Abstract: A planar motor is controlled by supplying a three-phase alternating current to a coil assembly. Each phase is supplied to one of three coils. The coils are positioned in a magnetic field generated by a magnet plate having alternating magnet poles at its surface for generating an alternating magnetic field. In operation, the phase of each current flowing through each coil determines the direction of a force generated due to the current in the magnetic field. For correct operation, the phase angle of each current is to be adapted to the local direction of the magnetic field by determining a commutation-offset angle. The commutation-offset angle is determined by generating a force in an unknown direction and varying the commutation-angle, and determining when the generated force is directed perpendicular to the magnet plate, while ensuring that the generated force does not exceed a horizontal friction force.

Abstract: A lithographic projection apparatus in which a reaction force is generated between a balance mass and a substrate table. The balance mass is elastically coupled to the base frame with a suspension eigenfrequency of between 0.3 and 10 Hz.