JPH05141422A - Magnetic bearing controller - Google Patents

Abstract

PURPOSE:To reduce rigidity of a bearing and avoid passing of resonant vibration by activating a notch filter at a predetermined engine speed during operation of a rotary machine on the basis of a signal output from a rotation detector. CONSTITUTION:A rotation detector 11 detects an engine speed of a rotating body. A comparison circuit 12 compares the detected speed with an engine speed previously set by a reference engine speed setter 13. A signal for operating a notch filter circuit 5 is output when the comparison result reaches the set value. The notch filter circuit 5 is connected in series to a proportional circuit 2, an integrating circuit 3 and a differentiating circuit 4 on the basis of the signal. The operation of the notch filter circuit 5 can deteriorate rigidity of a bearing so as to decrease a resonant frequency of the rotating body. Consequently, operation can be carried out while avoiding the resonant frequency, thereby reducing vibration generated in the rotating body. Therefore, it is possible to miniaturize a bearing main body and a power amplifier for controlling with reduced force required for magnetic bearing control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine that operates in a rotating body equipped with a magnetic bearing, beyond a third mode (bending first mode).

[0002]

2. Description of the Related Art Known examples close to the present invention include the Japan Society of Mechanical Engineers (C edition), 57, 534 (1991-2),
Pp. 582-585, "Passing critical speed by changing control gain of magnetic bearing".

Various methods have been studied for controlling vibrations when passing through the resonance frequency of the third-order mode (bending first-order mode) of a rotating body. Many of them use a method of reducing the vibration response level when passing through the resonance frequency.

The above-mentioned technique also attempts to avoid the resonance point by changing the gain in the same manner, but this method corresponds to the fact that the rigidity of the proportional control unit (P portion of PID control) is changed. There is. In this case, the purpose is to avoid the vibration of the primary or secondary mode (rigid body mode),
It can be avoided even if the rigidity change of the bearing is small. on the other hand,
In order to avoid the third-order mode (first-order bending mode), it is necessary to greatly change the rigidity, and it is not enough to reduce the gain of only the proportional controller.

[0005]

When passing through the resonance frequency of the third-order mode (bending first-order mode), a very large vibration is generated. It is necessary to reduce the amount of unbalance existing in the rotor and at the same time increase the damping in the bearing to lower the vibration level when passing through resonance. But,
In order to reduce the amount of unbalance with respect to the third-order mode (bending first-order mode), it is necessary to correct the balance with a high-speed balancer or the field balance. A large amount of equipment and work costs are required.

An object of the present invention is to avoid the third-order mode (bending first-order mode) and reduce the vibration response level by efficiently changing the bearing rigidity by a simple method.

[0007]

In the present invention, by operating one or a plurality of notch filters at a predetermined operating speed, the bearing rigidity is reduced and the passage of resonance frequency is avoided. The vibration amplitude in the bending first mode) is reduced.

[0008]

The rotation detector outputs a signal of the timing for operating the notch filter.

The rigidity of the bearing is changed by operating the notch filter.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram for control of the present invention.
The rotation detector 11 detects the rotation speed of the rotating body, and the comparison circuit 12 compares it with the rotation speed set in advance in the reference rotation speed setting device 13, and operates the notch filter circuit 5 when the set rotation speed is reached. Output the signal to The signal causes the notch filter circuit 5 to be connected in series to the proportional circuit 2, the integrating circuit 3, and the differentiating circuit 4, which have been used conventionally. When the narrow band notch filter 6 is used, a plurality of stages of notch filters 6-1, ... Are used in series as necessary.

