JP2002349566A - Magnetic bearing control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing control device capable of realizing a stable magnetic support control without depending on the revolution number of a rotating body and a temperature. SOLUTION: DSP part 19 of the magnetic bearing control device 1 reads out corresponding parameter ω from a memory part 25 corresponding to a variation of the revolution number of the rotor 103 and a variation of temperature. The parameter ω is for calculating a coefficient of a transfer function previously set so as to inhibit a resonance based on a result obtained by measuring a natural frequency of the rotating body 103. The transfer function is settled by a coefficient decided by this parameter ω and the DSP part 19 carries out a compensation adapted for the new revolution number and a temperature.

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, and more particularly to a magnetic bearing control device capable of performing stable magnetic support control without depending on the rotation speed and temperature of a rotating body.

[0002]

2. Description of the Related Art A turbo molecular pump 101 is, for example, shown in FIG.
As shown in a sectional view of FIG. 1, a plurality of rotor blades 102a, 102b, 10
.. Are provided in multiple stages.

The upper radial electromagnet 104 has four electromagnets arranged in pairs on the X axis and the Y axis. An upper radial sensor 107 composed of four electromagnets is provided in proximity to and corresponding to the upper radial electromagnet 104. The upper radial sensor 107 is configured to detect a radial displacement of the rotating body 103 and send it to a magnetic bearing control device (not shown).

In the magnetic bearing control device, based on the displacement signal detected by the upper radial sensor 107, the upper radial electromagnet 104 is passed through a compensation circuit having a PID adjustment function.
, And adjusts the upper radial position of the rotating body 103. Such adjustment is performed independently in the X-axis direction and the Y-axis direction.

A lower radial electromagnet 105 and a lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and
3, the lower radial position is adjusted.

Further, the axial electromagnet 106 is used to
03 are arranged with the metal disk 111 provided therebetween. An axial sensor 109 is provided to detect an axial displacement of the rotating body 103, and an axial displacement signal is sent to a magnetic bearing control device. And
The excitation of the axial electromagnet 106 is controlled by a magnetic bearing control device based on the axial displacement signal, and the rotating body 103 is magnetically levitated in the axial direction.

In the turbo-molecular pump 101, there is a natural frequency based on each of the rotor blades 102a, 102b, 102c,... Of the rotor 103, which is included in unbalanced vibration and displacement signals generated when the rotor rotates. Unstable vibration at the natural vibration frequency is excited by disturbance such as noise.

The natural frequency of the rotating body 103, as shown by the solid lines L1 and L2 in FIG.
Change in direction.

In order to attenuate the unstable vibration, a compensator for controlling the magnetic bearing is conventionally provided in a feedback loop of the magnetic bearing control device. With this compensator,
Compensation is performed by providing a phase lead characteristic or reducing the gain near the natural frequency by a notch filter or the like.

In order to cope with a change in the natural frequency accompanying a change in the rotational speed, in the case of a compensator based on the phase lead characteristic, the phase is advanced over a wide frequency range as shown in FIG. 8 or as shown in FIG. Local phase adjustment. In FIG. 7, the coefficient of the transfer function is represented by a parameter ω, and the parameter ω is changed according to the rotation speed detected by a rotation sensor or the like, so that the local phase characteristic is changed according to the rotation speed.

When a notch filter is used, the center frequency or the like of the notch filter is changed according to the number of rotations detected by a rotation sensor or the like. By performing such compensation, unstable vibration is prevented from occurring when the natural frequency fluctuates due to the rotation speed of the rotating body 103.

[0012]

However, the natural frequency is affected not only by a change in the rotational speed but also by a temperature change due to a change in the gas load or the like.

For example, in semiconductor manufacturing equipment and the like,
Many have processes in which a large amount of gas is continuously exhausted by a turbo-molecular pump. In this case, the temperature of the rotor of the turbo molecular pump may rise to a limit point (around 150 ° C. for an aluminum alloy) at which the material strength sharply decreases.

When the temperature of the rotor increases, the rigidity of the material (usually an aluminum alloy) decreases, so that the natural frequency decreases as shown by the dashed lines H1 and H2 in FIG.

When the temperature changes as described above,
The compensator in which the phase is advanced locally as shown in FIG. 7 is excellent in that the gain in the high frequency region does not increase so much. However, unless the phase advance region always follows the change in the natural frequency of the rotor blade in accordance with the rise in the rotor blade temperature, unstable vibration may occur outside the phase lead range.

