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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