JPH03154108A - Controller for magnetic bearing - Google Patents

Abstract

PURPOSE:To shortly suppress the overall length of a rotation axis by omitting a detection coil and to execute the rotation at a high speed by increasing the rotation axis natural frequency by combining an electromagnet coil with a position detection coil of the rotation axis. CONSTITUTION:An adder 28 adds a compensating signal outputted from a compensating circuit 27 and an output signal of a high frequency oscillator 29 provided in a position detector 24, a voltage is applied to a bearing stator coil 23 through an amplifier 30 and an electromagnet is excited. By an eddy current effect by a high frequency voltage superposed on a control voltage and applied to the coil 23, the impedance of the bearing stator coil 23 is determined in accordance with a distance of the coil 23 and a rotation axis 21. A variation of this impedance is detected by a position detector 24 and a position of the rotation axis 21 is detected. In such a way, a position detecting coil of the rotation axis can be omitted, and the overall length of the rotation axis can be suppressed shortly, therefore, by increasing a rotation axis natural frequency, the rotation can be executed at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for an actively controlled magnetic bearing.

Conventional technology In a magnetic bearing device that uses the magnetic attraction force of an electromagnet to support a rotating shaft in the air, it goes without saying that the position of the rotating shaft is detected and the electromagnetic attraction force is controlled to achieve a predetermined displacement. There is a need.

The conventional magnetic bearing device described above has a configuration as shown in FIG. A rotating shaft 1 is supported by an electromagnet consisting of a bearing stator core 2 and a bearing stator coil 3, and a position detector 4 detects the position of the rotating shaft 1. Based on this detection signal and the reference position of the rotating shaft l set in the shaft position reference device 5, a deviation signal representing the amount of deviation between the reference position and the actual position of the rotating shaft 1 is sent from the comparator 6 to the compensation circuit 7.
It is output to. This compensation circuit 7 applies a PI to the deviation signal.
D compensation and phase compensation are performed, power is amplified by an amplifier 8, and a voltage is applied to the bearing stator coil 3 to excite the electromagnet.

An eddy current displacement detector is often employed as the magnetic bearing position detector 4, and its operation is as follows. The output signal of the high frequency oscillator 9 is input to the detection coil 10 to generate an alternating current. Detection coil 10 through which alternating current flows
When the rotating shaft 1 approaches the rotating shaft 1, which is a conductor, an eddy current flows through the rotating shaft 1 to generate an alternating magnetic field, which acts on the detecting coil 10 and changes the impedance of the detecting coil 10.

This eddy current effect becomes smaller as the distance between the detection coil 10 and the rotating shaft 1 increases, so the impedance of the detection coil 10 is determined according to the distance between the two. This impedance change is extracted as a voltage signal by the tuned amplifier 11 and the AM detection circuit 12, and the DC amplifier 13
via the comparator 6 as a position detection signal of the rotating shaft 1.
Output to.

Problems to be Solved by the Invention However, in the above configuration, it is necessary to arrange the detection coil and the electromagnet in series in the thrust direction of the rotating shaft.
As the rotating shaft becomes longer, the natural frequency of the rotating shaft decreases, making it difficult to operate at high speeds (first issue).

In addition, for machine tool spindles that require high machining accuracy, the accuracy and resolution of the position detector has a large effect on the positioning accuracy of the rotary axis, and in order to perform high-precision positioning, it is necessary to have a rotation with high accuracy and high resolution that corresponds to the accuracy and resolution of the position detector. An axis position detector is required. As a position detector for magnetic bearings, a position detector with a wide measurement range that covers the movable range of the rotating shaft is required, but in general, position detectors with a wider measurement range have lower resolution, making it difficult to perform highly accurate positioning. Become (second challenge).

Therefore, the present invention provides a magnetic bearing control device for solving the above-mentioned problems.

Means for Solving the Problems The first invention solves the above problems by applying an output signal of a high-frequency oscillator to an electromagnetic coil in a superimposed manner with a control voltage, thereby causing an eddy current to flow through the rotating shaft and generating an alternating magnetic field. The present invention is characterized in that the position of the rotating shaft is detected by a detection circuit that converts impedance changes of the electromagnetic coil into voltage.

Moreover, the second invention converts the impedance change of the electromagnetic coil due to the alternating current magnetic field generated by eddy current flowing through the rotating shaft into voltage by superimposing the output signal of the high frequency oscillator with a control voltage and applying it to the electromagnetic coil. The detection circuit includes a first position detection means that detects the position of the rotary shaft over a wide measurement range, and a second position detection means that has high resolution in a narrow measurement range, and the rotary shaft position is detected by the second position detection means. If it is within the measurement range, feed back this output signal,
The present invention is characterized in that the first and second position detecting means are configured to be switched and used depending on the rotational axis position so that the output signal of the first position detecting means is fed back if it is out of the measurement range.

