Active Vibration Isolator Feed-Forward Control
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Solution Overview
Problem
Existing active vibration isolators face challenges in achieving precise control of vibrations in precision instruments like semiconductors due to deviations in estimated acceleration values, which are not subjected to feedback control, leading to interference with vibration control performance.
Innovation Solution
The active vibration isolator incorporates a stage condition obtaining unit that measures the actual thrust applied to the stage, combining it with the stage's position to generate a control force, thereby reducing vibrations caused by the stage's movement and torque, using a controller to adjust the actuator's control force in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the acceleration of the stage is estimated without using the acceleration sensor, then the manufacturing cost is reduced, but the estimated value deviates from the actual acceleration due to friction and other forces
Solution Approach 1:
The patent introduces feedback control for stage acceleration by using the acceleration sensor to detect actual acceleration and comparing it with the estimated acceleration. The deviation detection unit calculates the difference between actual and estimated acceleration, and this feedback is used to correct the estimation, thereby resolving the accuracy issue while maintaining cost-effectiveness.
Solution Approach 2:
The patent replaces the purely mechanical estimation method (based on stage control information) with a hybrid approach that incorporates sensor-based detection. The acceleration sensor substitutes for the insufficient mechanical estimation model, providing accurate real-time acceleration data that accounts for friction and other forces.
2Measurement precision
If feedback control is applied to stage acceleration, then the deviation between estimated and actual acceleration is eliminated, but the device complexity increases
Solution Approach 1:
The patent merges the acceleration feedback control with the existing vibration isolation control system. The deviation detection unit and acceleration feedback unit are integrated into the controller that already manages the vibration isolation table, combining multiple functions into a unified control architecture rather than adding separate independent systems.
Solution Approach 2:
The controller is designed to perform multiple functions: it estimates stage acceleration from control information, detects actual acceleration via the sensor, calculates deviations, and applies correction forces for vibration isolation. This multi-functional approach reduces overall system complexity by consolidating control tasks.
3Reliability
If the actuator control force is adjusted in real-time based on actual thrust, then vibration control performance is enhanced, but the response time requirement increases
Solution Approach 1:
The patent applies preliminary action by using feed-forward control based on estimated acceleration derived from stage control information. The control force is adjusted in advance based on predicted stage motion, preventing vibrations before they occur rather than reacting to them, which is especially important for actuators with long response lags.
Solution Approach 2:
The patent ensures continuous control by combining feed-forward control (based on estimated acceleration) with feedback control (based on actual acceleration measurement). This continuous adjustment of control force maintains optimal vibration compensation throughout the entire stage motion cycle, accommodating actuators with varying response characteristics.
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 configuration enhances vibration control performance by accurately accounting for friction and other forces, allowing for more precise control of vibrations, even with actuators that have long response lags, such as pneumatic actuators, thereby reducing shaking effectively.
Implementation Method 1
an actuator that imparts, to the vibration isolation table, a control force that reduces vibrations of the vibration isolation table
Data Source
AI summary
An active vibration isolator including a movable stage provides good vibration isolation performance. An active vibration isolator includes: a stage moving under thrust to position a mounted object; a vibration isolation table supporting the stage; a servo valve imparting, to the vibration isolation table, a control force that reduces vibrations of the vibration isolation table; a position/thrust obtaining unit obtaining a position of the stage on a movement track and the thrust actually applied to the stage with movement of the stage; and a vibration control FF control unit performing feed-forward control of the servo valve, based on what is obtained by the position/thrust obtaining unit, to allow the servo valve to generate a control force commensurate with vibrations of the vibration isolation table caused by the movement of the stage.