Safety sells. That statement seems to sum up the general feeling among automotive-components
makers and market analysts. Auto-component makers see a consistently upward track for activesafety
products - devices, systems, and assemblies that aid in crash prevention. And in a November
2006 Texas Instruments white paper titled "Transforming Performance Safety in Automotive
Applications," analysts forecast that active safety and advanced driver assistance systems (ADAS)
will be the top new technology for 2010.
Further affirmation comes from an August 2006 report from Strategic Analytics titled
"Automotive Semiconductor Forecast 2004-2013: Safety and Convenience Electronics Key to
Growth," which predicts high growth in the active-safety industry. Applications showing great promise include
lane-departure warning systems, drowsiness detection, and night vision. The report's authors prognosticate a
compounded average annual growth rate beyond 50% through 2011.
Mandates Mother Invention
Two causes inspire safety innovations: the need to meet governmental
mandates, and the need to add extra end-user value. An April 2005 mandate from the National Highway
Traffic Safety Administration required all new passenger cars and light vehicles manufactured for sale in the
U.S. to be equipped with tire-pressure monitoring systems (TPMS) by September 2007. Vehicles weighing up to
10,000 pounds must include TPMS technology by 2008.
Freescale Semiconductor addresses this initiative with the MPXY8300 TPMS, credited as the first TPMS containing
a capacitive pressure sensor (see "Tires Put Pressure On RF," Sept. 13, 2007, p. 40). Described as a system-
in-package, the MPXY8300 mounts on a board housed in a casing with the air valve. The package then
mounts within a tire (Fig. 1). In operation, the TPMS instantly notifies drivers when any individual tire, including
the spare, isn't at optimal pressure. It's programmable for transmitting measurements at certain tire-rotation
speeds and when the tires are stationary.
In addition to the pressure sensor, the MPXY8300 integrates a temperature sensor, an 8-bit microcontroller with
512 bits of RAM and 16 kbytes of flash memory, a single- or two-axis accelerometer, and an RF transmitter with charge pump at 315 and 434 MHz. It's also available without
an accelerometer. The sensor comes in two pressure ranges:
100 to 800 kPa for passenger cars and 100 to 1500 kPa for
heavy-duty vehicles and trucks.
Of particular note, proprietary low-power techniques
extend TPMS battery life beyond 10-year requirements. Other
features include a multiple baud rate and modulation scheme,
overtemperature shutdown, supply-voltage measurement, lowpower
wakeup timer, and a periodic reset driver. The chip
comes in a 20-pin small-outline IC (SOIC) package with an
operating temperature range from -40°C to 125°C.
Semiconductor maker NXP also has a stake in the TPMS
field with the P2SC family of signal conditioners. The senior
member of family, the PCH7970, performs signal conditioning
and data framing to constantly monitor individual tire
pressure. Enlisting an 8-bit micro RISC kernel, the device
provides general-purpose I/Os for external-circuit control
and a 12-bit analog-to-digital converter (ADC) that monitors
output voltages from a piezoresistive bridge sensor.
Two multiplexed sensors interface to the device with both the
sensor and ADC operating ratiometrically, and 128 bytes of
EEPROM store calibration data for digital-sensor signal processing.
The chip also packs 128 bytes of RAM, 4 kbytes of E-ROM
that allow flash-like programming, and 4 kbytes of ROM.
Value-Added Safety Systems
Delphi Electronics
also offers a range of OEM products. Though not addressing
any specific regulatory requirements, they include active
night vision, infrared side alert, lane departure warning, and
smart cruise-control systems.
The active night-vision system integrates near-infrared illuminators
into headlights and employs an infrared-sensitive
camera mounted behind the windshield paired with a display
or navigation screen. The illuminators light the forward
roadway while the camera captures and enhances images of
the road, which then appear on the display, providing a
bright, natural image of what's ahead (Fig. 2). Also, drivers
don't have to use the brights, preventing the possibility of
blinding oncoming drivers.
Deploying passive infrared sensors on side- and rear-view
mirrors, taillights, and/or the sides of light-duty vehicles, the
company's side-alert system measures adjacent lane temperature
over time. It detects vehicles entering the blind spots and
then delivers a visual indication in the mirrors.
An inverse variation, the company's lane-departure system
for cars and heavy-duty vehicles alerts drivers when they unintentionally
drift out of their lane. A camera using image-processing
algorithms detects lane markers up to 25 m ahead and
establishes the vehicle's direction and lateral position.
If the vehicle drifts, an alert initiates. The alert type is configurable
as simulated rumble strips (small speed bumps),
audible tones, and haptic alerts. Another notable feature of
the system includes lane-width and road-curvature estimation,
which can integrate with the vehicle's power-steering
and power-brake systems for further control.
Also, the smart cruise control and headway alert/stop-and-go
system reduces the driver's need to adjust speed, brake, or disengage
the cruise control in slow-moving conditions, which it
detects up ahead. It relies on a 76-GHz, long-range radar sensor
that interfaces with the car's braking and throttle systems.
Mechanically scanning a path up to 152 m, the cruise control
manages speed based on a time gap set by the user. The
stop-and-go feature manages speed to a stopped condition
and automatically resumes the set speed when the driver
touches the gas pedal.
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