JP3174864B2 - Magnetic bearing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing control device.

[0002]

2. Description of the Related Art A magnetic bearing control device controls an electromagnet of a magnetic bearing based on a detected air gap signal from a position sensor for detecting the size of an air gap with a rotor and a predetermined reference air gap signal. It has been known. In this type of control device, for example, as disclosed in JP-A-59-113315,
A method has been proposed in which the relationship between the control command signal of the electromagnet and the generated attractive force is linearized in various ways.

[0003]

In the conventional magnetic bearing control device as described above, the relationship between the control command signal of the electromagnet and the generated attraction force can be linearized. There is a problem that it is not possible to perform linearization.

That is, first, when the rotor rotates, the rotor expands due to the centrifugal force, so that the reference air gap amount changes according to the number of rotations, and when the temperature of the rotor rises, the rotor expands. Although the reference air gap amount changes, the conventional control device cannot completely linearize the reference air gap signal because the reference air gap signal is constant even if the rotation speed or the temperature changes. Also, regarding the geometric relationship between the electromagnet of the magnetic bearing and the position sensor, these positions are usually different, so the detected air gap signal, which is the output of the position sensor, is not necessarily the true air gap between the electromagnet and the rotor. However, in the conventional control device, since the output of the position sensor is used as it is as a true air gap between the electromagnet and the rotor for control, linearization cannot be performed in a strict sense.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide a magnetic bearing control device capable of linearizing the attraction force of an electromagnet without being affected by the rotation speed and temperature of the rotor or the geometric relationship between the electromagnet and the position sensor.

[0006]

According to the present invention, there is provided a magnetic bearing control apparatus which controls a magnetic bearing based on a detected air gap signal from a position sensor for detecting the size of an air gap with a rotor and a predetermined reference air gap signal. A device for controlling an electromagnet of a bearing, comprising: a temperature sensor for detecting a temperature of a rotor portion, a rotation sensor for detecting a rotation speed of a rotor, and a detection temperature signal from the temperature sensor and a detection speed signal from the rotation sensor. A reference air gap signal correcting means for correcting the reference air gap signal, and correcting the detected air gap signal to represent a true air gap between the electromagnet and the rotor based on a geometric relationship between the electromagnet and the position sensor. It is characterized by including a detected air gap signal correcting means.

[0007]

According to the present invention, the reference air gap signal is corrected based on the detected temperature signal and the detected rotation speed signal, and the detected air is represented so as to represent the true air gap between the electromagnet and the rotor based on the geometric relationship between the electromagnet and the position sensor. Since the gap signal is corrected, the attraction force of the electromagnet can be linearized without being affected by the rotation speed and temperature of the rotor or the geometric relationship between the electromagnet and the position sensor.

[0008]

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

FIG. 1 shows one of the magnetic bearing devices which rotatably supports the rotor (10) in a non-contact state, at one position in the axial direction of the rotor (10) in one radial direction (Y-axis direction). 2 shows a part of a control device of a radial magnetic bearing to be supported. The axis in the radial direction orthogonal to the Y axis is defined as the X axis.

In this radial magnetic bearing, the rotor (10)
It has two horseshoe-shaped electromagnets (11) and (12) arranged so as to be sandwiched from both sides in the axial direction. (13) (14) is an electromagnet (11)
This is the coil of (12). Further, (15) and (16) are two position sensors arranged so as to sandwich the rotor (10) from both sides in the Y-axis direction in order to detect the displacement of the rotor (10) in the Y-axis direction. (17) is a rotation sensor that detects the number of rotations of the rotor (10),
(18) is a temperature sensor for detecting the temperature of the portion of the rotor (10) provided with the electromagnets (11) and (12) and the position sensors (15) and (16), and (19) and (20) are the electromagnets (11). power amplifier for driving (12), (21) (22) is a multiplier, (23) a constant voltage circuit for generating a constant voltage corresponding to the bias current value I _b, (24) an adder, ( 25) is a subtractor, (26) is a PID control circuit, (27) is a subtractor, (28) is a calculator, (29) is a reference air gap signal setting circuit, (30) is an adder, and (31) is A subtractor, (32) is an arithmetic unit.

The geometric relationship between the rotor (10), the electromagnets (11) (12) and the position sensors (15) (16) is shown in FIG. In the figure, (O) represents the origin where the Y axis and the X axis intersect. The two position sensors (15) and (16) are symmetrically arranged on the Y axis with respect to the origin (O). The two electromagnets (11) and (12) are also arranged symmetrically with respect to the origin (O), and the two magnetic poles (11a) and (12a) of each electromagnet (11) and (12) are symmetrical with respect to the Y axis. Has become. Therefore, each electromagnet (11) (1
The positions of the two magnetic poles (11a) and (12a) in (2) are shifted by the same angle in the circumferential direction opposite to each other with respect to the corresponding position sensors (15) and (16). Note that the origin (O) and the electromagnet (11) (12)
The angle formed by a straight line passing through the magnetic poles (11a) and (12a) with the Y axis is represented by θ.

The two position sensors (15) and (16) detect the size of the air gap with the rotor (10) in the Y-axis direction, and their outputs are sent to a computing unit (28). These position sensors (15)
The output of (16), that is, the detected air gap signal is
₁ and Y ₂ . The position of the rotor (10) is represented by its center position, and the position when the rotor (10) is at the origin (O) is defined as the reference position of the rotor (10). When the rotor (10) is at the reference position, the size of the air gap between the two position sensors (15) (16) and the rotor (10) is equal to each other. The size of the air gap at this time is referred to as a reference air gap amount. The displacement in the Y-axis direction from the origin (O) of the rotor (10) is ΔY
Assuming that the lower side of FIG. 1 is the positive direction of ΔY, ΔY is given by the following equation:
It looks like (1).

ΔY = (Y ₁ −Y ₂ ) / 2 (1) In the arithmetic unit (28), the detected air gap signal Y ₂ from the second position sensor (16) and the detected air gap signal Y ₂ from the first position sensor (15) are obtained. The difference (Y ₂ −Y ₁ ) between the detected air gap signals Y ₁ is obtained, multiplied by 倍, and the output is sent to the subtracter (27). From the above equation (1), (Y ₂ −Y ₁ ) is [2 × (−ΔY)].
Therefore, the output of the arithmetic unit (28) is (−ΔY).
ΔY which is a signal obtained by changing the sign of the output of the arithmetic unit (28)
Is referred to as a detected displacement signal. Deviation of the subtractor (27), a predetermined positioning signal _{Y s (-ΔY) (Y s} + Δ
Y) is calculated. Position setting signal Y _s is representative target position in the Y-axis direction of the rotor (10) (set position) i.e. the target value of the displacement ΔY of the rotor (10) from the origin (O) (position setting). Normally, the setting position of the rotor (10) is the origin (O)
Since the position setting value is 0, the position setting signal Y _s
Is 0. Therefore, the output of the subtractor (27), that is, the detected deviation signal is ΔY, which is equal to the detected displacement signal. PI
The D control circuit (26) controls the electromagnet based on the detected displacement signal ΔY.
(11) (12) obtains a current command value I _c, and outputs it to the adder (24) and a subtractor (25). The adder (24) is a constant voltage circuit
It calculates the sum (I _b + I _c) of the bias current value I _b and the current command value I _c from (23), and outputs it to a first multiplier (21). The first multiplier (21) calculates the product of the output of the adder (24) and the output of the adder (30) described later.
Based on the output of (21), the first power amplifier (19)
The coil current flowing through the coil (13) of the electromagnet (11) is controlled. Subtractor (25) obtains a difference between the bias current I _b and the current command value I _c from the constant voltage circuit (23) (I _b -I _c), and outputs it to the second multiplier (22) . In the second multiplier (22),
The product of the output of the subtractor (25) and the output of a subtractor (31) described later is calculated, and a second
The coil current flowing through the coil (14) of the second electromagnet (12) is controlled by the power amplifier (20). And this gives
The rotor (10) is supported at a set position in the Y-axis direction.

