JP3536926B2 - Magnetic bearing - 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 capable of controlling a magnetic force of an electromagnet to levitate a rotor, and detecting a floating position of the rotor to maintain and maintain a constant floating position of the rotor. .

[0002]

2. Description of the Related Art In recent years, a magnetic levitation device capable of contactlessly transferring has been used as a transfer device in a place where a high clean environment is required, such as an IC manufacturing device. In this magnetic levitation device, a magnetic bearing is used that floats a rotor as a levitation body by the magnetic force of an electromagnet and controls the levitation position of the rotor to be kept constant by detecting the levitation position of the rotor.

FIG. 16 is a block diagram showing a configuration of a conventional magnetic bearing. This magnetic bearing includes two electromagnets 42a arranged at positions facing each other across the rotor 41,
42b and two position sensors 43a and 43b. The magnetic bearing further includes position sensors 43a, 43b.
, A comparator 46 for comparing the output signal of the bridge circuit 44 with the reference signal 45, and a signal processing circuit for performing processing such as advancing the phase of the output signal of the comparator 46 47 and the signal processing circuit 4
And amplifying circuits 48a and 48b which amplify the output signal of No. 7 and supply the amplified output signals to the electromagnets 42a and 42b.

In this magnetic bearing, the rotor 41 is connected to the electromagnet 4
It is levitated and held by the magnetic force of 2a, 42b. Rotor 4
The position of 1 is detected by the position sensors 43a and 43b, and a signal corresponding to the position of the rotor 41 is obtained by the bridge circuit 44 and sent to the comparator 46. The comparator 46 compares the output signal of the bridge circuit 44 with the reference signal 45 to obtain a signal corresponding to the difference between the reference position and the signal.
8b. Then, the amplifier circuits 48a, 48
The excitation current is supplied to the electromagnets 42a and 42b by b. Thus, the rotor 41 is controlled so as to be maintained at the predetermined position.

[0005]

In the conventional magnetic bearing, the position of the rotor is detected by using the position sensor. However, it is technically difficult to accurately detect the position of the rotor by the position sensor. In addition, there is a problem that a high-precision and expensive sensor is required to control the position of the rotor with high accuracy.

In the conventional magnetic levitation system, an integration element is often inserted into a feedback loop in order to increase the holding accuracy. However, such integrals are more or less approximate. For example, when the integration element is configured by an analog circuit, the DC gain cannot be made infinite due to the offset of the OP amplifier. Also, in the case of using a digital control device, due to AD conversion and quantization errors inside the computer,
Some deviation remained. As described above, in the conventional magnetic levitation system, there is a certain limit in improving the holding accuracy by disposing the integral element.

It is an object of the present invention to provide a magnetic bearing which can control the position of the rotor with high accuracy with a simple structure.

[0008]

In order to achieve the above object, a magnetic bearing according to the present invention comprises an electromagnet for levitating a rotor by magnetic force, a hysteresis amplifier for supplying an exciting current to the electromagnet, and Position control means for controlling the position of the rotor using a phase-locked loop that controls the exciting current supplied from the hysteresis amplifier in accordance with the switching phase in the hysteresis amplifier to control the switching frequency in the hysteresis amplifier. It is characterized by having.

In order to achieve the above object, a magnetic bearing according to the first aspect of the present invention provides an electromagnet for floating a rotor by a magnetic force, and an electromagnet by switching two levels of voltages by switching and applying the voltage to the electromagnet. A rotor using a hysteresis amplifier that supplies an excitation current, and a phase-locked loop that controls an excitation current supplied from the hysteresis amplifier in accordance with a switching phase in the hysteresis amplifier to control a switching frequency in the hysteresis amplifier. And a position control means for controlling the position of (1).

In order to achieve the above object, a magnetic bearing according to a second aspect of the present invention includes an electromagnet for levitating a rotor by a magnetic force, and a hysteresis for supplying an exciting current to the electromagnet by switching two levels of voltages by switching. An amplifier, a phase-locked loop that controls an exciting current supplied from the hysteresis amplifier in accordance with a switching phase in the hysteresis amplifier to control a switching frequency in the hysteresis amplifier, and a phase-locked loop in accordance with the switching frequency in the hysteresis amplifier. And a frequency-voltage servo system that controls an exciting current supplied from the hysteresis amplifier based on the obtained voltage and controls a switching frequency in the hysteresis amplifier, and controls the position of the rotor together. position It is characterized in that it comprises a control means.

