High-accuracy motion sensor makes smarter cars

STMicroelectronics has developed a new motion sensor that provides accurate measurements of vehicle movement for systems such as adaptive front lights, auto-leveling HID (high-intensity discharge) lamps, inertial brake lights, e-parking brake, advanced anti-theft systems and control of vehicle dynamics.

The AIS226DS is a two-axis in-plane accelerometer capable of greater accuracy than is possible using two individual sensors. The device senses acceleration up to plus or minus 6g, where one 'g' is the acceleration due to gravity. As an example, 3g is the approximate acceleration experienced in a manned rocket during launch into space. The new AIS226DS can also resolve incredibly tiny angles of incline, smaller than 0.02 degrees. The ability to accurately measure incline is important in auto-leveling lamp, e-parking brake, Hill Start Aid applications.

Motion is sensed using a tiny MEMS motion detector built on a silicon chip. An interface chip, available with an SPI or I²C output, is also integrated, enabling direct connection to the vehicle's electronic control unit.

Other vehicle systems that can use the AIS226DS include event recorders for monitoring accidents or abusive driving, and GPS navigation systems using movement data for improved dead reckoning when the satellite signal is lost. There are also many non-automotive applications, such as vibration sensing in industrial equipment, black-box security monitors for shipping containers, inclinometers, and robotic systems.

The AIS226DS owes part of its high sensing accuracy to the low intrinsic noise of the electronic interface chip, which includes high-precision 16bit ADCs. The low noise allows usable converter resolution of 14bits over a significant bandwidth, corresponding to a resolution of 0.25mg (on 2g full-scale). The sensor is also highly stable and maintains high accuracy (plus or minus 70mg) throughout the automotive temperature range -40°C to +105°C, offering offset drift in the range of 0.2mg per °C. The AIS226DS, assembled in a sturdy SO16W full-molded package, is qualified to the AEC-Q100 automotive quality standard.

The AIS226DS is sampling to lead customers, with volume production planned for Q1 10. Pricing is from $2.50 in quantities of 100,000 units.

For application notes on motion sensors click here.

Keywords: motion sensor   MEMS   accelerometer