According to the first invention, since the electromagnetic coil also serves as a position detection coil for the rotating shaft, the conventional detection coil can be omitted, and the total length of the rotating shaft can be kept short, so that the natural frequency of the rotating shaft can be reduced. increases and enables high-speed rotation.

Further, according to the second invention, in the first position detecting means for detecting the position of the rotary shaft over a wide measurement range, the electromagnetic coil also serves as the position detecting coil of the rotary shaft. It is possible to provide a second position detection means with high resolution within a range, and it can be constructed without increasing the total length of the conventional rotating shaft. Furthermore, since the two position detecting means are switched and used, it is possible to detect the position of the rotary shaft with high resolution, and it is possible to position the rotary shaft with high precision.

Embodiment A magnetic bearing control device according to a first embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a rotating shaft 21 is supported by a rotating shaft attracting electromagnet consisting of a bearing stator core 22 and a bearing stator coil 23, and a position detector 24 detects the position of the rotating shaft 21. This detection signal and the shaft position reference device 2
5, the comparator 26 outputs a deviation signal representing the amount of deviation between the reference position and the actual position of the rotary shaft 1 to the compensation circuit 27. This compensation circuit 27 performs PIDI compensation and phase compensation on the deviation signal and outputs it to an adder 28 as a compensation signal.

The adder 28 adds the compensation signal and the output signal of the high frequency oscillator 29 provided in the position detector 24, and adds the output signal to the amplifier 3.
0 to the bearing stator coil 23 to excite the electromagnet.

Further, the operation of the position detector 24 is as follows. The bearing stator coil 23 is superimposed on the control voltage as described above.
The high frequency voltage applied to generates an alternating current. When the bearing stator coil 23, through which an alternating current component current also flows, approaches the rotating shaft 21, which is a conductor, an eddy current flows through the rotating shaft 21, generating an alternating magnetic field, which acts on the bearing stator coil 23, causing the bearing stator coil 23 to The impedance of the coil 23 changes. This eddy current effect becomes smaller as the distance between the bearing stator coil 23 and the rotating shaft 21 increases.
The impedance of the bearing stator coil 23 is determined according to the distance between the two. In order to detect this impedance change, the voltage applied to the bearing stator coil 23 is input to the band pass filter 31 to extract only the oscillation frequency component of the high frequency oscillator 29, and the impedance change of the bearing stator coil 23 is detected by the tuned amplifier 32 and the AM detector. It is determined as a voltage signal by the circuit 33 and outputted to the comparator 26 as a position detection signal of the rotating shaft 21 via the DC amplifier 34. At this time, the response frequency of the control system of the magnetic bearing is less than IKHz, and the high frequency oscillator 29
If the output signal frequency is sufficiently high relative to the response of the control system and the output signal amplitude of the high frequency oscillator 29 is small compared to the output signal of the compensation circuit 27, problems such as vibration of the rotating shaft 1 will not occur.

The magnetic bearing control device configured as described above can omit the conventional rotary shaft position detection coil, making it possible to shorten the total length of the rotary shaft.

Next, a magnetic bearing control device according to a second embodiment of the present invention will be described with reference to FIGS. 2 and 3.

In FIG. 2, a rotating shaft 41 is supported by a rotating shaft suction electromagnet consisting of a bearing stator core 42 and a bearing stator coil 43, and a position detector 4 with a wide measurement range
4, the position of the rotating shaft 41 is detected over its entire movable range. In addition, a high-resolution position detector 45 with a narrow measurement range
detects the position of the rotating shaft 41 with high precision only in the center of the movable range of the rotating shaft 41. Window comparator 46
The output V of the high-resolution position detector 45 is vN<v×v,
Outputs a signal to determine whether the value is within the range of . The changeover switch 47 makes either a-c or b-c conductive according to the output of the window comparator 46. Therefore, the position signal of the rotating shaft 41 detected by either the position detector 44 or the high-resolution position detector 45 becomes the output of the changeover switch 47. The comparator 49 outputs a deviation signal between the position detection signal of the rotating shaft 41 outputted from the changeover switch 47 and the reference position of the rotating shaft 41 set in the shaft position reference device 48 to the compensation circuit 50. This compensation circuit 50 subjects the deviation signal to PID compensation and phase compensation, and outputs it to an adder 51 as a compensation signal. The adder 51 adds the compensation signal and the output signal of the high frequency oscillator 52 provided in the position detector 44, and applies a voltage to the bearing stator coil 43 via the amplifier 53 to excite the electromagnet.

