JPH0676808B2 - Magnetic bearing 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 bearing device for turbomachines and machine tools, and more particularly to a rotor yoke made of a magnetic material attached to a rotary shaft and an electromagnet stator having a coil wound on a casing. , The gap between the rotor yoke and the electromagnet stator is made minute, and a displacement sensor for measuring the relative displacement between the rotary shaft and the casing is provided, and a current is applied to the coil based on the output signal from the displacement sensor. The present invention relates to a magnetic bearing device that applies a magnetic attraction force between a rotor and an electromagnet stator to support a rotating shaft at the center of the stator.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional magnetic bearing device. In FIG. 4, reference numeral 1 is a casing, and the casing 1 has an electromagnet stator 2 provided with an exciting coil 3.
Is fixed. On the other hand, the rotor shaft 5 has a rotor yoke 5
Is stuck. A displacement sensor 6 is disposed adjacent to the rotary shaft 4, and the coil 3 is generated by the compensation circuit 7 and the power amplifier 8 based on the output signal from the displacement sensor 6.
A current is applied to the rotor yoke 5 and a magnetic attraction force is applied between the rotor yoke 5 and the electromagnet stator 2. Next, the operation of the magnetic bearing device having this configuration will be described. The displacement sensor 6 detects the displacement of the rotary shaft 4, and the compensation circuit 7 generates a compensation signal based on the deviation between the target position value of the rotary shaft 4 and the displacement signal detected by the displacement sensor 6. The power amplifier 8 is driven by the generated signal, a current is caused to flow through the coil 3 of the electromagnet stator 2 fixed to the casing 1, and a magnetic attraction force is applied between the rotor yoke 5 and the electromagnet stator 2 to rotate it. Support the shaft 4 near the center of the stator.

[0003]

However, in the above-described conventional magnetic bearing device, there is a problem that the rotor vibrates and oscillates at their natural frequencies due to some bending eigenmodes of the rotating shaft. there were. In other words, since the natural frequency of the rotating shaft has a relatively high frequency, sufficient compensation for phase lead cannot be performed by the compensating circuit, and unnecessary gain is controlled unnecessarily to cause vibration and oscillation. There was a problem. As a countermeasure for this, conventionally, a filter that advances the phase at the local frequency or a notch filter that lowers the gain at the local frequency is used. However, these filters must measure the natural frequency of the rotating shaft and make the filters accordingly. What is more difficult is that the natural frequency of the rotating shaft changes with rotation and also changes with the temperature of the rotating shaft. Furthermore, it also changes depending on the rigidity of the bearing that supports the rotating shaft. Since the above filters are tuned to the local frequency, if the natural frequency changes due to the above phenomenon, etc., the natural frequency will go out of the range of these filters, causing problems such as vibration and oscillation. There are many things that can happen. The present invention has been made in view of the above problems, and an object of the present invention is to eliminate the above problems and automatically correct the circuit even if the natural frequency of the rotating shaft is changed to obtain a natural vibration. It is an object of the present invention to provide a magnetic bearing device capable of solving the problems of vibration and oscillation by preventing unnecessary control by the number.

[0004]

According to the present invention, there is provided a rotor yoke mounted on a rotary shaft, an electromagnet stator mounted on a casing at a minute distance from the rotor yoke, the rotary shaft and the casing. A displacement sensor for measuring a relative displacement between them, and a magnetic bearing having a power amplifier and a compensation circuit for controlling a magnetic attraction force acting between the rotor yoke and the electromagnet stator based on an output signal from the displacement sensor. In the device, a transfer function setting unit that determines a transfer function of a predetermined rotary shaft system, and an adaptive digital filter that simulates the transfer function setting and generates a pseudo signal by the output signal of the compensation circuit or the power amplifier, It is provided on the input side or output side of this adaptive digital filter and only passes pseudo signals with a frequency higher than the control frequency (for example, rotation frequency). And the high-pass circuit, based on a signal obtained by subtracting the pseudo signal from the displacement signal, a magnetic bearing device having a compensating circuit for controlling the magnetic attraction force between the electromagnet stator and the rotor yoke.