[0011]

According to the first and second aspects of the present invention, a hysteresis amplifier having a property that a switching frequency is changed by an inductance is used as an amplifier for exciting the electromagnet. In the hysteresis amplifier, the inductance changes according to the gap change between the electromagnet and the rotor,
Accordingly, the switching frequency also changes. In the magnetic bearing of the present invention, the position of the rotor can be detected by using such a hysteresis amplifier without using a position sensor. The rotor is held at a fixed position by controlling the switching frequency to be constant using a phase locked loop. Then, based on the detected position of the rotor, the rotor is held at a fixed position by controlling the switching frequency to be constant using a phase locked loop.

According to the third aspect of the present invention, the second aspect is provided.
As in the invention described, a hysteresis amplifier having a property in which a switching frequency is changed by inductance is used, and a position sensor is used by utilizing the fact that the switching frequency of the hysteresis amplifier changes according to the position of the electromagnet with respect to the rotor. Without detecting the position of the rotor. In addition, by controlling the switching frequency to be constant using a phase locked loop based on the detected rotor position, the rotor is held at a constant position, and a voltage corresponding to the switching frequency is obtained. By performing frequency-voltage feedback control using the voltage, erroneous synchronization of the phase locked loop is prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the magnetic bearing according to the present invention will be described below in detail with reference to FIGS.
FIG. 1 is a block diagram showing a configuration of a magnetic bearing according to one embodiment of the present invention. As shown in this figure, the magnetic bearing of the present embodiment has two electromagnets 12a and 12b disposed at positions facing each other with the rotor 11 interposed therebetween, and switches between two levels of voltage by switching to produce the electromagnets 12a and 12b. , A hysteresis amplifier 13a, 13b for supplying an exciting current to the electromagnets 12a, 12b, and a switching waveform in each of the hysteresis amplifiers 13a, 13b, and a phase comparator 14 for detecting a phase difference between the two waveforms.
And a loop filter 1 that generates a command signal from the output of the phase comparator 14 so that the frequencies of both switching signals match and supplies the command signal to each of the hysteresis amplifiers 13a and 13b.
5 is provided.

In this magnetic bearing, the hysteresis amplifier 1
An excitation current is supplied to the electromagnets 12a and 12b from the magnets 3a and 13b, and the magnetic forces (attraction forces F1 and F2) of the electromagnets 12a and 12b are supplied.
Thus, the rotor 11 is levitated and held. The switching waveforms in the hysteresis amplifiers 13a and 13b are input to the phase comparator 14, and a DC output proportional to the phase difference between the two waveforms is detected. From the output of the phase comparator 14, the switching frequency fa of the hysteresis amplifier 13a is smaller than the switching frequency fb of the hysteresis amplifier 13b. That is, as described later, the switching frequency is substantially proportional to the gap between the electromagnet and the rotor.
When it is determined that the gap between the rotor 2a and the rotor is smaller than the gap between the electromagnet 12b and the rotor, the command current value to the hysteresis amplifier 13a is set small and the command current value to the hysteresis amplifier 13b is set large by the loop filter. Is done. Then, the excitation current of the electromagnet 12a decreases and the excitation current of the electromagnet 12b increases due to the operation of each hysteresis amplifier.
The attraction force of a decreases and the attraction force of the electromagnet 12b increases. Then, the position of the rotor moves away from the electromagnet 12a and the electromagnet 12b
, So that fa is large and fb is small. Conversely, if the switching frequency fa of the hysteresis amplifier 13a is higher than the switching frequency fb of the hysteresis amplifier 13b, that is, if it is determined that the gap between the electromagnet 12a and the rotor is larger than the gap between the electromagnet 12b and the rotor, the loop filter Accordingly, the command current value to the hysteresis amplifier 13a is set large, and the command current value to the hysteresis amplifier 13b is set small. Then, the excitation current of the electromagnet 12a increases and the excitation current of the electromagnet 12b decreases due to the operation of each hysteresis amplifier, so the attraction of the electromagnet 12a acting on the rotor increases and the attraction of the electromagnet 12b decreases. Then, the position of the rotor approaches the electromagnet 12a and moves away from the electromagnet 12b, so that fa is small and fb is large. Since the above operations are continuously performed, the rotor is finally maintained at a predetermined position where fa = fb, that is, the gap between the electromagnet 12a and the rotor is equal to the gap between the electromagnet 12b and the rotor. Will be. As described above, the phase locked loop (PL) is controlled by the hysteresis amplifiers 13a and 13b, the phase comparator 14, and the loop filter 15.
L) is formed, and control is performed such that the position X of the rotor 11 is maintained at a predetermined position.