The compensator in which the phase is advanced in a wide frequency range as shown in FIG. 8 has an increased gain in a high frequency region and is unstable at another natural frequency existing in a high frequency region. . Therefore, the magnetic bearing control device of the turbo-molecular pump may not be able to sufficiently attenuate the unstable vibration due to the temperature change by the conventional phase lead compensation or the compensation by the notch filter.

The present invention has been made in view of such a conventional problem, and does not depend on the rotational speed or temperature of the rotating body.
An object of the present invention is to provide a magnetic bearing control device capable of performing stable magnetic support control.

[0018]

SUMMARY OF THE INVENTION Therefore, the present invention (claim 1) provides a magnetic bearing control that adjusts a floating position of a rotating body in a radial or axial direction and compensates for suppressing resonance of the rotating body. Compensating means, rotating speed detecting means for detecting the rotating speed of the rotating body, temperature detecting means for detecting the temperature of the rotating body, and the magnetic bearing control which is obtained in advance so as to suppress resonance of the rotating body. The data corresponding to the rotation speed detected by the rotation speed detecting means and the temperature detected by the temperature detecting means are extracted from a parameter, an arithmetic expression, a characteristic diagram, or the like for determining a coefficient of a transfer function of the compensating means. Adjusting means for setting the coefficient of the function.

The relationship between the natural frequency of the rotating body, the rotational speed, and the temperature is measured in advance, and based on the measured results, data such as parameters, arithmetic expressions, and characteristic diagrams for determining coefficients of a transfer function capable of compensating for resonance. Get and save. The coefficient of the transfer function is obtained from the stored data according to the detected rotation speed and temperature, and the control characteristics of the magnetic bearing control compensation means are adjusted, so that unstable vibration due to the natural frequency is always attenuated. It becomes possible.

Further, according to the present invention (claim 2), the adjusting means includes a table representing a coefficient of the transfer function determined by a rotating speed and a temperature of the rotating body, and the rotating speed detecting means detects the table from the table. And coefficient setting means for taking out data corresponding to the detected rotation speed and the temperature detected by the temperature detection means and setting the data as a coefficient of the transfer function.

According to the magnetic bearing control device of the present invention, complicated control characteristics can be reliably set by using a simple transfer function coefficient table.

Further, according to the present invention (claim 3), the magnetic bearing control compensating means compensates for a radial or axial position signal of the rotating body, and the first compensating means. And a second compensating means for compensating the output of the rotating body so as to suppress the resonance of the rotating body, wherein the adjusting means sets a coefficient of a transfer function of the second compensating means. .

The magnetic bearing control device of the present invention can easily set a transfer function having a characteristic according to the purpose for each compensating means. Therefore, the design becomes easy.

[0024]

Embodiments of the present invention will be described below. FIG. 1 shows a functional configuration diagram of a magnetic bearing control device for a turbo molecular pump according to an embodiment of the present invention. The same elements as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The turbo molecular pump is provided with a rotation sensor 7 for detecting the rotation speed of the rotating body 103. A rotation speed detection circuit 13 is provided so that a rotation speed signal of the rotating body 103 detected by the rotation sensor 7 is sent to the A / D converter 23.

Similarly, a temperature sensor 9 for detecting a temperature signal of the rotating body 103 and a temperature detection circuit 15 for transmitting a temperature signal detected from the temperature sensor 9 to the A / D converter 23 are provided. ing. The temperature sensor 9 is configured by a non-contact infrared sensor or the like.

The displacement detection circuit 11 is configured so that a displacement signal detected by the upper radial direction sensor 107 is sent to the A / D converter 23. A DSP (Digital Signal Processor) unit 19 performs magnetic bearing control compensation based on the displacement, rotation speed, and temperature signals received via the A / D converter 23, and sends PWM signals to the amplification units 17, 17. Is configured.

The magnetic bearing control compensation compensates for the radial or axial support position of the rotating body 103 and sets the coefficient of the transfer function according to the number of rotations and the temperature in order to suppress the resonance of the rotating body 103. Is configured. In the memory unit 25, coefficient parameters for calculating the coefficients of the transfer function are stored in advance so as to be readable under the condition of the rotation speed and the temperature.

