Reluctance Motor Control for Lithographic Positioning Accuracy
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Solution Overview
Problem
Lithographic apparatuses face challenges with heat dissipation and control accuracy due to the use of Lorentz motors for short stroke modules, which are inefficient and prone to inaccuracies when high forces are required, and reluctance motors, which can cause nonlinear behavior and parasitic damping effects.
Innovation Solution
A control system that uses a combination of reluctance motors and another type of motor, with a controller adjusting the force applied by the reluctance motors based on feedback from force sensing elements and adjusting the gap between the motor's core and flux carrier bar to optimize performance, allowing for efficient and accurate positioning of the short stroke module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Lorentz motor is used for the short stroke module, then positioning accuracy is improved, but heat dissipation increases and efficiency decreases
Solution Approach 1:
The positioning system is segmented into two motor types: reluctance motors for coarse positioning and Lorentz motors for fine positioning. This segmentation allows each motor type to operate in its optimal performance range, with the Lorentz motor only needed for final precision adjustments rather than continuous operation.
Solution Approach 2:
The system dynamically switches between reluctance motors and Lorentz motors based on positioning requirements. The controller activates the appropriate motor type depending on whether coarse or fine positioning is needed, optimizing the balance between accuracy and energy efficiency throughout the positioning process.
2Loss of energy
If a reluctance motor is used for the short stroke module, then efficiency is improved and heat dissipation is reduced, but positioning accuracy deteriorates due to nonlinear behavior and parasitic damping
Solution Approach 1:
The positioning task is segmented into coarse positioning (handled by reluctance motors) and fine positioning (handled by Lorentz motors). This segmentation allows the reluctance motor to operate in its efficient range without requiring it to provide the final precision positioning.
Solution Approach 2:
The Lorentz motor acts as an intermediary for fine positioning adjustments. After the reluctance motor brings the stage near the target position, the Lorentz motor provides the precise final adjustments, compensating for the nonlinear behavior and parasitic damping of the reluctance motor.
3Measurement precision
If two types of motors are used with switching between them, then positioning performance is improved, but system complexity increases
Solution Approach 1:
The system merges two motor types (reluctance and Lorentz) into a unified positioning system with a single controller that manages both motor types. This integration allows coordinated operation of both motors through a single control interface, reducing operational complexity despite having multiple motor types.
Solution Approach 2:
The controller is designed with universal functionality to manage both reluctance motors and Lorentz motors. This multi-functionality allows the same control system to handle different motor types and positioning modes (coarse and fine positioning) without requiring separate control systems for each motor type.
4Measurement precision
If motor switching is implemented between coarse and fine positioning phases, then positioning accuracy is improved, but positioning time increases due to phase transitions
Solution Approach 1:
The reluctance motor performs preliminary coarse positioning to bring the stage close to the target position before the Lorentz motor takes over for fine positioning. This preliminary action reduces the distance the Lorentz motor must travel, minimizing the time spent in the fine positioning phase.
Solution Approach 2:
The transition between reluctance motor and Lorentz motor operation is designed to be continuous rather than interruptive. The motors are coordinated to operate seamlessly in sequence, with the Lorentz motor engaging as the reluctance motor approaches the target, maintaining continuous useful action throughout the positioning process.
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
This solution enables efficient and accurate positioning of the short stroke module by minimizing heat generation and parasitic effects, improving control accuracy and reducing interference between different motor types, allowing for continuous actuation without the need to switch motors during positioning.
Implementation Method 1
a force sensing element configured to sense an amount of force applied by a corresponding reluctance motor
Implementation Method 2
adjusting the gap between the motor's core and flux carrier bar to optimize performance
Data Source
AI summary
A control system controls a positioning device displaceable in at least one degree of freedom by a reluctance motor. A force sensing element and a controller adjust force applied by the motor responsive to a force sensing element configured to sense force applied by the motor. The controller receives a signal representing force applied by the motor from the force sensing element, obtain an acceleration trajectory plan associated with a velocity trajectory plan for the positioning device, obtain a force trajectory plan associated with the acceleration trajectory plan, compare the force applied with a required amount of force obtained from the force trajectory, and adjust the amount of force applied by the motor based on the comparison. Related methods are also presented.