Multiscale Design for Solid Freeform Fabrication

One of the advantages of solid freeform fabrication is the ability to fabricate complex structures on multiple scales, from the macroscale features of an overall part to the mesoscale topology of its internal architecture and even the microstructure or composition of the constituent material. This manufacturing freedom poses the challenge of designing across these scales, especially when a part with designed mesostructure is part of a larger system with changing requirements that propagate across scales. A setbased multiscale design method is presented for coordinating design across scales and reducing iterative redesign of SFF parts and their mesostructures. The method is applied to design a miniature unmanned aerial vehicle system. The system is decomposed into disciplinary subsystems and constituent parts, including wings with honeycomb mesostructures that are topologically tailored for stiffness and strength and fabricated with selective laser sintering. The application illustrates how the design of freeform parts can be coordinated more efficiently with the design of parent systems.Mechanical Engineerin

Multiresolution modeling and simulation of an air-ground combat application

The High Level Architecture (HLA) establishes a common modeling and simulation framework facilitating interoperability and reuse of simulation components. Since 1996, ONERA (French Aeronautics and Space Research Centre) carries out several studies on HLA in order to gain a better understanding of the underlying mechanisms of HLA implementations. The first critical step of this initiative was to develop our own RTI from the HLA specifications. In order to evaluate the cost of making a transition from legacy simulations to HLA, we first developed an HLA federation simulating an air-ground combat involving a set of aircraft's engaged against a surface to air defense system. Current studies on HLA distributed simulation include security, WAN simulations and multiresolution. Conventional simulations represent entities at just one single level of resolution. Multiresolution representation of entities consists in maintaining multiple and concurrent representations of entities. In this paper we address the problem of how HLA services may allow to achieve multiresolution modeling and simulation. Our goal is not to provide a general framework as a basis for designing simulations of entities at different levels of resolution concurrently. We focus on experience feedback we have obtained by migrating a single level resolution HLA federation to a multi-level resolution federation. The selected application is an air-ground combat simulation involving aggregated patrols of aircraft's engaged against a surface to air defense system. In this paper, we briefly describe the air-ground combat simulation application. We then detail the multiresolution representation of entities (patrols and aircraft's), and discuss the chosen mechanisms allowing triggering aggregation from an entity-level representation, and conversely, triggering disaggregation from an aggregate representation. We focus on the HLA services we have selected to maintain several levels of representation concurrently and on methodological issues in designing multiresolution HLA simulations. We have tackled some difficulties and we propose a new HLA service that should make easier the user's task. This multiresolution management service can be added to our RTI or written by using existing HLA services. Finally, future trends are discussed

IPAD: Integrated Programs for Aerospace-vehicle Design

Early work was performed to apply data base technology in support of the management of engineering data in the design and manufacturing environments. The principal objective of the IPAD project is to develop a computer software system for use in the design of aerospace vehicles. Two prototype systems are created for this purpose. Relational Information Manager (RIM) is a successful commercial product. The IPAD Information Processor (IPIP), a much more sophisticated system, is still under development

Coordination approaches and systems - part I : a strategic perspective

This is the first part of a two-part paper presenting a fundamental review and summary of research of design coordination and cooperation technologies. The theme of this review is aimed at the research conducted within the decision management aspect of design coordination. The focus is therefore on the strategies involved in making decisions and how these strategies are used to satisfy design requirements. The paper reviews research within collaborative and coordinated design, project and workflow management, and, task and organization models. The research reviewed has attempted to identify fundamental coordination mechanisms from different domains, however it is concluded that domain independent mechanisms need to be augmented with domain specific mechanisms to facilitate coordination. Part II is a review of design coordination from an operational perspective

PLM and early stages collaboration in interactive design, a case study in the glass industry

Product design activity is traditionally presented as a succession of four to six stages. In the early stages of design, during the search for concepts, multi-disciplinary teams are working together, sometimes on the fringe of the digital design chain. But it is during these stages, that most of the product development cost is committed. Therefore, collaboration should be emphasized, and PLM software should contribute to it strongly. This paper first defines the boundaries of the early stages of design. Then, we analyze designer collaboration in this stage and describe the knowledge necessary for efficient collaboration. Finally, we propose and test a concept for a tool to assist the early stages of design, to be integrated in a continuum with other existing digital design tools. A case study is presented in Verallia, specialized in the design and manufacturing of glassware

Modelling for data management & exchange in Concurrent Engineering - A case study of civil aircraft assembly line

This research aims to improve the dataflow performance of the Concurrent Engineering (CE) practice in the detail design stage of the aircraft Assembly Line (AL) in the C919 aircraft project. As the final integrator of the aircraft, Shanghai Aircraft Manufacturing Company Ltd. (SAMC) is responsible for developing the AL with global suppliers. Although CE has been implemented in AL projects to shorten lead time, reduce development cost and improve design quality, the lack of experience and insufficient infrastructure may lead to many challenges in cooperation with distributed suppliers, especially regarding data management/exchange and workflow control. In this research, the particular CE environment and activities in SAMC AL projects were investigated. By assessing the CE performance and benchmarking, the improvement opportunities are identified, and then an activity-oriented workflow and dataflow model is established by decomposing the work process to detail levels. Based on this model, a Product Data Management (PDM) based support platform is proposed to facilitate data management/exchange in dynamic workflow to improve work efficiency and interoperability. This solution is mocked-up on the Siemens Teamcenter 8.1 PLM(Product Lifecycle Management) software and its feasibility is checked. The mock-up is evaluated by SAMC experts and suppliers. The feedback shows the acceptance of the model by experts and the urgency of improving data/work flow design before PLM implementing. The result of this research is useful for enterprises in similar environments transiting from pre-PLM to implementing PLM and who wanting to strengthen CE in the new product development

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 217, March 1981

Approximately 130 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1981 are included in this bibliography. Topics include aerospace medicine and biology

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

Advanced flight control system study

The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed