Bearing device, magnetic gravity compensator, vibration isolation system, lithographic apparatus, method to control a gravity compensator having a negative stiffness, and spring

A magnetic gravity compensator, comprising:

• a first permanent magnet assembly mounted to one of a first part and the second part and comprising at least a first column of permanent magnets, the first column extending in a vertical direction, wherein the permanent magnets have a polarization direction in a first horizontal direction or in a second horizontal direction opposite to the first horizontal direction, wherein vertically adjacent permanent magnets have opposite polarization directions;
• and
• a second permanent magnet assembly mounted to the other of the first part and the second part and comprising at least one other column of permanent magnets, the at least one other column extending in the vertical direction, wherein vertically adjacent permanent magnets of the at least one other column have opposite polarization directions in the first horizontal direction or the second horizontal direction,
• wherein the first permanent magnet assembly at least partially encloses the second permanent magnet assembly.

A lithographic apparatus comprising:

• a support constructed to support a patterning device, the patterning device being capable of imparting to the radiation beam a pattern in its cross-section to form a patterned radiation beam;
• a substrate table constructed to hold a substrate;
• a projection system configured to project the patterned radiation beam onto a target portion of the substrate;
• wherein the lithographic apparatus comprises a bearing device arranged to support in a vertical direction a first part of the lithographic apparatus with respect to a second part of the lithographic apparatus, the bearing device comprising a magnetic gravity compensator, wherein the magnetic gravity compensator comprises:
• a first permanent magnet assembly mounted to one of the first part and the second part and comprising at least a first column of permanent magnets, the first column extending in a vertical direction, wherein the permanent magnets have a polarization direction in a first horizontal direction or in a second horizontal direction opposite to the first horizontal direction, wherein vertically adjacent permanent magnets have opposite polarization directions, and
• a second permanent magnet assembly mounted to the other of the first part and the second part and comprising at least one other column of permanent magnets, the at least one other column extending in the vertical direction, wherein vertically adjacent permanent magnets of the at least one other column have opposite polarization directions in the first horizontal direction or the second horizontal direction,
• wherein the first permanent magnet assembly at least partially encloses the second permanent magnet assembly.

A method to control a gravity compensator having a negative stiffness, and arranged between a first part of an apparatus and a second part of the apparatus, using a control system comprising:

• a first sensor arranged to provide a first measurement signal representative of a relative distance between the first part of the apparatus and the second part of the apparatus,
• a second sensor arranged to provide a second measurement signal representative of an acceleration of the first part of the apparatus, and
• a controller comprising a first sub-controller arranged to receive the first measurement signal and a second sub-controller to receive the second measurement signal, the controller being arranged to provide an actuator signal to drive an actuator device arranged between the first part of the apparatus and the second part of the apparatus on the basis of the first measurement signal and the second measurement signal,
• wherein the first sub-controller is arranged to add stiffness to the bearing device, therewith allowing a resonance, and
• wherein the second sub-controller is arranged to damp the resonance.