JPH05196040A - Magnetic levitation control device - Google Patents

Abstract

PURPOSE:To increase the stability of control by composing an electromagnet actuator which levitates a body, in a PWM method operating at a specific carrier frequency, and furthermore, providing a common oscillation circuit operating the carrier frequencies of the actuator and an object position sensor. CONSTITUTION:A tubular carrier board 10, which is a levitated object, is moved by magnetic levitation, into a tubular carrier tunnel 1 consisting of a nonmagentic substance, and while an electromagnet 4 for levitation is provided at the upper side of the carrier tunnel 1, a levitation displacement detecting sensor 8 is provided at the bottom. A carrier of a specific frequency produced by an oscillation circuit 24 is output from the sensor 8, and a sensor output signal whose wave height value is converted by the position of the carrier board 10 is output to a control circuit 21. A signal after applying a phase and gain compensation process in the control circuit 21 is input to the comparator of a PWM control circuit 22, it is compared with the frequency from the oscillation circuit 24, and the current carrying in an electromagnetic coil 5 through a PWM power 23 is controlled according to the comparison result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation control device provided with a position sensor for detecting the position of a levitated object and an electromagnet for levitating the levitated object.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional magnetic levitation control device. This shows a magnetic bearing type turbo-molecular pump and a control device. Radial displacement sensors 202 and 206 and a radial electromagnet 2 are provided outside the rotor 201 in the radial direction.
03 and 205 are provided. And the rotor 20
Thrust electromagnets 207, 2
07 and a thrust displacement sensor 208 are provided.

The outputs of the displacement sensors 202, 206 and 208 are input to the sensor circuit 220 via the line L201, sent to the PWM control circuit 222 via the control circuit 221, and then sent from the PWM control circuit 222 to the PWM power section 223. Appropriate control signals are emitted. The PWM power unit 223 supplies the electric power necessary for the rotor 201 to magnetically levitate to the electromagnets 203, 205 and 207.

In the device of FIG. 3, the sensor circuit 2 is conventionally used.
Oscillation circuits 224 and 225 were provided in the 20 (sensor unit) and the PWM control circuit 222 (driving unit), respectively.

[0005]

However, the drive unit 222
And the sensor unit 220 respectively include oscillation circuits 225 and 22.
As a result of providing No. 4, a beat is generated and control by disturbance is generated, even though the oscillation frequency is largely changed and a high frequency that does not affect even a component twice or three times those frequencies is selected. There is the problem of instability. In addition, there is a problem that the controlled object is affected by the high frequency. Further, it is difficult to adjust the oscillation frequency with the drive unit and the sensor unit.

It is an object of the present invention to easily provide a magnetic levitation control device that suppresses the occurrence of beats and obtains control stability.

[0007]

According to the present invention, in a magnetic levitation control device provided with a position sensor for detecting the position of a levitated object and an electromagnet for levitating the levitated object,
A PW for operating the drive part of the electromagnet at a certain carrier frequency
A common oscillation circuit that operates in the M system and operates the carrier frequency of the drive unit and the position sensor is provided.

[0008]

In the magnetic levitation control device constructed as described above, since the oscillation circuit of the drive section and the sensor section is made common, the occurrence of beat is eliminated, and therefore the control stability is obtained.

[0009]

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

FIG. 1 shows a first embodiment of the present invention.
The cylindrical transfer tunnel 1 is formed of a non-magnetic material, and a cylindrical transfer table 10 that is an object to be floated is moved inside by magnetic levitation. This transport tunnel 1
The levitation electromagnet 4 is provided on the upper part of the above, and the levitation displacement detection sensor 8 is provided on the bottom part.

Both ends of the yoke 6 around which the electromagnetic coil 5 of the electromagnet 4 is wound are inserted into the through holes 2 formed in the transport tunnel 1, and the end faces are flush with the inner face of the tunnel. The yoke 6 and the through hole 2 are closely attached by the brazing portion 7.

The displacement detection sensor 8 is the transport tunnel 1.
It is inserted into the through hole 3 formed in the hole, the end face thereof is formed flush with the inner surface of the tunnel, and the sensor 8 and the through hole 3 are in close contact with each other by the brazing portion 7.

