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Brian, <br>
<br>
I have a 9 x 20 Lathe sold by several vendors under various names that
I purchased used several years ago. I am a relative novice at machine
working but I have had a lot of fun with mine and it seems to do
everything I have wanted to do so far. My biggest complaint is that it
seems that nothing you buy will be ready to use "out of the box"
without some form of alignment or tweaking to get it set up properly.
The lead screws on the ways are kinda sloppy and the swivel base of the
tool post on my model is a very weak design. I have machined a lot of
"parts" on it from Delrin, bronze ,aluminum and even some steel, and as
long as you know the limitations of your machine and take your time you
can do some good work. I generally agree with DPA in that you have to
decide what it is you want to make with it before you can decide which
one to by. I always tend to underbuy and really regret it later. Maybe
I'll learn my lesson some day. I think DPA has some photos of his stuff
online that show how he added DRO's, etc to his lathe. Its fairly easy
to do and well worth the effort. I also made some attachments to do
horizontal milling on the lathe and it works "okay". I did finally
break down and spent the money on a vertical mill because some of the
parts I needed to make were too large to fit on the lathe. Machine
tooling makes great birthday presents from your family, even if you
have to buy them for yourself. Now if I can just figure out how to keep
the metal shavings out of the carpet.....<br>
<br>
Steve Garmon<br>
<br>
<a class="moz-txt-link-abbreviated" href="mailto:dprglist-request@dprg.org">dprglist-request@dprg.org</a> wrote:
<blockquote cite="mid:200805272016.m4RKGZV6025944@skutter.ncc.com"
type="cite">
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</pre>
<pre wrap="">
<hr size="4" width="90%">
Today's Topics:
1. Re: Absolute reference for angular position (Chris Jang)
2. Opinions on machine tools and sources? (<a class="moz-txt-link-abbreviated" href="mailto:brianmerritt@att.net">brianmerritt@att.net</a>)
3. RE: Absolute reference for angular position (Randy M. Dumse)
4. Absolute reference for angular position (dpa)
5. RE: Absolute reference for angular position (Sluggy!)
6. Opinions on machine tools and sources? (dpa)
7. Re: Absolute reference for angular position (Dale Wheat)
8. Re: Absolute reference for angular position (Dale Wheat)
9. Re: Absolute reference for angular position (Dale Wheat)
</pre>
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
Re: [DPRG] Absolute reference for angular position</td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
Chris Jang <a class="moz-txt-link-rfc2396E" href="mailto:christopher.jang@yahoo.com"><christopher.jang@yahoo.com></a></td>
</tr>
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<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 10:14:47 -0700 (PDT)</td>
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
Eric Sumner <a class="moz-txt-link-rfc2396E" href="mailto:kd5bjo@gmail.com"><kd5bjo@gmail.com></a>, Dale Wheat
<a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
</tr>
</tbody>
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<div class="headerdisplayname" style="display: inline;">To: </div>
Eric Sumner <a class="moz-txt-link-rfc2396E" href="mailto:kd5bjo@gmail.com"><kd5bjo@gmail.com></a>, Dale Wheat
<a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">CC: </div>
DPRG <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@dprg.org"><dprglist@dprg.org></a></td>
</tr>
</tbody>
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<br>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">Can anyone suggest an alternate method for measuring angular position with
</pre>
</blockquote>
<pre wrap="">a
</pre>
<blockquote type="cite">
<pre wrap="">high degree of accuracy and repeatability? All I really need is an "index
mark" to tell me when the robot returns to a specific heading and not a
continuous readout of angular position.
</pre>
</blockquote>
<pre wrap="">If you're only going to be using this to calibrate your rotation, you
could use a beacon and a directional receiver; a 38kHz IR receiver
module might work for this, if you restricted its field of view. You
could do something similar with a laser pointer and a photodetector;
whenever the laser is directly falling on the detector, its value will
go up sharply.
</pre>
</blockquote>
<pre wrap=""><!---->
Another possibility is to take photographs of the robot as it rotates.
Lay out some tape or other visual markers to establish a frame of
reference. Then if there is a DRO of the angular position in view of the
camera (maybe a laptop showing the angular readout - use a serial cable
from the robot to take readings), there are no issues synchronizing data
collection with the photos. One problem might be refresh of the DRO - may
not look right to the camera.
