JPH0914338A - Device and method for insulating vibration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a table itself stable and non-resonant by attaching a base to a vibration source and rotating a screw so that the base slides by the displacement of the vibration source and rotating a motor shaft in the direction that an absolute displacement of a nut or a substance attached to the motor side becomes zero. SOLUTION: When a base 10 is attached to a vibration source and is activated by disturbance vibration, the vibration is detected by an acceleration pickup 9 and a screw 4 is rotated using the detection signal and the signal of a potentiometer 6 for displaying an amount of revolution of the screw 4 so that the base 10 slides by the displacement of the vibration source and a motor shaft is rotated in the direction that an absolute displacement of a nut 3 or a substance attached to the motor 8 side becomes zero, thereby making a table 1 itself stable and non-resonant and thus insulating the vibration of a large amplitude.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration isolator. INDUSTRIAL APPLICABILITY The present invention is used to insulate the vibration of equipment used in a high-rise building, which has a large amplitude and slowly vibrates due to wind or the like, or for the purpose of insulating vibration to equipment due to an earthquake.

[0002]

2. Description of the Related Art Conventional conventional vibration isolators generally support a target device with a spring and a damper, and use a soft spring to insulate external vibration from the device. However, in this method, although vibration isolation can be achieved, the rigidity of the system is lowered, so that it is largely deformed by the force directly acting on the device itself and becomes unstable. In addition to this, there are methods using skyhook dampers, dynamic vibration absorbers, etc., but when using these methods and equipment,
Vibration isolation in the low frequency range is difficult.

In addition to the passive method described above, a vibration isolation method by active control has been developed in recent years. However, in the research so far, since all systems have spring elements, resonance exists in the system, and a method of lowering the resonance peak by damping due to a damper or velocity feedback is used. Furthermore, by making the actuator a piezoelectric actuator or a giant magnetostrictive actuator,
A method for controlling vibration isolation while increasing the rigidity of the system and stabilizing the system has also been developed, but the displacement amount of the actuator is small and the controllable displacement is limited to several μm to several tens of μm. It cannot be used for vibration isolation with a relatively large amplitude as described above.

[0004]

In the above-mentioned prior art,
In the low frequency range of about several Hz, it is difficult to reduce the transmissibility to less than 1, stable when a force acts on the table itself, non-resonant, and to insulate vibrations with large amplitude of about several mm. Met. The present invention provides a vibration isolator that solves all of these problems.

[0005]

A vibration isolator of the present invention comprises a motor, a threaded shaft coupled to the motor shaft, a nut mounted on the screw of the shaft, and a sensor for detecting displacement of the nut. A sensor that detects the displacement of the vibration source,
An object to be isolated from vibration is placed on a table equipped with a thrust bearing and attached to a nut or a motor side (the object may be directly attached to the nut).

FIG. 1 shows a cross-sectional view of one side of the vibration isolator of the present invention. In this figure, when disturbance vibration acts from the base 10 placed on the vibration source,
The vibration is detected by the acceleration pickup 9, and the signal and the signal of the potentiometer 6 representing the rotation amount of the screw are used to rotate the screw 4 by the displacement of the base 10 so as not to move the table 1.

The control used in this device is to make the absolute displacement of the table zero. As this method, one of the following two control methods is selected according to the target frequency. The first control method is to feed back the amount of the displacement of the table and the displacement of the floor, which can be used in a low frequency range. That is, when the displacement of the floor u, the table displacement was _{w (= θ m l / 2π} ) In this device,
Since the absolute displacement of the table is W = u + w, in order to make the table stand still, W = 0, that is, u = −θ _m l
It should be / (2π). Where θ _m is the rotation angle of the ball screw and l is the lead of the screw. Therefore, this control is possible in principle by setting W as the control deviation and feeding this back. That is, when the device of the present invention is used, the vibration isolation effect can be obtained even by the ordinary control method. A block diagram of this control is shown in Fig. 3 as f ₂ = f ₃ = 0.