The output of the rotation sensor (17), ie, the detected rotation speed signal N, and the output of the temperature sensor (18), ie, the detected temperature signal T
Is sent to the reference air gap signal setting circuit (29). The rotor (10) expands in the radial direction by centrifugal force generated by rotation, and the degree of the expansion changes according to the centrifugal force, that is, the number of rotations. Further, the rotor (10) expands in the radial direction due to a rise in temperature, and the degree of the expansion changes depending on the temperature. Therefore, the diameter of the rotor (10) changes according to the rotation speed and the temperature, and as a result, the reference air gap amount also changes. The reference air gap signal setting circuit (29) outputs the detected rotation speed signal N
And correcting the reference air gap amount on the basis of the detected temperature signal T, and outputs the reference air gap signals Y _o which corresponds to the corrected reference air gap amount to the adder (30) and a subtractor (31). If the diameter of the rotor (10) is known, the reference air gap amount can be known. Further, there is a certain relationship between the rotation speed and temperature of the rotor (10) and the diameter of the rotor (10). Therefore, there is a certain relationship between the rotation speed and temperature of the rotor (10) and the reference air gap amount. If these relationships are obtained in advance, the detected rotation speed signal N and the detected temperature signal T
Thus, the reference air gap amount of the rotor (10) at that time can be obtained.

The output of the subtractor (27), that is, the detected displacement signal ΔY, is also sent to a calculator (32), where ΔY is multiplied by COSθ, and the output (ΔY) of the calculator (32) is obtained. ×
COSθ) is sent to the adder (30) and the subtractor (31). The detected displacement signal ΔY corresponds to the displacement of the rotor (10) in the Y-axis direction. However, as described above, the magnetic poles of the electromagnets (11) and (12)
(11a) Since the positions of (12a) are shifted in the circumferential direction from the Y axis, the detected displacement signal ΔY indicates that the magnetic poles (11a) (12a) and the rotor (10)
The change in the air gap between the origin (O) and the magnetic pole (11
a) The displacement (magnetic pole direction displacement) of the rotor (10) in the direction connecting (12a) does not correspond exactly. Magnetic pole direction displacement ΔY _M
Then, between this and the detected displacement signal ΔY,
There is a relationship like (2).

ΔY _M = ΔY × COSθ (2) The output of the above-mentioned computing unit (32) is equal to ΔY _M in the equation (2), and the detected displacement signal ΔY is calculated by the computing unit (32).
This means that the magnetic pole direction displacement ΔY _M representing the change in the true air gap between (10) and the magnetic poles (1a) and (2a) has been corrected. The output of the calculator (32) is referred to as a magnetic pole direction displacement signal ΔY _M.

The air gap between the magnetic poles (11a) (12a) of each electromagnet (11) (12) and the rotor (10) is referred to as the air gap of each electromagnet (11) (12), and the first electromagnet (11) the air gap (first electromagnet direction air gap) the Y _M1, second electromagnet (1
The air gap of 2) (air gap in the direction of the second electromagnet) is set to Y
_{Assuming M2} , these are represented by the following equations (3) and (4).

[0018] _{Y M1 = Y o + ΔY M} = Y o + ΔY × COSθ ... (3) Y M2 = Y o -ΔY M = Y o -ΔY × COSθ ... (4) adders (30), the reference air gap signal reference air gap signal Y _o and the magnetic pole direction displacement signal [Delta] Y _M from the setting circuit (29)
(Y _o + ΔY _M ), and outputs this to the first multiplier (21). The output (Y _o + ΔY _M ) of the adder (30) is equal to Y _M1 of the above equation (3), and the first multiplier (21) outputs the output (Y _o + ΔY _M ) of the adder (30) as described above. Y _o + ΔY _M ) and the output (I _b + I _c ) of the adder (24) are calculated, and based on this, the first electromagnet (1) is output by the first power amplifier (19).
1) is controlled. Subtractor (31) calculates the difference between the reference air gap signal Y _o and the magnetic pole direction displacement signal [Delta] Y _M from the reference air gap signal setting circuit _{(29) (Y o -ΔY M} ), which second multiplier ( Output to 22). The output of the subtracter (31) (Y
_o −ΔY _M ) is equal to Y _{M2 in the} above equation (4), and the second multiplier (22) outputs the output (Y
_o −ΔY _M ) and the output (I _b −I _c ) of the subtracter (25) are calculated, and based on this, the second power amplifier (20) controls the second electromagnet (12).

