JPH03155381A - Vibration control method for rotary body - Google Patents

Abstract

PURPOSE:To enhance damping of vibration by detecting at least one of displacement, speed or acceleration as a motion parameter and feeding a control signal corresponding to the detected parameter back to a piezoelectric element. CONSTITUTION:A sensor 16 detects at least one of displacement, speed or acceleration as a motion parameter for a rotary body 10 being supported by piezoelectric elements 14, 14,.... A control signal DS corresponding to thus detected motion parameter is then provided through a sensor amplifier 17 to a signal processor 18. The signal processor 18 produces a control signal CS, which is fed back through a power amplifier 19 to the piezoelectric elements 14, 14,... thus controlling vibration of the rotary body 10. By such arrangement, vibration damping force is enhanced, load capacity is increased, maintenance is facilitated, damping characteristic can be modified according to the application and precise positioning can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a vibration control method for a rotating body suitable for use in a rotating mechanism such as a motor that is operated at a speed exceeding a critical speed.

"Prior Art" In recent years, there has been a demand for higher speed and higher performance of rotating machines such as motors. Among these demands, one of the important issues is prevention of whirling vibration of a rotating shaft in a rotating machine. This whirling vibration is caused by various causes. In particular, when the rotating shaft reaches a certain rotational angular velocity, severe whirling vibrations can occur, and when the amplitude of this vibration is large, it can immediately lead to plastic deformation or destruction of the shaft.

For example, when the center of gravity of a rotating body is slightly eccentric from the shaft center line, a biased centrifugal force (unbalanced force) acts on the rotating shaft, so that the rotational angular velocity matches the angular velocity of the whirling motion of the shaft. As a result, the whirling vibration of the shaft becomes intensely resonant. The critical speed that causes this resonance state occurs most commonly in rotating machines, and is the most severe vibration among the whirling vibrations of the rotating shaft (generally called unbalanced vibration).

For example, in textile motors, etc., the operating speed is higher than the critical speed as shown in Figure 4, so it must be used after passing through the critical speed, and a technology is required to safely pass this critical speed. It is said that In order to realize this technology, careful consideration is required, but in general, vibrations are so large that in many cases the above-mentioned critical speed cannot be exceeded. Therefore, the following method of adding a damping function to a bearing support portion has been proposed.

■First, a method that utilizes the elasticity and internal damping of rubber by using anti-vibration rubber, rubber O-rings, etc. in the bearing support.

■Next, consider the elasticity of rubber and metal springs (plate springs, coil springs,
A method that utilizes the elasticity and damping of an oil film, such as a tire phragm (or bellows), an oil film's squeeze film action, an orifice throttling action, and a static pressure bearing (floating bush bearings are also a type of this method).

(2) Recently, there has been a method in which an electromagnetic actuator (piezoelectric element) is provided around the bearing and a control voltage is applied to the actuator to suppress vibration.

Among the above-mentioned methods, for example, method (2) will be explained with reference to FIG. In this figure, an O-ring 2.2 is used as the elastic support for the bearing I, and supports the bearing I elastically.

Further, an oil film 4 is formed between the rotating shaft 3 and the bearing 1, and further between the O-ring 2 and the O-ring 2.
A squeeze film 5 is formed. The oil film 4, O-ring 2, and squeeze film 5 absorb and attenuate unbalanced vibrations caused by external disturbances.

Further, as a modification of the above-mentioned method (2), as shown in FIG. 7, a ball bearing 6 may be supported by an O-ring 2.2 and a squeeze film 5.

Next, the method (2) mentioned above will be explained with reference to FIG. In this figure, a plurality of piezoelectric elements 7 are provided around a bearing l. When unbalanced vibration occurs in the rotating shaft 3, the control device 8 applies a control voltage to damp the vibration to the piezoelectric elements 7, 7, . It is supplied to...

"Problems to be Solved by the Invention" By the way, the above-mentioned conventional methods (1), (2) and (2) have the following drawbacks.

(1) First, the damping force is small and a sufficient damping effect cannot be obtained.

(11) Secondly, the support rigidity is low, and the load capacity of the bearing portion is reduced.

(...) Also, maintenance is troublesome because oil and rubber are used.

(iv) Furthermore, the attenuation characteristics are uniquely determined and cannot be changed freely.

Furthermore, in the above method (2) using a piezoelectric element, although determining the control voltage to be applied to the piezoelectric element is important, the control method has not been clarified.

Therefore, the problem arises that it is difficult to realize.

This invention was made in view of the above-mentioned problems, and can provide a very large vibration damping force, a larger load capacity than conventional methods, and easy maintenance. Attenuation characteristics can be changed depending on the situation,
Furthermore, it is an object of the present invention to provide a vibration control method for a rotating body that allows precise positioning.

"Means for Solving the Problems" In order to solve these problems, the present invention detects at least one of displacement, velocity, and acceleration as a motion parameter of a rotating body supported by a piezoelectric element,
The vibration of the rotating body is controlled by feeding back a control signal corresponding to the motion parameter to the piezoelectric element.

