Re: [oopic] New range finder needed

I was trying for stereo vision such that the 2D position of the object was
determined by the difference in distance from the two eyes. Given sufficient
separation between the eyes, and given that they were receiving echoes off
the same object, this should have been possible. However, the inaccuracy
beyond about 70cm dwarfed the occular spacing, rendering the math fairly
pointless.

I am currently looking at averaging ten readings. The average stabilized
after ten readings such that it is consistent. But I need to check the
standard deviation, as I suspect that I am getting a tight average with a
wide variance. The 10th reading wouldn't do much to move the average of the
other nine, but if the variance is high, then I still don't really know the
location of the item very well.

The reason I liked the SRF08 was that it returned 17 echoes. I only used the
first five or six, but all other sonar sensors gave only a single echo. The
problem with a single echo was that I was intending to use the
identification of items to check my dead reckoning for location. Since I
can't really identify the location of any points, that isn't possible.
However, it may still be possible to do that roughly, but I'd have to
average ten readings (or thereabouts) to get a reasonable fix on an item,
and with a wide variance, even that would be dubious.

I'll try a vertical mount to see what that does.

dan michaels wrote:
>
>
> It's not clear what you mean by "binary pair". Are they interfering
> with each other by any chance ???
>
> In any case, you might be having problems with sidelobe pickup with
> the SRF0x units. I abandoned them myself, and went to the Ping sonars
> from Parallax. Other people mentioned the SRF0x units should be
> mounted "vertically", with the receiver transducer above the xmtr, so
> there is nothing for the sidelobes to reflect off of.
>
> I found the Ping units work well both close in, and at distances out
> to 12' or so. The only problem I did have was using them on a walker
> to turn at a wall, and align perpendicularly for moving away from the
> wall. When close in [about 6"], and positioned at an oblique angle to
> the wall, there appeared to be multiple reflections between the wall
> and the bot frame, and which produced spurious readings. However,
> once the bot was away from the wall 12" or more, the readings were ok.
>
>
>

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