Magnetic Gravity Compensator for Low-Stiffness Vibration Isolation
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Solution Overview
Problem
Current vibration isolation systems in lithographic apparatuses, especially in vacuum environments, fail to provide the required performance due to the combination of low stiffness and high mass, which negatively affects sensor performance and the lithographic process.
Innovation Solution
A magnetic gravity compensator with a bearing device comprising a first and second permanent magnet assembly, where vertically adjacent magnets have opposite polarization directions, supporting a lithographic apparatus to achieve low stiffness and high payload capacity, and a control system using sensors and actuators to manage resonance and damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional vibration isolation systems are used, then they can support high mass, but they have high stiffness which transfers vibrations
Solution Approach 1:
The magnetic gravity compensator uses permanent magnet assemblies to generate magnetic forces that counterbalance the gravitational force on the supported mass. The first and second permanent magnet assemblies create opposing magnetic fields that provide an upward force equal to the weight of the supported structure, effectively canceling gravity and enabling ultra-low stiffness support while maintaining high payload capacity.
Solution Approach 2:
The invention replaces conventional mechanical spring-based vibration isolation systems with a magnetic field-based gravity compensator. This substitution eliminates the need for mechanical elastic elements, allowing the system to achieve payload support through magnetic forces while providing vibration isolation through controlled negative stiffness magnetic interactions.
2Object-affected harmful factors
If low stiffness is achieved for vibration isolation, then vibration transfer is reduced, but the system becomes unstable due to negative stiffness
Solution Approach 1:
The system incorporates sensors that detect the position of the supported structure and feeds this information back to actuators. The actuators adjust the magnetic field strength in real-time to maintain stability, compensating for the inherent negative stiffness of the magnetic gravity compensator and preventing system collapse while preserving ultra-low stiffness vibration isolation.
Solution Approach 2:
The invention combines permanent magnet assemblies with active control elements (sensors and actuators) to create a composite system. The permanent magnets provide the passive negative stiffness characteristic for vibration isolation, while the active control system adds stabilizing positive stiffness, resulting in a composite system that achieves both ultra-low vibration transfer and stability.
3Force
If permanent magnet assemblies are configured with vertically adjacent magnets having opposite polarization directions, then gravitational compensation is achieved, but device complexity increases
Solution Approach 1:
The magnetic gravity compensator is divided into separate first and second permanent magnet assemblies, each with specific column configurations. This segmentation allows independent optimization of each assembly's magnetic field contribution to gravitational compensation while simplifying the overall design and assembly process compared to a single complex magnet structure.
Solution Approach 2:
The first permanent magnet assembly at least partially encloses the second permanent magnet assembly, creating a nested configuration. This nesting arrangement optimizes the magnetic field distribution for gravitational compensation while reducing the overall footprint and simplifying the structural support requirements compared to side-by-side magnet assemblies.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The magnetic gravity compensator significantly improves vibration isolation, achieving a higher payload-to-stiffness ratio and enabling stable operation in vacuum environments, enhancing sensor performance and the overall lithographic process.
Implementation Method 1
a magnetic gravity compensator comprising a first permanent magnet assembly mounted to a first part of the lithographic apparatus and comprising at least a first column of permanent magnets
Implementation Method 2
the permanent magnets have a polarization direction in a first horizontal direction or in a second horizontal direction opposite to the first horizontal direction
Implementation Method 3
vibration isolation systems are used to support a first part of the lithographic apparatus with respect to a second part, while at the same time transfer of vibrations from the second part of the lithographic apparatus to the first part
Data Source
AI summary
The invention relates to 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, comprising 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 the 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, 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.