerful tools in the quest for such frameworks are design automation (DA) and knowledge based engineering (KBE). The knowledge required is captured and stored as rules and facts to finally be triggered upon request. A crucial challenge is how and what type of knowledge should be stored in order to realize generic DA frameworks.In the endeavor to address the mentioned challenges, this thesis proposes High Level CAD templates (HLCts) for geometry manipulation and High Level Analysis templates (HLAts) for concept evaluations. The proposed methods facilitate modular concept generation and evaluation, where the modules are first assembled and then evaluated automatically. The basics can be compared to parametric LEGO® blocks containing a set of design and analysis parameters. These are produced and stored in databases, giving engineers or a computer agent the possibility to first select and place out the blocks and then modify the shape of the concept parametrically, to finally analyze it. The depicted methods are based on physic-based models, meaning less design space restrictions compared to empirical models.A consequence of physic-based models is more time-consuming evaluations, reducing the probability of effective implementation in an iterative intensive MDO. To reduce the evaluation time, metamodels are used for faster approximations. Their implementation, however, is not without complications. Acquiring accurate metamodels requires a non-negligible investment in terms of design space samplings. The challenge is to keep the required sampling level as low as possible.It will be further elaborated that many automated concurrent engineering platforms have failed because of incorrect balance between automation and manual operations. Hence, it is necessary to find an equilibrium that maximizes the efficiency of DA and MDO.To verify the validity of the presented methods, three application examples are presented and evaluated. These are derived from industry and serve as test cases for the proposed methods.