You’re driving down the highway and a box falls off the truck in front of you. As you swerve to avoid it, your car might fishtail--what engineers call yaw--and even go into an uncontrollable spin. If this happens, your antilock brakes won’t do much good, because they act with equal force to slow each wheel. What’s needed are brakes that can be applied to each wheel independently.
Engineer Armin Mueller and his team at Mercedes-Benz have devised a braking system, called the Electronic Stability Program, that can be used exactly that way. Its eight sensors, at various positions in the car, keep track of what the driver is doing and how the car is moving, and a watchful central computer looks for the precise set of conditions that indicate yaw. For example, to tell whether the driver is frantically trying to regain control of the car, a set of sensors measures the angle of the steering wheel and the pressure applied to the brake pedal. Other sensors measure whether the car is accelerating sideways, or whether the wheels are turning at different speeds. The key breakthrough, says Mueller, was being able to develop a yaw-rate sensor for automotive applications.
Once the computer decides the car is sliding or spinning, it automatically applies the brakes to stabilize it. For instance, if the car’s rear is sliding to the left, it applies the brake to the left front wheel. On a mixed surface--when one wheel is on, say, asphalt and another is on dirt--the system varies the braking pressure applied to each wheel, bringing the car to a smooth, stable halt. As a last resort, the system slows the car by throttling back or shifting gears.
The Electronic Stability Program is now available as standard equipment in Mercedes’ S600 and SL600 V-12 models and can be installed on V-8 models for an additional $1,870.
Saved by the Sausage
BMW/Simula Government Products’ Side-Impact Air Bag
InnovatorS: Klaus Kompass and Gershon Yaniv
Air bags have succeeded in reducing injuries from frontal collisions, but many head injuries still occur because of inadequate protection from side impacts. In 1993, when bmw safety engineering director Klaus Kompass and his colleagues considered protecting passengers’ heads with side air bags, they found that conventional air bags would not do the trick; they were too slow to deploy, the explosives needed to unfurl them were themselves dangerous, and the bags tended to get pinned to the side in a collision, rendering them useless. A radical new design was called for.
Fortunately, Gershon Yaniv, research director at Simula Government Products in Phoenix, had already begun developing a side-impact air bag, which he and Kompass adapted for bmw’s cars.
Leave it to a bunch of Bavarian engineers to name the five-foot- long hot-dog-shaped air bag the weisswurst, after their favorite local sausage. Officially known as the Inflatable Tubular Structure, it is pinned on one end to the top side corner of the dashboard and, on the other end, to the ceiling above the door catch. The whole thing tucks up behind the interior door trim.
Much of the inflation time of frontal air bags is the time they need to unfold, says Kompass. Our bag inflates in just 20 milliseconds. A small explosion fills the bag with superheated gas, which keeps it inflated for several seconds--long enough to protect the head in cases in which the car rolls.
To make the concept work, Kompass and Yaniv had to develop a balloon that could expand instantly, accept the hot gas without bursting, and be easy to stow in narrow spaces. They also came up with a thin sleeve strong enough to hold the balloon in its wiener shape. The hardest thing was to make the components reliable and still thin enough, Kompass says.
BMW engineers have put the finishing touches on the Inflatable Tubular Structure, in time for the company’s 1997 models.
Ergenics’s and National Renewable Energy Laboratory’s Cold-Start Catalytic Converters
Innovators: Mark Golben, David Benson, and Tom Potter
Catalytic converters are good at removing most of the noxious gases from car exhaust, but they have a big drawback: they work only when the car is warm. Consequently, automobiles emit as much as 70 percent of their pollutants in the first two minutes after starting up. Two engineering companies have independently come up with different ways of solving this cold-start problem and making converters more efficient.
Mark Golben got his inspiration from a newspaper article about a researcher who used an electric heater to warm a catalytic converter to working temperature in a few seconds. Rather than using costly electricity, however, Golben thought of heating the converter with the alloy metal hydride. When a hydride absorbs or releases hydrogen, the reaction creates instant temperature swings--often dramatic--that are very predictable, he says.
Golben and his research team at Ergenics in Ringwood, New Jersey, designed a heater to be mounted in the exhaust system just upstream of the catalytic converter. The heater includes two containers of metal hydrides-- one at a higher pressure than the other--separated by a valve wired to the vehicle’s ignition key. When the engine starts and the valve opens, the hydride in the pressurized container releases hydrogen, which flows to the low-pressure container and is absorbed. This reaction releases sufficient heat to warm the car’s exhaust to 750 degrees Fahrenheit, enough for the converter to begin working. As the engine warms up and the exhaust temperature rises to 1000° F or higher, the low-pressure alloy heats up and pushes the hydrogen back through the valve to its original container, resetting the mechanism for the next trip.
