JPH08179835A - Active damper - Google Patents

Abstract

PURPOSE: To provide the active damper with simple configuration by using a piezoelectric element as a sensor or an actuator. CONSTITUTION: A piezoelectric element 2 and a piece of mass 1 are serially connected and fitted in a vibrating direction A of a device 4 as a damping object. When a frequency ω of the device 4 is matched with the natural frequency of the spring mass system of the mass 1, the device 4 is turned to a standstill state. Since the piezoelectric element 2 is distorted when the device 4 is vibrated, that distortion output is fetched into a damping control circuit 6 and ω is calculated. By controlling the driving voltage of the piezoelectric element 2 according to this ω, the spring constant of the piezoelectric element 2 is controlled and the natural frequencies of both the systems can be matched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active damper, and more particularly to an active damper which is attached to a vibrating portion of a vibrating device to absorb vibration energy and suppress vibration.

[0002]

2. Description of the Related Art As an example of a conventional active damper of this type, there is, for example, a technique disclosed in Japanese Patent Laid-Open No. 63-221410. In this technique, a piezoelectric actuator, an accelerometer, and a vibration suppression control circuit that drives the piezoelectric actuator are provided to absorb vibration.
An example is shown in.

The mounting base 7 is for mounting the active damper on the object (mechanical device) 4 to be damped, and for aligning the operating direction of the entire parts, and is mounted on an object that vibrates with a screw or magnetic force.

The mass 1 and the piezoelectric actuator 2 are connected and fixed in series on the base 7 in the same direction as the vibration direction A of the mechanical device 4, and the base 7, that is, the mechanical device 4 which is the original vibration system. The accelerometer 9 detects the vibration acceleration d ² x1 / dt ² of the mass 1.
^The accelerometer 8 detects ² × 2 / dt ² . The vibration suppression control circuit 6 calculates the drive voltage E of the piezoelectric actuator 2 from the outputs of the accelerometers 8 and 9, and drives the piezoelectric actuator 2 by this.

Next, the operation will be described. By controlling the outputs of the accelerometers 8 and 9 by the damping control circuit 6 and controlling the drive voltage of the piezoelectric actuator 2 so as to attenuate the vibration,
The vibration of the mechanical device 4 is absorbed.

[0006]

In such a conventional active damper, the acceleration of the mechanical device 4 and the added mass 1 is measured by the two accelerometers 8 and 9, and the driving voltage E is calculated from the value. Therefore, the number of components is large and the vibration suppression control circuit 6 is complicated.

An object of the present invention is to provide an active damper which has a small number of constituent parts, a vibration damping control circuit can be simplified, and vibration can be suppressed even if a forcing force of any frequency acts.

[0008]

According to the present invention, there is provided an active damper, which is attached to a vibrating portion of a vibrating device to absorb vibration energy and suppress vibration, in the same direction as the vibration direction of the device. An active damper comprising: a piezoelectric element and a mass connected in series with each other; and a vibration damping control means for calculating a driving voltage for damping according to an output of the piezoelectric element and applying the driving voltage to the piezoelectric element. Is obtained.

[0009]

The above-mentioned object is achieved by using the piezoelectric element as an actuator and also as an accelerometer. That is, the circular frequency of the vibrating device is calculated from the output of the piezoelectric element, and the drive voltage of the piezoelectric element is controlled in accordance with this circular frequency to suppress the amplitude of the circular vibration to approximately zero.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention, and the same portions as those in FIG. 2 are designated by the same reference numerals. In FIG. 1, the mechanical device 4 to be damped is supported by a spring 5. The piezoelectric element 2 and the spring 3 are connected in parallel in the same direction as the vibration direction A, and the mass 1 is connected in series to the piezoelectric element 2 and the spring 3 in the same direction as the vibration direction A.

The vibration suppression control circuit 6 calculates a drive voltage from the distortion signal output of the piezoelectric element 2 and uses this drive voltage as the piezoelectric element 2.
To effectively suppress the vibration of the device 4.

The principle of the active damper according to the present invention will be described below by using mathematical expressions. Now, it is assumed that the periodic force Po = sin ωt acts on the device 4. The equations of motion of the apparatus 4 and the mass 1 at this time are shown by the equations (1) and (2), respectively.

Md ² x1 / dt ² = -k1x1-k2 (x1-X2) -α (x1-x2) + Posin ωt (1) md ² x2 / dt ² = -k2 (x2-x1)- α (x2-x1) ... (2) where M is the weight of the device 4, m is the weight of the mass 1, k1 is the spring constant of the spring 5, k2 is the spring constant of the spring 3, and α is the piezoelectric element. 2, the spring constant, x1 is the displacement of the device 4, and x2 is the displacement of the mass 1.

