A Year of Stability
“Your mileage may vary.” Yes, indeed—it could be as much as 30 percent lower than government ratings, as some new owners of hybrid-electric vehicles discovered, to their dismay, last year.
If 2004 began with drivers in the United States and a few other places giving hybrids a heartfelt hug, it ended with a more subdued embrace. One of the reasons was disappointment over real-world mileage. Official ratings for fuel use, based on the outdated driving patterns of U.S. government tests, turned out to be a poor predictor for what typical buyers could expect.
But if the hybrid honeymoon is over, the marriage is still in solid shape. In some areas, a buyer must wait months for a Toyota Prius. Toyota plans to build 100 000 Priuses in 2005, up from 67 000 last year. Waiting in the wings is the Lexus RH 400h luxury hybrid sport utility vehicle, now scheduled to go on sale 15 April in the United States. As of December 2004, buyers had already paid deposits for half of the year’s production of 20 000.
Hybrids are now also offered or planned by Ford, General Motors, Honda, Nissan, and Toyota. GM and DaimlerChrysler announced that they would get together to develop a full-hybrid system to be offered in the 2008 model year. Even Porsche confirmed that it might license Toyota’s hybrid technology for its sport utility Cayenne, infuriating die-hard fans of the company’s signature lithe, high-performance sports cars.
Still, though hybrids are hot, no single vehicle is likely to make as much of a splash this year as the revamped Prius did in 2004. The closest thing to a recurring theme in 2005 will be electronic stability control. It will shift from an expensive option to a necessity on the tall, heavy sport utility vehicles that still make up one of the most popular categories in the United States. Daimler, Ford, and GM announced that stability control would be standard on all their SUVs by the 2007 model year. The notice followed the release of a study by the U.S. National Highway Traffic Safety Administration that found stability-control technology reduced single-vehicle crashes in SUVs by 67 percent and fatal crashes by 64 percent.
Among concept cars, hybrid electrics are still going strong, and more of them are being built with lithium-ion batteries rather than the standard nickel-metal hydride. Lithium-ion, now used mostly in consumer electronics, offers close to twice the energy density of nickel-metal hydride. The wildest lithium-ion vehicle so far has to be the luxury-sedan concept Eliica from Keio University in Japan, reminiscent of nothing so much as the nuclear-powered, six-wheeled pink Rolls-Royce that ferried Lady Penelope Creighton-Ward in the 1960s children’s TV puppet show “Thunderbirds.” Built by a team from the Electrical Vehicle Laboratory at Keio University’s Faculty of Environmental Information, the Eliica has eight wheels and a projected top speed in excess of 368 km/h (229 mph). Unlike Lady Penelope’s car, it will not be offered with a machine gun that deploys from the front grille.
Elicia: Eight wheels, eight motors, no tailpipe
Eight-Wheelin’: There are no plans to put the stunning Eliica electric car in production. But that fact hasn’t prevented its designers from estimating that a massproduced version would sell for US $380 000. Photo: Bruce Osborn/Ozone
Aficionados know that every auto show has its share of malproportioned design exercises, technical oddities, and just plain weirdness. But to make jaws drop in awe at an international auto show—that takes some doing.
Hats off, then, to the students at the Electrical Vehicle Laboratory at Keio University’s Fujisawa, Japan, campus. Their , unveiled at the last Tokyo Motor Show, has a 60-kilowatt motor, including the reduction gear, wheel bearing, and brake, in each and every one of its wheels—all eight of them. The advantages of using eight small wheels rather than four larger ones, says the Keio team, include increased interior space, better road holding (owing to the greater tire contact area), and a more comfortable ride (because shock absorption is spread over twice as many wheels). It can supposedly go from zero to 100 km/h (62 mph) in four seconds. A version tuned for top speed is said to exceed the 368 km/h (229 mph) it has recorded in tests.
The 328-volt battery pack itself, along with the inverters and all control electronics, is sandwiched in a trough just 15 centimeters high in the vehicle’s flat floor. A version tuned for fastest acceleration can generate torque of 100 newton-meters at each wheel motor and can accelerate the car at a G-force of 0.8. That version’s range is approximately 320 km (200 miles); it requires up to 10 hours to recharge from full discharge.