As described above, in the present embodiment, the electromagnet 12 (1
2a and 12b. ) As an amplifier to excite
The switching frequency of the hysteresis amplifier 13 (representing 13a and 13b) having the property that the switching frequency is changed by the inductance is used to determine the switching frequency of the gap between the electromagnet 12 and the rotor 11, that is, the position X of the rotor 11. The position of the rotor 11 is obtained from the switching frequency of the hysteresis amplifier 13 by utilizing the change in response. Therefore, a position sensor becomes unnecessary.

In this embodiment, the switching frequency of the hysteresis amplifiers 13a and 13b
Since the switching frequency is supplied to the phase locked loop and the switching frequency of the hysteresis amplifier 13 is controlled to be constant in accordance with the obtained position of the rotor 11, the rotor 11 is controlled. It is held in a fixed position. Therefore, since the control error can be detected at the phase level, the position of the rotor 11 can be controlled with high accuracy. In particular, since the integral element of the phase locked loop control in the present embodiment is an ideal element based on a mathematical relationship that the phase is obtained by integrating the angular frequency, there is essentially no error, and high-precision control is performed. It can be performed.

Next, an outline of the operation of the hysteresis amplifier 13 will be described with reference to FIGS. As shown in FIG. 2, let V be the voltage applied to the coil of the electromagnet 12, and let I be the current flowing through the coil. Further, a gap between the electromagnet 12 and the rotor 11 is represented by x.

FIG. 3 is a waveform diagram showing the relationship between the current I and the voltage V. As shown in this figure, the hysteresis amplifier 13 has a ± 10 volts above and below the target current value (including the control component) I ₀ .
By providing a width of ΔI, the voltage V applied to the coil is switched to −V _m when the actual current value reaches the upper limit I ₀ + ΔI _p , and the voltage applied to the coil when the actual current value reaches the lower limit I ₀ −ΔI _m switch the V to V _p. In the present embodiment, the position of the rotor 11 is detected from the switching frequency by utilizing that the switching frequency of the voltage of the hysteresis amplifier 13 is substantially proportional to the gap x between the electromagnet 12 and the rotor 11.

FIG. 4 is a block diagram showing the configuration of the hysteresis amplifier 13. As shown in the figure, the hysteresis amplifier 13 includes a comparison amplifier 21 to which the current command value I ₀ is input, and a hysteresis comparator 22 to which the output V of the comparison amplifier 21 is input. Further, the hysteresis amplifier 13 is connected to the hysteresis comparator 2.
2 of the electromagnet 12 is switched by switching between two levels of voltage supplied from the power supply 24.
A switching element 23 for applying a current to zero and a current detection circuit 25 for detecting a current i flowing through the coil 20 of the electromagnet 12 and applying the current to the comparison amplifier 21 are provided.

The current command value I ₀ is determined by the coil 2 of the electromagnet 12
It is the value of the current to flow to 0, and is generally given by the sum of the bias current value and the control current value. Further, the current command value I ₀ is supplied by the loop filter 15 of FIG.
Comparison amplifier 21, a voltage proportional to the difference between the current command value I ₀ and the coil current _{i V (V = K v (} I 0 -i): where K
_v is a constant). Hysteresis comparator 22
Is a comparator whose threshold value changes according to the history of the input signal, and has a characteristic as shown in FIG. 5, for example. Here, the output voltage V 'of the hysteresis comparator 22
The high level side is set to V _ON and the low level side is set to −V _OFF . Further, -V _OFF an input voltage and [Delta] V _p, the output voltage from V _ON when the output voltage is changed to V _ON from -V _OFF
An input voltage when the change in the - [Delta] V _m.

