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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Doug/All,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I’d like to build an indoor robot using two standard drive wheels and two non-driving Omni Wheels to improve turning radius.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Are there any similar rules-of-thumb when using Omni Wheels?<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">A few more details for the curious:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Like to move precisely from one programmed point to another (+/- 6-inches within a house)<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Ability to take control via remote control if need be<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:Symbol;color:#1F497D"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Carry a payload of 20-lbs plus batteries to last 4 hours<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thank You & Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">David</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> DPRGlist <dprglist-bounces@lists.dprg.org>
<b>On Behalf Of </b>secretary--- via DPRGlist<br>
<b>Sent:</b> Wednesday, April 15, 2020 9:18 AM<br>
<b>To:</b> Murray Altheim <murray18@altheim.com><br>
<b>Cc:</b> DPRG <dprglist@lists.dprg.org><br>
<b>Subject:</b> [EXTERNAL] Re: [Dprglist] Odometry on Mecanum-wheeled robots?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><strong><span style="font-size:10.5pt;font-family:"Verdana",sans-serif;background:yellow">External Sender: Use caution with links/attachments.</span></strong><b><span style="font-size:10.5pt;font-family:"Verdana",sans-serif;background:yellow"><br>
<br>
</span></b><o:p></o:p></p>
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<p class="MsoNormal">Murray, <o:p></o:p></p>
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<p class="MsoNormal"> The rule of thumb with casters is that they can navigate bumps up to a maximum size of the radius of the wheel. The little ball casters usually have a really small radius.<o:p></o:p></p>
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<p class="MsoNormal">Regards,<o:p></o:p></p>
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<p class="MsoNormal">Doug P.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Wed, Apr 15, 2020 at 12:58 AM Murray Altheim via DPRGlist <<a href="mailto:dprglist@lists.dprg.org">dprglist@lists.dprg.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">I'm going to contradict myself. Regarding orientation sensors, I dug<br>
around a bit and found:<br>
<br>
<a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__blog.digilentinc.com_how-2Dto-2Dconvert-2Dmagnetometer-2Ddata-2Dinto-2Dcompass-2Dheading_&d=DwMFaQ&c=PskvixtEUDK7wuWU-tIg6oKuGYBRbrMXk2FZvF0UfTo&r=bmd3-eHvz8rWPqqbuyNFhtJ8IOIwEIOa0NDwscNoELg&m=OoiE4WcxCgmwH7PdKp0iX-e_kRb1RaVt3OuAB6yiRl4&s=9k6ePW5XS9SqXrEMSHSxUFnAJN4-ZeoZBsgZZE4jiKE&e=" target="_blank">
https://blog.digilentinc.com/how-to-convert-magnetometer-data-into-compass-heading/</a><br>
<br>
and am quite pleased to be getting a compass heading output from the<br>
magnetometer of an Adafruit LSM9DS1. I'm no mean Python programmer but<br>
in the interest of sharing, here goes:<br>
<br>
------------------------------------------------------------<br>
#!/usr/bin/env python3<br>
# -*- coding: utf-8 -*-<br>
#<br>
# reads an x,y,z value from the LSM9DS1 magnetometer and<br>
# displays a heading in degrees.<br>
<br>