The first two axles are mechanically steered, and the wheel angle on the rearmost one is varied electrically to assist in cornering. Shock absorbers on each wheel pair are hydraulically connected to spread the force of wheel movement. The driver can command the vehicle to park itself—in garage spaces or parallel—as well as to make U-turns.
The car was created in partnership with 38 companies. The drag coefficient of a model built to one-fifth scale is just 0.17, better than that of any current production vehicle, though no figures have been released for the full-size version. And there’s no typo in that name: it’s short for Electric Lithium Ion Car, of course.
2005 Land Rover Discovery/LR3: Switch-hitter
Like all Land Rovers, the (called the LR3 in the United States) offers permanent all-wheel drive, with power distribution constantly adjusted among the wheels based on traction. By itself, that isn’t a big deal—US $23 000 Subarus do the same. The advance comes in a new Land Rover system called Terrain Response, which adds a host of control features on top of the Dynamic Stability Control pioneered by Land Rover’s Ford-family sibling Volvo in the XC90 sport utility vehicle.
A rotary switch on the Discovery’s center console lets the driver select one of five terrain types: general on-road driving, mud and ruts, rock crawl, grass/gravel/snow, or sand. Based on this setting, Terrain Response alters key vehicle subsystems to optimize performance. Those subsystems are the engine management system, the air suspension on all four wheels, the six-speed automatic gearbox, and the center and rear differentials, which allocate power among the wheels, both back to front and side to side.
Depending on the conditions selected, the system alters the throttle’s programmed responses to inputs within the engine management system, as well as parameters in the other subsystems. For example, if the driver has chosen the grass/gravel/snow, mud-and-ruts, or rock-crawl setting, the gearbox will reduce torque at the wheels (to prevent slip) by selecting a higher gear with early upshifts and late downshifts.
For grass/gravel/snow, the differentials respond with increased preloading and more aggressive responses to slip. This response is at its highest in rock-crawl mode, when torque locking—which prevents each wheel from spinning faster than its counterpart on the other side of the vehicle—is held for a given steering input. That prevents wheel spin, which helps keep the vehicle from sliding sideways.
The results have generated raves from normally skeptical reviewers. In a private message, one driver of the first LR3 to reach Northern California wrote, “It is unfazed by wet, grassy slopes either up or down, and the hill-descent control is pretty amazing—it used the braking system to keep the vehicle at a walking pace. On an unplowed side road, it just crawled up the steep hill like nothing at all....You barely knew the surface was slippery.”
2005 Acura RL: All-wheel drive that handles like rear-wheel drive
Front-wheel- or all-wheel-drive automobiles now account for more than half the cars sold in the United States. It’s no wonder: with at least some power applied to its front wheels, a car has much better traction on icy or slick pavement. But for the highest-performance cars, engineers usually fall back on powertrains that deliver all or most of their power through the rear wheels.
The automotive ideal would be a car that combined rear-drive handling characteristics with the traction benefits of all-wheel drive. And the US $48 000 , which tackles the problem electronically, comes about as close as any car ever has. The largest and most powerful sedan offered by Acura, the RL has a 3.5-liter V6 engine with variable valve timing. It generates 223 kilowatts (300 horsepower) and 353 newton-meters (260 pound-feet) of torque. Among other advances, it has a five-speed automatic transmission that the driver can manually shift by pressing “paddles” mounted on the steering wheel—right paddle to upshift, left paddle to downshift—mimicking the sequential-shift systems on such exotic performance cars as Ferraris.
The RL’s all-wheel-drive system dynamically apportions torque not only front to rear but also between the two rear wheels. The basic idea is to compensate for the wheel spin that can occur when the inside wheel starts to lose adhesion as the weight of the vehicle shifts to the outside on curves and the car tries to “understeer,” or continue moving straight ahead.
