While working on some of the military's most important defense aircraft during the early 1990s, Lockheed Martin engineer Paul Bevilaqua spent countless hours hunched in front of a Commodore 64 computer, playing Chuck Yeager's Air Combat. Bevilaqua, a renowned aerospace designer who holds a Ph.D. in engineering and is chief engineer of advanced projects at Lockheed, was developing professional expertise by crashing virtual airplanes into the virtual earth. Along with his Lockheed colleagues, many of whom were also hooked on the software simulators, Bevilaqua played Chuck Yeager's Air Combat, Microsoft Flight Simulator and other games on machines ranging from Commodores to Ataris to plain old IBM clones.
And he learned from each of them. During his hours in front of the tube, Bevilaqua gained insight into some of Lockheed's stickiest design issues. He learned about the advantages of shortening the turn radius of the F-35 and found ways to use software to cut the qualification times for air-to-air refueling of the F-18. He also applied his game expertise to the study of so-called "viffing" (vectoring in forward flight) on the AV-8B Harrier, thus improving the aircraft's maneuverability.
"Sometimes, you can know the equations, but not really know the physics," Bevilaqua notes. "That's what the games did for us: They taught us the real physics behind the equations."
Indeed, Bevilaqua and other Lockheed engineers believe so deeply in the benefits of simulation that they've since taken the next step—merging it with design software wherever possible, thus enabling them to better understand issues ranging from engine maintenance to performance physics. They've used simulation to determine whether mechanics have enough room to do repairs on jet engines, and have simulated the performance of aircraft lift fans.
In that sense, the company's engineers have placed themselves at the forward tip of a growing trend that allows engineers to try out their designs within an integrated design simulation environment before building them.
"For a long time, simulation and CAD have been separate and unequal disciplines," notes Todd Evans, a spokesman for MSC.Software Corp., a maker of design software. "But over the last few years, that's been changing. Those disciplines have been moving towards each other."
To be sure, the Holy Grail of software design—the ability to "drive" a digitized version of a fully designed car or aircraft while simultaneously tweaking its design—is still five or more years away. That, however, hasn't stopped countless engineering teams from wanting it sooner.
"Lots of companies want that kind of 'immersion,'" says Richard Bush, product marketing manager for NX Simulation for UGS Corp., a software vendor. "They want to be able to take a virtual model of say, a mobile phone, pick it up off a desk, touch it, and feel it before building a prototype."
Indeed, such levels of virtual reality may be possible at some point during the next decade. Research engineers at such schools as Carnegie Mellon University, Iowa State University, and elsewhere are working on so-called "haptic" devices—sensor-laden gloves, goggles, and head-up displays that enable design engineers to more effectively engage the human senses while trying out software concepts.
Believers in the simulation concept say it adds a new dimension to the engineer's understanding of a product. "Software simulators can give you a gut feel and intuition that might otherwise take 20 years of design and flight test experience to attain," Bevilaqua says.
For now, engineers are taking the simulation concept, merging it with CAD, and applying it to less computationally intensive tasks, such as simulating the performance of a vehicle suspension. Racing teams and makers of all-terrain vehicles, for example, have employed UGS Corp.'s NX Simulation to tune the suspension on their vehicle as it traverses a race course. That way, they get to see how the suspension reacts when the vehicle is traveling over flat ground or when it hits a bump.
"The trick to making it happen is to provide the tools in a design environment, so that it can happen in the process of doing the design," Bush says.
Similarly, IBM Corp.'s Human Builder software enables engineers to place a virtual human in an ergonomic or manufacturing environment and see how they interact with it. In one application on the Joint Strike Fighter, for example, engineers used such virtual humans in a design study to simulate full maintenance of a lift fan. The study was done to show that full maintenance could be done on the engine in a work bay aboard an aircraft carrier.
Microsoft Flight Simulator and its competitors, such as Chuck Yeager's Air Combat game, became popular among software engineers in the aircraft companies during the late 1980s.