import time, board, busio, math, adafruit_lsm9ds1<br>
<br>
LSB = 0.48828125 #mG<br>
<br>
def convert_to_direction(mag_x, mag_y, mag_z):<br>
xGaussData = mag_x * LSB<br>
yGaussData = mag_y * LSB<br>
if xGaussData == 0.0:<br>
return 90.0 if yGaussData < 0.0 else 0.0<br>
else:<br>
direction = math.atan( yGaussData / xGaussData ) * ( 180.0 / math.pi )<br>
if direction > 360.0:<br>
return direction - 360.0<br>
elif direction < 0.0:<br>
return direction + 360.0<br>
else:<br>
return direction<br>
<br>
try:<br>
i2c = busio.I2C(board.SCL, board.SDA)<br>
sensor = adafruit_lsm9ds1.LSM9DS1_I2C(i2c)<br>
while True:<br>
mag_x, mag_y, mag_z = sensor.magnetic<br>
direction = convert_to_direction(mag_x, mag_y, mag_z)<br>
print('lsm9ds1 : direction: {0:0.2f}°;\tmagnetometer(G): ({1:0.3f}, {2:0.3f}, {3:0.3f})'.format(direction, mag_x, mag_y, mag_z))<br>
time.sleep(0.5)<br>
<br>
except KeyboardInterrupt:<br>
print('\nlsm9ds1 : Ctrl-C caught: keyboard interrupt.')<br>
<br>
#EOF<br>
------------------------------------------------------------<br>
<br>
with output like:<br>
<br>
lsm9ds1 : direction: 31.17°; magnetometer(G): (0.349, 0.211, 0.077)<br>
lsm9ds1 : direction: 21.02°; magnetometer(G): (0.413, 0.159, 0.095)<br>
lsm9ds1 : direction: 18.88°; magnetometer(G): (0.438, 0.150, 0.078)<br>
lsm9ds1 : direction: 8.52°; magnetometer(G): (0.356, 0.053, 0.105)<br>
lsm9ds1 : direction: 0.81°; magnetometer(G): (0.285, 0.004, 0.130)<br>
lsm9ds1 : direction: 2.04°; magnetometer(G): (0.248, 0.009, 0.114)<br>
lsm9ds1 : direction: 4.20°; magnetometer(G): (0.242, 0.018, 0.128)<br>
lsm9ds1 : direction: 6.50°; magnetometer(G): (0.232, 0.026, 0.128)<br>
lsm9ds1 : direction: 3.05°; magnetometer(G): (0.303, 0.016, 0.121)<br>
lsm9ds1 : direction: 346.79°; magnetometer(G): (0.308, -0.072, 0.258)<br>
<br>
On 15/04/20 3:50 PM, Murray Altheim via DPRGlist wrote:<br>
> [...] so the idea of taking a more "raw" output from a magnetometer and having to<br>
> process that for a value vs. an already-complete orientation value in radians or<br>
> degrees from the BNO055, well, that's pretty compelling. I'd both have to spend<br>
> a lot of time learning and debugging versus just getting a compass heading output<br>
> from the BNO055. While it might be somebody's cup of tea to work out that kind<br>
> of detail, it's not like there's not enough challenges in building a robot. And<br>
> time, hmm. Time.<br>
...........................................................................<br>
Murray Altheim <murray18 at altheim dot com> = = ===<br>
<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__www.altheim.com_murray_&d=DwMFaQ&c=PskvixtEUDK7wuWU-tIg6oKuGYBRbrMXk2FZvF0UfTo&r=bmd3-eHvz8rWPqqbuyNFhtJ8IOIwEIOa0NDwscNoELg&m=OoiE4WcxCgmwH7PdKp0iX-e_kRb1RaVt3OuAB6yiRl4&s=KzKpqKPjn73LZg46OUudZrUsv4pOgV-x27rdSPcp--U&e=" target="_blank">http://www.altheim.com/murray/</a>
=== ===<br>
= = ===<br>
In the evening<br>
The rice leaves in the garden<br>
Rustle in the autumn wind<br>
That blows through my reed hut.<br>
-- Minamoto no Tsunenobu<br>
<br>
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<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.dprg.org_listinfo.cgi_dprglist-2Ddprg.org&d=DwMFaQ&c=PskvixtEUDK7wuWU-tIg6oKuGYBRbrMXk2FZvF0UfTo&r=bmd3-eHvz8rWPqqbuyNFhtJ8IOIwEIOa0NDwscNoELg&m=OoiE4WcxCgmwH7PdKp0iX-e_kRb1RaVt3OuAB6yiRl4&s=o0FhP4VCkHehYWTgkwCvhSAY22byH5LGWlVUSxYKP6Q&e=" target="_blank">http://lists.dprg.org/listinfo.cgi/dprglist-dprg.org</a><o:p></o:p></p>
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