IMU integrates accelerometer, gyro
R Colin Johnson
5/24/2012 12:31 PM EDT
PORTLAND, Ore.—Inertial measurement units (IMUs) integrate a three-axis accelerometer and a three-axis gyroscope, which Bosch Sensortec now claims to have put into the smallest package yet available for consumer-grade applications such as mobile phones, tablets and digital cameras.
Frank Melzer, Bosch Sensortec CEO, announced the integration into a single inexpensive 3.0-by-4.5 millimeter package at the MEMS Business Forum Thursday (May 24) in Santa Clara, Calif.
Every smartphone today has a three-axis accelerometer to track motion—for automatically switching its screen from portrait to landscape—but for advanced gaming, gesture recognition and indoor navigational tasks, a three-axis gyroscope is needed, too. Accelerometers only track linear motion, but gyroscopes track rotation-in-place motion, thus providing a higher precision when tracking fine user movements. Packing both accelerometers and gyroscopes into a 3.0-by-4.5 millimeter package could enable any smartphone can upgrade to a full six-degree-of-freedom inertial measurement unit (IMU).
"Bosch Sensortec is now offering the smallest IMU available today," said Leopold Beer, director of global marketing at Bosch Sensortec. "We are the only MEMS manufacturer who makes accelerometers, gyroscopes, magnetometers and barometers in-house."
Bosch has both 6-inch and 8-inch MEMS fabs in Reutlingen, Germany, capable of building 1,500 wafers per day at 0.5 micron and 800 wafers a day at 0.18 micron, respectively. They are also the only manufacturer making two six-degree-of-freedom (6-DoF) parts with their own chips—an accelerometer/magentometer combo for e-compasses and navigation, and now an accelerometer/gyroscope combo for gaming and gesture recognition. With the addition of one of their barometer chips—for determining altitude—Bosch Sensortec now also has a complete 10-DoF intertial navigation unit (INU) as a two-chip solution.
Bosch Sensortec wire-bonds together into 3-D stacks the MEMS die and the ASIC holding its electronics all in a single package.Bosch's gyroscopes offer several operating modes to save power, enabling to power down by half and awaken in just 10 milliseconds or go into sleep mode and awaken in just 30 milliseconds, triggered by any user motion detected by the accelerometer. Both the accelerometer and the gyroscope can also be interrupt driven, plus include on-chip first-in-first-out (FIFO) memories for logging data values between polling periods. Accelerometers since plus or minus 2-to-16 Gs and gyroscopes run at form plus or minus 125-to-2000 degrees per second. Resolutions range from 12-bit for accelerometer to 16-bit for gyroscopes.
Source: Bosch Sensortec
Bosch's sensor fusion library also contains routines for all the common uses of accelerometers and gyroscopes such as background calibration to keep all sensors in tune, group delay compensation for real-time motion tracking, tremor cancellation for gaming and pointing, distortion detection and suppression for magnetic immunity and stability enhancement for indoor navigation. And an application programmer interface permits turnkey operating system integration with Android.