IBM engineers say that the company's software, including its Product Lifecycle Management (PLM) and well-known CATIA program, has also been employed to determine whether a mechanic could fit his or her hand through an access panel and remove bolts from an engine. Similarly, automakers have used the software to place a virtual human in the driver's seat of one of their vehicles as a means of checking out the blind spots in a rear view mirror from every imaginable angle.
"With the software, you could reach your hand up and position the mirror to determine where your blind spots would be, depending upon whether you're short or tall," an IBM spokesman explains.
Such efforts fall under the heading of simulated ergonomic studies, which are gaining momentum among OEMs who want answers before building prototypes. "Ergonomics is huge for some companies," says Tom Toomey, PLM Aerospace Center for Excellence Manager for IBM. "They're looking for a better way to understand the relationships between humans and objects, to see how hard or easy it would be for someone to reach a light fixture or open a bin on an airplane."
'Feeling' the Design
To realize the goal of simulated motion within a complex mechanical assembly, engineers have also begun employing kinematics-based physics simulations. Products such as MSC Adams, from MSC.Software, include: Adams/Aircraft, which enables engineers virtual aircraft prototypes; Adams/Car, which creates chassis, engine, and driveline subsystems; and Adams/3D Road, which allows creation of roads, parking structures, and race tracks. The Adams programs, which are also aimed at more than a half dozen other applications, are notable because they can be merged with CAD programs, such as CATIA.
Using UGS's NX software, designers of all-terrain vehicles can simulate the performance of the vehicle's suspension.
Such kinematic motion models advance the state of the art by enabling engineers to build a model in CAD, and then allowing them to import it to the motion simulator. Doing so enables engineers to test a mechanical assembly, such as a landing gear, to determine whether it deploys too slow, too fast, too far, or not far enough, as well as whether it interferes with any part of the aircraft.
Still, the Holy Grail—in which engineers race the virtual car or fly the virtual plane while designing—remains on the horizon. To make that happen, engineers say they will need better visualization systems, including higher-level graphics cards and microprocessors, as well as tactile feedback systems, such as sensor-laden suits, gloves, and goggles. Moreover, they'll need better software in order to create the rich kinds of software environments that provide a feel of reality to the "driver."
To date, most aerospace companies have taken it upon themselves to write their own software simulators, mainly because games don't provide the richness and exact aerodynamics that are needed.
UGS's NX software enables engineers to simulate the ergonomics of a cockpit to determine whether all controls are within reach.
IBM's Human Builder software simulates the actions of a mechanic working on an aircraft engine.
Even smaller aerospace firms, such as Scaled Composites Inc., have created their own software simulators. Jim Tighe, chief aerodynamicist for the company's famed SpaceShipOne aircraft, wrote his own software simulator after months of using a video game called X-Plane. Doing so took eight months, during which almost all his time was dedicated to the software simulator.
"There are limitations in terms of what the games like X-Plane or Microsoft Flight Simulator can do," Tighe says. "The dynamics of a real airplane are very complicated and nonlinear. There are all sorts of weird interdependencies that simply can't be modeled in a video game."
Tighe says that he doesn't foresee a day when a small company such as Scaled Composites could merge design software with his simulator. Still, many engineers believe it will happen in the bigger companies within the next few years. And when it does, they say, the advantages will trickle down to other arenas, such as automotive and machine tools.
"The real goal is to simulate the entire operation of a product, including stress, manufacturability, and performance simulation," says Toomey of IBM. "Will you be able to do the simulation and the design in real time? Yes, that should happen in the next decade."
Until then, proponents of the concept say that pure simulation—even without a link to CAD—serves as an important teaching mechanism for today's design engineers.
"You don't necessarily learn directly from it," Bevilaqua says. "It's about a gut level feel for engineers. Sometimes you can know something in your head, but it's another thing to feel it."
Reach Senior Technical Editor Chuck Murray at firstname.lastname@example.org.