Fifteen student engineering teams sweat the details in a competition to build a futuristic hybrid SUV
The Ford Explorer eases to a stop, the dying rumble of its engine replaced by the whirring of its electric motor, now acting as a generator. Energy that would otherwise waft from the brake pads as heat trickles instead to a battery pack, then pours right back out again a few seconds later when Nick Woulf, an electrical engineering student from the University of Wisconsin in Madison, stomps on the accelerator pedal.
A satisfied-looking grin appears on his face as he hears the groaning hum of both the motor and engine engaging, combining their efforts to accelerate us down the road. The truck does not accelerate as well as Ford's standard Explorer; it makes more noise and it needs more care. Then again, it is a student project. If it ”is not done well,” as Dr. Samuel Johnson said famously of a dog's walking on its hind legs, it is a wonder ”to find it done at all.”
It's a gorgeous late spring afternoon at Ford Motor Co.'s Michigan Proving Ground, in Romeo, where some 200 students on 15 university teams have gathered for the final tests in the annual FutureTruck competition. For the past school year, contestants have been leading a double life: mild-mannered engineering students by day, high-tech hot rodders by night. Fueled by who knows how many pizzas and liters of cola, each team has reengineered and rebuilt a brand-new, Ford-supplied, 2002 model-year Explorer SUV to boost fuel efficiency and minimize environmental impact.
Now, in this two-week climactic jamboree, judges meted out points for handling, towing power, off-road performance in sand pits and on steep grades, road clearance, comfort, assumed consumer acceptance, and even the quality of written and oral descriptions of the team's project, as well as for fuel economy and emissions.
The stated goal of the competition is to stimulate the development of hybrid electric vehicles, which save on energy and emissions by letting a gas or diesel engine run optimally at a steady speed and relying on an electric motor primarily to cover changes in load when climbing a hill or accelerating. Besides Ford, in Dearborn, Mich., which kicked in US $200 000 in seed money in addition to all those shiny new Explorers, the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy and over a dozen other companies offered material support to the teams. The program is managed by Argonne National Laboratory's Center for Transportation Research, in Argonne, Ill.
Each team also raised funds from local sponsors. Exact numbers were hard to come by, partly because many corporate contributions were given in kind rather than in cash, partly because the teams were cagey. But all acknowledged spending tens of thousands of dollars on their trucks, and rumor had it that the University of California at Davis hit six digits.
Innovation and perspiration
Is it really possible for a bunch of college kids to out-innovate the auto makers, with their vast R&D budgets and comparatively huge resources? No...and yes. There's hardly any room, of course, for revolutionary breakthroughs in a field so capital-intensive. These teams didn't build new engines, or experiment with exotic new magnets or ceramic superconducting wire in their motors. Still, there's lots that can be done that falls under the rubric of what Thomas Edison famously referred to as perspiration: eliminating a kilogram here or there, mixing and matching existing equipment, and fine-tuning it over and over again. It's a junior version of the work that goes into a Ferrari, say, where the difference turns not on Eureka! moments but on grinding work [photos,].
And though many of the teams' insights were useful and practical, the modified SUVs often were not. While these vehicles had to outperform a stock SUV, they had to do it only for the two weeks of competition. At Ford, on the other hand, ”we have to go for 100 000 miles,” says Tom Watson, manager of hybrid electric vehicle powertrain systems for Ford. And not all the SUVs actually lasted the two weeks. The University of Tennessee's entry broke a chain drive and was knocked out of the running. Electrical problems left many hybrids running on gas alone before the competition's many stages ended. One team taking reporters out for a spin had to get out and push the last 90 meters or so.
For the students, perhaps the biggest lessons weren't so much technical as organizational. Competitors had to learn how real engineers work in industry—no small accomplishment. When prospective employers gripe about technical schools, the refrain is almost always the same: too many newly minted engineers are unable to work with professionals in other disciplines, and they find it difficult to set priorities and get a complex job done. Also, rookie engineers struggling to work on different aspects of a given problem concurrently usually fail to communicate effectively about what they are doing.
The teams that succeeded in FutureTruck were the ones that surmounted those problems. Of course, a little fanaticism didn't hurt, either. ”There were about 40 people on the team, total, and probably 10 or so put in extreme amounts of time,” says Kathryn Orgish, a mechanical engineering student who has worked on Wisconsin's team since 1999, when the competition was still focused on cars. ”In earlier years, I wasn't one of the fanatics; it kind of grows on you.” As team leader this year, she averaged 40 hours a week and up to 80 hours toward the end. ”I slept in the garage, a lot,” she remembers.
