I saw a demo of the Analog Devices rate gyro at a show. They had
a 3-D gyro in a box attached to a PC which would display a graphic
representation of the box on the screen in the same orientation.
It was a cool demo, and I didn't see much drift. These sensors
designed for cars to sense rollover for correct airbag deployment
based on car attitude. I think a single axis sensor from analog.com
is about $36/unit; but you'll have to interface it to your controller.
The rate gyros for helicopters drift a bit (check the manufacturer
for drift rate spec); however, they usually have a seperated sensity
input to adjust how much to effect the servo output. They cost more,
but are complete units.
For absolute rotation sensor on robots, you can use an electronic
compass. Precision Navigation has some small 2D compass modules for
$50 that interfaces via SPI bus. I think they have a readout accuracy
of +-1deg. They have raw (uncalibrated) mode and a calibrated mode,
where you can map out soft iron declination. I have used them and
they work pretty well.
I don't know what the availability of any of these are in your
See ya, -ingo
What are you trying to sense? Low-end rate gyros are not
very accurate. Do you want to know which way is down, or
which way is north?
Rate gyro plus magnetic compass can produce a reasonably
good heading outdoors.
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