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Strategies for modeling geometry in Knowledge Based Engineering systems
2001 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this work, geometric modeling in object oriented engineering designs systems has been investigated. These new design systems present one approach directly addressing the immediate needs for rapid design and evaluation existing in today’s industry. Volvo Aero is a company in the aerospace industry and is currently developing new engineering design systems in this direction. One approach to the problem is to use KBE (Knowledge Based Engineering), which is an acronym for object oriented modelling system. Knowledge is built into the system using “knowledge objects” and linked databases. This is a very powerful tool with the ability to constrain geometry to abstract objects, (e.g. cost objects, manufacturing objects and organisation objects) with rules and databases. A challenge with this approach is that the system tends to expand and become wide ranging, beyond any possibility to survey. The trick appears to be how to keep it as simple as possible and to use KBE where it gains the most. This is where the objective for this thesis appears, “To which level of geometry detail is it worthwhile building models in a KBE-system?” Another aim for this thesis has been to enlighten the difference between traditional CAE (Computer Aided Engineering) and KBE. In early phases of design, decisions are of more fundamental character and have a large influence on the forthcoming product. Time is a severe restraint and modelling is usually time consuming. Flexible modelling, allowing design iterations in early phases, is a way to improve the decision base significantly. This is where KBE shows its strength. Within minutes the KBE system changes configuration possibilities constrained to rules and related data, presenting the new output in the way a designer has programmed the system. It can produce 3D geometry, product data sheets or/and blueprints. Normally, such activities take days or weeks and may not be carried out at all. The approach has been to study KBE and object oriented modelling in general. A test case has been defined to illustrate the difference between Traditional CAE and KBE. I-Deas has been used to illustrate traditional CAE. The KBE system has been defined in AML and explains the theory and thoughts around the conclusions. Products that will benefit with a KBE system are: • Products with a high degree of similarity in-between versions. • Products requiring a large number of design configurations (e.g. Geometry alternatives, material alternatives or color alternatives). • Products with a large number of design processes (e.g. FEA optimisations). By analysing the product specification and identifying those design activities that will benefit most from using a KBE system, a design cycle can be formed that produce a product model based on these activities. Creating a design cycle based on these design activities will generate a generative model with the minimum level of geometry necessary for the model. In general, design activities that are frequently repeated take advantage of the KBE systems ability to iterate through a variety of configuration possibilities. Tedious time consuming work such as computational pre-processing can be automated by integrating computational modeling as a part of the generative product model. The final product will then be modeled in a traditional CAE tool. Examples of activities where a generative model may be cumbersome to define are activities such as NC-code generation and mpeg visualization. These activities have a high impact on the level of complexity since the need of geometry precision is high. In addition such activities normally have a relatively low impact on the decision-making process.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Object oriented, KBE, STEP, level of detail, design processes, design configurations
Keyword [sv]
URN: urn:nbn:se:ltu:diva-58549ISRN: LTU-EX--01/178--SELocal ID: f21284a8-8863-412b-8a9a-b41f383085d1OAI: diva2:1031937
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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