The traditional solution is a limited-slip differential, which mechanically limits the two rear wheels to rotating at close to the same speed. Acura’s solution, which offers smoother power delivery without the occasional jerkiness of the mechanical solution, continuously analyzes and allocates torque between the two rear wheels to prevent that inside wheel spin. At the same time, in less strenuous driving or when adhesion (calculated from wheel-rotation rates) varies among the four wheels, the system dynamically allocates torque among them to confer the traction and stability advantages of all-wheel drive.
Acura calls the technology, with standard auto-industry bombast, the Super Handling AWD System. It builds a planetary-gear set into the transfer case, which apportions power to the wheels front to rear, varying torque distribution by up to 70 percent in either direction and increasing drive-shaft speed to the rear. To divide the torque between the rear wheels, the system monitors driver control inputs, engine-control-unit data, steering angle, G-forces, wheel rotation speed, and yaw rate to control two electromagnetic clutches in the rear differential. These apportion up to 100 percent of the torque to either wheel as needed, adding torque to the faster-rotating wheel in a turn. So far, critics have largely agreed that the RL handles like a rear-drive performance car.
Among the RL’s other technological attractions is the first North American application of a real-time traffic information system, which downloads continuously updated accident, road-construction, and traffic-flow data via XM Satellite Radio. This AcuraLink system also delivers maintenance reminders and engine diagnostic information directly to the car, offering the potential for on-the-fly software updates, along with the usual nagging to take the car to the dealer for its oil change.
2005 Toyota Vitz CVT4: Lithium-ion to go
Toyota often tests new and advanced technologies in the Japanese market years before launching them elsewhere. For example, all-wheel drive using only an electric motor to power the rear wheels—soon to be offered on the company’s Lexus RX 400h luxury hybrid sport-utility—was first seen on hybrid delivery vans sold only in Japan.
So it’s worth looking at one home-market version of the , a small four-door hatchback related to the Echo sold in North America. Along with a continuously variable transmission (CVT), the CVT4 model features a 14.4-volt, 12-ampere-hour, four-cell lithium-ion battery pack—the first in a low-cost production vehicle. The battery is part of the car’s idle-stop system, which shuts the engine off when the car stops, switching to those battery cells to power the lights, heater, air conditioner, and radio. The cells also restart the engine when the driver releases the brake. Unlike those in a full-hybrid system, the Vitz’s batteries don’t actually move the car.
The batteries are charged by the engine’s alternator as well as through regenerative braking. A motor-driven hydraulic pump keeps pressure on the pulley of the CVT to ensure the car can move away from stops without pause.
The small Vitz batteries store about 180 watthours, equivalent to a couple of laptop batteries. But the resulting fuel economy in highly urban Japanese driving cycles is impressive: 3.92 L/100 km (60 mpg), the highest in Japan for vehicles other than hybrids or microcars.
The Vitz is not the first Japanese-market auto ever to use lithium-ion batteries. The Nissan Almera Tino Hybrid was powered by a 1.8-liter, 74-kilowatt (99 horsepower) four-cylinder engine, combined with a three-phase 20-kW electric motor driving a CVT. Its 345-V, 25-kW lithium-ion battery pack lets the electric motor power the vehicle from a stop and at low speeds and also lets it supplement the engine under higher load conditions. Nissan built only 100 Tino Hybrids, however.
Lithium-ion batteries do have some drawbacks. Most use metal-oxide cathodes that are highly flammable when heated. Also, calendar life, as opposed to just accumulated charge-discharge cycles, is a concern for lithium-ion batteries. Still, energy densities of 110 to 130 Wh per kilogram, as compared with, typically, 60 to 70 Wh/kg for nickel-metal hydride, make them extremely attractive to automakers. Last June, Japan’s Hitachi, Hitachi Maxell, and Shin-Kobe Electric Machinery Co. announced they had formed a joint venture to make rechargeable lithium-ion batteries specifically for hybrid cars.
2005 Mercedes-Benz E320 CDI Feel the pressure
Mercedes-Benz introduced the world’s first diesel-powered passenger car, the 260D, in 1936. Sixty-nine years later, Benz is among the handful of European manufacturers setting the standard for diesel design. Diesels now make up 40 percent of the company’s global production, and in some European countries—including Austria, France, and Spain—more than half the cars sold are diesels, a result of such factors as favorable fuel taxes and relatively loose standards for particulate emissions.
