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Article Excerpt
Presently, low-g accelerometers are primarily used in automotive vehicle dynamic/stability control systems or in electronically-controlled suspension systems. However, silicon low-g accelerometers are also used in a diverse range of industrial, commercial, and medical applications, such as pacemakers, machinery vibration monitoring, earth moving equipment, platform leveling (on cranes or high-speed trains), measuring instruments, off-road vehicles and monitoring shock and vibration of goods during transport. In addition, very inexpensive, low-power silicon-based low-g accelerometers/inclination (tilt) sensors are finding realistic and emerging opportunities in very high-volume consumer applications, such as gesture-based scrolling in mobile phones PDAs, and other handheld electronic devices; navigation assistance in handheld GPS-based devices or in devices with an electronic compass; hard disk drive shock detection; as well as possibly game controllers, washing machines, input devices, and electronic games and toys..
The electronic stability control (ESC) system (which is often referred by some suppliers and OEMs as ESP, VSC, VDC, VSA, etc.) prevents a critical driving condition from occurring and helps the driver maintain control when the vehicle begins to skid by comparing input from the driver to the actual behavior of the vehicle. The basic ESC system takes input from a gyro (angular rate sensor) and a low-g lateral (Y-axis) accelerometer (which determines if the car is sliding laterally) to help stabilize the vehicle. The vehicle becomes stabilized by actuating the brakes on individual wheels and adjusting engine torque. An ESC system, moreover, also retrieves and evaluates data from the wheel speed sensors and from a steering wheel angle sensor.
As vehicles employ additional systems that need information from inertial sensors (gyros and accelerometers), there is an emerging migration toward designing and implementing inertial sensor clusters-comprised of at least two gyros for measuring yaw rate and roll rate and two accelerometers for measuring lateral and longitudinal acceleration (or one dual-axis gyro and dual-axis low-g accelerometer) -in a single unit to handle multiple functions, such as vehicle stability control, rollover prevention/mitigation, four wheel drive anti-skid braking systems, navigation systems, hill hold control, electronic parking brake, anti-theft systems, etc. The eventual scenario for integrating and streamlining the various inertial sensing functions/systems will lead to six-degree-of-freedom IMUs (inertial measurement units) consisting of a three-axis gyro and a three-axis low-g accelerometer.
VTI Technologies Oy (Vantaa, Finland, ++358-9-879181)(www.vti.fi), which maintains a North American office in Dearborn, MI (313-425-0850), has been a long-standing, dominant player in automotive market for silicon micromachined low-g accelerometers, and is also a key player in the non-automotive markets for low-g accelerometers. VTI Technologies, founded in 1991 to spearhead commercial opportunities for silicon sensing technology started at Vaisala, had sensor volume in excess of one million pieces per month in 2003 and projects a growth of 10-15% in 2004. VTI-formerly known as VTI Hamlin, and acquired by EQT Northern Europe, a private equity growth...
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