[0005]

In the present invention, the transfer function of the rotary shaft system is obtained by calculation or other means, or by the signal from the pulse generator and the displacement sensor or the output of the compensation circuit or the power amplifier and the sensor signal, and this transfer function is obtained. Is simulated by an adaptive digital filter, and a pseudo signal is generated by adding the output signal of the compensation circuit or power amplifier to this, and the displacement signal detected by the displacement sensor is passed through only the frequency higher than the control frequency (for example, rotation frequency). The current of the coil 3 is controlled by the compensating circuit and the power amplifier based on the signal obtained by subtracting this pseudo signal. Also, the identification error detection circuit may be provided, and the adaptive digital filter may be sequentially modified so that the error between the displacement signal and the pseudo signal is reduced by feeding back to the adaptive digital filter. Further, it is possible to generate a pulse at any time when the modification of the adaptive digital filter is insufficient.

Since the present invention is constructed as described above, even if the natural frequency of the rotary shaft changes, the adaptive digital filter follows the circuit characteristics sequentially or at any time to change the circuit characteristics, which causes a problem. By removing the frequency component of the bending eigenmode by subtraction, the rotating shaft can be stably controlled without vibrating or oscillating at the natural frequency of the rotating shaft in any rotating state.

[0007]

Embodiments of the control system of the magnetic bearing device according to the present invention will be described below with reference to the accompanying drawings. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 is a casing, to which an electromagnet stator 2 having an exciting coil 3 is fixed. On the other hand, a rotor yoke 5 is fixed to the rotary shaft 4. A displacement sensor 6 is disposed adjacent to the rotary shaft 4, and the displacement sensor 6 measures the displacement of the rotary shaft 4. The magnetic bearing device includes a system identification circuit 10, and the system identification circuit 10 includes a transfer function setting unit 11 and a canceller 14. The detection signal from the displacement sensor 6 is input to the transfer function measuring unit 12 of the transfer function setting unit and the adder 21. Also,
The transfer function setting unit 11 includes a pulse generator 13, and the pulse from the pulse generator 13 is input to the adder 23 and the power amplifier 8.

On the other hand, the canceller 14 includes an adaptive digital filter 15 and a high-pass circuit 16, and the transfer function measured by the transfer function measuring device 12 is input to the adaptive digital filter 15 and the adaptive digital filter 15 is supplied.
Simulates this transfer function. An output signal of the compensating circuit 7 or a power amplifier 8 (not shown) is input to the adaptive digital filter 15, and a pseudo signal according to the transfer function peculiar to the rotating shaft is generated. The low-frequency component of this pseudo signal is cut by the high-pass circuit 16, and only the high-frequency component is subtracted and input to the adder 21. Here, the high-pass circuit passes only the control frequency, for example, the frequency component that is higher than the rotation frequency of the rotation shaft. Therefore, in the adder 21, the output signal of the compensating circuit 7 or the power amplifier 8 is applied to the displacement signal of the displacement sensor by the adaptive digital filter 15, and the signal is simulated by the number of transmissions peculiar to the rotation axis and passed through the high pass circuit The components above the frequency are subtracted and applied. The output signal of the adder 21 is input to the identification error detection circuit 17, and the output signal of the identification error detection circuit 17 is input to the adaptive digital filter 15, which causes the adaptive digital filter 15 to generate a pseudo signal from the displacement signal. The subtracted signal is judged by the identification error detection circuit 17 and is sequentially corrected so that the error becomes smaller.

Next, the operation of the magnetic bearing device configured as described above will be described. The pulse generated by the pulse generator 13 in the transfer function setting unit 11 is input to the third adder 23, and passes through the power amplifier 8 to the coil 3 wound around the electromagnet stator 2 fixed to the casing 1. A current is caused to flow to give a disturbance due to an electromagnetic force from the electromagnet stator 2 to the rotating shaft 4, and the displacement sensor 6 measures the displacement of the rotating shaft 4 at that time. The pulse generated by the pulse generator 13 is a system identification pulse, white noise, or a chirp signal, and is used for measuring the transfer function of the rotating shaft system. The output of the displacement sensor 6 is input to the transfer function measuring device 12, the transfer function of the rotating shaft system is measured by the transfer function measuring device 12, and the measured transfer function is input to the adaptive digital filter 15. The adaptive digital filter 15 generates a pseudo signal based on the transfer function of the rotary shaft system from the transfer function measuring device 12. And
A high-pass circuit 16 cuts off a low-frequency part of the control signal, for example, a rotation frequency or less, and a pseudo signal having only a high-frequency component is subtracted and input to the adder 21. In the adder 21, the pseudo signal which is the output signal of the canceller 14 is subtracted from the displacement signal which is the output signal of the displacement sensor 6, and the subtracted signal is input to the error signal detection circuit 17, whereby the displacement signal and the pseudo signal are generated. The adaptive digital filter 15 is sequentially modified so that the error between and becomes smaller. Further, the error signal subtracted by the adder 21 is input to the adder 22, where it is subtracted from the position target value of the rotary shaft 4, and the subtracted signal is input to the compensation circuit 7 and from this compensation circuit 7. The power amplifier 8 operates in response to the output of ## EQU1 ## to cause a current to flow through the coil 3, and the position of the rotating shaft 4 is controlled by the electromagnetic attractive force generated between the electromagnet stator 2 and the rotor yoke 5.

