The virtual vehicle

By ALASTAIR SLOANE

Germany's Opel is one of many carmakers using three-dimensional "virtual reality" technology to cut development time of new vehicles.

The technology offers engineers and designers the advantage of basically "picturing" models long before the first prototypes are made.

Opel, a pioneer of computer-aided design (CAD), first experimented with the technology in 1968. In 1984 it was the first carmaker in the world to use a high-powered Cray computer for design.

Another important step was the introduction in 1995 of a computer-aided design system called Unigrafics, which had been used in the aerospace industry. Unigrafics has allowed Opel to reduce its CAD programmes from 30 to one.

Opel's virtual reality studio uses a graphics computer, special projectors, a pair of "active glasses" and a "power wall," a projection screen 6m wide and 2.2m high.

The projectors create a 3D picture of a complete vehicle. The computer software makes it possible for engineers using the active glasses to turn the vehicle every which way and change colours and shapes.

Another vital piece of equipment is the "cave," which uses four projectors. A picture is projected on to three sides of a cube that is made up of transparent projection screens and is open at one side.

The image causes corners and edges to disappear and permits a viewing angle of 180 deg. This creates a realistic sense of space, ideal for studies of the vehicle's interior.

Another important tool is "digital mock-up" - the computer-aided integration of components into a virtual reality model.

Once upon a time designers had to wait weeks for sample parts that were made from drawings and then built into a metal stand. Today, engineers move components around at will, fitting this to that and creating new parts within hours.

Integrating largely standard equipment like antilock braking and air-conditioning with things like catalytic converters is easy, too. Just visually push that part a little to the right and that to the left ...

Virtual reality allows engineers and designers to use every available millimetre of space, making for efficient design and servicing. Most importantly, it gives them an immediate impression of how best to position the occupants without the time-consuming need for real-life experiments.

Ninety 3D models of the human body, basically moving skeletons representing all shapes and sizes, makes it possible for engineers to simulate movements such as applying the handbrake, shifting gears, steering, or getting in and out of the vehicle.

The system also allows them to view occupants not only from outside the vehicle, but from the driver's perspective inside. Long before a physical model exists, the developers can determine the readability and user-friendliness of the instruments and the amount of room available for the head, shoulders, arms, legs and knees and to see how easy it is to get in and out of the vehicle. It is also possible to estimate how the seating design affects curvature of the occupants' spines and to analyse comfort and fatigue levels.

Thermal simulation gives an indication of the flow of air through the engine compartment and whether or not components will be sufficiently cooled by the airstream. It also shows the flow of induction air and fuel into the engine to the point of combustion, and hot and cold air through the cabin.

Some concepts which have come out of the virtually reality studio include the GMC Terradyne, Chevrolet SSR and Traverse.

The Terradyne is a megacab four-wheel-drive pick-up. It takes away the trade-offs between a standard pick-up, crewcab and sport utility. It carries five occupants and is powered by a choice of petrol or diesel engines.

The SSR has been described as a "stunning performance roadster that wraps 88 years of Chevrolet heritage in a design that only looks like a truck." It is rear-wheel-drive, powered by a V8 engine, and has a retractable roof.

The Traverse, says the blurb, "is not a car, not a truck but the best of both in this exploration to re-invent the Chevy family sedan. Truck-like attributes - comman-view seating, all-wheel-drive performance, and utility - are applied to a spacious interior with tall proportions and minimal overhangs."