Drivers in the United States, however, have yet to warm to diesel engines. Diesel fuel there isn’t significantly cheaper than gasoline. Worse, the engines have a reputation for smokiness and unreliability dating back to the notorious Oldsmobile diesel V8s of 1978 to 1985.
So the —one of just seven diesel passenger vehicles available in the United States this year—had to be bulletproof and more. The defining components of the E320 CDI, a turbocharged diesel variation of the popular E320 sedan, are its electronic engine-management system and its common-rail direct fuel injection. Together, these improve the accuracy of fuel metering, allowing unprecedented combustion control that keeps particulate emissions within U.S. standards—the strictest in the world.
Forcing fuel into each cylinder of a diesel engine through its own seven-nozzle solenoid injector, with a compression ratio of 18:1—twice that of spark-ignition gasoline engines—requires pressures of 159 000 kilopascals (23 000 pounds per square inch). That’s 70 percent more pressure than would be typical in an older diesel fuel-injection system using a distributor pump. Even a few years ago, to achieve this kind of pressure reliably was considered impossible.
In the new systems, electronics control not only the fuel pressure, injection timing, and injection duration but also key parameters of the turbocharger, an auxiliary pump driven by exhaust-gas pressure. The turbo’s purpose is to generate more power by cramming more air into the combustion chamber at greater pressure (or “boost”), enabling the engine to combust more fuel at the correct ratio. Electronics control the speed and boost of the turbocharger, whose output nozzle can be reduced in diameter automatically to provide higher pressure as the engine starts to rev from idle, and expanded for greater overall boost at higher engine speeds. This control more accurately pressurizes the charge at low revs, compensating for the effect known as “turbo lag,” in which the turbo takes a second or more to rev up to optimal boost pressure.
The turbodiesel is more economical, with fuel usage figures roughly equivalent to those of the Honda Accord Hybrid: 27/37 mpg (8.7/6.4 L/100 km) in the U.S. Environmental Protection Agency’s combined city/highway cycle. For comparison, the gasoline-powered E320 gets 20/28 mpg (11.8/8.4 L/100 km).
The diesel’s 3.2-liter, 24-valve inline six develops 150 kilowatts (201 horsepower) at 4200 revolutions per minute and 500 newton-meters of torque at a characteristically low 1800 to 2600 rpm. This year, the E320 CDI will be sold only in the 45 U.S. states that have not adopted the California emissions standards, which are even stricter than the U.S. federal ones. Mercedes-Benz expects the car to meet the California requirements once low-sulfur diesel fuel is available throughout the United States in late 2006.
Similar control and injection technology is used in the new Jeep Liberty CRD’s 2.8-L four-cylinder turbodiesel engine, from diesel specialist VM Motori SpA of Cento, Italy. By the way, the US $25 125 suggested retail price of the Liberty CRD is $2000 more than the price of the gasoline-powered equivalent but $25 000 less than that of the new Benz.
2005 Venturi Fétish Makes Ferraris seem so common
Yes, it is a production car. Only 25 copies, granted, each one built to order at a cost of ¤540 000 (roughly US $705 000)...but Venturi is a legitimate low-volume manufacturer that has been around since 1984. Based in Monaco since declaring bankruptcy four years ago, the formerly French company seized center stage at the Paris Motor Show last year by repositioning its as the world’s first production electric supercar.
It certainly has supercar specifications. The car weighs just 1100 kilograms, including the batteries, and the company says it accelerates from zero to 100 km/h (62 mph) in 4.5 seconds. That’s slightly faster than a Porsche 911 Carrera S. The advantage of an electric car, of course, is that peak torque is available immediately and pretty much noiselessly. The Fétish’s top speed, however, is a less enthralling 170 km/h (105 mph).
The car’s sole power plant is a 180-kilowatt (241-horsepower) electric motor that can spin at 14 000 revolutions per minute. It’s mounted behind the seats and powered by 350 kg of lithium-ion batteries. Venturi quotes a range of 350 km (220 miles), adding that the car’s 80-ampere recharger stores enough energy for 1.6 km every minute, “easily covering the needs of daily urban transport.” But let’s face it, does anybody really spend upwards of $700 000 on daily transport?