In this way, the signal after the displacement signal is subtracted by the pseudo signal mainly has a component below the control frequency necessary for controlling the rotating shaft, and the magnetic bearing is controlled based on this signal. As a result, the bending eigenmode component of the rotating shaft of the high frequency component, which has been a problem in the past, is eliminated, and unnecessary control is not performed, resulting in elimination of the problem of vibration and oscillation of the rotating shaft. The controlled control can be performed. In FIG. 1, S-1 in the figure shows the spectrum of the displacement signal detected by the displacement sensor 6, and S-2 shows the spectrum of the pseudo signal. The peak in the high frequency region of S-1 indicates the pole due to the bending eigenmode of the rotating shaft. S-2
Shows that the pole of the bending eigenmode of the rotation axis higher than the control frequency is formed by the simulation of the adaptive digital filter 15, and the low-frequency component is removed by the high-pass filter 16. S-3 is the spectrum after the pseudo signal is subtracted from the displacement signal, and at the frequency lower than the control frequency, it remains the displacement signal originally necessary for controlling the rotating shaft,
Above the control frequency, the bending eigenmode peak, which has been a problem in the past, disappears or, conversely, the spectrum becomes hollow.

Next, a second embodiment of the present invention will be described with reference to FIG. 2, constituent elements having the same functions and functions as those of the constituent elements of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In the present embodiment, the transfer function measuring device 12
Also, a transfer function setting device 31 is provided instead of the pulse generator 13 (FIG. 1), and the transfer function setting device 31 generates a predetermined transfer function of the rotary shaft system obtained by calculation or another means. To do. The transfer function of the bending eigenmode of the rotating shaft can be calculated by a separate computer simulation or the like. Also, in a bearing device of the same type, if the transfer function is experimentally measured for one rotating shaft,
This is because the transfer functions of similar ones can be inferred experimentally. According to this transfer function setting device, an expensive pulse generator and transfer function measuring device are unnecessary, which is economical.

Next, a third embodiment of the present invention will be described with reference to FIG. 3, constituent elements having the same functions and functions as those of the constituent elements of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. This embodiment differs from the second embodiment shown in FIG. 2 in that the identification error detection circuit 17 is omitted. The identification error detection circuit 17 evaluates an error obtained by subtracting the pseudo signal generated by the canceller circuit 14 from the displacement signal of the displacement sensor 6, and modifies the parameters of the adaptive digital filter so as to reduce the error. is there. Since the bending eigenmode of the rotating shaft changes depending on the number of rotations, temperature, rigidity, etc., it is necessary for the adaptive digital filter to strictly reduce the error by changing the parameter corresponding to these fluctuations. However, in practice, it may not be necessary to change the parameters, and at this time, the identification error detection circuit 17 becomes unnecessary.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 5, constituent elements having the same operations and functions as those of the constituent elements of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The present embodiment is different from the first embodiment shown in FIG. 1 in that the pulse generator is omitted and the output of the compensation circuit or the power amplifier is input to the transfer function measuring device 12. The transfer function measuring device 12 estimates the transfer function of the rotating shaft system from the output of the compensation circuit 7 or the power amplifier 8 and the displacement signal of the displacement sensor 6, and the adaptive digital filter 1
The parameter of No. 5 is modified. Secondly, the transfer function of the rotating shaft system is composed of a plurality of transfer function measuring devices and an adaptive digital filter, and is superposed from the output signal of another compensation circuit or power amplifier of the rotating shaft system and the displacement signal of the rotating shaft system. Then, it is requested and imitated. Therefore, when the present invention is applied between two bearings and two sensors as shown in the figure, four sets of transfer function measuring devices and adaptive digital filters are required. In the case of 5-axis control, 25 sets of transfer function measuring devices, adaptive digital filters, etc. are required if all the 5-axis correlations are taken. Such plucking control is effective because the transfer function of each rotary shaft system is correlated.