</pre>
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
[DPRG] Opinions on machine tools and sources?</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
<a class="moz-txt-link-rfc2396E" href="mailto:brianmerritt@att.net"><brianmerritt@att.net></a></td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 12:57:03 -0500</td>
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<div class="headerdisplayname" style="display: inline;">To: </div>
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<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">I am thinking about
buying a small lathe and/or vertical
mill, new or used. What are people’s opinions on minimum sizes, the
different manufacturers, and ease of converting the mill to CNC at some
point
in the future? Also, anyone know of good sources for these tools? I
have been watching eBay but it seems it would be tough to determine the
condition and would cost an arm and a leg to ship such big items. All
knowledgeable
feedback will be appreciated.</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"> </span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">Regards,</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;">Brian</span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial;"> </span></font></p>
<p class="MsoNormal"><font face="Arial" size="2"><span
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
RE: [DPRG] Absolute reference for angular position</td>
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<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
"Randy M. Dumse" <a class="moz-txt-link-rfc2396E" href="mailto:rmd@newmicros.com"><rmd@newmicros.com></a></td>
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<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 13:30:10 -0500</td>
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
"'Eric Sumner'" <a class="moz-txt-link-rfc2396E" href="mailto:kd5bjo@gmail.com"><kd5bjo@gmail.com></a>, "'Dale Wheat'"
<a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
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<div class="headerdisplayname" style="display: inline;">To: </div>
"'Eric Sumner'" <a class="moz-txt-link-rfc2396E" href="mailto:kd5bjo@gmail.com"><kd5bjo@gmail.com></a>, "'Dale Wheat'"
<a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
</tr>
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<div class="headerdisplayname" style="display: inline;">CC: </div>
'DPRG' <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@dprg.org"><dprglist@dprg.org></a></td>
</tr>
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<br>
<blockquote type="cite">
<pre wrap="">you could use a beacon and a directional receiver;
</pre>
</blockquote>
<pre wrap=""><!---->
Even simpler. Use a trouble lamp, or other bright source on the
floor in line with the robot, use a tube with a photo sensor on
the robot. The peak value will be when the tube is pointing
toward the lamp. The longer, narrower the tube, the more
accurate the pointing.
Randy
</pre>
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
[DPRG] Absolute reference for angular position</td>
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<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
dpa <a class="moz-txt-link-rfc2396E" href="mailto:dpa@io.isem.smu.edu"><dpa@io.isem.smu.edu></a></td>
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<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 13:50:38 -0500</td>
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@dprg.org">dprglist@dprg.org</a></td>
</tr>
</tbody>
</table>
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width="100%">
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<div class="headerdisplayname" style="display: inline;">To: </div>
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@dprg.org">dprglist@dprg.org</a></td>
</tr>
</tbody>
</table>
<br>
<pre wrap="">Howdy,
Dale wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I'm trying to calibrate Daphne's wheelbase dimension. Because the wheels are
not exactly round and the motor shafts are not exactly parallel, this is more of
an approximation than an actual measurement.
The method I'm using is to spin in place and measure the difference between
measured and actual rotation. To do this I need a very accurate method of
measuring the angular position. Daphne keeps up with what she thinks is her
current angular position using odometry. Comparing these two measurements will
help me determine the effective wheelbase dimension and allow me to increase the
accuracy of the odometry.
</pre>
</blockquote>
<pre wrap=""><!---->
I've done this with a two-wheel differential drive robot that is
capable of rotating in place, i.e., zero turning radius. The
method used was to align the robot with an "X" marked on the floor,
and then have the robot rotate in place multiple times, like 10 or
20 revolutions, to make the error large enough to measure, and stop
when the robot thinks it's back to zero. That is, if the robot's
odometry error is .5 degree, then 20 revolutions will make it 10
degrees, large enough to easily measure and correct.
However, it sounds from the following like you are looking for a
way for the robot to calibrate itself. Yes?
</pre>
<blockquote type="cite">
<pre wrap="">I'm thinking about stereo sonar as a reference point. Two identical sonar units
are aimed horizontally and diverge by 15 degrees or so. The sonar array should
return equal readings when the array is normal (i.e., 90 degrees) to the wall.
I believe dpa has used this technique to true up SR04 during long journeys such
as our Can-Can contest.
</pre>
</blockquote>
<pre wrap=""><!---->
Our friends from the University of Michigan suggest that you can do
this with a single sonar by placing the robot at a known location in
a corner. The robot uses the sonar to measure the distance to the
two corner walls by measuring the distance to one, rotating 90
degrees, and measuring the distance to the other one. Then run
your calibration procedure, and measure the distances again. This
gives both location and theta error, and the robot should be able
to calibrate itself. That would be pretty cool, and something
that would be easy to run each time you change wheels, or take
the robot apart and put it back together.
Having said all that, the spin-in-place calibration is a good way to
get a starting value for theta, but it has a couple of draw backs.
