Imagine you're driving home at night after a grueling day at work. You’re tired and preoccupied; you don’t notice when your car starts to drift out of the lane and into oncoming traffic. But fortunately, an onboard computer senses the vehicle leaving the lane and automatically pulls it back.
This “lane-keeping assistant” is the brainchild of Chris Gerdes, an assistant professor of mechanical engineering. It’s one of several projects under way at the Dynamic Design Lab on campus, where Gerdes and a cadre of graduate students tinker with the next generation of computerized cars, creating vehicles that will be safer and more fun to drive.
More than 40,000 people are killed in motor vehicle accidents each year in the United States. One-third of those fatal crashes are caused by a car drifting out of its lane—often because the driver is drowsy or distracted—and colliding with a stationary object. “A driver assistance system whose sole purpose is to keep the vehicle in the lane could go a long way toward reducing that number,” Gerdes says.
As a first step, Gerdes’s crew ripped the steering column out of a 1997 Corvette and replaced it with computer-driven motors to turn the wheels. They added GPS navigation and sophisticated algorithms, and the first-of-its-kind lane-keeping assistant was born.
Look, Ma, No Hands
On the roof of a parking structure near the Medical Center—the Dynamic Design Lab’s campus proving ground—orange traffic cones mark a more-or-less circular course. I am to drive (or be driven, as the case may be) as Gerdes and grad student Josh Switkes put the Corvette through its paces.
I strap myself in, grab hold of the steering wheel with both hands, and ease my foot down on the gas. Gerdes tells me the ’Vette will do highway speeds, but I keep it under 10 mph, just to be safe. At first, it feels no different than driving a regular car; then, as I turn wide around a bend, I can feel the slight tug on the steering wheel. On a straight, flat road, it would be less obvious, Gerdes says.
After a lap or two, I take my hands off the wheel, and something remarkable happens: the car advances toward the cones, then angles left and follows the curving path all on its own. I think: I could get used to this.
Switkes compares the lane-keeping assistant to a spring that connects the car to the lane’s center. When the car begins to drift out of the lane, it’s as if the spring is being pulled. In fact, as the car drifts, the steering system signals the computer controlling the wheels, which then gently nudges the car back toward the center.
Gerdes is quick to point out that the lane-keeping assistant “is not HAL behind the wheel.” It doesn’t make any judgments about how good—or bad—a driver you are; if you steer firmly, the car will obey. The lane-keeping assistant will “let you steer right off a cliff if that’s what you choose to do,” he says. The idea is not to take control away from the driver, but to lend an almost imperceptible hand. “Chris likes to say that there should only be one intelligence in the car,” Switkes says.
Hot Wiring
The key to assistive technologies like the lane-keeping system is “steer-by-wire.” By-wire means driver commands are conveyed electronically, not through mechanical means such as a steering shaft. And its implementation has already begun.
If you’re driving a newer car, chances are the gas pedal isn’t connected to anything but silicon. Most cars built since the late 1990s use throttle-by-wire, which means that when you put the pedal to the metal all it’s really doing is signaling a computer to direct fuel to the engine. Brake-by-wire is starting to show up in a few models, including the Mercedes-Benz E class.
One advantage of by-wire is the ability to combine information from different systems for more coordinated control. In the case of the lane-keeping assistant, the computer integrates inputs from the steering wheel with differential GPS (DGPS) coordinates received via three roof antennas. Using a high-resolution digital map of the road, it can discern the lane boundaries.
By-wire also makes cars more fuel efficient and lowers emissions. Moreover, it opens up a new world of design possibilities. Eliminating the bulky gear under the hood allows for more leg room, larger front windows and a steering wheel that slides easily from the left to the right side of the car. For that matter, who needs a steering wheel? You could steer by joystick or airplane-style U-shaped controller. You could brake with a button or accelerate with a lever.
