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Sensor fusion to power next generation of smartphones and tablets

Motion sensing capabilities in products like the iPhone and iPad are now set to move to the next level with the advent of sensor “fusion,” a more sophisticated approach that will spur a fundamental shift in the way tablets and smartphones are designed and used, according to a new report from market analysts IHS iSuppli. “Microelectromechanical systems (MEMS) sensors - mainly gyroscopes, accelerometers and compasses - are becoming ubiquitous in smartphones and tablets,” said Jérémie Bouchaud, director and principal analyst for MEMS and sensors at IHS. “While these sensors already provide user interface, gaming and navigation features that are essential to the appeal of today’s mobile electronics devices, taken individually they have limitations in areas including accuracy and responsiveness. To attain the next level of functionality, handsets and tablets must provide to developers a ‘fused signal’ that combines the outputs of these three types of motion sensors to greatly enhance the motion- based interface.”

Sensor fusion potentially could enhance interfaces of any tablet or smartphone that uses a combination of a 3-axis accelerometer, 3-axis compass and 3-axis gyroscope to provide “9-axis sensor fusion,” IHS predicts. It estimates there is a total available market for motion sensors that need 9-axis fusion amounting $850 million in 2012, and rising to $1.3 billion in 2015. Gyroscopes, accelerometers and compasses each provide a different form of motion sensing. However, each sensor type has its own limitations. For example, the gyroscope suffers a strong drift over time, the compass is sensitive to electromagnetic interference and the accelerometer works better for slow movement than for fast motions.

When the signals of the three sensors are fused together, each sensor function can compensate for the others’ inherent limitations. This will yield a truly enhanced motion sensing experience that is much faster, smoother and more accurate than is possible with each sensor used individually. However, the true benefit of combining

the three devices will only be evident when a 9-axis sensor fusion is included in the applications programming interface (API) for apps developers. “With the integration of 9-axis sensor support in the API, apps developers will be able to produce software with compelling

smartphone and tablet functionality, such as immersive games and very responsive and accurate augmented reality applications for outdoor use,” Bouchaud said. “The use of 9-axis sensor fusion will also enable full indoor navigation,”

Such a development will represent a major improvement for both the Apple iOS and Android operating systems, which at present don’t support full 9-axis integration from either a hardware or software perspective.

On iOS, the output signal of the

gyroscope is combined with that of the accelerometer to provide 6-axis fusion. While this enhances the motion-based use of an iPhone compared to the iPhone 3GS for augmented reality applications, the function falls short of the full 9-axis fusion. On Android handsets and tablets that

already have a gyroscope, only the raw data of the gyroscope is made available, with no combination with the accelerometer signal. Because of this, there is not a single noteworthy application on the Android Store that uses the gyroscope function. The software algorithms will be embedded in the sensors or may run on the application processors of tablets and smartphones. New concepts also are emerging to support a more power-efficient implementation.

IHS anticipates some handsets in 2012 will include a dedicated microcontroller to run the sensor fusion algorithms for simple processing tasks, while the application processor will be woken up only to conduct more complex applications such as indoor navigation. Eventually, sensor fusion also could run on a dedicated core in the application processor. The two leading gyroscopes suppliers for handsets and tablets, STMicroelectronics and InvenSense, have developed 9-axis sensor fusion engines that will enable original equipment manufacturers to implement unprecedented experiences with motion-based interfaces in handset and tablets very soon.

InvenSense in September announced that its combo sensor with embedded 9- axis sensor fusion now is in mass production for handsets and tablets. For its part, STMicroelectronics revealed its iNEMO 9-axis sensor fusion engine in March and announced that first handsets leveraging software algorithms should appear on the market before the end of 2011.

Components in Electronics November 2011 15

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