The robot's feedback system is too slow without tapping into the wiring
directly (forbidden for this project), and the ultimate goal is a self
contained bolt-on type upgrade, not just for this one particular robot but
for any bot.  This project is designed, in part, to compensate for the
limitations of the robot's feedback and correctional systems.  The robot
tilts to various degrees, and the robot does not mean to move the platform
from level.  I can't really say more due to a signed NDA.  Please take my
word that mechanical corrective solutions were investigated thoroughly, and
would not work for this particular project.

The gyros and adxl were chosen as the ideal solution for an independent
system, so we're concentrating on making them work.  The system, as a whole,
is about 95% finished and works great except for correcting high degrees of
tilt.  The only refinements left to manipulate are the code in the
microchip, and if anybody knows of a better method than what I've already
done (see original post) then please let me know!


----- Original Message -----
From: "Robert Rolf" <Robert.Rolf@UALBERTA.CA>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, April 12, 2004 5:10 PM
Subject: Re: [PIC]: Dynamic Platform Stabilization


> Since you presumably know the robot effector position from it's
> feedback system, why not just use that information directly?
> If you are mounted on some part of the robot, you just need to
> apply the appropriate scaling to the kinematic equations giving you
> position.
>
> I'm not clear one whether the robot is moving the platform on purpose
> or because of a poor design choice. e.g. it may be possible to
> stabilize your platform using parallelogram linkages to the robot frame.
> R
>
> "Robert B." wrote:
> >
> > I've been working on a microchip-based system to stabilize a sensor
platform
> > using an ADXL202 and an angular rate sensor.  The platform is moving
around
> > in all directions (it's mounted on a robot) so the linear ADXL can't
really
> > be trusted to give a consistent or even accurate reading.  It has been
off
> > by as much as 80 degrees in the limited testing I've done.  Most of the
> > correction is currently coming from the integrating the rate sensor, but
> > it's subject to too much drift and really needs the corrections from a
> > linear accelerometer.  Does anybody know a work-around to this problem?
> >
> > Right now it's integrating at about 60Hz, and checking tilt on the ADXL
> > every 100ms, then correcting 1/10th the offset indicated by the ADXL to
> > create a crude time delay filter.  This combination (so far) gives the
best
> > stability at low levels of tilt, but at high rates of tilting (<150
> > deg/second) the position vector takes too long to catch up to where it
> > should be.
> >
> > If you need or want more details let me know.
>
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