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

A magnetic gravity compensator, comprising:

• a first permanent magnet assembly mounted to one of a first part and a 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;
• the first part comprises a sensor frame;
• and
• the second part comprises an intermediate frame configured to:
• support the sensor frame;
• and
• be supported by a base frame;
• and
• the magnetic gravity compensator is configured to have a negative stiffness based on a combination of absolute control and relative control of an actuator.

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;
• and
• 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,
• wherein:
• the bearing device comprises a magnetic gravity compensator;
• 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;
• the first permanent magnet assembly at least partially encloses the second permanent magnet assembly;
• the first part comprises a sensor frame;
• and
• the second part comprises an intermediate frame configured to:
• support the sensor frame;
• and
• be supported by a base frame;
• and
• the magnetic gravity compensator is configured to have a negative stiffness based on a combination of absolute control and relative control of an actuator.

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, comprising:

• generating, by a first sensor, a first measurement signal representative of a relative distance between the first part of the apparatus and the second part of the apparatus;
• generating, by a second sensor, a second measurement signal representative of an acceleration of the first part of the apparatus;
• receiving, by a first sub-controller of a controller, the first measurement signal;
• receiving, by a second sub-controller of the controller, the second measurement signal;
• generating, by the controller, 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 gravity compensator is configured to have the negative stiffness based on a combination of absolute control and relative control of the actuator device;
• using a sensor frame for the first part;
• and
• using an intermediate frame for the second part, the intermediate frame configured to:
• support the sensor frame;
• and
• be supported by a base frame.

A vibration isolation system comprising a bearing device arranged to support in a vertical direction a first part of an apparatus with respect to a second part of the 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;
• the first part comprises a sensor frame;
• and
• the second part comprises an intermediate frame configured to:
• support the sensor frame;
• and
• be supported by a base frame;
• and
• the magnetic gravity compensator is configured to have a negative stiffness based on a combination of absolute control and relative control of an actuator.