It can't separate out the wheel base errors from the wheel size
errors. Consequently adjustments done using this technique are not
reliable for general navigating, as the errors when turing one way
will be more pronounced than turning the other.
The previous "simplified navigation calibrating and tuning" post
describes a method for using clockwise and counter-clockwise squares
to do odometry fine tuning once a starting value for theta has been
determined. If you think about it, this is also a method for
amplifying the errors, like spinning in place multiple times, in
addition to isolating the software from the hardware error soruces.
</pre>
<blockquote type="cite">
<pre wrap="">The only sonar module I've used before is the Devantech SRF04 module. It's a
simple trigger+echo interface. Unfortunately, I only have (or can only find)
one of them. I have several of the Mini-S modules but don't know how to use
them. They default to an automatic, fixed-distance operation. Also, they
require 12 volts and Daphne's battery is 7.4 volts.
I've also considered a small laser module and a pinpoint receiver.
</pre>
</blockquote>
<pre wrap=""><!---->
I've found that a small laser pointed accurately aligned to the
robot's main fore/aft axis is a mighty handy thing to have, both
for calibration and for general running. It's difficult otherwise
to tell exactly "where the robot is pointed." Alternately some sort
of boresight that can be sighted along for aligning the robot with
a particular course, like sight marks on a telescope, might be
helpful.
Dale, how about "All of the Above?"
cheers,
dpa
</pre>
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
RE: [DPRG] Absolute reference for angular position</td>
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<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
Sluggy! <a class="moz-txt-link-rfc2396E" href="mailto:sluggy9912@swbell.net"><sluggy9912@swbell.net></a></td>
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<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 12:16:58 -0700 (PDT)</td>
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
"'DPRG'" <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@dprg.org"><dprglist@dprg.org></a></td>
</tr>
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width="100%">
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
"'DPRG'" <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@dprg.org"><dprglist@dprg.org></a></td>
</tr>
</tbody>
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<br>
<pre wrap="">All the solutions given up to this point seem to be
towards the robot being self-calibrating. The only
problem with any of these is that it's adding another
sensor, one that is intentionally narrow in focus,
with all the problems that represents.
If this measurement is for one time (or even
occasional) manual calibration, how about a laser
pointer attached to the chassis and pointed to a spot
on the wall. Mark that spot. Rotate the robot under
program control to what it thinks is 360 degrees.
Using a high tech ruler, measure the error by where
the laser ended up pointing. Repeat many times,
perhaps averaging the results. Adjust the count in the
software.
Sluggy!
---
"The idea that unicycling is intrinsically funny does not explain the findings." Professor Sam Shuster.
</pre>
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width="100%">
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
[DPRG] Opinions on machine tools and sources?</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
dpa <a class="moz-txt-link-rfc2396E" href="mailto:dpa@io.isem.smu.edu"><dpa@io.isem.smu.edu></a></td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 14:56:18 -0500</td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@dprg.org">dprglist@dprg.org</a></td>
</tr>
</tbody>
</table>
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width="100%">
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@dprg.org">dprglist@dprg.org</a></td>
</tr>
</tbody>
</table>
<br>
<pre wrap="">Howdy,
Brian, this is a huge topic. What size of machine(s) are
you looking for? Table top? Like Taag and Sherline.
Sherline has a lot of CNC stuff. I think Dave/Jon
Hylands use Sherline and have quite a bit of experience
therewith.
You might also look at Grizzly
<a class="moz-txt-link-rfc2396E" href="http://www.grizzlyindustrial.com/"><http://www.grizzlyindustrial.com/></a>
and Blue Ridge Machinery
<a class="moz-txt-link-rfc2396E" href="http://www.blueridgeshoponline.com/category.sc?categoryId=18"><http://www.blueridgeshoponline.com/category.sc?categoryId=18></a>
for medium size machine tools.
A generally useful sequence is to start with a nice
drill press and add an X,Y table for layout, etc. Then add
a lathe (I love my Emco-Maier Compact 8). Between those
two you can do most robot building tasks, and the lathe
can be fitted with some fixtures to allow it to be used
as a horizontal milling machine. Later you can add a
vertical mill.
As always, assume you will spend about as much on
tooling as on the machines themselves.
A bench grinder for making and sharping tools is
really a must, along with a precision flat plate,
often made of granite, for doing layout.
