Active Vibration Isolation System With Segmented Control Loops
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Solution Overview
Problem
Current active vibration isolation systems face challenges in effectively compensating for vibrations generated by moving stages in the semiconductor industry, particularly due to the need for high force provision by actuators and instability issues arising from overdetermination in control systems.
Innovation Solution
An active vibration isolation system with a coupled control system architecture that integrates pneumatic isolators and actuators, utilizing a sensor-input-steering matrix and actuator-output-steering matrix to distribute control signals across all six degrees of freedom, allowing for comprehensive vibration compensation and minimizing waste heat from Lorentz motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all four pneumatic isolators are actively controlled, then vibration compensation effectiveness is improved, but control system stability deteriorates due to overdetermination
Solution Approach 1:
The control system is segmented into two independent control loops: a first control system handling horizontal degrees of freedom (Xt, Yt, Xr, Yr) and a second control system handling vertical degrees of freedom (Zt, Zr). This segmentation allows each subsystem to operate independently, avoiding the instability caused by overdetermination while maintaining comprehensive vibration compensation across all six degrees of freedom.
2Measurement precision
If electromagnetic actuators are used for vibration compensation, then compensation precision is improved, but waste heat generation increases
Solution Approach 1:
The system uses pneumatic actuators (pneumatic isolators with controllable valves) instead of electromagnetic actuators for vibration compensation. This substitution eliminates the waste heat generation problem associated with electromagnetic actuators while maintaining the ability to provide precise force control for compensating vibrations in all six degrees of freedom.
3Productivity
If heavy stages are moved on the base mass, then productivity is improved, but intrinsic vibrations increase requiring higher actuator force
Solution Approach 1:
The pneumatic isolators are designed to serve multiple functions: they provide both static load support and dynamic vibration compensation forces. By controlling the valve openings of the pneumatic isolators, the system can generate the necessary compensation forces for intrinsic vibrations generated by heavy stage movements, eliminating the need for separate compensation mechanisms and reducing overall actuator force requirements.
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 system achieves comprehensive vibration compensation across all six degrees of freedom, reducing instability and enabling the use of all pneumatic isolators actively, thereby improving the effectiveness and efficiency of vibration isolation while minimizing waste heat and operational challenges.
Implementation Method 1
a passive vibration isolation system... An air bearing and a polymer spring element for mounting are two examples of a passive vibration isolation system
Implementation Method 2
active vibration isolation is characterized in that the vibration is actively compensated. A movement induced by a vibration is compensated by a corresponding counter-movement. The resultant total acceleration of the load is zero.
Data Source
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AI summary
The invention relates to both a method for controlling an active vibration isolation system and an active vibration isolation system itself. The active vibration isolation system is used for vibration-isolated mounting of lithography equipment, wafer handling systems, and/or microscopes, such as scanning microscopes. It comprises the following components: a base mass for supporting a load to be isolated; pneumatic vibration isolators with adjustable valves for supporting the base mass against a support; position sensors for providing vertical position signals of the base mass; and a first control system (10) for vibration compensation in at least one translational degree of freedom and at least one rotational degree of freedom, as well as a second pneumatic control system (20) for vibration compensation in at least one of three vertically effective degrees of freedom.