Sensing and safety is fully embedded in vehicles.

New sensors, new uses of existing sensors, and the drive to integrate sensors and electronic control units (ECU) are making the various embedded systems sprinkled throughout today's vehicles more compact, economical, convenient, and reliable, as well as easier for automakers to install and invaluable to driver safety, emission control, and vehicle operation.

DOING A LOT MORE SAFETY WITH LITTLE

"Automotive safety in terms of active safety is starting to get a lot of traction, no pun intended," states Glenn Widmann, when explaining the trends in safety systems. He's the chief engineer for integrated safety systems for Delphi Corp. (Troy, MI; www.delphi.com). "Once you put cameras, radars, and lasers on a car, you start coming up with a plethora of new product ideas." In short, putting multiple functions and features on the same sensor reduces costs, increases functionality, and adds a lot of bang for the buck.

For instance, camera-based lane departure warning systems use a monocular camera mounted behind the windshield to track lanes in front of the vehicle. Software estimates lane width, road curvature, and determines the vehicle's heading and lateral position in the lane. If the vehicle strays out of its lane, the system issues an audible, tactile, or visual warning to the driver.

That same sensor--the camera--can diversify into pedestrian recognition, rain sensing, and intelligent headlight control (have headlights come on and off by themselves, change from high beams to low beams, etc.). This integration eliminates systems on vehicles today. For instance, some vehicles come with a specific sensor for differentiating day from night for headlight activation/deactivation. Widmann is quick to point out that a camera-based system would not be added just to distinguish day from night, "But if you're going to have the camera for, say, lane-departure warning, you can certainly do a lot more with it and eliminate some of the other sensors on the vehicle." Follow this trend. Rather than load vehicles with standalone safety modules and systems, where each one has its own ECU, says Widmann, soon there will be a single integrated safety module. This module will host multiple applications that respond to the various inputs coming from sensors planted throughout the vehicle. "You see this in most industries," continues Widmann. "Things start off as standalone systems and then they upwardly integrate."

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Right now there's a hitch to this approach. It's a chicken-and-egg problem, at least on the active safety side. Most of the current safety-related systems are optional. "It's hard to integrate these systems not knowing whether you'll have two or three of them in a vehicle all the time. But as active safety becomes more prolific, driving costs down, they will become standard equipment," says Widmann.

CREATING A "SAFETY COCOON"

What is becoming standard are pre-crash mitigation systems that enhance driver (and occupant) safety along the front, side, and rear of the vehicle, and even inside. For proof, look at adaptive cruise control (ACC), which has been available since the late 1990s. Now, ACC comes with collision warning and other features. These systems can recognize a crash is coming and can actively prepare the occupants in the vehicle for that crash. (Many times when an accident occurs, says Widmann, the driver wasn't doing anything to stop the vehicle. Here's an opportunity to use technology to see a crash coming--and initiate some effective countermeasures. "That's a good thing," muses Widmann.)

Delphi's Forewarn system for commercial vehicles uses a 76-GHz radar sensor to detect and classify vehicles in a truck's path up to nearly 500 feet ahead. The driver is able to set a distance between his vehicle and those ahead; a headway alert feature activates visual or audible alerts to the driver when the set distance shrinks below some predetermined amount. A forward-collision warning feature detects the possibility of accidents by monitoring slower moving or stopped vehicles ahead. When necessary, the system alerts the driver to take appropriate action.

In the last 400 to 500 milliseconds before a crash, the driver really can't do much to avert the accident from occurring. If the precrash sensing system determines that an accident is unavoidable, it will help protect occupants by pretensioning motorized seat belts and applying brakes. Through active braking, "you could probably scrub off 4 to 5 mph in that 400 to 500 milliseconds," says Widmann. "That's a fairly significant amount of crash energy reduction."

EMBEDDED CONTROL LEADS TO STABILITY

The electronic stability control (ESC) systems from TRW Automotive (Farmington Hills, MI; www.trwauto.com) automatically correct vehicle instability, helping drivers keep their vehicle in control. (According to TRW, ESC can save 7,000 lives per year, and avoid 56% of the single vehicle crashes.) ESC is the latest extension of automotive control technology. First came four-wheel anti-lock brake systems (ABS) in the early 1980s. Traction control was added a half-a-dozen years later. By 1995, ESC was available as optional equipment. Now the TRW ESC product family consists of the EBC 450 for passenger cars and the EBC 455 for light trucks/SUVs.

In operation, ESC monitors vehicle velocity information (wheel speed, yaw rate, and lateral acceleration) and driver inputs (such as steering, throttle, and master cylinder pressure). With this data, the ESC performs two functions. First, it determines the driver's intended path. Second, when the vehicle starts to diverge from the driver's intended path, the ESC intervenes and brings the vehicle back to the intended path. ESC intervention includes activating the brakes on one or more of the vehicle's wheels, as well as reducing engine throttle.

TRW is enhancing its ESC with electric steering systems--steering torque control (STC)--that "coach" a driver to correct vehicle instability by actually turning the steering wheel in the proper direction to avoid skidding/sliding. In so doing, STC helps reduce braking distances by as much as 8% at 50 mph on some road surfaces. TRW has also integrated ESC with ACC to provide precrash and automatic emergency braking. Together, the systems can slow a vehicle significantly--up to 0.6g--before a potential accident.

Says Carl Munch, senior technical specialist for TRW Automotive, Safety and Electronics Group, people don't see or feel these safety systems in 99% of the applications. "The only time they notice them is when something bad happens." Or better yet, they see these systems embedded as major selling points in car commercials, as is happening right now.

RELATED ARTICLE: "Printing" Sensors

Sensata Technologies, Inc. (Attleboro, MA; www.sensata.com) applied novel production techniques to their capacitive ceramic sensor technology, which is at the core of their APT products (automotive pressure transducer) used in automotive air conditioners, and in fuel, oil, and manifold air pressure applications. In the past, Sensata individually formed and pressed, then assembled, discrete ceramic elements to make APTs. No longer. Enter "APsquared," the next-generation APT. Sensata now "prints" these ceramic elements on a plate in a process akin to semiconductor wafer fabrication. Because the plates are formed in a high-volume process, the cost of the plates winds up being far less than the cost of the conventional individual elements. The sensors can handle pressures ranging from 100 to 3,400 kPa (other ranges are available), provide EMC protection to 200 V/m, and for generation II or III conditioning electronics, their accuracy is [+ or -] 1% Vcc. A new aluminum hexport of the APsquared pressure sensors is half the weight of their APT counterparts, and provides four times the corrosion protection.

By Lawrence S. Gould, Contributing Editor