The latest driver assistance systems and how they work

You’re driving down the road, and suddenly another car swerves behind you and approaches in your blind spot just as you were preparing to change lanes. Your car gives you a quick nudge on the steering wheel and a soft tap on the brakes, and you’re back in your lane — safe and sound.

Every car maker has at least one vehicle in its line-up equipped with technology-related aids such as automatic parking or adaptive cruise control. In car-industry parlance, these helpers are known as Advanced Driver Assistance Systems (ADAS). The Cadillac STS, the Buick Lucerne, the Mercedes E-350, the Ford Fusion, the Mazda3 and the Infiniti M are all equipped with features that aim to help drive a car better than a human could alone, or least make split-second decisions better.

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The TV commercials spell out the basics: an Audi A8 has lights that swivel around a dark corner in the road, and an Infiniti brakes automatically to prevent a collision. But you might wonder how these features actually work. What is the technical wizardry? To find out, I test-drove several of the models and asked the experts at each company for the nitty-gritty details.

Lane-departure warning

This feature debuted with the Infiniti M in 2001, and it has proven to be a major hit even in relatively less expensive vehicles such as the Buick Lucerne. During a test drive, the Lucerne displayed a subtle green icon in the dashboard showing proper lane alignment, but glowed amber when the vehicle veered off track.

According to John Capp, the global safety director at General Motors, both the Lucerne and several Cadillac models (such as the STS with a premium package) use a black-and-white camera mounted near the rear-view mirror to constantly scan the road using a pattern-recognition system. The camera looks for tonal intensity — interpreting the difference between a bright white or yellow line, for instance, versus a dull gray curb.

Lane assistance warns you when the car veers out of a lane on the highway. Here, a diagram shows how the camera spots white lines on the road and measures vehicle placement.

Capp says GM is evolving the camera to do more and more. In Europe, the Opel Insignia scans road signs to find the current speed and alerts you if you are going too fast, which can be an issue in countries like Germany where the driver might not notice the infrequent speed-limit signs. To make it work, GM programmed the Lucerne’s LDW (lane departure warning) camera for the Opel Insignia to read speed-limit signs.

On Lexus vehicles, lane warnings also use forward-scanning radar to look ahead of your car for other vehicles and identify lane markings and even a dark shoulder (or berm) to warn you about wandering out of your lane, according to Paul Williamson, a Lexus manager who helps train dealers in advanced technology. Models such as the Lexus HS250h can even nudge you back into the lane automatically.

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An upcoming model — the Mercedes GL450 — will also steer you back into the lane with a slight nudge. In the future, this autonomous control will go even further. Research at Stanford University for the DARPA Challenge suggests that auto makers will morph LDW to allow a vehicle to drive without human interaction for long stretches of the highway by using adaptive cruise control and lane-keeping to keep the car going.

Adaptive cruise control

Adaptive cruise control adjusts the speed of the vehicle automatically, according to a pre-set condition (such as 1.5 seconds or 3 seconds) between you and the car ahead. The Lexus LS-430 first introduced this feature in 2000 and called it the Dynamic Laser Cruise Control System. High-end Cadillac and Mercedes models have had this ability for some time, too.

Interestingly, while this feature seems complex, it relies mostly on a Doppler radar system (usually in the front grill) that scans for reflections. In some models, there is a second video camera mounted above the windshield.

Adaptive cruise is one of the most robotic features in cars such as the Mercedes E350. During my test drive, the E350 slowed down gradually, easing me back from a slow-moving vehicle several hundred feet ahead. The technology, called Distronic Plus, lets you configure when the car starts slowing based on distance to the vehicle ahead.

“Currently, the models we offer today work at highway speed but we are quickly moving towards vehicles that work at stop-and-go speeds, slowing you down for a construction zone or traffic jam,” says Capp. “What the system is doing is using a radar that’s picking up reflections and using them with Doppler radar technology. We calculate velocity and distance, and process the image to keep the space between you and the vehicles in front of you.”

This indicator on an Acura ZDX displays an icon that adaptive cruise control is enabled. Adaptive cruise uses radars — not unlike those used for tracking thunderstorms — looking for objects’ reflections.

“These systems have sweet spots in terms of the distance an object can be detected and at what cruising speeds,” adds Rob O’Reilly, a director of testing and measurement at Analog Devices, a company that makes the sensors and computer modules for autonomous controls. The systems run when the car is doing speeds from about 15MPH to 115MPH, and they can spot other vehicles that are up to 492 feet away. “Out of a handful of actual applications, most run in the 60GHz to 80GHz range” to measure the distance between cars, he says. The sensor outputs, in turn, are handed to the main computer — usually located under the dash — with the automatic steering module, brake assembly module and acceleration module located closer to the engine.