[0021] The switching element 23, the level of the input signal (V _ON, -V _OFF) in response to a negative voltage the voltage across the coil 20 from the high voltage (V _p) (-V _m) or sufficiently small low An element (transistor, FET, thyristor, etc.) for switching to the voltage (V _L ). The switching waveform supplied to the phase comparator 14 in FIG. 1 may be the output waveform of the hysteresis comparator 22 or the output waveform of the switching element 23. Also,
A waveform obtained by binarizing the output of the current detection circuit 25 may be used.

Next, the operation of the hysteresis amplifier 13 will be described. As shown in FIG. 6, the current flowing through the coil 20, around the target value I _0, varies triangular waveform. The reason will be described below. At some point, the coil current by _{I '(I 0 -ΔI m <} I'<I 0), the output V _ON of the hysteresis comparator 22, the voltage applied to the coil 20 and had a V _p.

Here, as shown in FIG. 7, the coil 20 can be considered as a series circuit of an inductance L and a resistor R, and it is assumed that V _p ≫ (I ₀ + ΔI _p ) / R is set. In this case, the coil current for the inductance L of the coil 20 is gradually increased to gradually and eventually becomes equal to I _0. At the same time, the sign of the output voltage of the comparison amplifier 21 also changes (for example, from positive to negative). However, due to the hysteresis characteristic of the hysteresis comparator 22, the output of the hysteresis comparator 22 remains at V _ON for a while. Therefore, the current rises further beyond the I _0.
Eventually, when the value of the output voltage V of the comparison amplifier 21 becomes smaller than −ΔV _m , the output of the hysteresis comparator 22 switches to −V _OFF and the voltage applied to the coil 20 also becomes V
It switched to -V _m from _p. Therefore, the current of the coil 20 starts to decrease. This hysteresis comparator 22
The current value at the point where the output of-switches to -V _OFF is I ₀ +
When [Delta] I _p, has been established relation K _v ΔI _p = ΔV _m.

Eventually, the current value decreases to I ₀ , but because of the hysteresis characteristic of the hysteresis comparator 22, the current value is not immediately switched to V _ON , and the current value further decreases. Eventually, when the value of the output voltage V of the comparison amplifier 21 becomes larger than ΔV _p , the output of the hysteresis comparator 22 switches to V _ON , so that the voltage applied to the coil 20 becomes V _p again, and the current starts to increase. If the value of the current at the point where the output of the hysteresis comparator 22 switches to V _ON is I ₀ −ΔI _m , K _v ΔI _m =
The relationship ΔV _p holds.

The hysteresis amplifier 13 repeats the above operation. Incidentally, as shown in FIG. 6, the time which the current flowing through the coil 20 is increased from I ₀ -.DELTA.I _m to I ₀ + ΔI _p and t _1, the time decreases from I ₀ + ΔI _p to I ₀ -.DELTA.I _m t _Assuming that ₂ , the switching period T is t ₁ +
At t ₂ , the switching frequency f is 1 / T. Next, the switching frequency of the hysteresis amplifier 13 is
The reason why the ratio changes substantially proportionally with the gap x between the rotor 2 and the rotor 11 will be described.

As shown in FIG. 8, the coil 2 of the electromagnet 12
0 can be considered that the inductance L and the resistance R are connected in series. Here, in the initial state,
As the coil current i _a (0) = 0, and multiplied by the stepped voltage V _a across the coil 20. That is, FIG.
As shown in FIG. 5, when time t <0, V _a = 0 and time t ≧
When 0, and V _a = V _h. Then, as shown in FIG. 10, the coil current increases to a final value (V _h / R). In the vicinity of t = 0, that is, i _a ≪ (V _h / R)
, The rate of current increase is (R / L) · (V _h /
R) = (V _h / L).

[0027] In operation of the hysteresis amplifier 13 as described _{above, (I 0 + ΔI p)} « By the time that satisfies the relationship _{(V h / R), I} 0 -ΔI m from I ₀ + ΔI _p time t current increases until ₁ is (V _h / L) · t ₁ =
From (ΔI _p + ΔI _m ), t ₁ = L (ΔI _p + ΔI _m )
/ A V _h. Similarly, from I ₀ + ΔI _p to I ₀ −ΔI _m
The time t _{2 at} which the current decreases to (I ₀ −ΔI _p ) +
When V _m is selected so as to satisfy the relationship of (V _m / R) ≫I ₀ + ΔI _p , t ₂ = L (ΔI _p + Δ
I _m ) / V _m . Therefore, the switching period T (=
t ₁ + t ₂ ) is T = L (ΔI _p + ΔI _m ) · (1 / V
_h + 1 / _Vm ).

