C. Greg Jensen

Model Consistency and Conflict Resolution With Data Preservation in Multi-User Computer Aided Design

Simultaneous multi-user computer aided design (CAD) allows multiple designers to contribute to the same model at the same time. The resulting parallel design workflow shortens product development cycles. In a replicated, simultaneous multi-user CAD system, modeling data must be kept consistent between clients. This paper presents a method that keeps independent copies of the models in sync between distributed CAD clients. This is accomplished by enforcing modeling operations to occur in the same order on all the clients. In case of conflict, a resolution method preserves conflicting operations locally for later reuse or resolution by the user. These methods are implemented in a commercial CAD system which has been enhanced to enable simultaneous multi-user. Validation tests are run to demonstrate that the methods implemented ensure model consistency and resolve conflicts while preserving conflicting operation data.

Automated Conflict Avoidance in Multi-user CAD

The NSF Center for e-Design, Brigham Young University (BYU) site has re-architected Computer Aided Design (CAD) tools enabling multiple users to concurrently create, modify and view the same CAD part or assembly. This technology allows engineers, designers and manufacturing personnel to simultaneously contribute to the design of a part or assembly in real time, enabling parallel work environments within the CAD system. Such systems are only as robust as their methods for managing conflicts (i.e. simultaneous edits of the same feature by multiple users). A heavy-handed conflict prevention would limit collaborative freedom. This paper discusses an automated feature reservation method which prevents multiple users from simultaneously editing the same feature. The method is implemented in a commercial CAD system. Results show that this methodology prevents data inconsistency that results from feature/self conflicts. This system prevents CAD modeling conflicts, while providing an agile user experience within the collaborative environment.

A Web Enabled Process for Accessing Customized Parametric Designs

Parametric design facilitates mass customization, concurrent engineering, optimization, and other product development integration processes used during preliminary and detailed design stages. Automated methods for regenerating and accessing parametric models can significantly reduce the time-to-market of new products. Applications that automate this process have inherent limitations based on the available features in commercial CAD systems. New technologies such as the component technology, used in conjunction with parametric and Internet-based design can eliminate current limitations of CAD applications based on Application Programming Interfaces. Joint educational/industrial examples will be used to illustrate where limitations have been reached with custom CAD applications built on commercial systems lacking the component technology. Furthermore, the CAD Services framework for the development of CAD and Computer-aided Manufacturing/Engineering (CAM/CAE) applications using the component technology will be discussed.Copyright

Architectural Limitations in Multi-User Computer-Aided Engineering Applications

The engineering design process evolves products by a collaborative synthesis of specifications, personnel and organizations. Unfortunately, collaborative effectiveness is thwarted by existing single-user computer-aided applications like computer-aided design, computer-aided analysis, and others. These applications and associated file management systems assign editing rights to one technical person, e.g., a designer, analyst, or a process planner. In the absence of collaborative computer-aided engineering applications, we conducted a survey to establish that product collaboration is limited to interactive, either formal or ad-hoc design sessions, social communication tools, serial model sharing, terminal/screen sharing, and to conference call interactions. Current computer-aided (CAx) tools do not permit simultaneous model changes by a collaborative team editing the same model. Although over a decade of prior research has demonstrated multi-user feasibility for computer-aided applications, the architectural breadth of this research has apparently not yet compelled developers and end-users to develop and adopt new multi-user computer-aided applications devoted to product development. Why have collaborative engineering CAx tools not been commercialized for mainstream use? This paper uses several multi-user prototypes, including the first Computer-Aided Engineering multi-user prototype called CUBIT Connect, to expose additional architectural hurdles to implementing new multi-user collaborative paradigms. These challenges relate to variable algorithmic performance times, multi-threading and event driven client notification processes, distributed access level security, and model change management in design sessions.

A CAD-centric Approach to CFD Analysis With Discrete Features

AbstractCAD models from conceptual design often follow the “over-the-wall” approach for downstream analyses such as FEA, CFD, heat transfer, and vibrations. The CAD-centric approach consists of using the CAD model as a source of data for downstream applications such as mesh generation, and CFD setup. The CAD model used in the CAD-centric approach contains the geometry to be analyzed and all non-geometric data required to mesh and solve the CFD model in the form of attributes. A special class of topology change, the discrete feature problem, is encountered when an array of features instances change in number. A method is proposed, developed and reported on that automates the CAD to CFD process, including fluid domain creation, while addressing the discrete feature problem that can occur during preliminary design.

