A positioning device with a drive unit with which an object table is displaceable over a guide which is fastened to a first frame thereof. A stationary part of the drive unit is fastened to a second frame thereof and dynamically isolated from the first frame while a reaction force of the object...http://www.google.com.au/patents/US5844666?utm_source=gb-gplus-sharePatent US5844666 - Positioning device with a vibration-free object table, and lithographic device provided with such a positioning device 