The second method of setting the absolute displacement of the table to zero can be used up to a relatively high frequency range, and senses the velocity (du / dt) and acceleration (d ² u / dt ² ) of the floor. ， By feeding them back to the motor, it can be used up to a relatively high frequency range. Given by Where l is the lead of the ball screw, J is the inertia ratio of the motor, c is the damping coefficient of the system including friction, K _m1
Is the torque constant of the motor, K _m2 is the back electromotive force constant, R is the resistance of the motor coil, f ₂ is the feedback coefficient of the velocity of the floor, and f ₃ is the feedback coefficient of acceleration. When comparing the right side and the left side in the above formula Therefore, by using the feedback gain represented by the equation (2), the disturbance can be completely cut off. But,
Since this device has a completely rigid system that does not use spring elements, the table may not return to a fixed position when disturbance cancellation is used.Vibration isolation can be achieved by disturbance cancellation alone, but the stable position of the table It is difficult to secure.
Therefore, in the present vibration insulation method, in addition to the feedback using the feedback coefficient of the equation (2), in order to secure the position of the table, the feedback of the rotation angle θ _m of the ball screw is added. That is, the input to the motor is f ₂ (du / dt) + f ₃ (d ² u / dt ² ) −g ₂ l / (2πθ _m ) (3). A block diagram of this control is shown in FIG. In this vibration isolation method, f ₂ = 0 is set in a system in which damping is unstable.

[0009]

This device has a completely rigid system that does not use a spring element, so even if a force acts directly on an object on the table connected to the nut (or an object directly connected to the nut) There is no displacement and no resonance. Also, large vibration isolation of several mm can be achieved by selecting the pitch of the screws.

Using this device, the vibration transmissibility can be reduced from a low frequency range to a relatively high frequency range which the motor can follow.

[0011]

EXAMPLE First, in order to confirm the usefulness of this vibration isolator, the effect of vibration isolation control using feedback of addition of table displacement and floor displacement was confirmed. In this case, g ₃ = 1 and f ₂ = f ₃ = 0 in the block diagram of FIG. As the vibration detection sensor in this case, the vibration acceleration of the floor is detected by the acceleration sensor, and it is integrated twice with respect to time to obtain the displacement, and the displacement of the table is obtained by attaching a rotary potentiometer to the screw, Was detected, and the table displacement was obtained from it. Experimental results obtained by this control are shown in FIGS. In these figures, FIG. (A) shows uncontrolled, that is, the vibration displacement of the floor, and FIG. (B) shows the result of performing this control using this device. When the control as in this example is used, the table displacement during control greatly differs depending on the feedback gain. The larger the gain, the greater the vibration isolation effect, but if it is too large, it diverges.
In each of FIGS. 4B to 5B, the gain is adjusted and the feedback gain that is considered to be optimal is used. In the figure, a good vibration isolation effect is obtained with this control up to a floor frequency of 3.6 Hz. However, when the frequency is higher than that, the vibration isolation effect is weakened.

In order to use the apparatus up to a higher frequency, it is preferable to feed back the acceleration of the floor and the displacement of the table. The feedback coefficient in this case is g ₃ = 0 in the block diagram of FIG. 3, and f ₂ and f ₃ are expressed by the equation (2).
Given by The results are shown in FIGS. 4 (C) to 5 (C). From these figures, even if this control is used, the vibration isolation effect diminishes in the high frequency range, but the table amplitude is 9.3.
It can be seen that even at 3 Hz, it is about half of the disturbance displacement, and at low frequencies (4 Hz or less), the table amplitude is suppressed to about 1/5 or less. 4 (B) to 5
When compared with (B), the results of this control show better vibration isolation effect in any case.

[0013]

Since the apparatus of the present invention has a completely rigid system without using a spring element, there is no resonance and no displacement occurs due to direct disturbance acting on the table. In addition, it is possible to insulate vibration of large amplitude in the low frequency range. Further, there is an advantage that the mechanism of the device is simple and the control circuit can be constituted by an analog circuit.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an example of an apparatus of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is an example of a control circuit for carrying out the present invention.

FIG. 4 shows a low frequency range (3.67) according to the device of the present invention.
It is the figure which showed the vibration isolation effect of (Hz).

FIG. 5 shows a high frequency range (9.33 by the device of the present invention).
It is the figure which showed the vibration isolation effect of (Hz).

[Explanation of symbols]

 1 Table 2 Slider 3 Nut 4 Ball Screw 5 Pulley 6 Rotation Potentiometer 7 Thrust Bearing 8 Motor 9 Accelerometer 10 Base 11 Belt

Claims (1)

[Claims] 1. A motor, a threaded shaft coupled to a motor shaft, a nut attached to the screw of the shaft, a sensor for detecting displacement of the nut, a sensor for detecting displacement of a vibration source, and a thrust bearing. The rotation of the screw is converted into a translational motion by the nut, one end (base) is attached to the vibration source, the screw is rotated so that the base slides by the displacement of the vibration source, and it is attached to the nut or motor side. A vibration isolator characterized by rotating a motor shaft in a direction in which the absolute displacement of an object becomes zero.