Patent ID: 7489054

Claim:
A planar direct drive, comprising: a passive unit, which includes a planar running surface with magnetic flux regions; an active unit with coil systems for generating a variable magnetic flux; a bearing unit, which allows near-frictionless two-dimensional relative motion of the active and passive units by maintaining a bearing gap; a position measuring system that includes a measurement standard and a measuring sensor that scans the measurement standard and supplies a position signal, the positioning system including a moving component and a quasi-stationary component, one of which is formed by the measurement standard, while the other is formed by the measuring sensor, such that both components are arranged outside the bearing gap and a distance from the running surface, the quasi-stationary component being arranged at a predetermined fixed point and substantially parallel to but separated from the running surface, the moving component being mounted on the active unit so that when the moving component reaches the quasi-stationary component the moving component comes into measuring contact with the quasi-stationery component, and the position control of the active unit being controlled or regulated by evaluation of the position signal supplied by the measuring sensor as long as the two components of the position measuring system are in a state of measuring contact.