"Operation" At least one of displacement, velocity, and acceleration is detected as a motion parameter of the rotating body supported by the piezoelectric element, and a control signal corresponding to the motion parameter is fed back to the piezoelectric element. Control vibration, easily pass critical speeds, and rotate at high speeds.

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In this figure, 10 is a rotating body, and the rotating shaft 1
1. The rotating shaft 11 is rotatably supported by ball bearings 12 at both ends thereof. These ball bearings 12 are connected to each other through a spacer I3.
It is supported by the bearing stand I5 by the piezoelectric elements 14 (8 pieces in total).

These piezoelectric elements 14, 14. ... expands and contracts in accordance with the supplied control signal, and brakes the rotating shaft 11 via the spacer I3 and the ball bearing 12.

The bearing stand I5 is attached to the rotating machine casing or the base. Next, 16 is a sensor, and the rotation axis 1
1 (or the rotating body 10) (displacement, speed, or acceleration), and at least two of them are provided on one side to detect movement in the vertical and horizontal directions. In this example, two sensors 16 are provided on one side, and a total of four sensors are used. This sensor 16 also receives a detection signal D corresponding to the movement of the rotating shaft 11 described above.
S is output to the sensor amplifier 17. The sensor amplifier 17 amplifies the detection signal DS to a desired level and then outputs it to the signal processing device 18. After performing various calculations, the signal processing device 18 sends the obtained control signal C8 to the power amplifier 19.
Output to. The power amplifier ■9 performs voltage and current amplification according to the control signal C8, and amplifies the piezoelectric element 14 described above.
, 14°...

Next, the operation in the above-described configuration will be explained. Here, to simplify the explanation, we will use a rotating body! Approximate the stiffness of 0 to one spring constant.

Further, it is assumed that the bearing stand (including the piezoelectric element 14 and the ball bearing 12) 15 is bilaterally symmetrical, and only one side will be considered. Considering the vibration direction only in the vertical direction, the second
The modeling shown in the figure becomes possible. Note that the spring constant of the piezoelectric element 14 is 1, which is a linear constant value, and gravity is ignored.

In this figure, M is the mass of the rotating body 1O, xt is the displacement of the rotating body 10, f is the disturbance acting on the rotating body 10, and kl is the spring constant of the rotating body 10. Also, x is the piezoelectric element when there is no load! displacement of 4, k.

is the spring constant of the piezoelectric element 14.

Next, the equation of motion of the model in the diagram is M・father t+
K(Xt Xt)-f ・・・・・・・・・・・・
It is given by (1). Here, the constant is K=+”kt ・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・(2)k+”k
Let it be t. Also, from the characteristics of the piezoelectric element 14, χ1 is x1=
A-e ・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・(3) Here, e is the voltage applied to the piezoelectric element I4 output from the power amplifier 19, and A is a constant determined by the type and size of the piezoelectric element 14.

Next, by substituting equation (3) into equation (1), M-! t
+ to −x t K−A−e = f −−・” (
4).

Next, a method (plurality) of minimizing the disturbance f or a method of controlling the position of the rotating body 1O in the illustrated system described above will be explained. Note that the structure and configuration of the rotation mechanism in each embodiment are the same.

a. First example.

First, in the first embodiment, the sensor 16 detects the rotating body 10.
A case will be described in which the displacement X of is detected, the detection signal DS is differentiated by the signal processing device 18 to be large, and a voltage e proportional to this expression is fed back to the piezoelectric element 14.

In this case, first, the voltage mentioned above. 6-c ・Large ・・・・・・・・・・・・・・・
......(5) -A C; Set -A to the gain. Substituting this equation (5) into equation (4), we get M-father, +c-sentence t+ K-x t= f ---・" (
6). Here, C is an attenuation constant due to the piezoelectric element 14. In addition, the above disturbance r (unbalanced force; f = F-
coscc+t), the special solution to equation (6) is as follows.

x v= X − cos (ω is one α) ・・・・・・
・・・・・・・・・(7) °°゛°(9)
Also, in this case, a rotating body! If the natural frequency of 0 is C7, then the frequency ω of the disturbance f and the natural frequency ω. The ratio, that is, the frequency ratio r, is as follows. Generally, the amplitude Xj due to the disturbance of the mass M is the third
As shown in the figure, when the frequency ratio r is around 1.0, that is,
The frequency ω is the natural frequency ω. It resonates and reaches a maximum at the point where it becomes equal to .

Furthermore, in the illustrated system, the damping ratio ζ is ζ-20M
,t,y. It is defined as °°°゛°°゛°゛°゛°°°゛゛゛°゛°゛ (II). From this equation (+1), it can be seen that by increasing the damping constant C of the piezoelectric element 14, the damping ratio ζ becomes larger. That is, when passing the critical speed (see point P1 in Figure 4), if the gain of the power amplifier 19 is increased, the damping ratio ζ increases, so the vibration amplitude (displacement xz) of the mass M becomes smaller as shown by the broken line in the figure. Become. As a result, the rotating body 10 reaches the operating range of high rotational speed at the critical speed shown in FIG. 4 without increasing the vibration amplitude.

