Piezo Actuator Assembly Feedback Control for Vibration-Free Positioning
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Solution Overview
Problem
In lithographic apparatuses, the precise positioning of substrates and optical elements using multiple piezo or electrostrictive actuators is challenging due to differences in expansion and contraction, leading to non-zero resultant forces that cause vibrations and stress in the load.
Innovation Solution
An actuator assembly comprising multiple piezo or electrostrictive actuators, where a correction unit determines an output voltage difference between the actuators and adjusts the power signals to ensure synchronized expansion and contraction, thereby reducing vibrations and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple piezo or electrostrictive actuators are used to position substrates and optical elements, then positioning capability is improved, but differences in expansion and contraction cause vibrations and stress in the load
Solution Approach 1:
The patent implements a feedback control system where the control unit monitors the operation of multiple piezo or electrostrictive actuators and adjusts their power signals in real-time. This feedback mechanism detects differences in expansion and contraction behavior among actuators and compensates for these variations by modifying individual actuator control signals, thereby eliminating vibrations and stress in the load while maintaining high positioning precision
Solution Approach 2:
The patent dynamically changes the power signal parameters supplied to each actuator based on their individual performance characteristics. By adjusting voltage, current, or pulse duration parameters in real-time, the system compensates for manufacturing tolerances and operational variations among actuators, ensuring synchronized expansion and contraction that prevents harmful vibrations and stress
2Length of moving object
If multiple piezo or electrostrictive actuators are used to achieve desired positioning, then positioning range is improved, but control synchronization becomes more difficult
Solution Approach 1:
The patent employs a universal control unit that manages multiple actuators through a unified control architecture. This multi-functional control system can simultaneously adjust the operation of different actuator types (piezo or electrostrictive) using standardized control algorithms and power signal generation, simplifying the coordination complexity while enabling precise control over extended positioning ranges
3Manufacturing precision
If piezo actuators are used to position optical elements and substrate, then positioning accuracy is improved, but manufacturing tolerances cause non-zero resultant forces
Solution Approach 1:
The patent applies a counterbalancing control strategy where the control unit calculates and applies compensatory forces to each actuator based on their individual deviations from ideal performance. By introducing opposing correction forces through adjusted power signals, the system neutralizes non-zero resultant forces that would otherwise arise from manufacturing tolerances, maintaining high positioning accuracy without harmful force imbalances
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 actuator assembly improves the control of piezo or electrostrictive actuators, reducing vibrations, stress, and deformations of the load, thereby enhancing the precision and accuracy of substrate and optical element positioning.
Implementation Method 1
a first piezo or electrostrictive actuator (101, 111) having an input terminal (102, 113) configured to receive a first power signal (201a, 201b) and an output terminal (103, 112), wherein the first piezo or electrostrictive actuator (101, 111) is configured to expand or contract in a first direction when a voltage difference is present between the input terminal (102, 113) and the output terminal (103, 112)
Implementation Method 2
a second piezo or electrostrictive actuator (101, 111) having an input terminal (102, 113) configured to receive a second power signal (201a, 201b) and an output terminal (103, 112), wherein the second piezo or electrostrictive actuator (101, 111) is configured to expand or contract in a second direction when a voltage difference is present between the input terminal (102, 113) and the output terminal (103, 112)
Data Source
AI summary
An actuator assembly including a first piezo actuator and a second piezo actuator. The piezo actuator has a correction unit configured to determine an output voltage difference representing a difference between a voltage at the output terminal of the first piezo actuator and a voltage at the output terminal of the second piezo actuator, and a first power correction for correcting the first power signal and/or a second power correction for correcting the second power signal, based on the output voltage difference.