CAD-Based Parametric Cross-Section Designer for Gas Turbine Engine MDO Applications

AbstractBecause gas turbine engines are among the most complicated mechanical assemblies produced to date, there is an increasing need for computer-aided modeling programs that facilitate the incorporation of Multi-Disciplinary Optimization at the conceptual design stage. Here we report the development of Cross-Section Designer, a software tool for manipulating gas turbine engine geometry using the UGS NX CAD system [1]. Cross-Section Designer provides the user with an editable version of the engine gaspath based on output from a cycle specification program in the form of geometric and thermodynamic parameters. The system was designed to accommodate multiple parameterizations, and allows users to manipulate the geometry according to various different design schemes that best fit the design intent. The multiple-parameterization modeling methods described in this paper can be extended to the design of any system, providing real cost savings via design time reduction.

Scalable Integration of Commercial File Types in Multi-User CAD

ABSTRACTCurrent commercial computer aided design (CAD) tools limit a parallel engineering design workflow by only allowing a single user in the CAD model at a time. The NSF Center for e-Design at BYU has recently developed multi-user CAD tools which enable a parallel design workflow by allowing multiple users to simultaneously contribute to the same CAD model in real time. The combined challenges of consistent distributed naming and robust interoperation with commercial file types have created scalability and usability issues for previous multi-user CAD implementations. This paper presents persistent naming methods and a file-based architecture that address these challenges. An implementation of these methods shows that multi-user design within commercial CAD is increasingly scalable.

Incorporating Computational Fluid Dynamics Into The Preliminary Design Cycle

AbstractIndustry is constantly seeking ways to bring new or derivative products to market in minimal time at minimal cost. To accomplish this, industry has adopted Computer Aided Engineering tools that perform structural, flow, manufacturing, and cost analysis. One of these tools industry often struggles with in the preliminary design phase is Computational Fluid Dynamics (CFD). Some of the challenges presented by CFD are the time required to create a CAD (air solid) model, generate a valid grid for analysis, obtain a solution, post-process results, and review the results. We present an approach that reduces the time to go from a concept to a solution ready for review. This approach addresses how to build a CAD model for use in downstream applications, automate the grid generation process, and automate the post-processing. In addition, it addresses how to automate results documentation with a Design Review Tool. This approach will enable the aerospace, automotive, and other industries to use CFD to more e...

Direct Process Control Using n-Dimensional NURBS Curves

AbstractDirect control allows CAD/CAM applications to pass native part geometry directly to a machine tool for part processing. Although highly efficient for 3-axis machines, one of direct control’s advantages is in implementing new algorithms for 5 and 6-axis machining, where the tool orientation is a more complex function of the surface geometry. This paper introduces a new extended n-dimensional NURBS vector that incorporates tool orientation into control parameters. By including state control parameters such as feed rate and spindle rpm, the n-D NURBS becomes the first mathematical representation to incorporate all required machining information.

Integrated, Synchronous Multi-User Design and Analysis

An integrated multi-user system for synchronous design and analysis improves collaboration and concurrent engineering across multiple engineering disciplines. This approach allows all members of a multidisciplinary team (i.e., a team made up of designers and structural analysts) to access the same shared model over a computer network and synchronously contribute to the model in real-time. Data for both design and analysis are directly based on the same mathematical representation of the geometry, eliminating the need for model translation between disciplines. All data are stored on a central server which allows simultaneous access by multiple users. Each user views and operates on the model in a way specific to his or her discipline. Updates to the shared model are seen in real-time. This system enables an enhanced parallel product development workflow, since users from multiple disciplines can simultaneously contribute to the same engineering model. A simple implementation of an integrated multi-user design and analysis system was developed to demonstrate this method. Preliminary results from two experiments suggest a reduction in the amount of time required to perform design and analysis operations when compared with traditional, single-user approaches. Future research is suggested.