Patent ID: 7375479

Claim:
A precision processing apparatus for processing an object ( 19 ) at accurately controlled positions, the apparatus comprising a working platform ( 12 ) for supporting the object ( 19 ) to be processed; a support structure ( 10 ) for providing support to the working platform ( 12 ), the working platform ( 12 ) being movable relative to the support structure ( 10 ) along a path, the support structure ( 10 ) containing a soft magnetic element ( 34 ) with a surface that extends in parallel with said path; an suspension actuator part ( 14 ) attached to the working platform ( 12 ), the suspension actuator part ( 14 ) comprising a soft magnetic core ( 24 ) with poles facing the surface of the soft magnetic element ( 34 ) and a winding ( 20 ) for application of a current to generate a magnetic field that runs through the core ( 24 ) via the poles and returns via the soft magnetic element ( 34 ); a position reference element ( 16 ), mechanically decoupled from the soft magnetic element ( 34 ); a sensor ( 17 ) for producing a sensing result indicative of a measured position of the suspension actuator part ( 14 ) relative to the position reference element ( 16 ); a control circuit comprising an outer control circuit ( 40 ) and an inner control circuit ( 42 ), the outer control circuit ( 40 ) receiving said sensing result and determining force set point information to regulate the measured position of the actuator part ( 14 ) to a required value, the inner control circuit ( 42 ) receiving the force set point information and controlling the current to realize a force between the actuator part ( 14 ) and the support structure ( 10 ) according to the force set point information.