Solid-State Actuator Control for Creep and Hysteresis Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Deviations between desired and actual strain in solid-state actuators due to hysteresis and creep effects, leading to delays in microlithographic projection exposure apparatus operations, are not adequately addressed by current control methods.
Innovation Solution
A method involving a correction model with correction functions for creep and hysteresis, using a feedforward approach, to ascertain a control variable for actuating solid-state actuators, and optionally using a separate energy source for continuous operation, to reduce the impact of creep and hysteresis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solid-state actuators are used to adjust optical elements, then positioning precision is improved, but creep effects cause deviation from target strain and delay system equilibrium
Solution Approach 1:
The patent applies preliminary action by pre-calculating creep compensation values and storing them in lookup tables before actual operation. The controller retrieves pre-computed compensation values based on current actuator state and target position, applying corrections before creep fully develops. This anticipatory approach eliminates waiting time for equilibrium while maintaining positioning precision.
Solution Approach 2:
The patent implements feedback by continuously monitoring actual actuator position and comparing it with target position. The controller uses this feedback information to retrieve appropriate compensation values from lookup tables and adjust control signals in real-time, counteracting creep effects and maintaining accurate positioning despite time-dependent deformation.
2Manufacturing precision
If solid-state actuators are used for optical element adjustment, then actuation precision is improved, but hysteresis effects cause deviation between desired and actual strain
Solution Approach 1:
The patent pre-calculates and stores hysteresis compensation values in lookup tables during system initialization or calibration phases. These pre-computed compensation values account for hysteresis effects across different actuator states and target positions. During operation, the controller retrieves appropriate compensation values based on current state, eliminating the need for real-time hysteresis calculation and ensuring accurate strain control.
Solution Approach 2:
The patent uses feedback mechanisms to monitor actual actuator strain and compare it with desired strain. Based on this comparison, the controller retrieves compensation values from lookup tables and adjusts control signals to counteract hysteresis effects, ensuring that actual strain matches desired strain despite hysteresis non-linearity.
3Manufacturing precision
If waiting for system equilibrium is implemented, then positioning accuracy is improved, but operational productivity is reduced due to delays
Solution Approach 1:
The patent eliminates equilibrium waiting time by pre-calculating compensation values for creep and hysteresis effects. The controller applies these pre-computed corrections immediately when actuation commands are issued, achieving accurate positioning without requiring the system to wait for creep to naturally subside or equilibrium to be reached, thus maintaining high operational productivity.
Solution Approach 2:
The patent uses real-time feedback to monitor actuator state and retrieve appropriate compensation values from lookup tables. This feedback-driven approach allows the system to dynamically adjust for creep and hysteresis effects during operation, achieving positioning accuracy without requiring prolonged equilibrium periods, thereby maintaining high operational speed.
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 method significantly reduces the time to achieve equilibrium and desired accuracy in solid-state actuators, ensuring precise control and reducing the delay in microlithographic projection exposure apparatus operations.
Implementation Method 1
solid-state actuators within the meaning of the present disclosure are electrostrictive or piezoelectric actuators
Implementation Method 2
solid-state actuators within the meaning of the present disclosure are electrostrictive or piezoelectric actuators
Implementation Method 3
An issue with creep for example is that the time constant is relatively long, and so the equilibrium state of the solid-state actuator is either not reached at all or only reached a relatively long time after the operating point has been set
Implementation Method 4
Deviations between the predetermined or desired strain (target variable) and the actual strain can arise, inter alia on account of hysteresis and creep effects
Data Source
AI summary
A method of operating at least one solid-state actuator in a microlithographic projection exposure apparatus comprises the following steps:requesting a target variable for the at least one solid-state actuator;ascertaining a control variable using a stored or storable correction model, the correction model comprising a correction function for creep; andactuating the at least one solid-state actuator using the control variable and switching the at least one solid-state actuator from a switched-off state into a switched-on state by feeding energy from an energy source.