On the other hand, in the electromagnet 12, the inductance L of the coil 20 is substantially inversely proportional to the gap x between the electromagnet 12 and the rotor 11. Specifically, as shown in FIG.
Assuming that the total number of turns of the coil 20 of the electromagnet 12 is N, the sectional area of the core 30 is A, and the rotor 11 is a ferromagnetic material (permeability μ ≒ ∞), L ≒ N ² Aμ ₀ / 2x = K _L / X. However, μ ₀ is the initial _{^{permeability, K L = N 2 Aμ 0}} /2
It is. Therefore, T = (K _L / x) · (ΔI _p + Δ
I _pm ) · (1 / V _h + 1 / V _m ), and the switching frequency f (= 1 / T) is f = K′x. However,
_{K '= (V h × V} m) / {K L (ΔI p + ΔI m) ·
( _Vh + _Vm )}. Therefore, the switching frequency f is substantially proportional to the gap x.

The present invention is not limited to the above embodiment,
For example, in the embodiment, the position of the rotor is controlled by comparing the switching phases of the two hysteresis amplifiers. However, the switching phase of one hysteresis amplifier is compared with the phase of a reference signal having a predetermined frequency, and the rotor position is controlled. The position may be controlled.

FIG. 12 is a block diagram showing another configuration of the hysteresis amplifier. This hysteresis amplifier 11
3, the comparison adder 21 shown in FIG. 4 is omitted, and the current command value I ₀ supplied from the loop filter 15 of FIG.
The output of the current detection circuit 25 is directly input to the hysteresis comparator 122.

The hysteresis comparator 1
Reference numeral 22 is configured to have a comparison amplification function. That is, the hysteresis comparator 122 is configured to output a voltage V proportional to the difference between the current command value I ₀ and the coil current i, and to change the threshold value according to the history of the output. 5 is provided.

FIG. 13 shows a second embodiment of the magnetic bearing according to the present invention.
1 shows the configuration of the embodiment. For the sake of simplicity, the same parts as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.
As shown in FIG. 13, in the second embodiment, the rotor 11 is arranged so that the rotation center axis is in the horizontal direction. The magnetic bearing includes an electromagnet 12c disposed above the rotor 11, and a hysteresis amplifier 13c for supplying an exciting current to the electromagnet 12c. Also, magnetic bearings
A reference signal output circuit 131 for outputting a reference signal, a reference signal and a switching waveform in the hysteresis amplifier 13c, and a phase comparator 14 for detecting a phase difference between the two waveforms. A loop filter 15 that generates a command signal such that the frequency of the switching signal of the hysteresis amplifier 13c matches the frequency of the reference signal and supplies the command signal to the hysteresis amplifier 13c.

In this magnetic bearing, the hysteresis amplifier 1
3c is exciting current to the electromagnet 12c is supplied from the rotor 11 is levitated held by the suction force F ₁ of the electromagnet 12c. Here, the constant value of the suction force F ₁ of the electromagnet 12c is
It defined so as to cancel the effects of gravity F ₂ acting on the rotor 11 when the rotor 11 is in the set position.
In the second embodiment, any of the hysteresis amplifiers shown in FIGS. 4 and 12 may be used.

FIG. 14 shows a third embodiment of the magnetic bearing according to the present invention.
1 shows the configuration of the embodiment. For the sake of simplicity, the same parts as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.
In the third embodiment shown in FIG. 14, two electromagnets 12a,
12b and two hysteresis amplifiers 13a and 13b,
The circuit configuration including the phase comparator 14 and the loop filter 15 is exactly the same as that of the first embodiment shown in FIG. 1, and the operation based on the circuit configuration part in the third embodiment is the same as that of the first embodiment shown in FIG. This is basically the same as the first embodiment.

