Smart sensors help keep you and your car out of harm's way.
Your car may soon be smarter than you, or at least intelligent enough to help you avoid a
Making its way into vehicles in about two years is the active passive-integration approach (APIA) to safety from Continental Teves, Auburn Hills, Mich (www.continentalteves.de). It ties together several automotive safety systems to reduce the chances of an accident to a greater degree than is possible with ABS or stability systems alone. APIA sends information about the driver, vehicle, and the environment to a central danger control module. This module continually assesses accident risk and intervenes when necessary to avoid an accident and prevent injury. Active systems include chassis management, steering, brake control, and stability systems. Passive refers to seat belts, air bags, headrests, and the passenger-safety cage.
Sensors play a key role in the APIA system. Mounted to the front of the car, they gather data on vehicle parameters such as speed and distance of objects in front of the car. A closing-velocity (CV) sensor features a wide short-distance detection range, to 150 m, detecting events in the immediate vicinity of the vehicle. Using infrared-coded laser pulses, the sensor detects the speed, direction, and distance of an approaching object.
The system intelligence is in the danger-control module. This is a piece of software that looks at data gathered from the various sensors, evaluates the data, and assigns a crash probability. Using input from the CV and other sensors, the danger control module can calculate the time before a probable collision to activate smart air bags. A 32-bit microcontroller does the processing and control using fuzzy-logic algorithms. The system uses a CAN bus as the main data link with a bandwidth limited to about one update every millisecond.
If the hazard-potential rating reaches a defined limit, the danger-control module initiates a staged hazard response. If two vehicles are driving nose to tail, various levels of accident risk can be determined from their relative speeds and the distance between them.
For instance, if the lead vehicle brakes, the APIA system warns the driver via a visual display and feedback from an accelerator pedal which can be up to 35 N of counterforce. If the lead vehicle brakes harder, the system registers a quicker rate of closing distance between the two cars. At this point, pressure is added in the brake system, the seat-belt pretensioners activate to take up slack, and side windows and the sunroof close. As the danger potential grows, there's more action such as actively applying the brakes.
The full range of responses described here is available on vehicles fitted with a brake system designed to accept external control signals and equipped with ESC and environmental sensors such as those featured in the adaptive cruisecontrol system. Automatic braking cannot be initiated without the signals from these radar or infrared distance sensors.
The first systems are expected in 2006 model cars, mostly higher-end European models. The system is expected to add about $500 to the sticker price of a new car.
PUTTING IT TO THE TEST
High in the lush green hills of central Germany, on an old U.S. airfield turned test track, I was part of a group of automotive journalists that put the APIA system through its paces, each maneuver posing an escalating chance of a crash.
A BMW 3-Series was outfitted with the CV sensor and the related safety systems. We drove the Beemer behind a dummy target, basically the back end of a car connected to a moving SUV by a boom arm. Sensors on the SUV detect if the test car came too close to the dummy target and would flip the target up to avoid an actual crash.
Depending on the crash potential the control module calculates, the system can take a number of actions to help prevent an accident. Actions in its repertoire include putting a force reversal on the accelerator pedal, applying brake pressure, tightening the belt pretensioner, adjusting the seats, and closing the windows and sunroof.
If we approached the target quickly, the in-dash display would signal we were getting too close. The next sensation was that of the accelerator pedal pressing your foot back and the car slowing down. In other tests the target would brake unexpectedly when we followed too closely. We'd hit the brake and experience a shorter-than-usual stopping time because the system had already been primed to go.
The worst-case scenario is when the system determines that a crash is imminent. Several actions take place almost simultaneously: The gas pedal pushes back, assisted braking kicks in, seat belts tighten, the seat automatically lifts, and the windows and sunroof close.
There are different levels of response to match the perceived danger. The more likely an accident, the more the system does. Yet the primary action, including the ability to manually override the system, is still up to the driver.