Another vehicle, the Volvo XC60, uses a new technology called City Safety that works on city streets. “If a driver is going less than 10 miles an hour in freeway traffic, the car will brake at full force, preventing you from hitting the car in front of you,” says Mike Caudill, an auto expert at NADA Guides, the used-car guides published by the National Automobile Dealers Association. Caudill explains that adaptive cruise at slow speeds would help mitigate fender-benders.

On GM models such as the Cadillac STS, adaptive cruise helps improve gas mileage on long commutes because the computer controls gradual acceleration and smoothes braking. Traditional (standard) cruise control requires “the driver to be on and off the brakes, thus turning the system on and off. Whenever you hit the brakes, it disengages the cruise control,” Caudill explains. “Adaptive Cruise Control allows the car to coast without hitting the brakes. Hitting the brakes forces the car to accelerate more quickly up to the previously set speed. Adaptive will maintain whatever the speed of the car in front of you is . . . and at the distance set by the driver. This helps you save on fuel.”

Assisted parking

Lexus and Toyota have a corner on assisted parking, where you pull up to a free spot and the car automatically parallel-parks for you. This form of robotics is important because, especially for some drivers, the movements can be tricky or even impossible to perform. Lexus’ Williamson says the calculations for self-park are incredibly complex, and include figuring the distance between parked cars, position of the wheels and current speed.

“First, you drive past the open spaces,” says Williamson. “Ultrasonic sensors detect the edge of the cars on each side of the space to determine whether the car can fit in a space,” says Williamson. “Next, we use visual imagery from the back-up camera to ask the driver to confirm which space to use. You click and drag with your finger to select the space, and the car backs you onto the space.”

Sensors on each corner of the vehicle send out a radio signal to bounce off nearby objects and detect obstructions, Williamson explains. Interestingly, the 2010 Lexus LS 600h also uses wheel-speed indicators along with radio sensors to collect, as you slow down, more and more data. For example, the Lexus knows you are at a “pre-park” speed and scans for obstructions in more detail.

On Ford vehicles such as the Flex and Taurus Sho, an Active Park Assist feature uses a combination of robotics and driver assistance. In a test drive, a Ford Flex scanned for open spots and prompted me to slow down, stop and put the car in reverse. Then, the vehicle backed up (rather quickly) and started to parallel park. With the Flex, the driver has to apply brakes as the car enters the spot, then again as the car movies forward. Jerry Krauth, a Luther Auto account manager, says Ford specifically wants to introduce robotics in a way that involves the driver and is not completely autonomous. The company will slowly introduce more AI-controlled features.

Ford’s Park Assist feature helps you find a free spot and park your car. Unlike other self-park features in Toyota and Lexus cars, Ford requires more driver interaction, especially for braking.

One interesting note: None of the car makers says it has plans to offer any extensive re-training for automated features, and there is no certification process in the U.S. for features such as self-parking. As autonomous vehicle operation becomes the norm, car companies may need to add classes or promote government-sponsored instruction for these advanced driving features.

Blind-spot warning

A blind-spot warning alerts the driver with lights near the side-view mirror.

Several current models — including the Buick Lucerne and Ford Fusion — use sensors to detect vehicles approaching next to you. According to GM’s Capp, most blind-spot warnings do not use an audible chime, which can distract the driver, but instead display a light near the side mirror, where the driver is supposed to be looking. This helps avoid crashes caused by distractions, he says. According to Capp, blind-spot sensors scan about six feet away from the vehicle.

Analog Devices’ O’Reilly says most cars with blind-spot warnings use a video camera to detect reflections or, as on the Mercedes E350, use ultrasonic sensors in the 20kHz range to detect movement. The sensors tie into a CPU in the vehicle and compare the data to information from accelerometers for speed detection and steering wheel angle, and link up with gyroscopes that detect the rate at which the wheel is turning (slow, fast or idle).

On the Acura ZDX, the blind-spot sensors use two 24GHz radars to transmit a short radio blip and then listen — using multiple antennas on the car — for a return blip. If the car calculates that the return blip is from another vehicle within a set distance, the car will show the blind-spot warning in the side mirrors.

