Method and apparatus for operating a vibration isolation system having electronic and pneumatic control systems

• US 6,523,695 B1
• Filed: 09/15/2000
• Issued: 02/25/2003
• Est. Priority Date: 09/15/2000
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Binnard, Michael, Ueta, Toshio
• Primary Examiner(s): Graham, Matthew C.
• Application Number:
  US09/662,840
• Time in Patent Office: 893 Days
• Field of Search: 188/378, 188/379, 188/380, 267/64.11, 267/140.14, 267/140.15, 267/64.28
• US Class Current: 267/136
• CPC Class Codes: F16F 15/0275 Control of stiffness
• CPC Class Codes: G03F 7/709 Vibration, e.g. vibration detection, compensation, suppression or isolation

Abstract

A method and apparatus for implementing an active vibration isolation system (AVIS) is provided. The AVIS includes a pneumatic control system and an electronic control system. The pneumatic control system supports a mass sensitive to vibration and isolates the mass from high frequency external disturbances. The electronic control system isolates the mass from low frequency external disturbances. The pneumatic control system includes a compliance chamber filled with a fluid to pneumatically support the mass, pressure sensor to measure the pressure level in the compliance chamber, and pneumatic actuator to control the pressure level to minimize the effects of pressure variation in the compliance chamber. The electronic control system includes at least one motion sensor to measure the actual position of the mass as the mass moves due to vibration, at least one feedback system to generate a corresponding signal, an electronic controller to generate signal(s) representing the calculated electronic force needed to compensate for the vibration, and an electronic actuator to generate the electric force to isolate the mass from the external disturbances. The pneumatic and electronic control systems work together to provide high frequency response and eliminate heat dissipation from the electronic control system.

Claims

1. A method for operating a vibration isolation system having a pneumatic control system and an electronic control system, comprising the steps of:

monitoring a motion error signal of a mass in the electronic control system, the motion error signal being used to generate an electronic error signal;

delivering the electronic error signal to the pneumatic control system;

generating a pneumatic force in the pneumatic control system to support the mass, the pneumatic force being determined based on a combination of the electronic error signal and a pressure level in a compliance chamber, the pressure level being controlled in response to a pressure error signal;

delivering the pressure error signal to the electric control system; and

generating an electronic force in the electronic control system to isolate the mass from vibration, the electronic force being determined based on the pressure error signal.

2. The method of claim 1, wherein the step of monitoring a motion error signal in the electronic control system, further comprises:

measuring a motion of the mass to generate a motion signal; and

generating the motion error signal based on the motion signal and a reference motion signal.

3. The method of claim 2, wherein the step of measuring a motion, further comprises:

measuring a position of the mass.

4. The method of claim 3, wherein the step of generating the motion error signal, further comprises:

determining a position signal based on the measured position; and

comparing the position signal with a reference position signal to generate the motion error signal.

5. The method of claim 2, wherein the step of measuring a motion, further comprises:

measuring a velocity of the mass.

6. The method of claim 5, wherein the step of generating the motion error signal, further comprises:

determining a velocity signal based on the measured velocity; and

comparing the velocity signal with a reference velocity signal to generate the motion error signal.

7. The method of claim 3, further comprising:

determining the reference motion signal.

8. The method of claim 7, further comprising:

determining a motion force error signal based on the motion error signal.

9. The method of claim 8, further comprising:

generating a disturbance canceling force signal to counteract the motion force error signal, and resulting in an electronic error signal.

10. The method of claim 9, wherein the step of generating a disturbance canceling force signal, further comprises:

determining the disturbance canceling force signal.

11. The method of claim 1, wherein the step of generating a pneumatic force in the pneumatic control system, further comprises:

measuring the pressure level of the compliance chamber; and

determining a pressure signal based on the measured pressure level.

12. The method of claim 1, wherein the step of generating a pneumatic force, further comprises:

comparing the pressure signal with a reference pressure signal, and combining the electronic error signal thereto to generate a pressure error signal.