Ed K. has one of the 3-in-1 lathe/mills perhaps
he'll chime in here and report on his experience
with it.
best,
dpa
</pre>
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<div class="headerdisplayname" style="display: inline;">Subject:
</div>
Re: [DPRG] Absolute reference for angular position</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
Dale Wheat <a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 14:09:51 -0600</td>
</tr>
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<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
dpa <a class="moz-txt-link-rfc2396E" href="mailto:dpa@io.isem.smu.edu"><dpa@io.isem.smu.edu></a></td>
</tr>
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width="100%">
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<div class="headerdisplayname" style="display: inline;">To: </div>
dpa <a class="moz-txt-link-rfc2396E" href="mailto:dpa@io.isem.smu.edu"><dpa@io.isem.smu.edu></a></td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">CC: </div>
<a class="moz-txt-link-abbreviated" href="mailto:dprglist@dprg.org">dprglist@dprg.org</a></td>
</tr>
</tbody>
</table>
<br>
David,
<br>
<br>
> However, it sounds from the following like you are looking for a
<br>
> way for the robot to calibrate itself. Yes?
<br>
<br>
Ultimately, yes. In the short term, I would assist somewhat. :)
<br>
<br>
> Our friends from the University of Michigan suggest that you can
do
<br>
> this with a single sonar by placing the robot at a known location
in
<br>
> a corner. The robot uses the sonar to measure the distance to the
<br>
> two corner walls by measuring the distance to one, rotating 90
<br>
> degrees, and measuring the distance to the other one. Then run
<br>
> your calibration procedure, and measure the distances again. This
<br>
> gives both location and theta error, and the robot should be able
<br>
> to calibrate itself. That would be pretty cool, and something
<br>
> that would be easy to run each time you change wheels, or take
<br>
> the robot apart and put it back together.
<br>
<br>
Is that described in more detail in the "Where Am I?" paper? I have
enough sonar units (i.e., 1) for that procedure.
<br>
<br>
> I've found that a small laser pointed accurately aligned to the
<br>
> robot's main fore/aft axis is a mighty handy thing to have, both
<br>
> for calibration and for general running. It's difficult otherwise
<br>
> to tell exactly "where the robot is pointed." Alternately some
sort
<br>
> of boresight that can be sighted along for aligning the robot with
<br>
> a particular course, like sight marks on a telescope, might be
<br>
> helpful.
<br>
<br>
Something I and Dr. Evil both plan to include in the near future, if
it's not too much to ask.
<br>
<br>
> Dale, how about "All of the Above?"
<br>
<br>
Probably the best suggestion so far!
<br>
<br>
<br>
Thanks,
<br>
<br>
Dale Wheat
<br>
<br>
(972) 486-1317
<br>
(877) DALE WHEAT
<br>
<a class="moz-txt-link-freetext" href="http://dalewheat.com">http://dalewheat.com</a>
<br>
<br>
<br>
<br>
<br>
<hr size="4" width="90%"><br>
<table class="header-part1" border="0" cellpadding="0" cellspacing="0"
width="100%">
<tbody>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">Subject:
</div>
Re: [DPRG] Absolute reference for angular position</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
Dale Wheat <a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 14:13:47 -0600</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
"Sluggy!" <a class="moz-txt-link-rfc2396E" href="mailto:sluggy9912@swbell.net"><sluggy9912@swbell.net></a></td>
</tr>
</tbody>
</table>
<table class="header-part2" border="0" cellpadding="0" cellspacing="0"
width="100%">
<tbody>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
"Sluggy!" <a class="moz-txt-link-rfc2396E" href="mailto:sluggy9912@swbell.net"><sluggy9912@swbell.net></a></td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">CC: </div>
'DPRG' <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@dprg.org"><dprglist@dprg.org></a></td>
</tr>
</tbody>
</table>
<br>
Sluggy!
<br>
<br>
> All the solutions given up to this point seem to be
<br>
> towards the robot being self-calibrating. The only
<br>
> problem with any of these is that it's adding another
<br>
> sensor, one that is intentionally narrow in focus,
<br>
> with all the problems that represents.
<br>
<br>
Right now that's how I'm planning to use it, but a sonar array or even
a single unit would also be useful for general purpose obstacle
avoidance or targeting, once I get up to those lofty levels.
<br>
<br>
> If this measurement is for one time (or even
<br>
> occasional) manual calibration, how about a laser
<br>
> pointer attached to the chassis and pointed to a spot
<br>
> on the wall. Mark that spot. Rotate the robot under
<br>
> program control to what it thinks is 360 degrees.
<br>
> Using a high tech ruler, measure the error by where
<br>
> the laser ended up pointing. Repeat many times,
<br>
> perhaps averaging the results. Adjust the count in the
<br>
> software.
<br>
<br>
That sounds like the simplest way to achieve what I want to do. I have
lots of lasers of all sizes laying around.