By performing such control, the outputs of the power amplifiers (19) and (20), that is, the electromagnets are controlled in the same manner as in the case of the invention described in Japanese Patent Application Laid-Open No. Sho 59-113315.
(11) The relationship between the control command signal in (12) and the generated suction force can be linearized. At this time, the reference air gap signal _Yo is corrected based on the rotation speed and the temperature of the rotor (10), and is detected based on the geometric relationship between the rotor (10) and the electromagnets (11) and (12). The displacement signal ΔY is the magnetic pole direction displacement signal ΔY.
_M and the air gaps Y _M1 and Y _{M2 of the} two electromagnets (11) and (12) are obtained from these _Yo and ΔY _M , so that the rotation speed and temperature of the rotor (10) and the rotor (10) and The attraction force of the electromagnets (11) and (12) can be accurately linearized without being affected by the geometric relationship between the electromagnets (11) and (12).

The support of the rotor 10 in the X-axis direction at this position is performed in the same manner as described above. In addition, rotor (10)
Is radially supported by a radial magnetic bearing in the Y-axis direction and a radial magnetic bearing in the X-axis direction at other positions in the axial direction. In addition, the rotor (10)
Are supported in the axial direction by a suitable axial magnetic bearing.

FIGS. 3 and 4 show another example of the control device for the radial magnetic bearing in the Y-axis direction. FIG. 3 shows an example of the mechanical configuration of the rotor (10), and FIG. 4 shows an example of the electrical configuration. In FIGS. 3 and 4, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.

As shown in FIG. 3, this radial magnetic bearing has a total of four horseshoe-shaped electromagnets (33), (34), (35), (36) arranged two on each side of the rotor (10) in the Y-axis direction. ). The two position sensors (15) and (16) are arranged symmetrically with respect to the origin (O) on the Y-axis as in the case of the above embodiment. The first electromagnet (33) and the second electromagnet (34) on one side are arranged slightly apart in the circumferential direction so as to be symmetric with respect to the Y axis. Similarly, the third magnetic bearing (35) and the fourth magnetic bearing (36) on the opposite side are also slightly spaced in the circumferential direction so as to be symmetric with respect to the Y axis. The origin (O) and each electromagnet
The angle between a straight line passing through the centers of (33) to (36) and the Y axis is represented by α. At this position, a radial magnetic bearing in the X-axis direction is also provided. FIG. 3 shows two position sensors (37) and (38) for detecting displacement of the rotor (10) in the X-axis direction. ) Are only shown. These position sensors
(37) and (38) are arranged symmetrically with respect to the origin (O) on the X axis.

In FIG. 4, outputs of the two position sensors (37) and (38) of the radial magnetic bearing in the X-axis direction are sent to a calculator (39). These position sensors (37) (38)
Is detected in the X-axis direction. The output of these position sensors (37) (38) i.e. a detection air-gap signal respectively to X ₁ and X _2. The position of the rotor (10) in the X-axis direction is represented in the same manner as the position in the Y-axis direction, the displacement of the rotor (10) in the X-axis direction from the origin (O) is represented by ΔX, and the right side of FIG. In the positive direction, ΔX is given by the following equation (5).

ΔX = (X ₁ −X ₂ ) / 2 (5) In the calculator (39), the detected air gap signal X ₂ from the X-axis second position sensor (38) and the X-axis first position sensor ( The difference (X ₂ −X ₁ ) of the detected air gap signal X _{1 from} (37) is obtained, multiplied by 倍, and the output is sent to the subtractor (40). From the above equation (3), (X ₂ −X ₁ ) is [2 × (−
ΔX)], the output of the computing unit (39) is (−ΔX)
Becomes Note that ΔX which is a signal obtained by changing the sign of the output of the arithmetic unit (39) is referred to as a detected displacement signal. Subtractor (40)
In a deviation of a predetermined position setting signal X _s (-ΔX) (X
_s + ΔX) is calculated. Position setting signal X _s, the rotor
The target position (set position) in the X-axis direction of (10), that is, the origin
(O) represents the target value (position setting value) of the displacement ΔX of the rotor (10) in the X-axis direction from (O). Usually rotor (10)
Set position of an origin (O), because the position setting value is 0, the position setting signal X _s is 0. Therefore, the subtractor
The output of (40), that is, the detected deviation signal is ΔX, which is equal to the detected displacement signal.

