Vibration isolating apparatus for table for mounting device sensitive to vibrations and method therefor

• US 6,536,735 B2
• Filed: 10/09/2001
• Issued: 03/25/2003
• Est. Priority Date: 10/10/2000
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Watanabe, Katsuhide, Haga, Takahide, Jouno, Yoshinori
• Primary Examiner(s): King, Anita
• Assistant Examiner(s): Le, Tan
• Application Number:
  US09/971,666
• Publication Number:
  US 20020074474A1
• Time in Patent Office: 532 Days
• Field of Search: 248/550, 248/637, 248/639, 248/638, 248/562, 248/636, 188/267, 736/62, 736/63, 267/136
• US Class Current: 248/550
• CPC Class Codes: F16F 15/02 Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems F16F15/005 takes precedence ; layered products B32B; suppression of vibration in ships B63; relieving load on bearings, using magnetic means F16C39/06
• CPC Class Codes: G02B 21/24 Base structure
• CPC Class Codes: G03F 7/709 Vibration, e.g. vibration detection, compensation, suppression or isolation
• CPC Class Codes: G05D 19/02 characterised by the use of electric means

Abstract

There are disclosed a vibration isolating apparatus and a vibration eliminating method imposed less restrictions on the positioning of components, such as active actuators, forming part of the vibration isolating apparatus. The vibration isolating apparatus can be implemented with a relatively simple controller (such as an analog circuit) and can limit the interference of control forces to a practically ignorable degree. The vibration isolating apparatus has a table for mounting thereon a device vulnerable to vibrations, a plurality of sensors 15-20 for detecting motions of the table and a plurality of active actuators 11-14 for controlling positions of the table. Processing and controlling means converts values measured by the respective sensors and control forces exerted by the respective active actuators to control and operating amounts for motions in a total of six degrees of freedom: one each for translation in the vertical direction and for rotation about the axis of the translation of the device vulnerable to vibrations, resiliently supported by the vibration isolating apparatus, or the table, and two each for translations on a horizontal plane and rotations about the axes of the translations. The conversion is performed on the assumption that the resilient supporting center matches the center of gravity, and based on the two-dimensional positional relationship between the resilient supporting center and the sensors and the active actuators.

Claims

1. A vibration isolating apparatus for removing a vibration of a table on which a device vulnerable to vibrations is mounted, said table being movable along anyone of a first axis, a second axis and a third axis, said second and third axes being orthogonal to said first axis, said apparatus comprising:

actuators for holding said table in a predetermined position, at least one of which is positioned in each of four quadrants partitioned by said second axis and said third axis;

at least three first sensors for detecting a translational motion along said first axis;

at least two second sensors for detecting a translational motion along said second axis;

at least one third sensor for detecting a translational motion along said third axis, and

a calculating unit responsive to outputs from said first, second and third sensors to produce an activating signal so as to minimize a difference between forces generated by said actuators.

2. A vibration isolating apparatus for removing a vibration of a table on which a device sensitive to vibrations is mounted, said apparatus comprising:

sensor means for detecting three-dimensional motions of said table and outputting three-dimensional detection outputs;

actuator means for holding said table in a predetermined position in response to activation signals, said activation signals being applied to said actuator means; and

a calculating unit for converting the three-dimensional detection outputs from said sensor means to the activation signals for activating said actuator means, on the assumption that the center of resilient support by said actuator means matches the center of gravity;

wherein said calculating unit comprises;

a first conversion unit for converting detection outputs from said sensor means to a translational motion component representing a translational motion of said table and a rotational motion component representing a rotational motion of said table;

a second conversion unit for converting said translational motion component and said rotational motion component to a force required for removing vibrations of said table; and

a third conversion unit for converting said force to an electric signal for actuating said actuator means;

wherein said sensor means is disposed to detect a translational motion along a first axis vertical to said table, a translational motion along a second axis vertical to said first axis and parallel to said table, and a translational motion along a third axis vertical to said second axis and parallel to said table, and wherein said calculating unit is operable to calculate translational motion components along said first to third axes and rotational motion components about said first to third axes on the basis of the detection output of said sensor means to produce activation signals from said translational motion components and said rotational motion components for activating said actuating means; and

wherein said actuator means comprises actuators at least one of which is positioned in each of four quadrants partitioned by said second axis and said third axis,

wherein said sensor means comprises at least three first sensors for detecting a translational motion along said first axis, at least two second sensors for detecting a translational motion along said second axis and at least one third sensor for detecting a translational motion along said third axis, and

wherein said calculating unit produces said activating signal so as to minimize a difference between forces generated by said actuators.

3. A vibration isolating apparatus according to claim 2, wherein said at least two second sensors have detecting axes different from each other.

4. A vibration isolating apparatus according to claim 2, wherein said actuator means comprises:

at least one first actuator disposed on said second axis;

at least one second actuator disposed in either one of two quadrants of four quadrants partitioned by said second axis and said third axis, said two quadrants being opposite to said first actuator with respect to said third axis; and

at least one third actuator disposed in the other of the two quadrants of the four quadrants, said two quadrants being opposite to said first actuator with respect to said third axis,

wherein said sensor means comprises;

at least three first sensors for detecting a translational motion along said first axis;

at least two second sensors for detecting a translational motion along said second axis; and

at least one third sensor for detecting a translational motion along said third axis,

and wherein said calculating unit produces said activating signal so as to minimize a difference between forces generated by said first to third actuators.

5. A vibration isolating apparatus according to claim 4, wherein said at least two second sensors have different detecting axes each other.