The third embodiment differs from the first embodiment in that a frequency-voltage servo system 30 is added to the same circuit components as in the first embodiment. The frequency-voltage servo system 30 includes the hysteresis amplifiers 13a and 13a.
b: a frequency-to-voltage converter (hereinafter referred to as “F / V converter”) 3 that takes in the switching signal and obtains a voltage signal proportional to the frequency of the switching signal
5a, 35b and these F / V converters 35a, 35
b, and a stabilization control circuit 37 for forming a servo signal based on the deviation signal from the adder 36 and supplying the servo signal to the hysteresis amplifiers 13a and 13b. It is composed.

The F / V converter 35a takes in the switching signal in the hysteresis amplifier 13a and can obtain a voltage signal proportional to the frequency of the switching signal. The F / V converter 35b also takes in the switching signal in the hysteresis amplifier 13b and can obtain a voltage signal proportional to the frequency of the switching signal. Each voltage signal of the F / V converters 35a and 35b is subtracted by the adder 36. The deviation of each voltage signal from the adder 36 indicates the gap (position) between the rotor 11 and each of the electromagnets 12a and 12b.
And the gap between each of the electromagnets 12a and 12b indicates an appropriate state. If the deviation indicates a positive or negative value, it indicates that the rotor 11 is biased, for example, to either the electromagnet 12a or the electromagnet 12b. .

That is, as the deviation signal from the adder 36, a signal proportional to the displacement X of the rotor 11 is obtained. Therefore, the stabilization control circuit 37 uses the hysteresis amplifier 13 based on the deviation signal from the adder 36.
By performing, for example, proportional-integral (PD) control on a and 13b, the entire system can be stabilized.

In the magnetic bearing according to the third embodiment, as described above, the two levels of voltages are switched by the hysteresis amplifiers 13a and 13b, and the electromagnet 12 is switched.
a, 12b to be applied to the electromagnets 12a, 12b.
b, and the rotor 11 is levitated and held by the magnetic force (attraction force F ₁ , F ₂ ) of these electromagnets 12a, 12b. F / V servo system (F / V converter 35a,
35b, the adder 36, and the stabilization control circuit 37) are used in combination to prevent delay of synchronization pull-in and error synchronization caused by the PLL control, for example, at the beginning of operation.
We are trying to stabilize the whole system.

In the third embodiment, first, in a PLL control system similar to that used in the first embodiment, the switching signals in the hysteresis amplifiers 13a and 13b are input to the phase comparator 14 and the phase difference between the two waveforms is obtained. From the output of the phase comparator 14 to generate a command signal such that the frequencies of both switching signals coincide with each other by the loop filter 15 and supply it to the hysteresis amplifiers 13a and 13b.
The stabilization of the switching frequency of the hysteresis amplifiers 13a and 13b is controlled, that is, the position X of the rotor is maintained at a predetermined position.

In the third embodiment, the switching signals from the hysteresis amplifiers 13a and 13b are proportional to the frequency by the F / V converters 35a and 35b by the F / V servo system in addition to the PLL control. These voltage signals are converted into a voltage signal, and a deviation of these voltage signals is taken by an adder 36. Based on the deviation, the stabilization control circuit 37
Then, PD control is applied to the hysteresis amplifiers 13a and 13b to stabilize the switching frequency of the hysteresis amplifiers 13a and 13b, that is, to control the position X of the rotor 11 to be maintained at a predetermined position.

As described above, in the third embodiment, as the amplifier for exciting the electromagnets 12 (representing 12a and 12b), the hysteresis amplifier 13 (13a, 13a,
13b. ) And the switching frequency of the hysteresis amplifier 13 is
The position of the rotor 11 is obtained from the switching frequency of the hysteresis amplifier 13 by utilizing the gap between the hysteresis amplifier 13 and the position X of the rotor 11. Further, since the frequency indicates the position of the rotor 11, the F / V servo system is used in combination with the PLL control based on these frequencies to stabilize the entire system.
Also in the third embodiment, a position sensor is unnecessary.

FIG. 15 is a block diagram showing the dynamic characteristics of the third embodiment. FIG. 15A shows an example of the dynamic characteristics of the third embodiment, and FIG. Each shows a simple example of the dynamic characteristics of the embodiment. The third embodiment shown in FIG. 14 can be represented by a dynamic characteristic block as shown in FIG. In FIG. 15A, the block [b /
(S ² -a)] The output from 301 (displacement X of rotor 11) is input to phase comparator 14 via blocks (Kf) 302a and 302b. The phase comparator 14 includes a subtractor 303 for phase comparison, and a phase detector (Kd / S) 304 that performs phase detection from a phase deviation from the subtractor 303.