The Fétish gains a measure of credibility from electric-vehicle R&D firm AC Propulsion Inc., of San Dimas, Calif. Company founder Alan Cocconi has designed many electric drivetrains, including the one for the GM Impact, forerunner of the late, lamented GM EV1 electric car. Venturi uses AC Propulsion’s drive and battery systems in the Fétish—essentially the same technology that is going into another AC Propulsion project: all-electric conversions of Toyota’s boxy, utilitarian Scion xA and xB vehicles.
2005 Honda Accord Hybrid: The invisible hybrid
Toyota’s coolly futuristic Prius is instantly recognizable—one automotive writer likened it to a “set piece from a Kubrick film.” Honda, on the other hand, has lately taken a different design tack with its hybrids. Its tiny two-seat Insight, introduced five years ago, was designed from the ground up as a unique vehicle, but since then Honda’s hybrids have been visually indistinguishable from standard models. In 2002, the Civic Hybrid offered a “mild hybrid” system—the electric motor supplements the gasoline engine but cannot move the car by itself—and now the company has taken the same approach with the larger .
Honda’s Integrated Motor Assist System consists of a 12-kilowatt (16-horsepower) electric motor, just 68 millimeters wide, mounted between the engine and the transmission. It is powered by a 6-ampere, 144-volt nickel-metal hydride battery pack. The motor is mated to the same 179-kW (240-hp), 3-liter V6 engine that powers top-of-the-line Accords. The added power, instantly available from the electric motor on takeoff, cuts the hybrid’s zero-to-60 mph (97 km/h) acceleration time to 7.5 seconds, from the 7.9 seconds of a regular V6 Accord, according to Honda.
The car’s idle-stop feature shuts off the engine whenever the car stops. When the engine is off, Honda, like most manufacturers, maintains the functions of its accessories, such as the air-conditioning compressor, by switching them from mechanical to electric power.
While full hybrids such as the Toyota Prius and the Ford Escape use continuously variable transmissions (CVTs) to maximize mileage, the Accord Hybrid uses a conventional, electronically controlled five-speed automatic. The resulting driving experience is identical to that in a regular car, whereas a CVT user is sometimes nonplussed to find the engine speed rising or falling independently of road speed.
At cruising speed, Honda shuts down half of the cylinders in the V6 hybrid to cut down on fuel usage. The problem with running on three cylinders is that the uneven firing of the odd number of cylinders causes a booming vibration. Honda cleverly masks it with an active noise-control system that uses input from the engine-control unit and microphones in the headliner and the rear parcel shelf to generate opposite-phase “negative noise” through the audio system.
At a price of US $29 990, the Accord Hybrid costs $3400 more than its closest nonhybrid counterpart, the luxury Accord EX Sedan.
2007 Saturn Vue Hybrid A “value hybrid” Among major automakers, General Motors will arrive relatively late to the hybrid party. Its first high-volume offering, a mild-hybrid version of the sport utility, won’t arrive in showrooms until fall 2006.
The company’s goals are ambitious: provide a low-cost system that is simple and modular enough to be easily integrated into other vehicles, perhaps one day becoming more common than today’s inefficient alternators. GM’s stated target for fuel savings is a 10 percent improvement over the conventional Vue in combined city and highway use, says Steve Tarnowsky, the assistant chief engineer for the system.
The vehicle will use a 2.4-liter version of GM’s ubiquitous Ecotec four-cylinder engine. However, the hybrid will shut it off during idling, deceleration, and stops. A motor/generator unit will sit in the same position as the conventional car’s alternator, replacing both it and the starter.
The extra control logic for the hybrid system is integrated into GM’s highest-capability engine-control module—one usually fitted to big engines with multiple cam phases rather than the Vue’s simpler four-cylinder. This module controls the power electronics that convert the generator’s three-phase, 42-volt ac into dc to charge the hybrid system’s 36-V battery during regenerative braking and when engine load is low. It also inverts that battery’s voltage to power the motor, so it can supplement the engine, and it replaces the alternator to charge the separate 12-V lead-acid battery used for lights, power steering, air conditioning, and the like.