Do the math: this contest is about love, not money. If the 10 fanatics each averaged 40 hours a week and the other 30 averaged 15, then the total number of person-hours comes to about 35 000. First prize is $6000, and winning in a few specialized categories, such as ”best fuel economy” and ”best off-road performance,” could add a couple of thousand more. The upshot is that the winning team is rewarded for its labors at a rate of approximately 37 cents an hour.
Lose weight, gain mileage
There are two basic types of hybrid: parallel and series. In the parallel, an engine drives the vehicle when it is cruising at a constant speed and charges its batteries, then calls on them to run an electric motor during acceleration. When the load is heavy, during acceleration or climbing a hill, say, both the engine and the motor can drive the wheels. In a series setup, the engine drives a generator that feeds one or more motors at the wheels and charges the batteries. In a series hybrid, the electric motors alone propel the car.
Not only do both designs allow the engine to run at its optimally efficient speed, increasing fuel efficiency, but they also permit the use of regenerative braking, to increase it further. By thus using less fuel, a hybrid produces less greenhouse gases and, if all goes well, less of the other polluting emissions, too.
In building hybrids, the teams had to grapple with two bugbears: weight and complexity, in part because they undermine the goal of saving energy. Wisconsin opted for a mild parallel design, which uses the electric motor only for acceleration and regenerative braking. And like most teams, Wisconsin reengineered its Explorer almost completely, changing the truck's frame, engine, powertrain, and most of the emissions-control equipment. ”The only thing we kept was the body,” says leader Orgish.
For its conventional drive system, Wisconsin decided on Ford's Mercury Lynx PS115 engine, a 1.8-liter inline, four-cylinder variable turbo developing 115 horsepower (85 kW) and 185 foot-pounds of torque (250 Newton-meters). A diesel, it can be tuned to burn a range of fuels; Wisconsin chose a blend including biofuel made from soybeans. Although the Lynx developed 23 percent less torque and 15 percent less power than the 2.5-liter, five-cylinder Land Rover engine that they'd used the previous year, it weighed in at just 158 kg, a 91-kg savings.
To compensate for the slightly weaker engine, the Wisconsin engineers chose the relatively powerful Delphi EV1 electric motor, which General Motors Corp. used in its now-discontinued all-electric EV1 vehicle, introduced in 1996. As the team explains in its technical report, the EV1's advantages showed up after a second battery pack was added to the vehicle. The team wrote that ”last year's custom motor was already magnetically saturated” and maxed out on a single pack. With the two packs, the EV1 was clearly superior.
In the end, the new hybrid system generated slightly more power than last year's version did. The team estimated that it would deliver 25 kW more to the wheels during the 200-meter-long acceleration test. If it did, though, it didn't improve the bottom line: Wisconsin averaged just 14.1 seconds over seven runs of that test—1.2 seconds slower than last year's time.
Wisconsin's big breakthrough was a new, lighter frame for the truck, which the team nicknamed Moolander, a play on the state's dairy heritage. They took the Ford-issue steel frame, spray-painted it white, added black polka dots, then had it photographed from every angle and modeled in three dimensions. They then took eight-inch aluminum, donated by Alcoa Inc., in Pittsburgh, and had it cut to those dimensions. An industrial engineering student, Jason Peto, welded it all together.
That saved about 91 kg, which with other slimming techniques was enough to get the weight down to 1996 kg—even after the addition of 115 kg for the electric motor, batteries, and packaging. It beat the standard-issue Explorer, which weighs 2159 kg off the assembly line. Still, ”lightest in show” honors went to Michigan Tech, in Houghton, which weighed in at just 1976 kg, after having substituted a frame made out of metal tubing and stripping the vehicle down to the bare essentials. Other teams went over the weight of the standard Explorer by 100 kg or more.
Of the many tradeoffs made during the competition, one of the most fundamental involves weight, fuel efficiency, and pulling power. A critical trial is the towing test [photo], which requires that each truck haul a 907-kg trailer at ”a reasonable speed” between 25 and 55 miles per hour (40 to 90 km/h) around a 6-km, variable-grade course, including less than a kilometer up a very steep 17 percent incline. Wisconsin got 45 out of 50 towing points.
But thanks in part to its mild-hybrid design, which saved battery weight, Wisconsin got the highest fuel-efficiency rating. Michigan Tech, the lightest entry, ”might have had better fuel economy if they'd installed our electric drive train,” says Wisconsin's Woulf. ”But they might still have lost the overall competition because they cut corners on consumer acceptability” areas like seat assemblies.
