Newsgroups: comp.robotics
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From: jack@robotics.jpl.nasa.gov (Jack Morrison)
Subject: Re: Attitude sensors... and a few more thi
Message-ID: <1994Sep16.163929.1069@llyene.jpl.nasa.gov>
Sender: news@llyene.jpl.nasa.gov
Reply-To: jack@robotics.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
References: <357l52$kcv@falcon.ccs.uwo.ca>
Date: Fri, 16 Sep 1994 16:39:29 GMT
Lines: 37

In article kcv@falcon.ccs.uwo.ca, ppicot@irus.rri.uwo.ca (Paul Picot) writes:

>>>>  We are working on a project to make a flying robot that has wired
>>>>stability, so we need to have a fair amount of Feedback as far as
>>>>attitude is concerned.  I mean I could play around with some glass tubes,
>>>>wires and a bit of mercury, but it would be nice if there was something
>>>>out there all ready.
...

>rstevew@armory.com (Richard Steven Walz) wrote:
>>Anybody considered a rotary encoder or a pot with a weighted pendulum on
>>it???
>
>This has been tried, and works, but it is clunky.  And unless a Gray
>Code encoder were used, it would require zeroing on every power up.
>Weighted pots will have long settling times.  The Applied Geomechanics
>device is a very nice little ready-to-run unit.

Also, for two axes of tilt you probably want to mount two pots on a 
gimbal mechanism.

Another possible device (if a bit expensive at approx $1K) I just tried out
is a tiny (a cube just under 1" on a side) three-axis accelerometer from
Summit Instruments (216/659-3312). The scale factor is a bit low for
inclination measurement, but it could be done.

>However, this whole family of gravity-referenced attitude semsors all
>suffer from the same problem of being sensitive to acceleration, as well
>as tilt, as one other poster has already noted.

If that's a problem (likely on a flying robot), gyroscopes are probably 
the way to go.
---
"How am I typing? Call 1-818-354-7782"               jack@robotics.jpl.nasa.gov
Jack Morrison/Jet Propulsion Lab/MS107-102 4800 Oak Grove Dr, Pasadena CA 91109


