Newsgroups: comp.robotics
Path: brunix!cat.cis.Brown.EDU!agate!howland.reston.ans.net!swrinde!elroy.jpl.nasa.gov!ucla-cs!oahu.cs.ucla.edu!cardo
From: cardo@oahu.cs.ucla.edu (Ric Crabbe)
Subject: Re: using mice for positioning info
Nntp-Posting-Host: oahu.cs.ucla.edu
References: <1994Jul8.114839.23422@gteds.com> <CsMnvz.Hqy@world.std.com>
Message-ID: <1994Jul08.184844.15862@cs.ucla.edu>
Date: Fri, 08 Jul 94 18:48:44 GMT
Organization: UCLA, Computer Science Department
Lines: 39

pbrennan@world.std.com (Patrick M Brennan) writes:

>Jeffrey Graham (dtcjsg1@PROBLEM_WITH_INEWS_GATEWAY_FILE) wrote:

>: To avoid the inherent problems with shaft encoders,i.e., slippage, I want
>: to use 2 computer mice located strategically beneath the robot base (which
>: is a tank-type drive).

>What makes you think that there is some difference between a shaft
>encoder and a mouse encoder?  They are exactly the same devices.
>A mouse is just as prone to slippage as a wheel.   With
>a shaft encoder, you have more immediate knowledge of your motor
>speed.

>Patrick

Not that you asked me, but I think the behavior will be quite different
for a variety of reasons.  Mostly, the mouse balls are not connected
to the drive system. eg. At UCLA we often have 
one robot stuck on another one, so that the wheels are spinning
but the robot isn't moving.  The encoder information is useless
then, but the mice would correctly tell us that there is no movement.

On the other hand, I think the mice would fail in different ways.
changes in things as simple as how dirty the floor is
would effect the performance of the system. And on rough surfaces,
the balls might not touch the ground at times.  On smooth surfaces,
the mice would skip just as they do on our tables w/o pads.
Finally, I bet the mice would fill up with floor fuz and dust bunnies,
there would be breaks for mouse cleaning at regular intervals.

but what do I know, I'm a software guy.

ric

-- 
Hell must be a pretty swell spot, because the guys that invented religion have  
sure been trying hard to keep everybody else out.       -Al Capone 
cardo@cs.ucla.edu