It was a shrewd weighing of the tradeoffs, born of experience. Another lesson of experience was seen in the overall trend away from series hybrids, which use the engine strictly to generate electricity for the batteries and motor. Only Virginia Tech went for it this year. ”In series, it's harder to optimize engine speed because the loads change so much,” Woulf says.
”We knew we'd win the on-road fuel economy test,” Woulf explains. ”We had been getting 30 to 35 miles per gallon, but we did worse in the competition because it was very windy and hilly, and for the first 53 miles we didn't have the turbo working, so the engine ran inefficiently.”
Under the hood, it is volume, as much as weight, that is at a premium. From the outside, all the SUVs look unremarkable, save for the odd solar panel or periscopic sight. Look into their guts, however, and you'll see strange hoses, high-current cables, and electronic control boxes. In place of Ford's 4-liter, gasoline-burning V-6, the teams typically used a much smaller engine, important not only for weight but also for packaging—engine and motor must coexist under the hood. Wisconsin chose the Lynx engine partly because it fits into a much smaller space.
One way the Wisconsin team saved space was by running the drive shaft right through the center of their Delphi EV1 motor. To bring the motor down to a manageable speed, they used a 3:1 Ballard planetary gear reduction. For power, they resorted to a pair of Panasonic nickel-metal hydride battery packs, linked in parallel, from the Toyota Prius electric car. Together with packaging, the batteries weighed 89 kg and stored 3.5 kWh.
Another way the FutureTruck competition differed from the realities of auto makers was that design teams faced no explicit competition events for safety. Cramming ever more stuff under the hood inevitably compromises the ”crush space” that ”real” cars have to absorb the force of a head-on collision.
Each vehicle does undergo a safety inspection to make sure it's mechanically sound and to confirm that it meets contest rules and specifications before it is allowed onto the road events. Even so, not all the hot new technologies were allowed under FutureTruck rules. ”There's no drive-by-wire or brake-by-wire,” says Wisconsin's Woulf. ”You really want a reliable braking system,” and, of course, no possibility of a contestant truck careening out of control.
What role did Woulf play as one of his team's principal EEs? ”Mainly monitoring batteries, temperature, voltage, current, amp-hours,” he says. Data was logged using LabView software. ”We also used a Motorola MPC555 Powertrain Control Module, an embedded controller that takes user inputs, like signals from the pedal and the brake, and tells the motor and engine what to do,” he continues. ”We programmed that ourselves. Fortunately, we have a dynamometer in our facility, so we were able to test our strategy and work out the major kinks.”
All the teams used digital design tricks. Joseph DiGiovanni, who in May received his M.S. in electrical and computer engineering from Georgia Tech, in Atlanta, was in charge of his team's engine/motor control system. He modeled the system on a computer screen with LabView and FieldPoint software packages, which National Instruments Corp. offered to all the teams, along with a two-day software course at the company's Austin, Texas, offices. It was a worthwhile two days. On 3 June, DiGiovanni started work there.
And the winner was...
When all the votes in all the categories were tallied, Wisconsin edged out UC Davis for first place. Wisconsin also won the categories of on-road fuel efficiency, vehicle design, off-road performance, workmanship, and technical report. The results weren't completely shocking—Wisconsin and UC Davis have done well in recent years, and teams that hit on good ideas one year can refine them the next. These teams also have received more publicity—hence more corporate donations. ”Companies call and say, ’Hey, we've got something we think you'll like,' ” says Woulf. ”We put their sticker on our truck.”
Wisconsin team leader Orgish landed a three-month gig in Ford's final assembly department this summer, helping to prepare the Dearborn truck plant for the 2004 F-150. ”I'm sure FutureTruck work helped get me this job,” she says.
Besides the interdisciplinary experience, though, the students got a taste of how engineering really is, with two steps forward often followed by one backward. Overcoming the inevitable glitches was incidental to the stated drive for a greener automotive economy, but it probably constituted the main educational advantage of the exercise, which is that things are harder than they appear in textbook analyses.
”Things are harder than they appear”—put that into Latin and you have a fitting motto for any engineering school.
To Probe Further
During the two-week contest, the FutureTruck Web site was updated daily with competition news. That rundown and more can be found at http://www.futuretruck.org.
Each team maintains a Web site about its modified SUV and the road to the competition. Visit the University of Wisconsin-Madison's entry at http://www.cae.wisc.edu/~vehicle/; or see the complete list of team Web sites at http://www.futuretruck.org/teams/index.html.
Wisconsin's technical report on Moolander can be found at http://courses.engr.wisc.edu/cgi-ecow/getbig/me/299/futuretruc/2003wisconsintechpaper.pdf.