JPH01126424A - Electromagnetic bearing control device - Google Patents

Abstract

PURPOSE:To allow vibration to pass through its resonant point with a small resonant amplitude so as to be prevented from developing in its self-excitation by extracting a frequency component to be controlled out of the detected signal components of a rotor displacement by means of a tracking filter. CONSTITUTION:Rotor displacement signals x, y in X direction and in Y direction are input to control circuits 4x, 4y respectively and the results of calculation concerned are input to a power amplifier 5 to force a control current to flow in an electromagnet coil 2. The displacement signals x, y are input to a tracking filter 7 for a rotational frequency component so as to extract only the rotational synchronous component. X signal is multiplied by alphax to be additionally input into a channel in Y direction and y signal is multiplied by alphay to be subtractively input into a channel in x direction. Thus, when the vibration of passes through its resonant point, it can pass through with a small resonant amplitude to be prevented from developing in its self-excitation.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control device for a magnetically levitated rotor supported by an electromagnetic bearing, and particularly to a control device for a magnetically levitated rotor supported by an electromagnetic bearing. This invention relates to an electromagnetic bearing control device.

[Conventional technology]

The outline of the configuration of a rotating machine supported by an electromagnetic bearing with a suction type electromagnet as a bearing is shown in Figure 2.
On the other hand, the electromagnetic coils 2 are arranged on the left and right sides.

In this state, when the rotor 2 moves to the right, a control current i flows through the electromagnet coil 2 on the left, and an attractive force acts on the rotor 1 to displace it to the left.On the other hand, when the rotor 1 moves to the left, the control current i flows through the electromagnet coil 2 on the left. A control current i flows through 2, and an attractive force acts on it. In this manner, a control current i is applied to the electromagnetic coil 2 on the opposite side in accordance with the left and right displacement of the rotor 1, and the attraction force thereof performs servo control so that the rotor 1 is located at the center position. In general.

Position control of the rotor 1 using the magnetic bearings involves two-dimensional position control in the X direction and the X direction. Therefore, the servo circuits having the same specifications are arranged in two series, one for the X direction and one for the X direction.

That is, the displacement sensor includes an X-direction sensor 3x and an X-direction sensor 3Y, and the control circuit is also 4X.

It has two 4Y circuits, each of which is connected to a power amplifier 5.

As a conventional device using a rotation speed synchronized tracking filter circuit as a method of reducing resonance amplitude in the electromagnetic bearing control device as described above, for example, Japanese Patent Application Laid-Open No. 52-93853
There are some listed in the issue.

In this critical frequency damping device, for example, an X displacement signal is input to the control circuits 4X and 4Y to reduce the resonance amplitude in the X direction, and at the same time, only the rotation synchronization component is extracted from the X displacement signal. The xo times signal is also used for servo control. The same applies to the X direction. By using the xo-fold signal and the yo-fold signal for servo control, the coefficient a is used for the rotational speed synchronous component.

By adjusting b and gain, it becomes possible to provide phase lead characteristics. This gives a damping effect to the rotor, allowing the resonance amplitude to pass through with a small amplitude.

The essence of this method is to pass the detected displacement signals X and y through a differentiating circuit to create speed signal quantities and y, and to pass these displacement signals and speed signals through a rotation synchronization tracking filter. It is intended to use only the rotational synchronous components of displacement and speed to control only the unbalanced vibration of the axially oriented one rotational speed synchronous component. The structure allows the bearing rigidity to be adjusted depending on the magnitude of the displacement component, and the bearing damping to be adjustable depending on the magnitude of the speed component.

[Problem that the invention seeks to solve]

In the conventional control method described above, it is necessary to create a speed signal from the displacement signal using a differentiating circuit, which has the disadvantage of complicating the circuit.In addition, the displacement signals in the X direction and the X direction are passed through a rotation synchronization tracking filter. Since only the rotationally synchronous components of displacement and speed are extracted and added and input in each of the X and X directions, unbalanced vibrations synchronous with one revolution cannot be sufficiently reduced.

The purpose of the present invention is to reduce the resonance amplitude of unbalanced vibrations synchronous with one rotational speed, and also to reduce fluctuation vibrations. An object of the present invention is to provide a control device for a magnetic bearing.

[Means for solving problems]

The above purpose is to use a servo circuit as a control device for an electromagnetic bearing, which has two channels in the X direction and a circuit that controls the current supplied to the electromagnetic coil in response to displacement signals in the X direction and X direction in the radial direction of the rotor. The servo circuit is configured with a selective extraction means, for example, a rotation speed tracking filter for extracting the rotor's rotation synchronized component, and the X-direction signal and the This is achieved by adding addition inputs to the circuit.

In other words, to cross the X direction signal is to add and input the X direction signal to the X direction servo circuit, and to manually subtract the X direction signal to the X direction servo circuit, or
Subtract and input the direction signal to the X direction servo circuit, and
This is to add and input the direction signal to the X direction signal.

In addition, the output of the tracking filter and the displacement signal are added to the signal input to the control circuit, and the rotational speed component is canceled out, leaving only the fluctuation component. Therefore, the control circuit is simple, and a control device with a damping effect can be achieved. .

[Effect]

Vibrations generated by the rotation of the rotor can be prevented by controlling the single selection extraction means and by crossing the X-direction and X-direction signals.

In general, bearings have anisotropic characteristics, which causes elliptical orbits or unbalanced vibrations. In order to suppress forward-facing vibrations, a rotation-synchronized tracking filter is used to extract the forward-facing natural frequencies and perform channel crossing.
This improves stability for forward-facing natural frequencies.