The switching waveforms from the blocks 302a and 302b are compared in phase by a phase comparison subtracter 303, and the comparison result is phase-detected by a phase detector 304. The output from the phase detector 304 is a block [a ₀ / (S + b ₀ )] 3 representing the loop filter 15.
05 is input. The output of block 305 is applied to adder 306. The output of the adder 306 is a block (Ka) representing each of the hysteresis amplifiers 13a and 13b.
307a and 307b are input. Block 3
The outputs of 07 a and 307 b are added by an adder 308 and act on a block 301.

On the other hand, the output of the block 301 (the rotor 11
Is input to blocks (Kv) 310a and 310b representing the F / V converters 35a and 35b via blocks (Kf) 302a and 302b. These blocks 310a and 310b output a voltage signal proportional to the displacement X. These voltage signals are subtracted in a block 311, which represents an adder 36, and the deviation thereof is determined by the stabilization control circuit 3.
7 (Pd + SPv) 312. The servo signal from block 312 is applied to block 306 to correct the control signal of the PLL control system and to stabilize the entire system.

The control block shown in FIG. 15A can be represented in a simplified manner as shown in FIG. This is shown for simplification of calculation, and is shown as shown in FIG. 15B by expressing Ka, Kf, and Kv in FIG. 15A as one. That is, the configuration shown in FIG.
02a and 302b as one block 302, and blocks 307a and 307b as one block 307.
In this example, the blocks 310a and 310b are defined as a single block 310, and the blocks 303, 308 and 311 are omitted.

In the configuration shown in FIG.
For example, PD control is adopted by using the F / V converted signal as the switching signal, the feedback coefficient can be freely set, and the loop filter (block 30) is used.
4) Assuming that a first-order low-pass filter is used as 15, the closed-loop transfer function of the system shown in FIG.
Equation 1 is obtained.

[0047]

T (S) = [b (S ² + b ₀ )] / [S ⁴ +
(A ₂ + b ₀ ) S ³ + (a ₁ + a ₂ b ₀ ) S ² + a ₁ b
₀ S + a ₀ b] where a ₁ = bPd−a, a ₂ = bPv Here, the characteristic polynomial of the closed-loop system is specified by the following equation 2.

[0048]

G (S) = S ⁴ + g ₃ S ³ + g ₂ S ² + g ₁ S + g ₀ At this time, each coefficient of the filter and the feedback coefficient are represented by the following Equation 3.

[0049]

G ₃ = a ₂ + b ₀ , g ₂ = a ₁ + a ₂ b ₀ , g
It can be determined from the relationship of ₁ = a ₁ b ₀ and g ₀ = a ₀ b.

As described above, the third embodiment can be expressed by the dynamic characteristic block shown in FIG. 15B by using the F / V servo together with the PLL control, and the hysteresis amplifier is a self-excited chopper circuit. 13a and 13b, and the switching frequency f of the electromagnets 12a and 12b
The control is performed such that the position X of the rotor 11 is maintained at a predetermined position by utilizing a relationship that is substantially proportional to a gap x between the rotor 11 and the rotor 11.

This is because the integration element of the phase locked loop control (PLL control) in the third embodiment is an ideal one based on a mathematical relationship that the phase is obtained by integrating the angular frequency. Error does not occur,
In addition to being able to perform high-precision control, the point where it is difficult to quickly pull into the synchronization state by PLL control in the early stage of operation and the point where error synchronization is caused can be promptly achieved by using the F / V servo system together. It is possible to accurately and synchronously pull in the data.

In the third embodiment, it goes without saying that either of the hysteresis amplifiers shown in FIGS. 4 and 12 may be used. In the third embodiment, in the FV servo system, the F / V converter 35a,
The deviation of the voltage output from 35b is obtained by the adder 36, and the deviation becomes a signal proportional to the displacement X of the rotor 11, as described above. Therefore, utilizing the deviation from the adder 36, the hysteresis amplifier 13
A fourth embodiment in which a stable floating state of the rotor 11 can be obtained only by the FV servo system without using the PLL control system if PD control is performed on the a and 13b based on, for example, a deviation. Can be realized. This fourth
According to the embodiment, no sensor is required and the rotor 11
A stable floating state can be obtained.

