JPH11287248A - Control type magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict an exciting current flowing into a power amplifier and an electromagnet, making them protectable, and also to simplify the structure of an electromagnet controlling means into inexpensiveness. SOLUTION: This control type magnetic bearing unit is equipped with a magnetic bearing 4 having a pair of electromagnets 2 and 3 noncontactually supporting a rotator 1 at a target position in holding it between both sides in the controlling axial direction, a position detecting device 5 detecting the position of the rotator 1, and an electromagnet control unit 23 controlling an exciting current to be fed to the electromagnets 2 and 3 on the basis of a position detecting signal out of this position detecting device 5, respectively. In this constitution, this electromagnet control unit 23 is equipped with a digital signal processor 17 capable of a software program, and in turn, this digital signal processor 17 is equipped with two limiting means 27 and 28 for limiting a exciting current value to these electromagnets 2 and 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control type magnetic bearing device which is used in, for example, a turbo-molecular pump and the like, in which a rotating body is magnetically levitated by a magnetic bearing and is supported at a predetermined target position in a non-contact manner.

[0002]

2. Description of the Related Art As a control type magnetic bearing device of this kind, there is a 1
There is known a set of axial magnetic bearings and two sets of radial magnetic bearings that support a rotating body in a non-contact manner. The axial magnetic bearing is provided with a pair of electromagnets arranged so as to sandwich the rotating body from both sides in one axial control axis (axial control axis) direction. Each radial magnetic bearing is provided with a pair of electromagnets arranged so as to sandwich the rotating body from both sides in the radial control axis direction for each of two radial control axes (radial control axes) orthogonal to each other. An exciting current is supplied from an electromagnet controller to a pair of electromagnets in each control axis direction in each magnetic bearing. The electromagnet control device controls an excitation current supplied to a pair of electromagnets in the control axis direction based on a position detection signal from a position detection device that detects the position of the rotating body in one control axis direction. The excitation current supplied to the pair of electromagnets is obtained by adding and subtracting a constant bias current to a control current that changes according to a position detection signal. That is, the exciting current supplied to one of the pair of electromagnets is obtained by adding the control current to the bias current, and the exciting current supplied to the other is obtained by subtracting the control current from the bias current. Then, the electromagnet control device calculates a control current value for the pair of electromagnets based on the position detection signal, and sets a value obtained by adding a constant bias current value and the control current value as an excitation current value for one electromagnet. A value obtained by subtracting the control current value from the bias current value is set as an exciting current value for the other electromagnet.

FIG. 1 shows a radial magnetic bearing (4) having a pair of electromagnets (2) and (3) for supporting a rotating body (1) in one radial control axis direction in a non-contact manner. A position detection device (5) for detecting a position in the control axis direction, and a conventional method for controlling an excitation current supplied to the electromagnets (2) and (3) based on a position detection signal output from the position detection device (5). Electromagnet controller (6)
Is shown.

A pair of electromagnets (2) and (3) are arranged so as to sandwich the rotating body (1) from both sides in the control axis direction, and a control device is provided.
The rotating body (1) is attracted to the opposite side in the control axis direction by the excitation current supplied from (6) and is supported in a non-contact manner.

The position detecting device (5) includes a pair of position sensors (7) and (8) and a subtractor (9) arranged so as to sandwich the rotating body (1) from both sides in the control axis direction. I have. Each position sensor (7)
(8) is for outputting a signal proportional to the size of a gap with the rotating body (1), and the subtracter (9) is provided with one of the pair of position sensors (7) and (8). By subtracting the other output signal from the output signal, a position detection signal proportional to the position (displacement) of the rotating body (1) with respect to the target position in the control axis direction is output to the control device (6).

[0006] The electromagnet controller (6) includes a control current calculator (1).
0), an adder (11), a subtractor (12) and two power amplifiers (1
3) (14) is provided.

The position detection signal ΔX from the position detection device (5)
Is input to the control current calculation unit (10), and the control current calculation unit (10)
Calculates the control current value Ic for the electromagnets (2) and (3) by, for example, PID calculation. The control current value Ic output from the control current calculation unit (10) is calculated by the adder (11) and the subtractor (1).
Supplied to 2). A constant bias current value Io is input to the adder (11) and the subtractor (12) in addition to the control current value Ic. The bias current value Io is set to a predetermined positive value by adjusting a potentiometer, for example. The adder (11) adds the bias current value Io and the control current value Ic, and supplies a signal (Io + Ic) obtained as a first excitation current signal to the first power amplifier (13). The first power amplifier (13) amplifies the first exciting current signal (Io + Ic) and generates an exciting current proportional to the first exciting current signal (Io + Ic).
To the electromagnet (2). The subtractor (12) subtracts the control current value Ic from the bias current value Io, and supplies the resulting signal (Io-Ic) as a second excitation current signal to the second power amplifier (14). . The second power amplifier (14)
, And supplies an exciting current proportional to this to the second electromagnet (3). As a result, the rotating body (1) is supported at the target position in the control axis direction.

