<div dir="ltr">It might be a better fit for the team since they run on a fairly uniform surface. Too late for this season - State Championship is next week and there's nothing beyond that since Worlds was cancelled. But it should make a good summer project. <br><br>I wasn't necessarily thinking it would be great for outdoor robots with much more varied terrain. But we'll try that out too. It might be a good additional way to detect and compensate for wheel slippage.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jun 8, 2021 at 6:25 PM Murray Altheim <<a href="mailto:murray18@altheim.com">murray18@altheim.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Karim,<br>
<br>
I'll be very interested in hearing how you and yours figure out the best way to<br>
use these new sensors. I think overall they'll be very helpful to those wanting<br>
some sort of optical odometry, or at least some kind of optical assist. As I<br>
mentioned, even if it can't be used for truly accurate odometry over varied<br>
surfaces it still might be very handy for driving in a straight line, or other<br>
tricks we haven't even thought of yet.<br>
<br>
Cheers,<br>
<br>
Murray<br>
<br>
On 9/06/21 9:34 am, Iron Reign wrote:<br>
> Thanks Murray. Very helpful. I've ordered a brace of them. They're not in the Amazon store yet, so gotta wait on international shipping.<br>
> <br>
> On Tue, Jun 8, 2021 at 4:18 PM Murray Altheim via DPRGlist <<a href="mailto:dprglist@lists.dprg.org" target="_blank">dprglist@lists.dprg.org</a> <mailto:<a href="mailto:dprglist@lists.dprg.org" target="_blank">dprglist@lists.dprg.org</a>>> wrote:<br>
> <br>
> Hi Karim,<br>
> <br>
> I'll try to get the post, which is about half ready, posted ASAP, though I've<br>
> got a lot going on right now at home and work.<br>
> <br>
> I think it's definitely worth a look. My initial play with it was using the<br>
> existing PMW3901 Python library, as suggested by the Pimoroni techs, and I'd<br>
> tested it out over nine different surfaces and with that library I found the<br>
> image complexity was clearly related to the measured velocity, but Pimoroni<br>
> updated their library, and while the update doesn't entirely eliminate that<br>
> issue, it's much less significant than before. I don't think you'll be able<br>
> to use the sensor solely to measure distance over significantly varied<br>
> surfaces with accuracy, but over a relatively constant surface I think it's<br>
> pretty good, within a few percent.<br>
> <br>
> It outputs a simple stream of x,y values when moving, clearly on an interrupt<br>
> basis as that stream stops when the movement stops. I measured the 'x'<br>
> dimension (oriented as it was) over one meter and so long as I stayed on the<br>
> kind of surface that I calibrated it for the measurements were quite accurate.<br>
> An interesting notion might be to use the other axis with a PID controller to<br>
> travel in a straight line, as while dragging my little robot sled over the<br>
> test surface I'd get small 'y' values that could be used for course correction.<br>
> <br>
> With the new Python library I think the minimum to maximum of the nine<br>
> surfaces I tested on (tile, wood floor, lawn, concrete, rug, etc.) varied by<br>
> something like 10-15%, but on any given surface the ten runs of my test<br>
> varied by only a few percent max, often less than 1%. Repeatable results.<br>
> <br>
> It'd be possible to calibrate the sensor over different surfaces and switch<br>
> calibrations based on the surface if it were possible to detect the surface<br>
> type, possibly using a camera or spectrometer sensor like the Pimoroni<br>
> AS7262 that could detect color (which actually works pretty well, e.g.,<br>
> it's easy in my house to know the difference between my tile, wood and<br>
> carpet flooring by color). I've got a spreadsheet of results that will be<br>
> part of the review/blog post.<br>
> <br>
> At £18.90 (US$26.75 / NZ$37) it's not cheap but I think worth a look, yes.<br>
> The only downside really, which was entirely predictable, is that its<br>
> operating range is 10-35mm, suitable for hanging underneath a small robot,<br>
> but not so much under say, a Mars rover, whose bottom is likely higher than<br>
> 35mm. In that case the PWM3901 would be more suitable, but not necessarily<br>
> as accurate,<br>
> <br>
> Cheers,<br>
> <br>
> Murray<br>
> <br>
> On 9/06/21 8:52 am, Karim Virani wrote:<br>
> > How about at least a teaser? Worth a look?<br>
> ><br>
> > On Tue, Jun 8, 2021 at 3:49 PM Murray Altheim via DPRGlist <<a href="mailto:dprglist@lists.dprg.org" target="_blank">dprglist@lists.dprg.org</a> <mailto:<a href="mailto:dprglist@lists.dprg.org" target="_blank">dprglist@lists.dprg.org</a>> <mailto:<a href="mailto:dprglist@lists.dprg.org" target="_blank">dprglist@lists.dprg.org</a> <mailto:<a href="mailto:dprglist@lists.dprg.org" target="_blank">dprglist@lists.dprg.org</a>>>> wrote:<br>
> ><br>
> > Hi,<br>
> ><br>
> > FYI, Pimoroni has finally announced stock availability on their new PAA5100JE<br>
> > Near Optical Flow Sensor, which I'll be posting a review on hopefully soon.<br>
> ><br>
> > PAA5100JE Near Optical Flow SPI Breakout<br>
> > Detect motion of close-up surfaces with this Breakout Garden compatible<br>
> > optical navigation breakout - great for floor tracking for ground dwelling robots!<br>
> > <a href="https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout" rel="noreferrer" target="_blank">https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout</a> <<a href="https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout" rel="noreferrer" target="_blank">https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout</a>> <<a href="https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout" rel="noreferrer" target="_blank">https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout</a><br>
> <<a href="https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout" rel="noreferrer" target="_blank">https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout</a>>><br>
> <br>
> ...........................................................................<br>
> Murray Altheim <murray18 at altheim dot com> = = ===<br>
> <a href="http://www.altheim.com/murray/" rel="noreferrer" target="_blank">http://www.altheim.com/murray/</a> <<a href="http://www.altheim.com/murray/" rel="noreferrer" 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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...........................................................................<br>
Murray Altheim <murray18 at altheim dot com> = = ===<br>
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= = ===<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>
</blockquote></div>