Control of a particular coarse-fine micro-positioning system based on a magnetic actuation

The device whose control is presented here allows to push micro-objects located in a drop of water between two glass panes. The distance between both glass panes is a few hundred micrometers. Objects are pushed with a small ferromagnetic particle whose size is 100 /spl times/ 100 /spl times/ 20 /spl mu/m/sup 3/, and which is moved thanks to a permanent magnet. The authors previously (2002) presented the dynamic behavior of this micromanipulation device. We present here an original control strategy which use the manipulator orientation to achieve a good precision despite the "stick slip effect". The position precision obtained is 1 /spl mu/m and is limited by the camera resolution.