Note that in this example, the mechanical damping was ignored because it was much smaller than the damping caused by the piezoelectric element 14.

b. Second Example Next, in the second example, the rotating body IO is detected by the sensor 16.
The displacement X is detected, and a voltage e proportional to this displacement X is fed back to the piezoelectric element 14.

In this case, first, the voltage e mentioned above is expressed as e-K' ・X, ......
...(12) -A K and -A are set as the gain. Substituting this equation (12) into equation (4), we get M-51, + (K + K') x! = f
”...(13). Therefore, it can be seen from the above equation (13) that by changing the gain of the power amplifier 19, the spring constant K changes, although it appears to be better.

Also, the natural frequency ω in this case. Ha, ω. = F1 "(14), and by changing Ko, the natural frequency ω
It can be seen that , changes. Therefore, as shown in FIG. 5, at point P2 where the rotational speed approaches the critical speed, by reducing the gain of the power amplifier 19, the natural frequency ω is instantaneously reduced. can be made smaller. When the natural frequency ω becomes momentarily small, the rotational angular velocity (frequency ω) at that time is larger than the natural frequency ω after the change, so the frequency ratio r mentioned above becomes larger than 1.0. Resonance is avoided.

As a result, the critical speed moves to the low speed side as shown in FIG. 5, and the rotational speed of the rotating body 10 reaches the high speed operating range without passing through the critical speed.

C1 Third Embodiment Next, in the third embodiment, the rotating body lO is detected by the sensor 16.
Detects the displacement X, and converts this displacement X to the signal processing device 18
Let's divide the two aircraft's acceleration into the acceleration factor. Then, a voltage e proportional to this acceleration is fed back to the piezoelectric element 14.

In this case, first, the voltage e mentioned above is expressed as 6-M'・father, ・・・・・・・・・
・・・・・・・・・(15) −A M°nigain is set to −A. Substituting this equation (15) into equation (4), (M+M') father t+ K-x t= f ---(1
6). Therefore, it can be seen from the above equation (16) that by changing the gain of the power amplifier 19, the mass M of the rotating body 10 changes, although it appears to be the case. In addition, the natural frequency ω in this case is ωn = knob 1 (17), and by changing M', the natural frequency ω
. It can be seen that the changes. Therefore, the second
Similarly to the embodiment, by increasing the gain of the power amplifier 19 at the point P2 shown in FIG. 5 where the rotational speed approaches the critical speed, the natural frequency ω is instantaneously reduced. can be made smaller.

As a result, the critical speed moves to the low speed side as shown in FIG. 5, and the rotation speed of the rotating body 10 reaches the high speed operating range without passing through the critical speed.

d. Fourth embodiment.

Next, in the fourth embodiment, the rotating body lO is detected by the sensor I6.
Detects the displacement X, and converts this displacement
shall be. Then, the voltage e corresponding to the displacement X2, velocity X, and acceleration is fed back to the piezoelectric element 14.

In this example, the above equation (3) is (M+M')
・! tic ・large t” (K ten’) x t=f −(
18). In other words, the equation of motion of this system is a combination of the equations of motion of the embodiments a''-c described above.Therefore, in this example, the gain of the power amplifier 19 is changed as in the embodiment described above. As a result, more advanced vibration control is performed.As a result, the rotational speed of the rotating body 10 reaches the operating range of high rotational speed.

e. Fifth embodiment.

Next, in the fifth embodiment, the sensor 16 detects the rotating body lO
The signal processing device I detects the displacement X2 of
Integrate by 8. Then, by feeding back the voltage e corresponding to this integral value to the piezoelectric element 14, the rotating body IO is supported at a desired axial center position.

In addition, in this embodiment, as described above, the rotating body 10 can be precisely positioned, and the support spring rigidity can be increased in the low frequency range, so that the advantage of improving the load capacity is obtained.

"Effects of the Invention" As explained above, according to the present invention, the motion (displacement, velocity, and acceleration) of the rotating body is detected, and the corresponding control voltage is fed back to the piezoelectric element to The effect shown can be obtained.

■Vibration damping force can be extremely large.

■Load capacity can be increased compared to conventional methods.

■Attenuation characteristics can be changed according to usage conditions.

■Precise positioning is also possible.

■Maintenance is easy because no oil or rubber is used.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a cross-sectional view and a vertical cross-sectional view of a support portion of the vibration prevention device according to an embodiment of the present invention, respectively, and FIG. 2 is a longitudinal sectional view of the support portion of the same embodiment. 3 is a characteristic diagram showing the relationship between frequency ratio and amplitude, FIG. 4 is an explanatory diagram for explaining the operation of the first embodiment, and FIG. 5 is a diagram of the second embodiment. Explanatory drawings for explaining the third embodiment, FIG. 6, FIG. 7, and FIG. 8 are cross-sectional views showing the structure of a conventional vibration prevention device. +1... Rotation axis, C8... Control signal, e... Voltage.

Claims (1)

[Claims] At least one of displacement, velocity, and acceleration is detected as a motion parameter of a rotating body supported by a piezoelectric element, and a control signal corresponding to the motion parameter is fed back to the piezoelectric element to suppress vibration of the rotating body. A vibration control method for a rotating body, characterized in that: