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Tracking the Flight of Birds

I have used accelerometers based on microelectromechanical systems (MEMS) for both hobbyist projects and more legitimate designs. In the latter category, I used one as an inclinometer. As the name suggests, I was measuring the angle of inclination (more properly, the deviation from the perpendicular) as part of a CT scanner gantry. We needed to know the angle the gantry was tilted before we shot X-ray beams through the patient.

The accelerometer provided absolute position information. We also used a potentiometer coupled to the gantry's tilt axle, so that we had a redundant method (using a different technology) to measure the tilt angle. In medical diagnostic equipment, it is good design practice (i.e., essential and mandatory) to use redundant systems to monitor certain vital parameters. Any subsystem that moves the patient or moves equipment around the patient — and could cause injury to the patient or artifacts in the imaging — must be carefully managed.

A MEMS accelerometer contains a micromachined beam that deflects when external forces act on it. The deflection can be measured by different means, but measuring the capacitance between the beam and nearby electrodes is a common method. The external forces are either gravity (the inclinometer application) or acceleration acting on the beam's inertial mass (f=ma).

(Source: STMicroelectronics)

(Source: STMicroelectronics)

The hobby project to which I referred also used an ADI device, but this time, it actually measured acceleration. I used it in an automotive application to monitor and display positive and negative acceleration. The display itself was amusing. However, there is more to that than room here will allow. I'll leave that for another blog.

If you combine a three-axis accelerometer with a three-axis magnetometer (functionally a compass), you can create a reasonably good subsystem to track motion and, by extension, location. Of course, it helps if you know where you are to start with, and it helps even more if you can double-check where you are every so often in some absolute sense.

(Source: STMicroelectronics)

(Source: STMicroelectronics)

Researchers at the University of Amsterdam have teamed up with STMicroelectronics to develop a bird-tracking system that does pretty much what I described above. They are using an IC that is a three-axis accelerometer and a three-axis magnetometer, all in a 28-pin, 5mm-by-5mm land grid array (LGA) package.

Their system also uses a GPS positioning subsystem that checks absolute location every three seconds, a data logging subsystem, temperature sensors, and a lithium battery plus solar cell to charge it. This all weighs about as much as a 25-cent piece, so it can actually be attached to a bird — probably a small hawk, not a house finch.

A raptor with an electronics backpack. (Source: STMicroelectronics)

A raptor with an electronics backpack.
(Source: STMicroelectronics)

Knowing the bird's absolute position every three seconds — and using the accelerometer and magnetometer to fill in data in the interim — the researchers can log the bird's flight accurately. Even the bird's orientation (pitch, tilt, and yaw) can be tracked, so the scientists can tell how it is dealing with crosswinds.

The information is used to verify computer models for bird behavior and to analyze migration patterns. By extension, the researchers can draw conclusions regarding the environment and climate change.

8 comments on “Tracking the Flight of Birds

  1. Brian Dotson
    February 20, 2013

    Brad,

    That is a very cool application for a MEMS accelerometer! It would be fun to try and do a version of this that was minituarized enough to actually tag smaller birds (common songbirds) with. Of course, one would have to catch them, first:-)

  2. Brad Albing
    February 20, 2013

    Exercise caution – PETA will come after you.

  3. eafpres
    February 20, 2013

    I think it would be fun to have one of these for my cat, and an app for my iPhone to watch her (in x-y-z-phi-theta-theta-acceleration space).  She sure can change direction quickly and in multiple axes with rotation!

    FYI, IHS (market research firm) says MEMS motion sensors amounted to over $1.3B last year!

  4. Brad Albing
    February 20, 2013

    That would be cool. We have 3 inside cats and one outside cat. Might be interesting to see what they are doing all day; altho' based on observations, mostly all they're doing is stacking Zzzz'z's.

  5. SunitaT
    February 21, 2013

    Magnetometer provides fixed reference point and determine absolute orientation in the NESW plan.Accelerometer provides information about changes in positions and determine absolute orientation sensor in the UP-DOWN plane.

    When magnetometer and accelerometer are combined together we get information about birds flight, body angle of the birds flying in a crosswind. These information are useful to unlock the mysteries of bird migrations.

    GPS addition allows us to check the position against the reference and the update the calculations.

  6. David Maciel Silva
    February 21, 2013

    Performing a quick search, I found a company that specializes in equipment for animal tracking.

    As the link below:

    http://www.technosmart.eu/index.php

    I also found an article reporting on accelerometers IN THE BIRD'S NEST Olympics in 2008.

     

    http://www.ventajamarketing.com/writing/cust/samples/Tanner_MEMSIC_JWhite.pdf

     

    There is a world of applications for telemetry systems acceleration, displacement, location. A good combination would be a Zigbee network with GPS +, it is already in use in the Amazon, Brazil, collecting information about animals.

  7. karenfield
    February 25, 2013

    You knew this was coming Brad – can you present your hobby project in our Gadget Freak Lab at DESIGN West this year?

  8. Brad Albing
    February 25, 2013

    Perhaps that would be a good idea. But only if it's likely that there will be members in the audience interested in MEMS-based accelerometers and who are also train fans.

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