Not a simple answer to this I am afraid; the problem with absolute
positioning for mobile robots, as you have no doubt discovered in the myriad
of literature out there, is that you need more than one positioning device
to even out the errors one accumulates. Typically, one uses wheel encoders
and some other sort of triangulation methods (IR, RF etc) on a periodic
basis to correct the errors accumulated by the wheel encoder measurement
(due to wheel slippage). Since you have a walking and not a rolling base,
one option is to use IR triangulation. This works on the principle of three
or more IR emitters (each distinct from the other say in the frequency at
which they turn on and off) and a receiver that can be rotated on the base
to receive these emissions. One could also use RF along the same lines and
that will give you greater freedom at the cost of increased complexity. Some
groups have used barcodes placed at strategic points in the environment and
a scanner on the mobile base. Some others use fixed markers that emit IR at
strategic locations. The key is to get multiple inputs and then use software
to obtain the best estimate.
Madhu

> I wonder if there's anyone that have any good? ideas about small-scale
> positioning?
> Scenario: You have a small robot walking around finding obstacles. When
you
> find
> these you want to store the position.
> As this is just a hobby thing it can't cost too much so things like gps is
> not in
> question, if even applicable.
>
> TIA
> Niklas
>
> --
> Niklas Lovgren

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