13. The method of claim 12, wherein the step of generating a pneumatic force, further comprises.

controlling the pressure level in the compliance chamber in response to the pressure error signal.

14. The method of claim 12, wherein the step of generating a pneumatic force, further comprises:

determining the reference pressure signal.

15. The method of claim 1, wherein the step of generating a pneumatic force in the pneumatic control system, further comprises:

maintaining a constant pressure level in the compliance chamber.

16. The method of claim 1, wherein the step of generating an electronic force in the electronic control system, further comprises:

determining the electronic force based on the pressure error signal.

17. A method for operating a vibration isolation system having a pneumatic control system and an electronic control system, comprising the steps of:

comparing an actual motion signal of a mass in the electronic control system with a reference motion signal to generate a motion error signal;

determining an electronic error signal based on the motion error signal;

delivering the electronic error signal to the pneumatic control system;

comparing a pressure signal of a compliance chamber in the pneumatic control system with a reference pressure signal, and combining the electronic error signal thereto to generate a pressure error signal;

controlling the pressure level in the compliance chamber in response to the pressure error signal, the compliance chamber generating a pneumatic force proportionate to the controlled pressure level to pneumatically support the mass;

delivering the pressure error signal to the electronic control system;

determining an electronic force in the electronic control system based on the pressure error signal to isolate the mass from vibration.

18. The method of claim 17, wherein the step of comparing an actual motion signal in the electronic control system, further comprises:

measuring a position of the mass;

determining a position signal based on the measured position; and

comparing the position signal with a reference position signal to generate the motion error signal.

19. The method of claim 17, wherein the step of comparing an actual motion signal in the electronic control system, further comprises:

measuring a velocity of the mass;

determining a velocity signal based on the measured velocity; and

comparing the velocity signal with a reference velocity signal to generate the motion error signal.

20. The method of claim 17, wherein the step of determining an electronic error signal in the electronic control system, further comprising:

determining a motion force error signal based on the motion error signal.

21. The method of claim 20, wherein the step of determining an electronic error signal in the electronic control system, further comprising:

generating a disturbance canceling force signal to counteract the motion force error signal, and resulting in the electronic error signal.

22. The method of claim 17, wherein the step of comparing a measured pressure signal in the pneumatic control system, further comprises:

measuring the pressure level in the compliance chamber to generate a pressure signal; and

determining the pressure signal based on the measured pressure level.

23. The method of claim 17, wherein the step of controlling the pressure level in the pneumatic control system, further comprises:

maintaining a constant pressure level in the compliance chamber.

24. A vibration isolation system having a pneumatic control system and an electronic control system, comprising:

a motion sensor to generate a motion error signal of a mass in the electronic control system, the motion error signal being used to generate an electronic error signal;

a compliance chamber and a pressure sensor in the pneumatic control system, the pressure sensor controlling a pressure level in the compliance chamber to generate a pressure error signal;

a pneumatic force generator connected to the compliance chamber and electronic control system, the pneumatic force generator generating a pneumatic force that supports the mass based on the results of a combination of the electronic error signal and the pressure level in the compliance chamber;

an electronic force generator connected to the pneumatic control system, the electronic force generator generating an electronic force that isolates the mass from vibration based on the pressure error signal.

25. A vibration isolation system having a pneumatic control system and an electronic control system, comprising:

a first controller to compare an actual motion signal of a mass in the electronic control system with a reference motion signal to generate a motion error signal, and to determine an electronic error signal based on the motion error signal;

a second controller to compare a pressure signal of a compliance chamber in the pneumatic control system with a reference pressure signal, and to combine the electronic error signal thereto to generate a pressure error signal;

a third controller to control the pressure level in the compliance chamber in response to the pressure error signal, the compliance chamber generating a pneumatic force proportionate to the controlled pressure level to pneumatically support the mass;

a fourth controller to determine an electronic force in the electronic control system based on the pressure error signal to isolate the mass from vibration.