| Tikalon Blog is now in archive mode.
An easily printed and saved version of this article, and a link
to a directory of all articles, can be found below: |
|
This article |
| Directory of all articles |
Pattern Recognition for Accelerometers
December 9, 2013
At the first major
energy crisis in
1979, people were willing to explore
commuter transportation modes other than the personal
automobile. The
corporate headquarters campus at which worked at that time contained both
business offices and
research laboratories and a huge number of
employees. The
parking lots were as huge as those of many
shopping malls, and desk employees got some needed
exercise walking long distances from their cars to their offices.
Whether conscious to the needs of its employees, or spurred into action by some
governmental mandate, my
employer started a
partially-subsidized commuter
van pool fleet. There were nearly twenty vans at its peak, each van capable of transporting twelve-fifteen employees from nearby
suburbs to their workplace. The
drivers were the employees, themselves, who would rotate the driving task in some vans, while in other vans there was a designated employee driver who got a free ride.
There were benefits beyond my
chauffeured ride to work. We
scientists in the lab are mostly shielded from the business operations of a
corporation, but in the van I had the enjoyment of hearing how the other half worked. At the same time, my fellow commuters got an education in some of the science happening in nearby buildings.
Fantasy carpool, circa 1943, featuring two men and eight women.
From a World War II poster promoting fuel conservation.
(Office of War Information poster, via Wikimedia Commons.)
The only downside was a somewhat bumpy ride to work.
New Jersey has a moderately intense
winter season, and the multiple
freeze-thaw events take their toll on the roads (If you know New Jersey, you'll know why that's an intended
pun). If I sat at the back of our van, the
vibration assured that I would be fully-awake when I arrived at work. I often thought about bringing an
accelerometer along for the ride to see exactly how bad the bumps were. From accelerometer data, a van ride to work could be distinguished from an automobile ride.
As its name implies, an accelerometer is a
sensor for measuring
acceleration. There are
high accuracy accelerometers for
inertial navigation applications, but today's
MEMS technology makes it very easy to manufacture inexpensive, moderate accuracy accelerometers. They are so inexpensive that
smartphones and
tablet computers use them to select
page orientation.
Accelerometers in
mobile computing devices can be used, also, for other applications. I haven't checked, but there must be a few applications designed to have your
cellphone say, "Ouch," when it's dropped on the floor. A multi-
megapixel camera is not that useful when it's hand held, but an accelerometer can be used for
image stabilization.
Scientists at the
Berkeley Seismic Laboratory have proposed using mobile device accelerometers as an
earthquake early warning system. Accelerometers would transmit data to a central
server which would use an
algorithm to sort
seismic tremors from the
random motions of individual devices and
transmit an alarm. At this time, mobile device accelerometers can only detect earthquakes above 5.0
magnitude, but they might contain more sensitive accelerometers in the future.[1]
Computer scientists at the
University of Helsinki have reported on their system of using mobile device accelerometers to determine commuter transportation habits.[2-5]
Finland is a hotbed of
computer science, enabled by its excellent
Internet connectivity,[6] and users of the
Linux operating system might recognize the University of Helsinki as the
alma mater of
Linus Torvalds, first
developer and proponent of the
Linux kernel. Torvalds is still active in Linux development; and, yes, Linux is named after him.
Linus Torvalds, first developer of the Linux operating system, at a meeting in Tianjin, China, September 11, 2012
(World Economic Forum photograph, via Wikimedia Commons.)
The Helsinki team has
verified my informal
hypothesis that vibration monitoring can distinguish one mode of transportation from another, and they've summarized their system for this, called TMD-Peaks, in a paper for the
11th ACM Conference on Embedded Networked Sensor Systems (SenSys'13, Rome, Italy).[3]
Project leader,
Samuli Hemminki, mentions the same random background problem faced by the Berkeley seismic sensor team,
"Extracting vehicular movement information from smartphone accelerometers is challenging as the placement of the device can vary, users interact with the phone spontaneously, and as the orientation of the phone can change dynamically. We overcame these challenges by developing novel algorithms for processing and analyzing accelerometer measurements."[3]
Some typical data are shown in the following figure.
Experiments have shown that the mode of transportation can be determined with 80% accuracy.[3] The team is working on an
Android implementation.[2]
Vehicle accelerometer data.
Top to bottom: train, bus, stationary, metro, tram, automobile.
(University of Helsinki image, reformated for presentation.)
![]()
References:
- Jonathan Amos, "Smartphones to be pocket seismometers," BBC News, December 5, 2012.
- TMD-Peaks: Accelerometer-Based Transportation Mode Detection on Smartphones, University of Helsinki Web Site.
- Smartphone accelerometers distinguish between different motorized transportation modalities, University of Helsinki Press Release, November 13, 2013 (PDF file).
- S. Hemminki, P. Nurmi and S. Tarkoma, "Accelerometer-Based Transportation Mode Detection on Smartphones," Proceedings of ACM SenSys, 2013 (In Press, PDF File).
- TMD-Peaks Presentation Slides (PDF File).
- Top 50 Countries With The Highest Internet Penetration Rate, Internet World Stats. At the time of this article, Finland was ranked tenth best in the world with 88.6% of the population having access, with the US lagging at 27th place, with 78.3% of the population having access.
Permanent Link to this article
Linked Keywords: Energy crisis; 1979; commuting; commuter; transportation; automobile; corporate headquarters; campus; business; office; research; laboratory; employee; parking lot; shopping mall; physical exercise; government; employer; subsidy; subsidized; van; pool; fleet; suburb; driver; chauffeur; chauffeured; scientist; corporation; fantasy; carpool; car pool; 1943; men; women; World War II; poster; fuel; conservation; United States Office of War Information; Wikimedia Commons; New Jersey; winter season; freeze-thaw event; pun; vibration; accelerometer; sensor; acceleration; accuracy and precision; inertial navigation application; MEMS technology; smartphone; tablet computer; page orientation; mobile computing; mobile computing device; mobile phone; cellphone; megapixel; camera; image stabilization; Berkeley Seismic Laboratory; earthquake early warning system; server; algorithm; seismic tremor; randomness; random; motion; warning system; alarm; moment magnitude scale; University of Helsinki; Finland; computer science; Internet access; Internet connectivity; Linux operating system; alma mater; Linus Torvalds; software developer; Linux kernel; Tianjin, China; World Economic Forum; statistical hypothesis testing; hypothesis; 11th ACM Conference on Embedded Networked Sensor Systems (SenSys'13, Rome, Italy); project management; Project leader; Samuli Hemminki; experiment; Android; train; bus; rapid transit; metro; tram; automobile.