Active Aerostatic Bearing with Conical Gap Deformation
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Solution Overview
Problem
Aerostatic bearings face limitations in static stiffness and geometrical inaccuracies, leading to inaccuracies in high-precision machines, particularly in semiconductor manufacturing, due to the complexity of pressurized chambers and limited bandwidth in active compensation methods.
Innovation Solution
An active aerostatic bearing design featuring a first plate with a central recess and conical deformation, actuated by a voice coil motor, which uses a parallelogram structure with pivoting points and leaf springs to achieve high passive mechanical stiffness and servo compliance, allowing for linear gap deformation and pressure distribution control without requiring gap measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If passive load compensation methods using deformable membranes are used, then static stiffness is increased, but manufacturing complexity increases due to pressurized chambers
Solution Approach 1:
The patent removes the complex pressurized chambers from the system and replaces them with a simplified structure consisting of a deformable membrane and a single actuator. The membrane itself becomes the load compensation mechanism, eliminating the need for additional pressurized chambers while maintaining infinite static stiffness.
Solution Approach 2:
The patent employs a deformable membrane as the core component for load compensation. This thin film structure can deform under load to maintain constant pressure, providing infinite static stiffness without requiring complex rigid pressurized chambers. The membrane's flexibility allows it to adapt to load changes while maintaining system simplicity.
2Manufacturing precision
If flow restriction control is used for active compensation, then geometrical inaccuracies can be compensated, but bandwidth is limited due to latency in response
Solution Approach 1:
The patent replaces flow restriction control with direct mechanical actuation of the membrane. Instead of controlling air flow rates to compensate for geometrical inaccuracies, a single actuator directly deforms the membrane to achieve the desired shape adjustment. This mechanical substitution eliminates the latency inherent in flow control systems and provides immediate response for bandwidth enhancement.
3Ease of operation
If gap geometry control with electromagnetic actuators is used, then servo compliance is improved, but design complexity increases due to plate deformation requirements
Solution Approach 1:
The patent uses a deformable membrane instead of a rigid plate with electromagnetic actuators. The membrane's inherent flexibility allows it to deform easily under actuator force, providing high servo compliance without requiring complex electromagnetic actuation systems. This approach simplifies the design by replacing complex actuator-plate assemblies with a simple membrane-actuator configuration.
4Stability of the object's composition
If membrane-like thin plates are used to obtain high mechanical stiffness, then passive stiffness is improved, but local deformation occurs under point loading limiting servo impact
Solution Approach 1:
The patent segments the loading area by distributing the actuator force across the entire membrane surface rather than concentrating it at a single point. This segmentation of the force application prevents local deformation and ensures uniform pressure distribution across the bearing pad, maintaining both high mechanical stiffness and accurate servo control.
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 design achieves quasi-infinite stiffness and high load capacity with low actuator force, enabling precise positioning and load capacity adjustment, overcoming the limitations of prior art by balancing pressure and deformation, and maintaining position stability under load changes.
Implementation Method 1
an electromagnetic actuator mounted on the edge of the pad to deform the plate
Implementation Method 2
Pressurized air is forced into a pad. The orifice acts as an inlet restrictor
Implementation Method 3
A deformable membrane can replace the pad's lower surface. In this case, the response of the pad involves both rigid body motion and the deformation of the membrane
Data Source
Figure 1~2
Figure 3(a)~3(c)
Figure 4
AI summary
An active aerostatic bearing is described, comprising a lower plate (1) with a central recess area (R) including an orifice (O) forming an inlet restrictor for pressurized air from a central nozzle (N). An air gap is formed between a guiding surface (S) and the lower plate. The active aerostatic bearing comprises a force actuator (VC, M) acting to deform the lower plate and thus changing the shape of the air gap. The actuator causes a conical deformation of the first plate. Preferably, the first plate, a second plate (2) and four pivoting points (P1, P2, P3, P4) are forming a parallelogram, the shape of the parallelogram being changeable by actuating the actuator.