FIG. 2 shows the relationship between the rigidity of the bearing supporting the rotating body and the natural frequency. The figure shows the relationship between bearing rigidity and natural frequency when supported by magnetic bearings. The alternate long and short dash line 26 in the figure shows the change in rigidity during operation. When a heavy rotating body is supported by magnetic bearings, the operating range is third-order mode (bending first-order mode) 23 and fourth-order mode (bending second-order mode).
It often enters between 24. In this case, the third mode 23 must be passed during the operation. Usually, the PID control gives a phase lead and gives a damping to the magnetic bearing part.
The damping provided by the PID control is such that for the third-order mode (bending mode) 23, the first-order 21 and the second-order mode 22
Since it is smaller than, the large vibration is generated when passing through the third mode 23. Therefore, when the operating speed comes between the natural frequency 23a of the third-order mode and the natural frequency 23c of the third-mode when the rigidity of the magnetic bearing is zero, the notch filter circuit 5 composed of one or a plurality of units is used. Make it work. When the notch filter circuit 5 operates, the rigidity of the magnetic bearing portion decreases according to the characteristics of the notch filter. As the rigidity decreases, the operating point moves from 25a to 25b.
The point 25b after the movement is located beyond the third mode 23. Therefore, by operating the notch filter circuit 5, the rigidity of the magnetic bearing changes, and the passage of the natural frequency of the third-order mode can be avoided.

FIG. 3 shows the relationship between bearing rigidity and natural frequency during PID control. FIG. 4 shows the relationship between bearing rigidity and natural frequency when one notch filter circuit 5 in a wide band is operated. The resonance frequency of the third-order mode is lowered by the operation of the notch filter circuit 5. If the use of the wide band notch filter 6 can significantly reduce the attenuation for the fourth order mode, it cannot be used. In this case,
It is possible to reduce the natural frequency by combining a plurality of narrow band notch filters 6, 6-1 ... As shown in FIG.

[0013]

The bearing rigidity can be reduced by operating the notch filter circuit. Since the rigidity of the bearing decreases, the resonance frequency of the rotating body also decreases. Therefore, by operating the notch filter circuit between the resonance frequency corresponding to the third-order mode when supported by only the PID control circuit and the resonance frequency corresponding to the third-order mode when the notch filter circuit is inserted in series, The resonance frequency of the rotating body is lowered, and the state of being operated under the tertiary mode before the operation is changed to the state of being operated above the tertiary mode after the operation. Therefore, it becomes possible to operate while avoiding the resonance frequency, and the vibration generated in the rotating body is reduced. Further, since the vibration generated in the rotating body is reduced, the force required for controlling the magnetic bearing can be reduced, and the magnetic bearing body can be downsized.
Further, the power amplifier for control can be downsized.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit of the present invention.

FIG. 2 is an explanatory diagram of bearing rigidity and natural frequency.

FIG. 3 is an explanatory diagram of gain and natural frequency in PID control.

FIG. 4 is an explanatory diagram of a gain and a natural frequency when the notch filter circuit operates.

FIG. 5 is an explanatory diagram of a gain and a natural frequency when the notch filter circuit operates.

[Explanation of symbols]

1 ... PID control circuit, 5 ... Notch filter circuit, 7 ... Power amplifier circuit, 8 ... Magnetic bearing body, 9 ... Displacement sensor,
11 ... Rotation detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Fukushima 603 Jinritsu-cho, Tsuchiura-shi, Ibaraki Hirate Manufacturing Co., Ltd. Tsuchiura factory (72) Inventor Shumi Matsushita 603, Kintate-cho, Tsuchiura-shi, Ibaraki Hitsuritsu Co., Ltd. (72) Inventor, Mitsuho Yoneyama, 603 Jinritsucho, Tsuchiura, Ibaraki Prefecture

Claims (1)

[Claims] 1. A rotating machine equipped with a magnetic bearing for controlling shaft vibration by PID control, wherein one or a plurality of rotating machines are provided at a predetermined number of revolutions during operation of the rotating machine based on a signal detected by a rotation detector. A magnetic bearing control device characterized in that a plurality of notch filters are operated, and the function of the notch filter is stopped at another predetermined number of revolutions as necessary.