Regarding the control device for this magnetic bearing, first, the position detector 44
The operation will be explained. As described above, the high frequency voltage applied to the bearing stator coil 43 while being superimposed on the control voltage generates an alternating current. When the bearing stator coil 43, through which an alternating current component current also flows, approaches the rotating shaft 41, which is a conductor, an eddy current flows through the rotating shaft 41, generating an alternating magnetic field, which acts on the bearing stator coil 43, causing the bearing stator coil 43 to The impedance of the coil 43 changes. This eddy current effect becomes smaller as the distance between the bearing stator coil 43 and the rotating shaft increases, so the impedance of the bearing stator coil 43 is determined according to the distance between the two.

In order to detect this impedance change, the voltage applied to the bearing stator coil 43 is filtered through a band pass filter 54.
, only the oscillation frequency component of the high-frequency oscillator 52 is extracted, the impedance change of the bearing stator coil 43 is determined as a voltage signal by the tuned amplifier 55 and the AM detection circuit 56, and the position of the rotating shaft 41 is detected via the DC amplifier 57. It is output to the changeover switch 47 as a signal.

At this time, the response frequency of the control system of the magnetic bearing is less than IKHz, the output signal frequency of the high frequency oscillator 52 is sufficiently high with respect to the response of the control system, and the output amplitude of the high frequency oscillator 52 is compared to the output signal of the compensation circuit 50. If the rotation axis 41 is small, problems such as the rotation shaft 41 being photographed will not occur.

Next, switching between the position detector 44 and the high-resolution position detector 45 will be explained. FIG. 3 is a diagram showing the relationship between the output of the high-resolution detector 45 and the position of the rotating shaft 41. When the rotational axis position χ is outside the measurement range of the high-resolution position detector 45 (χ<χ, or χ, χ), the window comparator 46 sends an output to the changeover switch 47 so that conduction occurs between b and c. put out. Conversely, when the rotational axis position χ is within the measurement range of the high-resolution position detector 45 (χ, x x x N)
, the window comparator 46 is switched to the changeover switch 47.
Output is output so that conduction occurs between a and C. therefore,
By switching between the position detector 44 and the high-resolution position detector 45 depending on the rotary shaft position, the rotary shaft position can be detected with high precision (χ, χ, χ,).

Effects of the Invention In the first invention, since the electromagnetic coil also serves as a position detection coil for the rotating shaft, the conventional detection coil can be omitted.
Since the total length of the rotating shaft can be kept short, the natural frequency of the rotating shaft can be increased and high-speed rotation can be achieved.

Further, in the second aspect of the invention, in the first position detection means for detecting the position of the rotating shaft over a wide measurement range, the electromagnetic coil also serves as the position detecting coil for the rotating shaft. However, it is possible to provide a second position detection means with high resolution, and it can be configured without increasing the total length of the conventional rotating shaft. Furthermore, since the two position detection means are switched and used, it is possible to detect the position of the rotating shaft with high resolution, and it is possible to position the rotating shaft with high precision.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a magnetic bearing control device according to a first embodiment of the present invention, FIG. 2 is a block diagram of a magnetic bearing control device according to a second embodiment of the present invention, and FIG. 3 is a block diagram of a magnetic bearing control device according to a second embodiment of the present invention. FIG. 4, which is a diagram showing the relationship between the output of the resolution position detector and the position of the rotating shaft, is a block diagram of a conventional magnetic bearing control device. 21.41... Rotating axis, 23.43...
・Bearing stator coil, 24.44...Position detector, 31°54...Band pass filter, 32
．． 55... Tuned amplifier, 33.56...
・AM detection circuit, 34.57...DC amplifier,
45... High resolution position detector, 46...
・Window comparator, 47...changeover switch.

Claims (2)

[Claims] (1) A magnetic bearing that is equipped with a control circuit that detects the position of the rotating shaft and controls the current by applying a control voltage to the electromagnetic coil based on the feedback of this detection signal, and that holds the rotating shaft at a set position. By superimposing an output signal with the control voltage and applying it to the electromagnetic coil, the rotation is controlled by a detection circuit that converts the impedance change of the electromagnetic coil due to an alternating magnetic field generated by an eddy current flowing through the rotating shaft into a voltage. A control device for a magnetic bearing, characterized in that it is configured to detect the position of a shaft. (2) A magnetic bearing that is equipped with a control circuit that detects the position of the rotating shaft and controls the current by applying a control voltage to the electromagnetic coil based on the feedback of this detection signal, and that holds the rotating shaft at a set position. The rotating shaft is controlled by a detection circuit that converts the impedance change of the electromagnetic coil due to an alternating current magnetic field generated by an eddy current flowing through the rotating shaft into a voltage by superimposing an output signal with the control voltage and applying it to the electromagnetic coil. The first position detecting means detects the position in a wide measuring range, and the second position detecting means has high resolution in a narrow measuring range. For example, the first and second position detecting means are configured to be switched and used depending on the rotary shaft position so that this output signal is fed back, and if it is out of the measurement range, the output signal of the first position detecting means is fed back. A magnetic bearing control device featuring: