JPH0226338A - Precision vibration eliminator - Google Patents

Abstract

PURPOSE:To make an extensive vibration detectable with a simple device as well as to perform a yet more accurate vibro-elimination by installing such a sensor that detects the vibration of a surface plate in dividing it into a vibration in a floor on which a precision vibration eliminator is set up, and a relative vibration of the surface plate to this floor, respectively. CONSTITUTION:Vibrations in a surface plate 2 are divided into a vibration in a floor 3 on which a precision vibration eliminator is set up, and a relative vibration in the surface plate 2 to this floor, detecting each with a floor vibrograph 22 or a sensor with no natural frequency characteristic and a measurer 21. Each output signal out of these floor vibrograph 22 and measurer 21 is composed at a control part 23 and, after setting it down to the vibration of the surface plate 2, it is subjected to a signal process, outputting a control signal of opposite phase to the vibration. A force actuator (active damper) 8 is operated by this control signal, and the vibration of the surface plate 2 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a precision vibration isolator having an active vibration isolator for isolating vibrations from the floor and excitation of precision equipment mounted on a tower itself.

[Problems to be solved by the prior art and the invention] Precision equipment such as electron microscopes and holography devices that apply light and electron beams may suffer from vibrations that obstruct the optical path, and LSI manufacturing equipment such as steppers may be placed in the same location. Because circuits are drawn one after another, alignment may not be possible due to vibration,
Since the processing time may be long, it is used by placing it on a vibration isolator. As such a vibration isolator, there has conventionally been a passive vibration isolator that damps vibrations using vibration absorbing means such as an air spring, a coil spring, or a vibration isolating rubber. However, although such a passive vibration isolator can isolate vibrations from the floor, it cannot effectively isolate vibrations such as the self-excitation of the precision equipment itself or the natural vibrations of the vibration isolation table surface plate. Therefore, there is an active vibration isolator that detects the vibration of the surface plate and operates an actuator or the like in the opposite phase to the vibration to actively isolate the vibration. In such an active vibration isolator, as shown in FIG. The vibration of the surface plate 2 is detected by the sensor 6, and the signal from the sensor 6 is processed by the control section 7, and the force actuator 8 is actuated to excite vibrations having the opposite phase to the vibrations generated in the surface plate 2. Vibration isolation is being performed. As the actuator 8, a hydraulic actuator, an air actuator, an electromagnetic force actuator, etc. are used, but generally an electromagnetic force actuator such as a linear motor is installed directly on the surface plate 2 to perform active vibration isolation.

The sensor that detects the vibration of the surface plate of a precision vibration isolator that performs such active vibration isolation has its own natural frequency,
If a vibration with the same frequency as the sensor's natural frequency occurs, it will resonate and produce an output with phase and amplitude characteristics. For this reason,
Large-scale correction is required, and detection becomes impossible at vibration frequencies that are difficult to correct.
It has the disadvantage that it can only detect vibrations in a limited range of about Hz and therefore cannot isolate vibrations over a wide range.

In order to eliminate the above-mentioned drawbacks, an object of the present invention is to provide a precision vibration isolator that detects a wide range of vibrations and has a damping effect.

[Means for Solving the Problems] A precision vibration isolator of the present invention that achieves the above object includes a surface plate on which a precision instrument is placed, a passive brake that supports the surface plate, and a passive damper for supporting the surface plate. In a precision vibration isolator comprising a sensor that detects vibration, a control unit that processes the output of the sensor and outputs a control signal having a phase opposite to that of the vibration, and an active damper that operates according to the control signal, the sensor comprises a floor vibration meter installed with the precision vibration isolator and a measuring meter for detecting the relative vibration of the surface plate with respect to the floor, and the control unit combines the outputs of the floor vibration meter and the measuring meter to It is characterized by having a means for making the surface plate vibrate.

[Example] Preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 is a schematic structural diagram of a precision vibration isolator according to the present invention. In FIG. 1, a surface plate 2 on which a precision instrument 1 is placed is supported by an air spring 4 and a viscous brake 5, which are passive brakes, while being isolated to some extent from vibrations of a floor 3. Furthermore, the surface plate 2 responds to the output of a regulator 23, which is a control unit, which simultaneously processes the measured values of a displacement meter 21 and a floor vibration meter 22, which are measuring meters of vibration relative to the floor, and outputs a control signal by phasing the measured values. It is actively supported by a motor actuator 8 that is driven by a motor.

The displacement meter 21 of the precision vibration isolator having such a configuration has no frequency characteristics, vibrates together with the floor 3, and can measure the relative vibration of the surface plate 2 with respect to the floor 3. As shown in the schematic diagram of FIG. 2, the displacement meter 21 is approximately 5KH.
The core frame 24 fixed to the surface plate 2 moves up and down with vibration through the coil a through which a current of z is passed, and the current flowing through the coil b is measured at the point b, between b2, and b2, b. The position of the core frame 24 is detected and the vibration of the surface plate 2 relative to the floor 3 is measured.

The floor vibration meter 22 that measures floor vibration is a servo type vibration meter that measures acceleration using a feedback control system. Since the servo-type vibrometer has a high natural frequency and is large, it is inconvenient to install the servo-type vibrometer directly on the surface plate 2, and if it is installed directly on the surface plate 2, the natural frequency of the surface plate 2 will be However, floor vibrations can be measured without any problems in the measurement frequency range from a few Hz below the decimal point to 100 Hz.

After measuring the vibration acceleration of the floor and the displacement of the surface plate relative to the floor in this way, as shown in the circuit diagram of FIG. Displacement is processed by a differential circuit and synthesized as vibration of the floor + vibration of the surface plate relative to the floor to obtain the vibration of the surface plate, which is reversed in phase and amplified by an amplifier to output a drive signal. Active vibration isolation can be performed by driving the actuator. Although the integrating circuit and the differentiating circuit also have frequency characteristics, they may be selected to have circuit constants that do not affect the vibration isolation range.

In the above-described embodiment, the vibration of the floor was measured using a servo-type vibration meter, and the vibration of the surface plate relative to the floor was measured using a displacement meter. However, the present invention is not limited to this. A known sensor without frequency characteristics may also be used.

C action] The precision vibration isolator described above does not directly detect the vibration of the surface plate, but separates it into the vibration of the floor on which the precision vibration isolator is installed and the vibration of the surface plate relative to the floor, and detects the natural vibration. Measurements are taken using sensors without numerical characteristics, and the measured values are synthesized to determine the absolute vibration of the surface plate and perform vibration isolation.

[Effects of the Invention] As is clear from the above description, according to the precision vibration isolator of the present invention, vibrations of the surface plate can be directly detected.

Due to the sensor's natural vibration, a wide range of vibrations could not be detected, and therefore only a narrow range of vibrations could be isolated.However, with a simple device, it is now possible to detect a wide range of vibrations, and more accurate vibration isolation can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a structural schematic diagram of one embodiment of a precision vibration isolator using the present invention, Fig. 2 is a partial schematic diagram of one embodiment, Fig. 3 is a circuit diagram of one embodiment, and Fig. 4 is a conventional one. FIG. 2 is a diagram showing a precision vibration isolator. 2... Surface plate 3... Floor 4... Air spring (passive brake) 5...
... Viscous brake (passive brake) 8 ... Actuator (active brake) 21 ... Displacement meter (measuring meter) 22 ... Floor vibration meter 23 ...・Adjuster (control unit)

Claims (1)

[Claims] A surface plate on which precision equipment is placed, a passive brake that supports the surface plate, a sensor that detects the vibration of the surface plate, and a signal processing of the output of the sensor to output a control signal having a phase opposite to that of the vibration. In the precision vibration isolator, the sensor includes a vibration meter on a floor installed in the precision vibration isolator and a relative vibration of the surface plate with respect to the floor. A precision vibration isolator comprising a measuring meter, wherein the control section has means for combining the outputs of the floor vibration meter and the measuring meter to produce vibrations of the surface plate.