Golben finished the heating system last summer, and Ergenics is looking for partners to help commercialize it. Expected to cost no more than $100, the heater could be retrofitted to an old car. Right now our heater assists a vehicle’s catalytic converter, Golben says. Eventually, it could become the converter.
David Benson and Tom Potter at National Renewable Energy Laboratory in Golden, Colorado, took a different approach. They developed a catalytic converter so well insulated that it stays warm almost indefinitely. To trap heat, the converter is surrounded by vacuum insulation--two sheets of metal with a vacuum between them--which works like a thermos bottle, Benson explains. The half-inch space between the insulation and the converter is filled with an aluminum-magnesium alloy, which melts and absorbs heat when the converter gets hot. Later, when the converter cools, the alloy solidifies, giving up heat to the converter.
To keep this well-bundled converter from overheating, Benson’s group also adds a bit of metal hydride to the vacuum layer to help regulate the temperature. As the converter’s temperature rises above 1100° F, the hydride begins to release hydrogen into the vacuum. The hydrogen conducts the excess warmth away. When the engine is turned off and the converter begins to cool, the hydride reabsorbs the hydrogen and restores the vacuum layer’s effectiveness.
In tests, the National Renewable Energy Laboratory’s converter was found to stay warm for 61 hours after the engine was turned off. Since 98 percent of all car trips occur within 24 hours of each other, that amounts to a possible reduction of more than 70 percent in auto emissions. We’re being encouraged by the Big Three automakers, Benson says. We’re on a fast track with this.
Awake at the Wheel
Nissan’s Drowsiness Monitor
Innovator: Hideo Obara
To keep drivers from nodding off, Nissan developed a device back in 1983 that triggered an alarm when the steering wheel moved erratically. But the auto company found that by the time the driver begins moving the wheel, it is sometimes too late to prevent an accident.
In 1990, Nissan engineer Hideo Obara and his team came up with a way of catching drowsy drivers earlier. They mounted a camera on the dashboard to peer into the driver’s eyes and make sure they were open and alert.
When the driver starts the car, the camera takes a snapshot of his face and records an image of his eyes. Throughout the trip, the camera continuously scans the driver’s face while an onboard computer compares the pictures with the original image to make sure the eyes are still open and that they aren’t drooping or being diverted for too long from the road. The computer uses all this information to generate an alertness rating, and if it falls too low, a loud buzzer startles the driver back to full consciousness. At night an infrared lamp illuminates the driver’s face.
Although the system is still stumped by drivers who wear sunglasses, the most difficult problem in creating it was helping the computer locate the driver’s eyes and do it within a set period of time, recalls Obara. Our technique begins by measuring the driver’s facial outline and then defining the possible areas where the eyes might be.
Obara and his team completed tests of the drowsiness monitor in 1995, but until there is consumer demand for what would be a pricey system, Nissan has no plans to build the monitor into any of its cars.
Nissan developed the monitor as part of a demonstration of several new safety technologies, including a device that releases a bracing fragrance when the driver dozes, and another that brakes the vehicle and flashes its warning lights if the driver can’t be roused.
Volkswagen’s Quiet Diesel Engine
Innovator: Karl-Heinz Neumann
Because diesel fuel is cheaper than gasoline and burns more efficiently, with less carbon monoxide in its exhaust, diesel-powered cars are, in principle, a good idea. The problem is noise. Instead of using spark plugs to ignite their fuel, diesel engines rely on pistons to compress the fuel-air mixture, creating enough heat to set off a loud explosion. A diesel engine would roar like a tank without modifications that end up sacrificing its wonderful fuel efficiency.
Ever since the U.S. auto industry’s brief infatuation with diesel cars in the 1970s, their waning popularity has bothered Karl-Heinz Neumann, the director of diesel engineering at Volkswagen. After studying the problem for 15 years, Neumann and his team of engineers came up with a quieter way to ignite the fuel. Instead of dumping fuel into the cylinder and exploding it in one big bang, Neumann’s method is to squirt in the same amount of fuel but slowly, over a longer period of time. As a result, the fuel burns in a series of small, quiet explosions. Called turbo direct injection, or tdi, this engine ensures more thorough burning of fuel.
To make the process work, Neumann had to devise an elaborate electronic circuit that translates the pressure of the driver’s foot on the gas pedal, and dozens of other factors, into perfectly timed explosions of fuel in the cylinders. A particularly delicate challenge was to design the engine geometry to ensure optimum efficiency--each piston ends in a bowl shape, for instance, to promote better mixing of the fuel. The amount of fuel the tdi injects is calculated against the precise diameter of the injection holes and also the shape of the hole, Neumann says. This is the basis of the tdi system.
Volkswagen introduced Neumann’s turbo direct injection engine in its 1996 Passat, which gets 45 miles to the gallon on a highway and 37 miles to the gallon in city traffic--all the while puffing out 20 percent less carbon dioxide than today’s typical gasoline engine.