Engineer - your post got me thinking. I had always "just assumed" that gyros were fairly insensitive to gravity, so that all that mattered was the orientation of the rotation axis to which it is sensitive.
In my case, I've just rotated the gyro board 90deg about the sensitive axis, so it should still be sensitive to the same rotations as the shoulder mounted device. The problem I figure you were getting at was, are these boards compensating for gravity and therefore need to placed flat like on the shoulder? That's an interesting question . . .
If these things were sensitive to gravity (i.e. like an accelerometer, gravity = acceleration) I would have thought they'd be no good in helicopters during aerobatics (but they seem to be ok, not that I'm a model heli pilot)
So . . . just to check things out, I popped open my RN-1's head and looked at the sensor chip in the PG-03. A little detective work shows that it is made by Murata in Japan
And from their website . . .
This product is an angular velocity sensor that uses
the phenomenon of Coriolis force, which is generated
when a rotational angular velocity is applied to the
vibrator.
Murata's original, small ceramic bimorph vibrator and
simple Cap-Base structure realize their ultra-small
size, about 0.2cc. Their small and lightweight shape
increase flexibility of installment and help your
apparatuses to be downsized.
They are surface mountable device, can be mounted by
automatic surface mounter.
Analog devices have a nice page about this class of gyro, and they say
It should be noted that the gyro may be placed anywhere on the rotating object and at any angle, so long as its sensing axis is parallel to the axis of rotation.
So that says to me that the chest mounted gyro does the same job as the shoulder mounted gyro, assuming that their sensitive axes are parallel, and gravity be damned. No doubt they are sensitive in some small, negligible way but we at least can overlook it by the sounds of things. I suspect temperature drift from being next to a hot servo is going to be a worse problem.
I did look at putting the gyro in the shoulder cavity but suspect I decided that I wanted enough room for the foam pad too or better access to the adjustment screws (can't remember now). Anyhow, either place is out of the way and therefore good
.Cheers
Tim
Statistics: Posted by Tim — Tue Jan 29, 2008 3:06 pm
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