The KUKA YouBot Omni-Directional Mobile Platform with Arm is a small, arm-on-a-skateboard type of robot that can perform simple tasks. Recently Ross Knepper, a robotics reseacher at MIT, and his team hacked up a couple of them to assemble store-bought IKEA furniture. While it was primarily an exercise, versus designing a commercially-viable product, we were pretty impressed by his solution for screwing the legs into the Lack sidetable that you'll see here:
The YouBot doesn't come with an "end effector" that can perform the rotating motion you and I would do with two hands to get that leg into the table. Knepper's team devised an elegant workaround, using rubber bands attached to two different rings:
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