Proactive Desk II, developed by Shunsuke Yoshida, Haruo Noma and Kennichi Hosaka of ATR Media Information Science Labs, is a "digital desk with force feedback" that can simultaneously apply different forces on multiple physical objects on it.

Its predecessor, Proactive Desk, enabled force feedback on a desk using two linear induction motors (LIM) -- it worked without using mechanical links or wires. However, Proactive Desk could only apply force on a single object on it.

By the way, Proactive Desk was used for a media art project called Suminagashi, a digital painting canvas with force feedback. "The user can enjoy the process of creating a picture not only with a visual sensation, such as colors, but also with a tactile sensation, such as the feeling of the drawing through the pen and the hands."

Proactive Desk II controls multiple physical objects on it using a 12x12 Linear Induction Motor (LIM) array that is connected to a PC through control boards. A camera mounted over the desk first detects positions of objects and then a computer controls multiple local magnetic fields on a desk. I think it's a quite technically challenging project and the system looks very elaborate and complex (despite my simplistic description.)

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