editor's blog
Subscribe Now

What’s In a Name

We’re all still getting calibrated on sensors, and we can sometimes get tripped up on terminology. In discussions about their sensor fusion IP, Movea explicitly included some definitions to make sure we were aligned.

Most prominent is their finessing of the mythical 9-axis or 9-DoF sensor. They do this by distinguishing between true degrees of freedom and axes. Spatial motion involves only six true degrees of freedom: 3 dimensions linear and three dimensional rotational. That’s all there is. The problem is that when accelerometers (which handle 3D linear) and gyroscopes (which handle 3D rotational) are joined by magnetometers, which also position in 3 dimensions, many marketers blithely add the degrees of freedom together to get 9 of them.

The problem is, the magnetometer’s three degrees of freedom overlap those of the other two sensors. We haven’t magically entered a new world that has three completely new ways of moving; we’re just getting a new view of the existing six degrees of freedom.

Movea is more permissive with the term “axis,” allowing each sensor its own axes and making them additive. So an accelerometer/gyroscope/magnetometer combo, in their parlance, has six degrees of freedom and nine axes.

Other lexical distinctions they provide:

–          Axial sensors, which provide, essentially, a vector result, with a value for each axis; versus scalar sensors, like pressure sensors, which simply provide one number as a result

–          Motion sensing categories, from detection, which is Boolean – either there is motion or there isn’t – to classification, which categorize movements like gestures into discrete buckets, to estimation, where a value from a continuous range is reported – part of what separates full motion processing from gesture recognition.

Leave a Reply

featured blogs
Mar 20, 2019
Over the past few years, 3D modeling capabilites on Samtec.com have progressed immensely. We’ve gone from a small library of static files to a massive library of dynamically generated models, that can be downloaded as virtually any file type, in just a few seconds. Thou...
Mar 20, 2019
One big highlight of the RSA conference is always The Cryptographers' Panel. This year the panel was: Ronald Rivest, the R of RSA. Whitfield Diffie, legendary cryptographer. Paul Kocher, who... [[ Click on the title to access the full blog on the Cadence Community site....
Mar 19, 2019
Deeper Dive into Non-Trivial Bug Escapes and Safety Critical Designs This blog is a continuation of a series of blogs related to the 2018 Wilson Research Group Functional Verification Study (click here).  In my previous blog (click here), I presented verification results fin...
Jan 25, 2019
Let'€™s face it: We'€™re addicted to SRAM. It'€™s big, it'€™s power-hungry, but it'€™s fast. And no matter how much we complain about it, we still use it. Because we don'€™t have anything better in the mainstream yet. We'€™ve looked at attempts to improve conven...