The biggest design challenge actually didn’t involve the control electronics, Tarnowsky says. Rather, it was creating a sufficiently robust accessory belt system so the motor/generator could both receive power from the crankshaft and spin the crankshaft when restarting the engine after idle-stop. On nonhybrids, this belt uses torque from just a single source—the engine’s crankshaft—to spin the alternator and other accessories, such as an air-conditioning compressor. Coping with the two different torque modes greatly increases the mechanical demands on the Vue’s belt, which has seven plies (one more than usual). And the designers ultimately had to deploy two different belt tensioners, rather than the usual one, to keep the belt tight enough to drive all the components on it.
Ahnold’s Hummer: Hydrogen or Hot Air?
No stranger to elaborate photo ops, California Governor Arnold Schwarzenegger arrived at a newly built hydrogen fueling station at Los Angeles International Airport this past October in a gleaming dark-blue hydrogen-powered Hummer. The cameras clicked and the video rolled as 300 dignitaries watched the smiling governor lift a hose from the pump and put it into the Hummer’s fuel filler. The implication: his “hydrogen highway” of refueling stations, a key promise of his campaign, had arrived.
What’s wrong with this picture? First, no hydrogen was actually transferred into the Hummer; the station wouldn’t open for another month. Second, it wasn’t Schwarzenegger’s Hummer at all, but a one-off research vehicle constructed by General Motors. Third, GM had actually built the vehicle at his personal request. And fourth, the station is unlikely to open to the general public for five or more years.
The is so far GM’s only foray into hydrogen-powered internal combustion (IEEE Spectrum covered the Ford Hydrogen Hybrid Research Vehicle, or H2RV, in last year’s “Top 10 Tech Cars”). The H2H uses the Hummer H2’s standard 6-liter V8 engine, which delivers 134 kilowatts (180 horsepower) under hydrogen power with the addition of a supercharger. The 350-bar compressed hydrogen fuel system includes three carbon-fiber fuel tanks, storing a total of 5.5 kilograms of hydrogen. Despite all that fuel storage, the 2950-kg vehicle can go only 97 km (60 miles) after a fill-up.
The U.S. armed forces, which buy the military Humvee that sired the consumer Hummer, have no interest in the hydrogen Hummer. The U.S. Marine Corps, for example, is now testing a fast, quiet vehicle called the Reconnaissance, Surveil-lance, and Targeting Vehicle, or RST-V, nicknamed “the Shadow” [see “U.S. Military Goes for Hybrid Vehicle,” IEEE Spectrum, March 2004]. Even with armor, this diesel-electric hybrid weighs half as much as a standard military Humvee, which has no armor. It’s driven by four 50-kW in-hub motors, two lithium-ion battery packs with peak power delivery of 80 kW and a 20 kilowatthour capacity, and a 103-kW (138-hp) turbocharged 2.5-liter diesel engine. It can travel at 100 km/h and go 32 km on battery power alone, allowing silent movement with low thermal signatures. A 60-kW generator is built in, and the Shadow is small and light enough to be carried in a V-22 Osprey tilt-rotor aircraft.
It just makes the Hummer seem...oh, very last year, doesn’t it?
Michelin “Concept”: It’s all in the wheels
In just six years, the Michelin Challenge Bibendum has become the showcase for environmentally friendly automotive technology. Last year’s event, held in Shanghai, China, in October, attracted more than 150 vehicles. And for the first time, sponsor Michelin entered two concept vehicles of its own creation, which it designed with partners at its network of research centers. While the company doesn’t plan to enter the car market, according to Michelin engineer and spokesperson Pierre Varenne, it does want to offer new electromechanical technologies to its automaking customers.
One of the two research vehicles, known simply as the , was a skeletal structure that served as a platform for the company’s new Active Wheel Technology. The car contains a 73-kilowatt (98 horsepower), 1.1-liter, air-cooled flat-twin gasoline engine, but that’s hardly the point. In fact, the engine has no mechanical connection to the car’s drive wheels. It simply powers a central generator, whose outputs to four electric motors—one in each wheel—actually move the vehicle. The electric power also operates the electric active-suspension and chassis-stability control systems.