The displacement detection sensor 8 is connected to a control circuit 21 via a sensor circuit 20 by an electric circuit L1.
The electromagnetic coil 5 is connected to the control circuit 21 via the PWM control circuit 22, the PWM power unit 23, and the electric circuit L2. An oscillation circuit 24 is connected to the sensor circuit 20 and the PWM control circuit 22.

During control, the sensor 8 outputs a carrier of a certain frequency created by the oscillation circuit 24, and its crest value changes depending on the position of the carrier 10. This signal is passed through the PWM control circuit 2 through the control circuit 21 including phase and gain compensation.
Enter in 2. Then, the signal from the control circuit 21 and the frequency from the oscillation circuit 24 are input to the comparator of the PWM control circuit 22 to operate the PWM power unit 23. As a result, a current is passed through the electromagnetic coil 5 to determine the floating position of the carrier 10.

FIG. 2 shows a second embodiment of the present invention.
FIG. 2 shows a turbo molecular pump and its control mechanism to which the present invention is applied, and the turbo molecular pump includes a rotor 101, which is a rotating body, and an impeller. In the upper part of the pump housing, the radial displacement sensor 102 and the radial electromagnet 103 are arranged in this order from the upper side of FIG. 2, the motor 104 is arranged in the middle part of the pump housing, and the radial electromagnet 105 is arranged in the lower part. A radial displacement sensor 106 is provided, and thrust electromagnets 107, 107 and a thrust displacement sensor 108 are provided further below. The sensors 102 and 106 and the electromagnet 10
3, 105, 107 are also arranged to face the rotor 101 on the opposite side (not shown).

The sensors 102, 106, 108 are connected to the control circuit 1 via the sensor circuit 120 by the line L101.
21, a PWM control circuit 122 and a PWM power unit 123 are connected to the control circuit 121. Then, electric power is supplied from the PWM power unit 123 to the electromagnets 103, 105, 107, 107 via the line L102. Further, the sensor circuit 120 and the PWM control circuit 122 are connected to the same oscillation circuit 124. Here, lines and circuits are provided for 5 axes (control).

During control, the sensor outputs a carrier of a certain frequency created by the oscillation circuit 124, and its peak value changes depending on the position of the rotor 101. This signal is passed through the control circuit 121 including phase and gain compensation, and the PWM control circuit 1
Enter in 22. Then, the signal from the control circuit 121 and the frequency from the oscillation circuit 124 are fed to the PWM control circuit 122.
And the PWM power unit 123 is operated. As a result, the electromagnets 103, 105, 107,
A current is passed through 107 to determine the position of the rotor 101.

[0018]

Since the present invention is constructed as described above, it has the following effects.

By making the oscillation circuit common, it is possible to eliminate the occurrence of beats.

Therefore, stability of control can be obtained.

Further, the influence of the conventional high frequency on the controlled object can be reduced.

Further, the conventional circuit can be simplified.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional technique.

[Explanation of symbols]

1 ... Transport tunnel 2, 3 ... Through hole 4 ... Levitation electromagnet 5 ... Electromagnetic coil 6 ... Yoke part 7 ... Brazing part 8 ... Levitation position detection sensor 10 ... Carrier 20, 20, 220 ... Sensor circuit 21, 121, 221 ... Control circuit 22, 122, 222 ... PWM control circuit 23, 123, 223 ... PWM power section 24, 124 224, 225 ... Oscillation circuit 101, 201 ... Rotor 102, 106, 202, 206 ... Radial displacement sensor 103, 105, 203, 205 ... Radial electromagnet 107, 207 ... Thrust electromagnet 108 , 208 ... Thrust displacement sensor

Claims (1)

[Claims] 1. A magnetic levitation control device comprising a position sensor for detecting the position of an object to be levitated and an electromagnet for levitating the object to be levitated, wherein a drive unit of the electromagnet is operated by a PWM system at a certain carrier frequency. A magnetic levitation control device comprising a common oscillation circuit configured to operate the carrier frequency of the drive unit and the position sensor.