When the equations (1) and (2) are modified, Md ² x1 / dt ² + (k1 + k2 + α) x1- (k2 + α) x2 = Posin ωt ... (3) md ² x2 / dt ² + (k2 + α) ) X2- (k2 + α) x1 = 0 ... (4).

Here, if the natural circular frequency of the spring-mass system with mass 1 is Ω2, then Ω2 ² = (k2 + α) / m, so the equation of motion is (M / m) d ² x 1 / dt ² + Ω2 ² {1 + k1 / (k2 + α)} x1 −Ω2 ² x2 = (Po / m) sin ωt ………… (5) d ² x2 / dt ² + Ω2 ² x2-Ω2 ² x1 = 0 ………… (6) ).

Therefore, the motion of the device 4, mass 1 is a stationary vibration with a circular frequency equal to the circular frequency ω (2π times the frequency) of the forcing force, x1 (t) = (Po / k1) {( 1−λ2 ² ) ² / D} ^1/2 sin ωt (7) x2 (t) = (Po / k1) (1 / D) ^1/2 sin ωt (8)

In addition, D is D = [1- {1+ (1+ (M / m) λ2 ² ) (k2 +
α) / k1 + (M / m) λ2 ⁴ ) (k2 + α) / k
1}] ² and λ2 = ω / Ω2.

Focusing on the forced vibration x1 (t) of the device 4, and letting its amplitude be X1, X1 / (Po / k1) = (1-.lambda.2) ² / [1- {1+ (1+ (1 + M / m) (K2 + α) / k1)} λ2 ² + (M / m) λ2 ⁴ (k2 + α) / k1] (9)

In the equation (9), when λ2 = ω / {(k2 + α) / m} = 1 (10), X1 = 0, and the amplitude of the forced vibration (X
It can be seen that 1) becomes 0 and the vibration disappears.

Therefore, in order to suppress the vibration of the apparatus 4, it is sufficient to control α so that λ2 = 1 according to the circular frequency ω of the forcing force.

Here, when the forcing force of the circular frequency ω is applied, the displacement amount of the piezoelectric element 2 is (x1-x2), and this displacement amount is a function of the circular frequency ω, and (7), (8) the formula, x1-x2 = (Po / k1) ^{[{(1-λ2 2) 2} / D} 1/2 - (1 / D) 1/2 ] expressed as sin .omega.t ......... (11) Be done.

Therefore, the displacement amount of the piezoelectric element 2 (x1-x
By measuring the distortion output corresponding to 2) in the damping control circuit 6 for a certain period of time and taking it in, the circular frequency ω of the forcing force can be calculated.

The vibration suppression control circuit 6 controls the drive voltage of the piezoelectric element 2 in accordance with the calculated current circular frequency to obtain λ2.
Control α so that = 1. Spring constant α of piezoelectric element 2
Can be expressed as a function of only the driving voltage if the size and material of the piezoelectric element are determined. Therefore, it is possible to control α by the driving voltage so that λ2 in the equation (10) becomes 1.

The vibration of the device 4 can be damped by repeating the process of measuring ω by the strain output from the piezoelectric element 2 and determining the drive voltage.

Although the spring 3 is connected in parallel to the piezoelectric element 2 in FIG. 1, this spring 3 may be omitted. In this case, the constant k2 of the spring 3 in the above equations is used.
Should be 0.

[0027]

As described above, according to the present invention, since the piezoelectric element is used as a sensor and also as an actuator, it has an effect that it is very small and has a vibration damping action against any forcing force. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional active damper.

[Explanation of symbols]

 1 Mass 2 Piezoelectric element 3, 5 Spring 6 Vibration suppression control circuit

Claims (3)

[Claims] 1. An active damper attached to a vibrating portion of a vibrating device to absorb vibration energy and suppress vibration, wherein a piezoelectric element and a mass are connected in series in the same direction as the vibration direction of the device. And a damping control means for calculating a driving voltage for damping according to an output of the piezoelectric element and applying the driving voltage to the piezoelectric element. 2. The vibration damping means calculates a circular frequency ω of the device from the output of the piezoelectric element, and controls the drive voltage according to the circular frequency ω. The active damper according to claim 1. 3. The driving voltage is controlled so that ω / (α / m) ^1/2 = 1 when α is a spring constant of the piezoelectric element and m is a weight of the mass. The active damper according to claim 2.