[0053]

As described above, according to the first and second aspects of the present invention, the position of the rotor can be detected from the switching frequency of the hysteresis amplifier, so that a position sensor is not required. Since the control error can be detected at the phase level by the phase locked loop, there is an effect that the position of the rotor can be controlled with high accuracy with a simple configuration. According to the third aspect of the present invention, since the position of the rotor can be detected from the switching frequency of the hysteresis amplifier, not only the position sensor is not required, but also the control error can be reduced by the phase locked loop. Can be detected with
By using the frequency-voltage servo system together with the phase-locked loop control, the rotor position can be controlled with high accuracy with a simple configuration, and the phase locking loop synchronization pull-in delay and error synchronization are prevented. There are effects that can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of a magnetic bearing according to the present invention.

FIG. 2 is an explanatory diagram showing an electromagnet and a rotor in one embodiment.

3 is a waveform diagram showing a relationship between a current flowing through a coil of the electromagnet of FIG. 2 and an applied voltage.

FIG. 4 is a block diagram showing a configuration of a hysteresis amplifier in FIG.

FIG. 5 is a characteristic diagram showing characteristics of the hysteresis comparator in FIG.

6 is a waveform diagram showing a current flowing through a coil by the hysteresis amplifier shown in FIG.

FIG. 7 is a circuit diagram showing an equivalent circuit of an electromagnet coil in one embodiment.

8 is an explanatory diagram showing a voltage applied to the circuit shown in FIG. 7 and a flowing current.

9 is a waveform chart showing a step-like voltage applied to the circuit shown in FIG.

FIG. 10 is a characteristic diagram showing a change in current when the step-like voltage shown in FIG. 9 is applied to the circuit shown in FIG. 8;

FIG. 11 is an explanatory diagram showing an electromagnet and a rotor in one embodiment.

FIG. 12 is a block diagram showing another configuration of the hysteresis amplifier.

FIG. 13 is a block diagram showing a configuration of another embodiment of the magnetic bearing of the present invention.

FIG. 14 is a block diagram showing a third embodiment of the present invention.

FIG. 15 is a block diagram showing dynamic characteristics of the third embodiment.

FIG. 16 is a block diagram showing a configuration of a conventional magnetic bearing.

[Explanation of symbols]

11 Rotor 12a, 12b, 12c Electromagnet 13a, 13b, 13c, 113 Hysteresis amplifier 14 Phase comparator 15 Loop filter 20 Electromagnetic coil 21 Comparison amplifier 22, 122 Hysteresis comparator 23 Switching element 24 power supply 25 Current detection circuit 35a, 35b F / V converter 36 Adder 37 Stabilization control circuit 131 Reference signal output circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16C 32/04

Claims (3)

(57) [Claims] An electromagnet for causing a rotor to levitate by a magnetic force; a hysteresis amplifier for supplying an exciting current to the electromagnet; and a phase locked loop according to a phase of a switching signal in the hysteresis amplifier.
A magnetic bearing comprising: a position control means for controlling a position of a rotor by controlling an excitation current supplied from a teresis amplifier . 2. An electromagnet for levitating a rotor by magnetic force, a hysteresis amplifier for supplying an excitation current to the electromagnet by switching two levels of voltage by switching and applying the voltage to the electromagnet, and a phase of a switching signal in the hysteresis amplifier. Using a phase-lock loop in accordance with
A magnetic bearing comprising: a position control means for controlling a position of a rotor by controlling an excitation current supplied from a teresis amplifier . 3. An electromagnet for levitating a rotor by magnetic force, a hysteresis amplifier for switching between two levels of voltage by switching to supply an exciting current to the electromagnet, and a position of a switching signal in the hysteresis amplifier.
Excitation supplied from the hysteresis amplifier according to the phase
A phase locked loop for controlling the current and the hysteresis
Depending on the frequency of the switching signal in the lysis amplifier
Voltage and obtains a voltage based on the voltage.
A magnetic bearing, comprising: a frequency-voltage servo system for controlling an excitation current supplied thereto ; and a position control means for controlling the position of the rotor in combination with the frequency-voltage servo system.