Next, the memory section 25 will be described in detail. FIG. 2 shows an example of the data configuration in the memory. In FIG. 2, the data in the memory unit 25 is a parameter ω for determining the coefficient of the transfer function of the DSP unit 19 according to the rotation speed and the temperature of the rotating body 103. The parameter ω can be obtained by measuring the natural frequency of the rotating body 103 under a condition in which the rotating speed and the temperature are combined.

That is, how the natural frequency of the rotating body 103 changes according to the combination condition of the rotation speed and the temperature is measured in advance. From this measurement result, the transfer function of the compensator is set in advance so that unstable vibration is sufficiently attenuated under each condition.

The data of the parameter ω as a variable for determining the coefficient of the transfer function is calculated. In this example, the data of the parameter ω is stored as a list in an array format, with the horizontal axis representing temperature and the vertical axis representing rotation speed. By storing this list in a memory or the like, the parameter ω corresponding to the rotation speed and the temperature is determined according to the rotation speed and the temperature.

The magnetic bearing control device of the present invention has the same configuration as all the five-axis configurations of the magnetic bearing shown in FIG. That is, the upper radial electromagnet 104 and the lower radial electromagnet 10
A magnetic bearing controller is configured for each of the axial electromagnets 106 of the magnetic bearing 5 and the axial magnetic bearing.

Next, the operation of the magnetic bearing control device for a turbo-molecular pump according to the present invention will be described. When the turbo molecular pump is started, displacement data of the rotating body 103 in the upper radial direction is detected by the upper radial sensor 107. Similarly, displacement data in the lower radial direction is detected by the lower radial sensor 108, and displacement data in the axial direction is detected by the axial sensor 109, respectively.

Each displacement data is supplied to a displacement detection circuit 11, A /
It is sent to the DSP unit 19 via the D converter 23. DSP
The unit 19 performs PID control to correct the displacement, and sends a PWM signal to the amplifier 17.

At this time, the DSP unit 19 includes the rotating body 103
The parameter ω corresponding to the new condition is read from the memory unit 25 in accordance with the change in the rotation speed and the change in the temperature. This parameter ω is for calculating a coefficient of a transfer function that is set in advance so as to suppress resonance based on the result of measuring the natural frequency of the rotating body 103.

The coefficient of the transfer function is updated by this parameter ω, the transfer function is determined, and resonance is compensated. Therefore, under any conditions, the gain and phase of the compensator are changed according to the rotation speed and the temperature, and optimal resonance compensation is performed. Therefore, it is possible to always attenuate unstable vibration due to the natural frequency. Become.

Next, the detailed configuration of the DSP unit 19 will be described. FIG. 3 shows a functional configuration diagram of the first configuration example of the control processing unit, and FIG. 4 shows a functional configuration diagram of the second configuration example. In FIG. 3, a PID compensator 31 receives a displacement signal and performs compensation control of a radial or axial support position of the rotating body 103 by PID control. The resonance compensator 33 has a response characteristic for resonance compensation, and is configured to receive an output signal of the PID compensator 31 to perform compensation for avoiding resonance and output a signal.

The coefficient setting section 35 is configured to take out corresponding data from the memory section 25 based on the detected rotation speed and temperature, and to set the coefficient of the transfer function of the resonance compensator 33 using this data as a parameter. ing. A PWM conversion unit 37 for converting a control signal of the resonance compensator 33 into a PWM signal is provided, and the PWM signal is output from the DSP unit 19 to the amplification unit 17.

Next, the operation will be described. The parameter ω is read from the memory unit 25 in accordance with the conditions of the rotation speed and the temperature. The coefficient of the transfer function of the resonance compensator 33 is set by the parameter ω. The output signal of the PID compensator 31 is compensated by the resonance compensator 33 so as to suppress resonance. This compensated signal is output to the PWM converter 3
7, the signal is converted into a PWM signal and sent to the amplifying unit 17,
Excitation control is performed so that resonance of the rotating body 103 is suppressed.

In the DSP section 19, since the PID compensator 31 and the resonance compensator 33 are configured for respective functions, the respective transfer functions can be easily designed according to the desired functions. Note that the PID compensator 31 and the resonance compensator 33 may be integrally formed.

