Limited Editions

Large-scale displays help engineers create highly customized vehicles

By Karen Moltenbrey

When you order a new vehicle, the manufacturer typically lets you "design" your own by choosing from an array of manufacturer options such as a sunroof, CD player, or leather interior. But this level of customization pales in comparison to what the Diesel Di vi sion of General Motors (DDGM) offers for its line of Light Armored Vehicles (LAV).

Whenever an LAV customer, typically a branch of the military, places an order for a vehicle, it's usually for a highly customized product. Because an LAV can operate in many capacities-such as an antitank mortar platform, a mobile electronics station, an ambulance, or a troop carrier-its overall design can vary considerably, depending on the required features. More over, even when an order is placed for, say, a troop carrier, a previous design is rarely reused because the vehicle must accommodate the specific needs of a particular customer.

These constraints create a unique design challenge for the group at DDGM. On one hand, a customer's laundry list of configuration-altering specifications makes it impossible to apply a cookie-cutter design process. On the other, the limited number of vehicles per order-customers sometimes request as few as a dozen units-makes it cost-prohibitive to create physical prototypes. Therefore, DDGM opts to conduct its design reviews using a full-scale virtual prototype, displayed with large-scale immersive visualization technology supplied by Fake space Systems (Kitchener, Ontario, Canada) and SGI (Mountain View, CA).

Because most orders for Light Armored Vehicles (LAVs) call for unique specifications, the Diesel Division of General Motors conducts design reviews of virtual models on large-scale immersive displays to eliminate the costs associated with physical prototy

"This technology has revolutionized the way we run a design review," says Joe Attard, manager of Concurrent Product De vel op ment at DDGM in London, Ontario. "In car manufacturing, a company may make 50 prototypes, which it tests and evaluates before making a production model. We don't have that luxury. For us, the first one we build is the first one we sell. So there's not much room for design error."

Since DDGM began manufacturing LAVs two decades ago, Attard estimates that the company has produced about 25 to 30 variations of the basic vehicle. Given this variability, achieving efficiencies in engineering development without using physical prototypes was practically im pos sible. DDGM also lacked the ability to visualize its huge files of CAD data prior to building actual components. As a result, the group had to perform a significant amount of rework on the manufacturing floor.

This build-to-order process meant that DDGM's very first units of an order-which included a hand-built model for engineering verification and a preproduction model for validating production tooling-became part of the customer's order. "Unfortunately, those first two vehicles were generally not up to the same level of quality as the others," explains Attard. "For in stance, if we welded some tapped pads [threaded steel bars] onto the hull and then decided that we needed to relocate them, we'd have to get approval from the customer to make the change, since we were leaving a soft spot in their hull." Because of such quality issues, some customers used the initial vehicles for training purposes only.

Using large-scale visualization enables the DDGM team to see the entire full-scale design of an LAV. Prior to implementing this technology, the designers could only view pieces of their models because of their huge size.

However, all that changed a little over a year ago, when DDGM became a founding member of Canada's Virtual Environment Technologies Center (VETC) in London, Ontario. This membership gives DDGM liberal usage of the center's immersive display systems-including rear-projected Fake space WorkWalls and a fully immersive CAVE-to conduct LAV design reviews. According to Attard, using the center's resources to review realistic stereoscopic models has helped speed the design-review process and has enabled designers, manufacturers, and customers to resolve me chan ical, manufacturing, and maintenance issues before any metal (an expensive extra-hard armored steel) is cut.

As a division of General Motors, DDGM uses the standard suite of tools adopted throughout the company to produce commercial cars and trucks. For its CAD and modeling software, the group uses applications from Unigraphics Solutions (St. Louis, MO), including Unigraphics for CAD and iMAN for product data management, as well as ProductVision for visualization, running in an HP Unix environment. Based on the Vis suite from EAI (Ames, IA) and bundled into GM's own configuration of Unigraphics software, ProductVision re duces the size of solid-modeling files through tessellation and proximity filtering, making them quicker to load and easier to manipulate in real time.

"Our models are created in a math-based computing environment and viewed in-house on standard 2D monitors. Since the things we build are quite large in scale, we were never able to see the full models, even in a 2D format," says Attard. "The first demonstration of our models on a Fakespace display was an eye-opener; almost instantly we found several errors in our data."

Large-scale visualization has helped DDGM communicate more easily and effectively with its customers in the early stages of designing a vehicle. As a result, this has helped resolve some design issues and human factor concerns, such as how many people cou

That initial model-a 120mb file with about 2 million polygons-took about 30 minutes to load on VETC's SGI Onyx2 InfiniteReality. "We immediately saw that a fitting was floating in space, and we identified interferences that normally wouldn't have been uncovered until much later in the design cycle," Attard recalls.

Prior to using the immersive technology, DDGM's design review entailed the arduous task of producing 2D drafting views of its models that were plotted and hung on the walls of a meeting room. When design problems like those uncovered at the VETC were discovered, it was often during the product production process, so the team would have to go back and locate and fix the problem within the Unigraphics layout. Not only was that an expensive process, Attard says, it also caused significant delays.

Now, however, the team can evaluate two or three virtual prototypes in the time that it previously took to review a single concept. Also, the group can identify problems earlier in the design cycle, when changes are easily integrated without having to rebuild parts.

"Previously, we just could not see problems in the data," Attard says. Interference issues were especially difficult to detect, as the Unigraphics CAD software version the group was using at the time allowed two solid objects to occupy the same space without providing any warnings or visual cues for the user. "You wouldn't know there was a problem until after you already built the prototype, then you'd go back through the same vicious cycle again," says Attard.

In just over a year, visualization technology has become an integral part of DDGM's design process. As the group creates native Unigraphics files, it concurrently builds an optimized file in ProductVision, called a JT file, resulting in two master files that are continually updated. "The [JT] master model concept is absolutely key," Attard says. "You continually evolve the entire vehicle design homogeneously, rather than the sum of all the parts, like we used to do it."

By using the tessellated (stripped-down) ProductVision file, the designers have, for the most part, eliminated the need to produce 2D drawings for design reviews, a process as lengthy as the design stage. "We bring in the same group of people for a review, but now we project the JT files [onto a screen] in mono-format in a conference room and interactively navigate through them," says Attard. For a more in tri cate review, the multidisciplinary teams meet at the VETC for stereo viewing.

Although DDGM has not been able to eliminate making audit units out of the first two vehicles in an order, the company is getting closer to that realization with digital mockups. And while DDGM is just beginning to leverage the advantages of immersive visualization, Attard believes there are far more benefits to be had. For instance, the technology will allow service, quality assurance, procurement, and human factors groups to get involved in the development process much earlier.

Although every LAV model is unique, each starts with the same drivetrain created in Unigraphics. Power is diverted from the engine and transmission into the transfer case in the center of the vehicle, then directed to the front and rear differentials.

"In addition to improving design and reducing time to market, the facility will also help us streamline remote collaboration with partnering companies and our suppliers," he says. "And that is just the tip of the iceberg."

WorkWall and the CAVE CS4 immersive display systems, Fake space Systems (www.fakespacesystems.com)