MEMS Sensors Let Cars Navigate Without GPS

Bosch’s SMI230 six-axis inertial MEMS sensor helps to keep a car on track even under poor GPS signal conditions. The sensor integrates an accelerometer and gyroscope in a single package. Briefly stated, with this sensor onboard, navigation systems will not take their eye off the destination, even when the GPS signal is interrupted.


The SMI230 provides the navigation system with motion data, enabling the current position of the travelling vehicle to be determined even when the GPS signal is weak or nonexistent. Navigation systems will become even more precise and reliable. The sensor precisely measures the yaw rate and acceleration of the vehicle. In this way the onboard navigation system continuously calculates the travel direction and position while the car is moving. The navigation is not disrupted when inside a tunnel or an urban canyon.

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The SMI230 combines one three-axis MEMS accelerometer with one three-axis MEMS gyroscope in a single compact package. Both sensors run digitally in 16-bit mode and the gyroscope and accelerometer can either be operated individually or interconnected for data synchronization purposes.


Specs include a noise figure of 0.02°/s/√Hz (rms) for the gyroscope and 0.12 mg/√Hz (rms) for the accelerometer. Temperature coefficient offset (TCO) is typically below 0.2 mg/K and temperature coefficient sensitivity (TCS) is 0.002 %/K. Typical bias instability of the gyroscope is well below 2°/h. In terms of power consumption, the sensor supports three power saving modes: accelerometer suspend mode, gyroscope suspend mode, and deep suspend mode.


The SMI230 is pin-for-pin compatible with Bosch’s SMI130, and offers an identical gyroscope programming interface. The SMI230 is housed in a16-pin standard LGA package, measuring just 3 mm x 4.5 mm x 0.95 mm and will be available in May 2019. For more info, visit Bosch.

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