FIG. 4 shows an example in which a D / A converter 39 for receiving an output signal from the resonance compensator 33 of the DSP unit 19 is provided. The coefficient setting unit 35 controls the resonance compensator 33 via parameters corresponding to the conditions of the rotational speed and the temperature in the same manner as described above.
Set the transfer function coefficient of. An output signal of the resonance compensator 33 based on this transfer function is converted into an analog current command signal via a D / A converter 39, and converted into an upper radial electromagnet 104,
The excitation of the lower radial electromagnet 105 or the axial electromagnet 106 can be controlled.

The data stored in the memory unit 25 is not limited to the coefficient parameter for calculating the coefficient of the transfer function.
The coefficient itself of the transfer function may be used. Further, the stored data is not limited to the above-described array format, and the transfer function coefficient may be calculated by a relational expression based on the rotation speed and the temperature, a characteristic diagram, or the like. When the coefficients are calculated by the relational expression, the configuration can be simplified because a large number of data in a table is not required.

[0043]

As described above, according to the present invention, the magnetic bearing control device is provided with the adjusting means for setting the coefficient of the transfer function of the magnetic bearing control compensating means according to the conditions of the rotational speed and the temperature. Even when the rotation speed and the temperature fluctuate in a wide range, it is possible to always attenuate the unstable vibration due to the natural frequency.

[Brief description of the drawings]

FIG. 1 is a functional configuration diagram of a magnetic bearing control device of a turbo molecular pump according to an embodiment of the present invention.

FIG. 2 is an example of a data configuration in a memory of FIG. 1;

FIG. 3 is a functional configuration diagram of a first configuration example of a DSP unit according to the present invention.

FIG. 4 is a functional configuration diagram of a second configuration example of the DSP unit according to the present invention.

FIG. 5 is a sectional view of a turbo-molecular pump.

FIG. 6 is a characteristic diagram of a natural frequency of a rotating body of a turbo-molecular pump according to a rotation speed and a temperature.

FIG. 7 is a characteristic diagram of a transfer function in which a phase is locally advanced.

FIG. 8 is a characteristic diagram of a transfer function in which a phase is advanced in a wide frequency range.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 magnetic bearing control device 7 rotation sensor (rotation speed detecting means) 9 temperature sensor (temperature detecting means) 19 DSP section (magnetic bearing control compensating means) 25 memory section (adjusting means) 31 PID compensator (first compensating section) 33 Resonance Compensator (Second Compensation Unit) 35 Coefficient Setting Unit (Adjustment Means) 103 Rotating Body 104 Upper Radial Electromagnet (Magnetic Bearing) 105 Lower Radial Electromagnet (Magnetic Bearing) 106 Axial Electromagnet (Magnetic Bearing) 107 Upper radial sensor (displacement detector) 108 Lower radial sensor (displacement detector) 109 Axial sensor (displacement detector) ω parameter

Claims (3)

[Claims] 1. A magnetic bearing control compensating means for adjusting a floating position of a rotating body in a radial direction or an axial direction and for suppressing resonance of the rotating body, and a rotating speed for detecting a rotating speed of the rotating body. A detecting means, a temperature detecting means for detecting a temperature of the rotating body, and a parameter and an arithmetic expression for determining a coefficient of a transfer function of the magnetic bearing control compensating means which are obtained in advance so as to suppress resonance of the rotating body. Or adjusting means for extracting data corresponding to the rotation speed detected by the rotation speed detection means and the temperature detected by the temperature detection means from a characteristic diagram or the like and setting the data as a coefficient of the transfer function. Magnetic bearing control device. 2. The method according to claim 1, wherein the adjusting unit includes a table representing a coefficient of the transfer function determined by a rotation speed and a temperature of the rotator; and a rotation speed and the temperature detection unit detected by the rotation speed detection unit from the table. 2. The magnetic bearing control device according to claim 1, further comprising coefficient setting means for extracting data corresponding to the detected temperature and setting the data as a coefficient of the transfer function. 3. The magnetic bearing control compensating means includes first compensating means for compensating for a radial or axial position signal of the rotating body, and resonance of the rotating body with respect to an output of the first compensating means. 3. The apparatus according to claim 1, wherein said adjusting means sets a coefficient of a transfer function of said second compensating means, wherein said adjusting means sets a coefficient of a transfer function of said second compensating means. Magnetic bearing control device.