Parts Sorter
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In this demo we show the UPM as a parallel parts sorter: 4 blue and 4 red poker chips are scattered randomly on the UPM's horizontal plate as shown below:

The idea is to sort the red chips to the right and the blue chips to the left, in parallel. This illustrates how the UPM's 3-dof's are sufficient to manipulate a system with a much larger -- 16 in this case -- # of dof's.

Using the overhead (color) camera, each poker chip is assigned to a color group -- "red" or "blue".

Sorting is accomplished via a round-robin procedure: for each part on the table, displace it a small amount in the appropriate direction: left for blue, right for red. A special motion primitive is used which allows a single part to be displaced while keeping all others immobile. The round-robin procedure is repeated until all parts reach their respective sides (use vision to correct for errors).

Below a sequence of snapshots of the sorting operation is shown, read from left-to-right, top-to-bottom:

sort-01.jpg (51626 bytes) sort-03.jpg (49305 bytes)
sort-06.jpg (49123 bytes) sort-09.jpg (48529 bytes)
sort-12.jpg (49997 bytes) sort-15.jpg (46553 bytes)

A video of this interesting motion is available both in MPEG and RealVideo8  350kbps and 34kbps formats.

2000 Dan S. Reznik, <>