Creating High Quality Manufacturable Free-Form NURB Surface Using Constrained Optimization:
Program Summary

Statement of Research Problem:
The research proposes to develop advanced NURBS (Non-Uniform Rational B-Spline) surface tools using the state-of-the-art energy method to solve three CAD design problems:

1. creation of surfaces with bounded slopes and curvatures,
   
2. automatic detection and removal of abnormal surface curvatures, and
   
3. constrained modification capable of holding significant features of a model unchanged while globally or locally altering it, for instance, stretching the wheel base of a vehicle and having the model scaled accordingly without loss of the original smoothness conditions among patches or the shapes of selected components, such as wheels.

Projected Ford Benefits (Sponsor's comments):
This research would benefit the Ford Product Development process. In more specific terms, it would benefit Ford's C3P (CAD/CAM/CAE/PIM) and CAD-the-Master strategies by providing an array of more efficient and effective CAD tools for designing high quality, manufacturable automobile body surfaces.

This research would provide an opportunity for Ford to explore the ability to address and incorporate manufacturability issues early in the surface development process. Having this ability would help reduce both the cost and cycle time of the product development process.

The sponsor is a member of the C3P core team and will be able to distribute the results of the study to most concerned. Furthermore, this proposal has been discussed with and given the support of the C3P leadership.

Background:
Design of high quality, manufacturable surfaces is an important and challenging task in today's manufacturing industries. Although significant progress has been made in the last decade in developing and commercializing production quality CAD tools, demand for more effective tools is still high due to the ever increase in model complexity and the needs to address and incorporate manufacturing requirements in the early stage of surface design. Within this content, the proposed research has identified and attempts to solve three surface design problems.

The first problem is constrained design. For instance, a surface with regions of large curvature may be difficult to produce because the sheet metal may not be able to sustain the stamping tension. Hence, the capability to directly control the bound of surface curvature in the process of design is of significant importance.

The second problem is the lack of automatic fairing capabilities. The current process relies heavily on the designers to visually identify regions with curvature irregularities and to fix them manually by, for instance, correcting the control points of the NURBS surface. This is often an experience-based, trial-and-error, and time-consuming process. Furthermore, the complexity of the problem often exceeds what the human designer can cope with, in which case solution has to be sought through the use of physical models. Thus, the ability to automatically detect and correct local surface curvature anomalies is strongly requested by the design community.

The third is the lack of constrained modification capabilities. Tools are needed, for instance, that would hold certain components of a vehicle model unchanged while globally stretching the entire model to increase the overall dimension of the wheel base. Examples include, but are not limited to, wheels, standard door handle pockets or even an entire door subassembly. It is, therefore, of practical interest to explore such constrained modification capabilities.

Significant Milestones:
Yr_1:
Literature search; preparation; problem formulation; interface design; development and implementation of curvature estimation techniques; and constrained curve interpolation.

Yr_2:
Development and implementation of constrained n-sided hole filling techniques, constrained local/global fairing techniques; initial integration and testing.

Yr_3:
Development and implementation of constrained scaling techniques, constrained surface interpolation techniques; system integration and testing.

University/Ford Interaction Plan:
In the initial phase of the project, the university representative will visit Ford to gather information about the Ford design process. Throughout the project the university representative and the Ford representative will visit each site at least twice per year. At the end of each year, the university representative will submit a report to the sponsor and will give a presentation to interested personnel at Ford. After a substantial amount of results is produced from the project, Ford will start including SRDC in the interaction plan to facilitate preparation of technology transfer into I-DEAS Master series. At the completion of the project, a final report will be submitted which summarizes the results of the project.