Each of the four 30-kW electric motor/generators powers its own wheel and regeneratively brakes it, too, in combination with more traditional disk brakes. Packaged with each motor are not only the traditional springs that suspend the wheel but also electrically actuated dampers. Together they constitute the suspension. All shock absorbing and attitude control is done by the electric dampers, so the driver can vary the car’s handling and other factors—including ground clearance, which can be raised from 10 to 35 centimeters. Basically, the handling can be varied from a smooth ride that absorbs bumps to firmer, lower-roll settings for more aggressive driving. And as Lotus demonstrated to amazed journalists 20 years ago on an experimental Esprit, such a suspension even lets a car be programmed to bank inward on turns, as a motorcycle does.
The approach offers vehicle designers tremendous packaging flexibility by removing lots of components from the mix. With the electrical technologies integrated into the wheels, the Concept needs no transmission, clutch, differential, drive shafts, constant-velocity joints, shock absorbers, or antiroll bar.
Traditionally, the drawback to wheel motors is what designers call “unsprung weight,” or the relatively high mass of the motor components in addition to that of the wheels, whose movements the suspension must accommodate. The more mass in the wheels, the beefier the suspension must be—increasing weight and complexity. Michelin’s Varenne, however, notes with pride that the mass of each wheel and its motor unit is just 30 kg, roughly comparable to that of a wheel in a standard vehicle.
2006 Infiniti M Series: More alert than you are?
Drivers in the United States have shown little tolerance for audible warning systems in their vehicles. Recorded voices that complained of doors ajar have become amusing footnotes in automotive history, and most drivers will grudgingly tolerate a few seconds of buzzing at most to be reminded that a seat belt is not buckled.
So you’ve got to admire Infiniti’s audacity. The forthcoming series of luxury performance sedans will offer an optional lane-departure warning system to warn, with a buzzer and flashing dashboard light, if the car seems to be drifting out of its lane.
There’s good reason to hope that this system does not go the way of the talking dashboard. A study of 2001 data by the U.S. National Highway Transportation Safety Administration recently concluded that 55 percent of fatal accidents involved lane departure. Developed by Iteris Inc. of Anaheim, Calif., and Valeo S.A. of Paris, Infiniti’s system consists of a tiny digital video camera mounted above the rearview mirror and facing forward through the windshield. At speeds above 72 km/h (45 mph), control algorithms interpret the camera’s image-processed output to interpret lane markings in the area 6 to 10 meters ahead of the car. Based on vehicle speed, the car’s distance from the lane marking, and the lateral velocity toward the marking, the system judges whether the vehicle is about to move out of the lane.
The warning system operates only when it can discern lane markings—and it is silenced if the driver activates the turn signal (the driver can also switch it off at any time). The entire package—including a low-power Intel microprocessor, ASICs, and a CMOS image-processing circuit—is contained on a single circuit board slightly larger than a credit card. Francis Memole, general manager for automotive sensors at Iteris, boasted that his company’s system is the only one so far that can handle the challenging task of making visual sense of North American roads, which are often scarred from snowplowing and other abuse and which may be adorned with raised “Bott’s Dots” and other reflective markers.
Infiniti actually launched the lane-departure system last fall on the 2005 FX45, the company’s audaciously styled sport utility built on a version of the Nissan 350Z sports-car platform. Besides lane-departure warning, the M series will offer active rear steering, in which electronically controlled actuators slightly vary the geometry of the rear wheels based on front-wheel steering inputs, acceleration, speed, and other factors. This system provides better handling and slightly tighter turns.
About the Author
John Voelcker has written about automotive technology, home building, and other topics for 20 years. He covered software and microprocessor design for IEEE Spectrum from 1985 to 1990. A connoisseur of vintage British automobiles, he has owned five Riley One-Point-Fives, four Morris Minors, three Pontiac GTOs, and a handful of Subarus.