In the conventional magnetic bearing device as described above, the control in the electromagnet control device is mainly analog PID control, and has only a function of outputting an output signal (excitation current signal) corresponding to an input signal (position detection signal). Since it is not provided, there were the following problems.

Since the exciting current supplied to the electromagnet is controlled in accordance with the position detection signal from the position detection device as described above, the position detection is performed when the whirling of the position detection signal becomes large or other abnormalities. When the signal becomes particularly large, the exciting current flowing from the power amplifier to the electromagnet increases. Therefore, conventionally, a fuse and a current limiting circuit are added to limit the exciting current flowing through the power amplifier and the electromagnet so as not to exceed a certain value to protect them. Therefore, a hardware configuration such as a fuse and a current limiting circuit is required, and the configuration of the electromagnet control device is complicated and expensive. When a fuse or the like is used, the control of the electromagnet becomes impossible due to the disconnection of the fuse, so that the rotating body may touch down, and it is also difficult to repair.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to protect the power amplifier and the electromagnet by limiting the exciting current flowing through the electromagnet and to simplify the configuration of the electromagnet control means. Another object of the present invention is to provide a control type magnetic bearing device which is inexpensive.

[0011]

SUMMARY OF THE INVENTION A control type magnetic bearing device according to the present invention includes a pair of non-contact supporting members which sandwich a rotating body at a target position in the control axis direction while sandwiching the rotating body from both sides in one control axis direction. A magnetic bearing having an electromagnet, and position detecting means for detecting a position of the rotating body in the control axis direction,
Based on the position detection signal from the position detection means,
A control type magnetic bearing device comprising: an electromagnet control unit for controlling an excitation current supplied to a pair of electromagnets, wherein the electromagnet control unit includes a digital processing unit capable of performing software programming, and the digital processing unit includes It is characterized in that it is provided with limiting means for limiting the exciting current value for each electromagnet.

As digital processing means capable of performing software programming, for example, an MPU (microprocessor), a digital signal processor, or the like is used. Digital Signal Processor (Digital Signal P)
The term “recessor” refers to dedicated hardware that inputs a digital signal, outputs a digital signal, is software-programmable, and is capable of high-speed real-time processing. Hereinafter, this is abbreviated as “DSP”.

[0013] The limiting means limits the exciting current value to the electromagnet to a predetermined limit value or less. The limit value of the exciting current value is
It is set to be equal to or less than the allowable current value of the power amplifier or the electromagnet. When a fuse is also used, the limit value of the exciting current value is set to be equal to or less than the capacity of the fuse. Desirably, the limit value of the exciting current value can be arbitrarily changed from outside. Also, preferably, when the exciting current value is limited by the limiting means, it is determined that there is an abnormality, and a warning is issued.

According to the control type magnetic bearing device of the present invention,
By the limiting means of the digital processing means of the electromagnet control means, the exciting current flowing from the power amplifier to the electromagnet can be limited to a predetermined limit value or less, thereby protecting the power amplifier and the electromagnet. Moreover, since the limiting means of the digital processing means limits the exciting current value by software, it is not necessary to add a hardware configuration such as a conventional current limiting circuit. Therefore, the configuration of the electromagnet control means is simple and inexpensive.

For example, the electromagnet control means obtains a control current value for the pair of electromagnets based on a position detection signal from the position detection means, and adds the control current value to a constant bias current value. Outputting the subtracted value as an exciting current value for the pair of electromagnets, wherein the digital processing means includes a control current calculating means for obtaining the control current value, and an absolute value of the control current value being equal to or less than a predetermined value. And the limiting means for limiting the exciting current value.

Further, for example, the electromagnet control means includes:
Based on the position detection signal from the position detection means,
A control current value for the pair of electromagnets is obtained, and a value obtained by adding and subtracting the control current value to and from a constant bias current value is output as an excitation current value for the pair of electromagnets. A control current calculating means for obtaining the control current value, an exciting current calculating means for obtaining the exciting current value, and the limiting means for limiting the exciting current value by setting the exciting current value to a predetermined value or less. Have.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 and FIG. 3 show the first embodiment. FIG. 2 is a drawing corresponding to FIG. 1. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In the case of the first embodiment, the electromagnet control device (electromagnet control means) (15) includes an AD converter (16), a DSP (17) as digital processing means, a ROM (18), and a non-volatile storage device. Flash memory (19), DA converter (20),
Further, an adder (11), a subtractor (12), and two power amplifiers (13) and (14) similar to those in FIG. 1 are provided.