<br>
<br>
<br>
Thanks,
<br>
<br>
Dale Wheat
<br>
<br>
(972) 486-1317
<br>
(877) DALE WHEAT
<br>
<a class="moz-txt-link-freetext" href="http://dalewheat.com">http://dalewheat.com</a>
<br>
<br>
<br>
Sluggy! wrote:
<br>
<blockquote type="cite">All the solutions given up to this point seem
to be
<br>
towards the robot being self-calibrating. The only
<br>
problem with any of these is that it's adding another
<br>
sensor, one that is intentionally narrow in focus,
<br>
with all the problems that represents.
<br>
<br>
If this measurement is for one time (or even
<br>
occasional) manual calibration, how about a laser
<br>
pointer attached to the chassis and pointed to a spot
<br>
on the wall. Mark that spot. Rotate the robot under
<br>
program control to what it thinks is 360 degrees.
<br>
Using a high tech ruler, measure the error by where
<br>
the laser ended up pointing. Repeat many times,
<br>
perhaps averaging the results. Adjust the count in the
<br>
software.
<br>
<br>
Sluggy!
<br>
<br>
---
<br>
<br>
"The idea that unicycling is intrinsically funny does not explain the
findings." Professor Sam Shuster.
<br>
_______________________________________________
<br>
DPRGlist mailing list
<br>
<a class="moz-txt-link-abbreviated" href="mailto:DPRGlist@dprg.org">DPRGlist@dprg.org</a>
<br>
<a class="moz-txt-link-freetext" href="http://list.dprg.org/mailman/listinfo/dprglist">http://list.dprg.org/mailman/listinfo/dprglist</a>
<br>
<br>
</blockquote>
<br>
<br>
<hr size="4" width="90%"><br>
<table class="header-part1" border="0" cellpadding="0" cellspacing="0"
width="100%">
<tbody>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">Subject:
</div>
Re: [DPRG] Absolute reference for angular position</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">From: </div>
Dale Wheat <a class="moz-txt-link-rfc2396E" href="mailto:dale@dalewheat.com"><dale@dalewheat.com></a></td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">Date: </div>
Tue, 27 May 2008 14:17:15 -0600</td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
Eric Sumner <a class="moz-txt-link-rfc2396E" href="mailto:kd5bjo@gmail.com"><kd5bjo@gmail.com></a></td>
</tr>
</tbody>
</table>
<table class="header-part2" border="0" cellpadding="0" cellspacing="0"
width="100%">
<tbody>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">To: </div>
Eric Sumner <a class="moz-txt-link-rfc2396E" href="mailto:kd5bjo@gmail.com"><kd5bjo@gmail.com></a></td>
</tr>
<tr>
<td>
<div class="headerdisplayname" style="display: inline;">CC: </div>
DPRG <a class="moz-txt-link-rfc2396E" href="mailto:dprglist@dprg.org"><dprglist@dprg.org></a></td>
</tr>
</tbody>
</table>
<br>
Eric,
<br>
<br>
> If you're only going to be using this to calibrate your rotation,
you
<br>
> could use a beacon and a directional receiver; a 38kHz IR receiver
<br>
> module might work for this, if you restricted its field of view.
You
<br>
> could do something similar with a laser pointer and a
photodetector;
<br>
> whenever the laser is directly falling on the detector, its value
will
<br>
> go up sharply.
<br>
<br>
The IR demodulator works too well at an angle. They have AGC circuits
and other voodoo to pluck weak signals out of the air. I need
something that falls off dramatically as the signal goes out of phase.
<br>
<br>
What would be the best detector for a red laser beam? CdS sensor?
Photodiode? Any other ideas along these lines?
<br>
<br>
<br>
Thanks,
<br>
<br>
Dale Wheat
<br>
<br>
(972) 486-1317
<br>
(877) DALE WHEAT
<br>
<a class="moz-txt-link-freetext" href="http://dalewheat.com">http://dalewheat.com</a>
<br>
<br>
<br>
<br>
<br>
<pre wrap="">
<hr size="4" width="90%">
_______________________________________________
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<a class="moz-txt-link-freetext" href="http://list.dprg.org/mailman/listinfo/dprglist">http://list.dprg.org/mailman/listinfo/dprglist</a>
</pre>
</blockquote>
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<p class="MsoNormal"><b>Steve Garmon</b><br>
Geotechnical Manager<br>
C&C Technologies<br>
10615 Shadow Wood Drive<br>
Suite #100<br>
Houston, TX 77043<br>
(713) 468.1536<br>
<span style="color: blue;"><a href="mailto:steve.Garmon@cctechnol.com">steve.garmon@cctechnol.com</a></span>
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