Of course, consumers may not be ready to give up mechanical control of steering, let alone the wheel itself (a “pretty ingenious device,” as Gerdes puts it). “Already we’re separated from the throttle, and we’re kind of separated from the brakes, but people are attached to the steering solidly,” he says. “I think it’s going to be a difficult thing for people to accept at first—the idea that they no longer have the rigid mechanical connection that they trust.”
They will have some time to get used to it. The power-hungry electric motors and other devices of a completely by-wire car “will use more electric power than is available” through today’s 12-volt electrical systems, wrote industry analyst Joe Constance of Technical Insights in a July 2004 report covering trends in automotive electronics. “They may have to wait for 42-volt electric systems before they see widespread installation.” That may not be for another 10 to 15 years.
Those craving a lane-keeping assistant will also have to wait for the nation’s small DGPS network to expand to cover the 4 million miles of road criss-crossing the country. The GPS navigation systems in today’s cars can’t always detect what lane you’re in, let alone when you leave it. DGPS is a more accurate system with built-in error correction. Still, the technology is not infallible, since tall buildings can deflect signals. Gerdes points out that “the lane-keeping assistant need not work everywhere to be effective”; most accidents occur on open roads, often rural highways, where DGPS works well. “In any commercial system, you would want to merge the GPS sensing with cameras to have a more robust lane-sensing system,” he adds.
What Gerdes aims to show is that a by-wire car can be safer than a conventional one. “We don’t want to stop with making it as good, we want it to be improved,” he says. “And with electronics and sensors, there’s definitely a lot of capability to do that.”
His group is testing some safety enhancements on the P1, an all-electric by-wire prototype that looks like an overgrown RC dune buggy. Left and right wheels are controlled independently, as is rear-wheel drive, allowing the researchers to experiment with steering-system redundancy. Another unique solution they’ve come up with involves turning both rear wheels in and snowplowing to a stop. If all else fails, the P1 is equipped with a giant red “power kill switch” that Gerdes says is exactly what it looks like: a panic button.
Although he did his PhD work in the field of highway automation, Gerdes stops short of trying to develop cars that drive themselves. As powerful as today’s computers are, he explains, they simply can’t take everything into account, whereas people are actually extremely good at reacting quickly to changing conditions. “It’s a very rapidly changing picture out on the highway,” Gerdes says. “I think it’s more realistic to work on the things that people don’t do well, give them some assistance with that, and let people do the things they do well.”
Besides, he says, “it would bug a lot of people in this lab if we took away driving entirely because a lot of people here really enjoy driving.”
Cars Just Wanna Have Fun
Indeed, experimenting with by-wire technology isn’t just about making cars safer; it’s about making them snazzier. The lane-keeping assistant is installed on a Corvette, after all.
“Used to be people would work on their car—pop the hood, tinker with the engine, change the suspension—people don’t tend to do that anymore. But what if we could use by-wire technologies to make it all programmable?” Gerdes says. “These are applications that could really drive the technology from the fun perspective.”
To that end, graduate student Judy Hsu is working on a simulation that might one day make it possible for anyone to feel like Jeff Gordon behind the wheel. “What’s cool about race car drivers is that they’re used to driving at the limits of handling all the time, so they’re very sensitive to the tire forces that are fed back through the steering wheel,” she says.
But when your average NASCAR dad feels the tires begin to slip, he tends to panic and brake too hard, which can send the car into a skid. Hsu says a vehicle outfitted with GPS and tire sensors could sense when the car is pushing the limit and automatically compensate, without the driver even realizing it.
Even with a smart stability system, Hsu says, you won’t be able to “drive crazy and be fine.” Real race cars, she points out, are high-performance vehicles. But she admits that part of the motivation for the research is lab members’ Daytona dreams.
By-wire control could usher in a whole new age of automotive customization. Handling characteristics like the steering ratio—how much you have to crank the wheel in order to turn the tires—could be tailored for every member of the family. Gerdes sees a future of people tweaking their cars and swapping the specs over the Internet, just like video gamers do now.
Sign me up for the SUV that drives like a sports car.
GRETA LORGE, '97, is an assistant editor at Wired magazine.