A / D converter (16), DSP (17), ROM (1
8), flash memory (19) and DA converter (20)
Provided on one DSP board. ROM (16) contains
A processing program in the DSP (17) is stored. The flash memory (19) stores a control parameter table that stores control parameters of the magnetic bearing, a limit value table that stores a limit value of a control current value described later, and the like.

The DSP (19) functionally includes a control current calculating means (21) and a control current limiting means (22).

The position detection signal from the position detection device (5) is
The digital value is converted into a digital value by the AD converter (16), and the digital value position detection signal ΔX is input to the DSP (17). The control current calculating means (21) calculates the control current based on the displacement detection signal ΔX.
For example, a control current value for the electromagnets (2) and (3) is calculated by PID calculation. The control current value can take any of positive and negative values depending on the position (direction of displacement) of the rotating body (1).
The control current limiting means (22) limits the exciting current value to a predetermined limit value or less by setting the absolute value of the control current value to a predetermined limit value or less. The control current value calculated by the control current calculation means (21) is output to the DA converter (20) as it is, and the absolute value is limited. If it exceeds the value, the absolute value of the control current value calculated by the control current calculation means (21) is set to the same value as the limit value and output to the DA converter (20). Next, the processing in the control current limiting means (22) will be described in more detail with reference to FIG. FIG. 3 shows the relationship between the input value and the output value of the control current limiting means (22), where the horizontal axis represents the input value and the vertical axis represents the output value. Further, the absolute values of the positive limit value and the negative limit value are equal to each other. As is clear from FIG. 3, when the input value is equal to or less than the positive limit value and equal to or greater than the negative limit value, the input value is directly used as the output value. When the input value is larger than the positive limit value, the positive limit value is set as the output value, and when the input value is smaller than the negative limit value, the negative limit value is set as the output value. As a result, as described above, the absolute value of the control current value output to the DA converter (20) is limited to the limit value or less. The control current value output from the control current limiting means (22) is converted into an analog value by the DA converter (20), and the control current value Ic of this analog value is supplied to the adder (11) and the subtractor (12). Supplied. The rest is the same as in FIG.

In the control current limiting means (22), the absolute value of the control current value is limited to the limit value or less as described above, so that the power amplifiers (13) and (14) supply the electromagnets (2) and (3). The maximum value of the exciting current value is a value obtained by adding the bias current value and the absolute value of the limit value. Therefore, if the limit value is set so that the value obtained by adding the absolute value of the bias current value and the limit value is equal to or less than the allowable current value of the amplifiers (13) (14) and the electromagnets (2) (3), The value of the exciting current flowing through these is suppressed to the allowable current value or less.

Although not shown, the electromagnet control device (15) is provided with an operation panel and a liquid crystal display. The operation panel can arbitrarily set a limit value stored in a table of the flash memory (19). It can be changed. Further, the control current value calculated by the control current calculation means (21) exceeds the limit value, and the control current limit means
When this is limited to the limit value in (22), it is determined that there is an abnormality, and a warning of the abnormality is given using the display. Also, the flash memory (19)
It is also possible to connect to a personal computer via a serial communication board and a cable, and to use the personal computer to change the limit value or warn of an abnormality.

FIGS. 4 and 5 show a second embodiment. FIG. 4 is a drawing corresponding to FIG. 2. In FIG. 4, the same parts as those in FIG. 2 are denoted by the same reference numerals.

In the case of the second embodiment, the electromagnet control device (electromagnet control means) (23) includes an AD converter (16), a DSP (17),
ROM (18), flash memory (19), two DA converters
(24) and (25) and two power amplifiers (13) and (14).

AD converter (16), DSP (17), ROM (1
8), flash memory (19) and DA converter (24) (25)
Are provided on one DSP board. The flash memory (19) stores a bias current value table storing the bias current value Io in addition to the above-described table.

The DSP (19) functionally includes a control current calculating means (21), an exciting current calculating means (26), and two exciting current limiting means (27) and (28).