The output (I _b + I _c ) of the adder (24) is the first
The signal is sent to the multiplier (41) and the third multiplier (43). Subtractor (25) output (I _b -I _c) a second multiplier (42) and the fourth multiplier (4
Sent to 4).

As described above, the reference air gap signal setting circuit (29) calculates the reference air gap amount based on the detected rotation speed signal N from the rotation sensor (17) and the detected temperature signal T from the temperature sensor (18). After the correction, the reference air gap signal _Yo is output to the adders (45) and (46) and the subtractors (47) and (48).

The detected displacement signal ΔY which is the output of the subtracter (27)
Is sent to a computing unit (49), where ΔY is multiplied by COSα, and the output (ΔY × COSα) of this computing unit (49) is sent to a subtractor (50) and an adder (51). The X-axis detection displacement signal ΔX, which is the output of the subtracter (40), is sent to the calculator (52), where ΔX is
Multiplied by COSβ, and the output of this calculator (52) (ΔX × COSβ)
Is sent to the subtractor (50) and the adder (51). In addition,
The angle β represents (90 ° −α).

Since the positions of the electromagnets (33) to (36) are shifted in the circumferential direction from the Y axis, each of the electromagnets (33) to (36) and the rotor (10)
The magnitude of the actual air gap between
Y does not correspond exactly. The air gap with the rotor (10) on the center line of each of the electromagnets (33) to (36) is
(33) to (36), the first electromagnet
The air gap (air gap in the first electromagnet direction) of (33) is Y _M1 , the air gap of the second electromagnet (34) is Y _M2 , the air gap of the third electromagnet (35) is (Y). The third electromagnet direction air gap) is Y _M3 , and the fourth electromagnet (3
6) Air gap (fourth electromagnet direction air gap) is set to Y
_{Assuming M4} , these are represented by the following equations (6) to (9).

[0029] _{Y M1 = Y o + ΔY ×} COSα-ΔX × COSβ ... (6) Y M2 = Y o + ΔY × COSα + ΔX × COSβ ... (7) Y M3 = Y o -ΔY × COSα + ΔX × COSβ ... (8) Y M4 = Y _o −ΔY × COSα−ΔX × COSβ (9) In the subtractor (50), the output of the arithmetic unit (49) (ΔY × COS
α) and the output (ΔX × COSβ) of the arithmetic unit (52) (ΔY ×
COSα−ΔX × COSβ) is calculated, and this is added to the adder (45).
And sent to the subtractor (47). The adder (45), the reference air gap signal Y _o a subtractor output (50) ([Delta] Y × cos [alpha]
−ΔX × COSβ) (Y _o + ΔY × COSα−ΔX × C
OSβ) is calculated, and this is sent to the first multiplier (41).
The output of the adder (45) (Y _o + ΔY × COSα−ΔX × C
OSβ) is equal to Y _M1 in the above equation (6), and the first multiplier (41)
Now, this Y _M1 and the output of the adder (24) (I _b + I _c )
Is calculated, and based on this, the first electromagnet (33) is controlled by the first power amplifier (53). In the subtractor (47),
The reference air gap signal _Yo and the output of the subtractor (50) (ΔY ×
COSα-ΔX × COSβ difference _{of) (Y o -ΔY × COSα +} Δ
X × COSβ) is calculated and sent to the third multiplier (43). The output of this subtracter (47) (Y _o −ΔY × COSα + Δ
X × COSβ) is equal to Y _{M3 in the} above equation (8). In the third multiplier (43), this Y _M3 and the output of the adder (24) (I _b +
I _c ) is calculated, and based on this, the third power amplifier is calculated.
The third electromagnet (35) is controlled by (55). In the adder (51), the sum (ΔY × COSα + Δ) of the output (ΔY × COSα) of the arithmetic unit (49) and the output (ΔX × COSβ) of the arithmetic unit (52) is obtained.
X × COSβ) is calculated and sent to the adder (46) and the subtractor (48). The adder (46), the output of the reference air gap signal Y _o adder (51) (ΔY × COSα + ΔX × C
OSβ) is calculated (Y _o + ΔY × COSα + ΔX × COSβ), which is sent to the second multiplier (42). This adder
The output of (46) (Y _o + ΔY × COSα + ΔX × COSβ) is equal to Y _{M2 in the} above equation (7). In the second multiplier (42), this Y _M2 and the output of the subtractor (25) (I _b− I _c ) is calculated, and based on this, the second power amplifier 54
The electromagnet (34) is controlled. Subtractor (48), the reference air gap signal Y _o an adder output (51) (ΔY × COSα + Δ
Difference _{X × COSβ) (Y o -ΔY} × COSα-ΔX × COS
β) is calculated and sent to a fourth multiplier (44). The output of this subtracter (48) (Y _o -ΔY × COS α−ΔX × COS
β) is equal to Y _M4 in the above equation (9), and the fourth multiplier (44) calculates the product of Y _M4 and the output (I _b −I _c ) of the subtracter (25). The fourth electromagnet (36) is controlled by the fourth power amplifier (56) based on.