In addition, the rearward direction is extracted using the next counter-rotating rotation speed synchronized tracking filter, and the stability with respect to the backward direction natural frequency is improved by channel crossing.

In addition, since the components extracted by the rotation synchronization tracking filter are subtracted and input to the control circuit from the original signal, the synchronization components are canceled and only the low frequency fluctuation components are input. Since this is a good thing, a simple circuit can be used as the control circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The displacement signal X that detected the rotor displacement in the X direction is sent to the control circuit 4X.
The calculation result is input to a power amplifier 5 and a control current is passed through the electromagnetic coil 2. The same applies to the X direction.

The detected displacement signals X and y are input to the rotation period component tracking filter 7, and the
Extract only rotational synchronous components X and y.

When the bearing is isotropic, the amplitude in the X direction and the X direction is aH, and the phase delay seen from the rotation angle is θN.

What should be noted here is ;cN=-ΩyN, :IN=ΩXN-
The relationship (2) is established. This is related to the fact that unbalanced vibrations proceed in a circular orbit from the X axis to the Y axis in the same direction as the rotation. In such a circular orbit, 9 of the X vibration
The vibration before 0° is predicted to be a −yX vibration, and the vibration 90° before the X vibration is predicted to be an X vibration.

This prediction means differential operation, so the above equation makes sense physically.

If we focus only on the unbalanced vibration component, equation (2) holds true, so we can regard the output signals XN and yN of the tracking filter 7 as differential signals 3FN and -XN, respectively. Therefore, in order to provide a damping effect in the X direction, the X signal is multiplied by α8 and added and input to the single channel in the Y direction. On the other hand, in order to provide a damping effect in the X direction, the X signal is multiplied by 01 and subtracted and input to the X direction channel. By inputting addition and subtraction in the channel cross in this manner, the purpose of improving the damping performance against forward vibration of the rotor is achieved.

Generally, bearings have anisotropic characteristics, which causes elliptical orbits or unbalanced vibrations.

The method for suppressing forward vibration in this case is as described above. How to suppress backward component vibrations.

It is sufficient to perform the reverse processing of the forward-facing processing.Therefore, the method of addition/subtraction input of the output channel cross of the rotation synchronization filter 8 of the reverse rotation of the tracking filter is αX, αy
It is sufficient to take 91 times βxl, which has the opposite sign.

Further, when the signal input to the control circuit is input by subtracting the output of the forward tracking filter, the forward rotation synchronization component is canceled. Then, by subtracting and inputting the output of the signal extracted by the next backward tracking filter, the backward rotation synchronization component is canceled out. Due to these, the signal input to the control circuit is only the fluctuation vibration component.

A feature of the present invention is that a tracking filter extracts the frequency component to be controlled from among the detected signal components, cross-couples the extracted signal to generate a differential signal, that is, a damping effect, and adds it to the original signal. By subtracting and inputting, the rotation synchronous component is removed and only the fluctuation component is input to the control circuit. This simplifies the control circuit because the rotation synchronization component is not input to the control circuit and only the fluctuation component is controlled.

Furthermore, there are various structures of rotating bodies, and there are self-excited vibrations that occur regardless of the number of rotations. In order to prevent these self-excited vibrations, an oscillator signal that generates a frequency equal to the natural frequency of the self-excited vibrations is input to the tracking filter as a trigger instead of the rotation pulse. And detected X
This self-excited vibration component Xi in the vibration displacement in the direction and the X direction
and y.

Extract. By inputting this extracted signal y, which is negative to the X channel and 4xz, which is positive to the Y channel, by gross addition, a damping effect that suppresses self-excited vibrations as well as unbalanced vibrations can be generated.

〔Effect of the invention〕

According to the present invention, the damping force against forward vibration when passing through a resonance point can be improved without providing a new differentiation circuit, and unbalanced vibration can be passed with a small resonance amplitude. Furthermore, even if the balance accuracy of the rotor is somewhat poor, it is possible to pass through the resonance point.

In addition, the control circuit controls only the fluctuation component of the signal, and the control circuit becomes simple. Furthermore, since the damping force against self-excited vibrations can be improved, there is an effect of preventing self-excited vibrations.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the servo control system of the present invention, FIG. 2 is a servo circuit configuration diagram of an electromagnetic bearing supporting rotor, and FIG. 3 is a block diagram of a conventional critical frequency damping device. 1... Rotor, 2... Electromagnetic coil, 3... Displacement detector. 4... Control circuit, 5... Power amplifier, 6... Differential circuit, 7.8... Filter.

Claims (1)

[Claims] 1. An electromagnetic bearing control device having means for detecting the radial position of the rotor from two orthogonal directions, the X direction and the Y direction,
A servo circuit having two channels in the X direction and Y direction is configured to control the current supplied to the electromagnetic coil in response to the displacement signal output from the detecting means so as to hold the rotor at a preset radial position. The servo circuit is provided with means for extracting a frequency component to be controlled from vibrations of the rotor, displacement signals in the X direction and Y direction are input to the selection extraction means, and the output of the signal is means for adding and inputting a signal in one direction of the direction signal and the Y-direction signal to a servo circuit in the other direction, and subtracting and inputting the signal in the other direction to the servo circuit in the one direction; What is claimed is: 1. An electromagnetic bearing control device characterized in that the main control circuit is configured to subtract and input the following from a displacement signal, and to control a component excluding a rotation synchronous component. 2. An electromagnetic bearing control device 3 according to claim 1, characterized in that the frequency to be controlled is made to correspond to the number of rotations; An electromagnetic bearing control device characterized by matching a determined natural frequency.