The exciting current calculating means (26) adds the bias current value Io stored in the flash memory (19) and the control current value Ic calculated by the control current calculating means (21), and obtains the result. The value (Io + Ic) is output as a first exciting current value to the first exciting current limiting means (27), and the control current value Ic is subtracted from the bias current value Io.
The value (Io-Ic) obtained as a result is output to the second exciting current limiting means (28) as a second exciting current value. The bias current value Io is a positive value, and its absolute value is the control current value Ic.
Greater than the absolute value of Therefore, the first exciting current value (Io + Ic) and the second exciting current value (Io-Ic) are:
Always a positive value. Each of the exciting current limiting means (27) and (28) limits the exciting current value to a predetermined limit value or less, checks the exciting current value calculated by the exciting current calculating means (26), and determines whether the value is limited. If the value is equal to or less than the value, the exciting current value calculated by the exciting current calculating means (26) is output to the DA converters (24) and (25) as it is, and the exciting current value calculated by the exciting current calculating means (26) is If the limit value is exceeded, the exciting current value is set to the same value as the limit value and output to the DA converters (24) and (25). Next, with reference to FIG. 5, the processing in each of the excitation current limiting means (27) and (28) will be described in more detail. FIG. 5 shows each excitation current limiting means (27).
The relationship between the input value and the output value of (28) is shown, with the horizontal axis representing the input value and the vertical axis representing the output value. As is clear from FIG. 5, when the input value is equal to or less than the limit value, the input value becomes the output value as it is, and when the input value is larger than the limit value, the limit value is set as the output value. As a result, as described above, D
Excitation current values output to the A converters (24) and (25) are limited to the limit value or less. The exciting current value output from the exciting current limiting means (27) (28) is converted into an analog value by the DA converters (24) (28) and supplied to the amplifiers (13) (14). After that, the first
This is the same as in the embodiment.

In the exciting current limiting means (27) and (28), the exciting current value is limited to the limit value or less as described above, so that the power amplifiers (13) and (14) supply the electromagnets (2) and (3). The maximum value of the exciting current value to be performed is a limit value. Therefore, if the limit value is set to be equal to or less than the allowable current value of the amplifiers (13) and (14) and the electromagnets (2) and (3), the exciting current value flowing through these is suppressed to the allowable current value or less.

In the second embodiment, similarly to the first embodiment, the bias current value and the limit value stored in the table of the flash memory (19) can be arbitrarily changed from the operation panel. When the exciting current value calculated by the exciting current calculating means (28) exceeds the limit value, the exciting current limiting means (2
7) When this is restricted to the limit value in (28), a warning of abnormality is made using the display.
In addition, using a personal computer,
It is also possible to warn of a change in the limit value or an abnormality.

In the above embodiment, the radial magnetic bearing has been described, but the same applies to the axial magnetic bearing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a magnetic bearing device showing a conventional example.

FIG. 2 is a configuration diagram of a main part of the magnetic bearing device according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between an input value and an output value in the control current limiting means of FIG. 2;

FIG. 4 is a configuration diagram of a main part of a magnetic bearing device according to a second embodiment of the present invention.

FIG. 5 is a graph showing a relationship between an input value and an output value in the exciting current limiting means of FIG.

[Explanation of symbols]

(1) Rotating body (2) (3) Electromagnet (4) Magnetic bearing (5) Position detector (15) Electromagnet controller (17) Digital signal processor (D
SP) (21) Control current calculating means (22) Control current limiting means (23) Electromagnet controller (26) Exciting current calculating means (27) (28) Exciting current limiting means

Claims (3)

[Claims] 1. A magnetic bearing having a pair of electromagnets for holding a rotating body in a non-contact manner at a target position in the control axis direction while sandwiching the rotating body from both sides in one control axis direction, and a position of the rotating body in the control axis direction. A control type magnetic bearing device, comprising: a position detecting means for detecting the position of the electromagnet; and an electromagnet control means for controlling an exciting current supplied to the pair of electromagnets based on a position detection signal from the position detecting means. The control type magnetic bearing device, wherein the control means includes digital processing means capable of executing a software program, and the digital processing means includes limiting means for limiting an exciting current value for each of the electromagnets. 2. The electromagnet control means calculates a control current value for the pair of electromagnets based on a position detection signal from the position detection means, and adds the control current value to a constant bias current value. Outputting the subtracted value as an exciting current value for the pair of electromagnets, wherein the digital processing means includes a control current calculating means for obtaining the control current value, and an absolute value of the control current value being equal to or less than a predetermined value. 2. The control type magnetic bearing device according to claim 1, further comprising: said limiting means for limiting said exciting current value. 3. The electromagnet control means calculates a control current value for the pair of electromagnets based on a position detection signal from the position detection means, and adds the control current value to a constant bias current value. Outputting the subtracted value as an excitation current value for the pair of electromagnets, wherein the digital processing means includes: a control current calculation means for obtaining the control current value; an excitation current calculation means for obtaining the excitation current value; 2. The control type magnetic bearing device according to claim 1, further comprising: said limiting means for limiting said exciting current value by setting said exciting current value to a predetermined value or less.