Also in this case, by performing the above control, the outputs of the power amplifiers (53) to (56),
The relationship between the control command signals (33) to (36) and the generated suction force can be linearized. Then, a reference air gap signal Y _o corrected by the rotational speed and the temperature of the rotor (10), the rotor (10) and an electromagnet (33) - on the basis of the geometric relationship of (36) four electromagnets ( 33)-(36) Air gaps Y _M1 , Y _M2 ,
Since Y _M3 and Y _M4 are obtained, the electromagnet can be accurately determined without being affected by the rotation speed and temperature of the rotor (10) and the geometrical relationship between the rotor (10) and the electromagnets (33) to (36). (33)-(36) The suction force can be linearized.

The other points are the same as those in FIGS. 1 and 2.

[0032]

According to the magnetic bearing control device of the present invention, as described above, the attractive force of the electromagnet is not affected by the rotational speed and temperature of the rotor and the geometrical relationship between the electromagnet and the position sensor. Can be linearized.

[Brief description of the drawings]

FIG. 1 is an electric block diagram of a main part of a control device for a radial magnetic bearing according to an embodiment of the present invention.

FIG. 2 is an enlarged front view showing a part of the rotor of FIG. 1;

FIG. 3 is a front view of a rotor portion of a control device for a radial magnetic bearing according to another embodiment of the present invention.

FIG. 4 is a block diagram showing an electrical configuration of the control device shown in FIG. 3;

[Explanation of symbols]

 (10) Rotor (11) First electromagnet (12) Second electromagnet (15) First position sensor (16) Second position sensor (17) Rotation sensor (18) Temperature sensor (29) Reference air gap signal setting circuit ( 32) Computing unit (33) First electromagnet (34) Second electromagnet (35) Third electromagnet (36) Fourth electromagnet (49) Computing unit (50) Subtractor (51) Adder (52) Computing unit

Claims (1)

(57) [Claims] An apparatus for controlling an electromagnet of a magnetic bearing on the basis of a detected air gap signal from a position sensor for detecting the size of an air gap with a rotor and a predetermined reference air gap signal. Temperature sensor that detects the temperature of the rotor, a rotation sensor that detects the rotation speed of the rotor, a reference air gap signal correction that corrects the reference air gap signal based on a detected temperature signal from the temperature sensor and a detected rotation speed signal from the rotation sensor Means, and a detection air gap signal correction means for correcting a detection air gap signal so as to represent a true air gap between the electromagnet and the rotor based on a geometric relationship between the electromagnet and the position sensor. Magnetic bearing control device.