During my test drive with the Buick Lucerne, the blind-spot indicators were exceptionally precise: Any approaching vehicle would immediately set off an alert in the side mirror. On the other hand, embankments, railings or buildings did not cause a warning.

Collision detection

Several models come equipped with a collision detection and prevention system. For example, the Audi A8 will not only brake slightly if the car senses another car ahead, but will apply brakes in full force if impact is imminent. O’Reilly says these braking systems use an accelerometer — not that different from the one in the Apple iPhone — that senses a rapid change in the tilt of the accelerator. If you are driving normally and suddenly release the gas pedal, the car will boost the brakes with fluid for better braking.

Albert Austria, a senior evaluation engineer at car Web site, says the most advanced collision-detection systems, such as those in Mercedes and Audi vehicles, use sensors to detect the tail lights of the car in front of you. The sensors know the difference between a truck and a tree but, he says, most collision-detection systems cannot identify a fully stopped car because the sensors scan for moving objects. Collision detection works similarly to blind spot and lane-departure warning systems.

“The sensors pick up the objects of interest and send the information to several of the vehicle’s electronic control units (ECUs) which have many microprocessors,” says Austria. “The ECUs have complex algorithms that calculate vehicle intervention and course of action based on many inputs” such as vehicle speed, throttle position, closing distance to object, brake application, yaw (side to side), roll (pivot along a straight line) and pitch (up and down).

On the Acura ZDX, the collision-detection system uses a millimeter-wave radio — the highest radio-frequency band — in the front grille, scanning about 300 feet ahead. Interestingly, this feature, called the collision mitigation braking system, uses responses from the driver to determine how to brake. It first tracks an obstruction in real-time, then alerts the driver visually and audibly, waits for a response, applies slight braking, displays more warnings, then applies full brakes and tightens seatbelts automatically.

Other automation

Some cars use technology to help control other features. One of the more recent models is the Mazda3 (the Grand Touring model with advanced technology package), which has headlights that turn automatically when you drive around a bend in the road instead of just pointing off into the darkness; a weight sensor that moves headlights if you load up the trunk so the headlights point in the right angle and direction; and rain-sensing windshield wipers so you don’t even need to turn them on when it rains.

These sensors on the back of the Buick Lucerne help with parking.

The headlights move by reading the location of the steering wheel, your speed and the pitch of the car on the road via an accelerometer. For adjusting the height of the headlights based on cargo load, the car uses an accelerometer on the right side of the vehicle that determines the current pitch and also takes current speed and the angle of the road (based on ride height) into account. For rain sensing, there is an infrared sensor that projects lights through the windshield. If obscured or diffracted in all directions (e.g., caused by rain water), the windshield wipers start working automatically.

Future features

NADA’s Caudill says other advancements will involve facial recognition and monitoring the health of the driver. For its part, GM is already testing these types of features, Capp says. One of the newest 2010 sensors involves the monitoring of the oxygen and breathing levels of the driver, Caudill says. “It also monitors if the head starts to dip, fall in a way that indicates fatigue.”

Edmunds’ Austria says GPS technology will allow new forms of robotic control. In the future, your vehicle may adapt to changing road geometry such as curves and hills through interaction of the GPS data and your vehicle’s Driver Assist System, says Austria. For example, if you are driving too fast for an approaching decreasing-radius turn, your future vehicle will receive detailed map data from the GPS satellites. “Your car then gives you braking assist, cuts maximum throttle input and the yaw control is heightened to help avoid a spin.”

In the end, technology assists have not only improved vehicle operation, but could even improve the way we drive. “The technology is designed to save lives and it does this,” Caudill says. “It either helps prevent accidents or, in the worst case, helps save lives after the accident has occurred.” Another plus, he says, is that technology like LDW, with its audible alert, makes people more aware of how they drive.

Editor’s Note

Computerworld thanks the following Minnesota- and North Dakota-based car dealerships that allowed our writer to test-drive their vehicles for this story:

MN Motors (Buick Lucerne)

Valley Imports (Mercedes 350)

Luther Auto (Ford Flex)

But in the end, Caudill adds, “We, as a collective industry, need to ensure drivers are paying attention to driving instead of checking their BlackBerrys, e-mail and other forms of distraction. . . in no way are [the technology assists] to be used as a crutch for poor driving habits.”

John Brandon is a veteran of the computing industry, having worked as an IT manager for 10 years and a tech journalist for another 10. He has written more than 2,500 feature articles and is a regular contributor to Computerworld.


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