Next, a fifth embodiment of the present invention will be described with reference to FIG. 6, constituent elements having the same functions and functions as those of the constituent elements of FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The present embodiment differs from the first embodiment shown in FIG. 1 in that, firstly, the transfer function setting unit is the eigenmode measuring instrument 25. The natural mode measuring device 25 estimates the natural vibration mode of the rotary shaft system from the displacement signal of the displacement sensor 6 and generates a pseudo signal simulating the natural vibration frequency component by the adaptive digital filter 15. Secondly, the transfer function of the rotating shaft system is simulated by being superposed by a plurality of eigenmode measuring devices and adaptive digital filters as shown. With such a configuration, if the variation range of the natural frequency is known in advance, it can be handled by preparing an adaptive digital filter corresponding to each natural frequency. Will be needed.

[0015]

As described above, according to the present invention, the transfer function of the rotating shaft is simulated by the adaptive digital filter, the low frequency component is removed, and the high frequency bending eigenmode component is subtracted to obtain the rotating shaft. It is added to the displacement signal. Therefore,
Conventionally, a magnetic bearing device that can stably control the rotating shaft is obtained because the peak on the spectrum of the high-frequency component above the control frequency, which is the cause of vibration and oscillation due to the bending eigenmode of the rotating shaft, is removed. It was realized. Since this device is an adaptive digital filter that simulates the transfer function of the rotating shaft system, the conventional local notch filter etc. is not required, and the parameters can be changed even for magnetic bearing devices of different shapes and capacities. As it can be used, it is extremely versatile. Further, a magnetic bearing device capable of automatically responding to fluctuations in the transfer function of the system due to fluctuations in the rotational speed and temperature by detecting the identification error has been realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a control system of a magnetic bearing device according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the control system of the magnetic bearing device according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of the control system of the magnetic bearing device according to the present invention.

FIG. 4 is a block diagram showing a control system of a conventional magnetic bearing device.

FIG. 5 is a block diagram showing a fourth embodiment of the control system of the magnetic bearing device according to the present invention.

FIG. 6 is a block diagram showing a fifth embodiment of the control system of the magnetic bearing device according to the present invention.

[Explanation of symbols]

 1 Casing 2 Electromagnet Stator 3 Coil 4 Rotating Shaft 5 Rotor Yoke 6 Displacement Sensor 7 Compensation Circuit 8 Power Amplifier 10 System Identification Circuit 11 Transfer Function Setting Section 12 Transfer Function Measuring Device 13 Pulse Generator 14 Canceller 15 Adaptive Digital Filter 16 High Pass Circuit 17 Identification error detection circuit 25 Eigenmode measuring instrument 31 Transfer function setter

Claims (7)

[Claims] 1. A rotor yoke mounted on a rotary shaft, an electromagnet stator mounted on a casing at a minute distance from the rotor yoke, and a displacement for measuring relative displacement between the rotary shaft and the casing. In a magnetic bearing device having a sensor, a compensating circuit for controlling a magnetic attraction force acting between the rotor yoke and the electromagnet stator based on a displacement signal from the displacement sensor, and a power amplifier, a predetermined rotation A transfer function setting unit for setting the transfer function of the shaft system, and an adaptive digital filter for simulating the transfer function set by the transfer function setting unit and generating a pseudo signal by inputting the output of the compensation circuit or the power amplifier. , A high-pass circuit provided on the input side or output side of this adaptive digital filter, and a signal obtained by subtracting the pseudo signal from the displacement signal Magnetic bearing device having a compensating circuit for controlling the magnetic attraction force based. 2. A system identification circuit for detecting a signal obtained by subtracting the pseudo signal from the displacement signal by an identification error detection circuit, and successively correcting the adaptive digital filter so that the error becomes small. The magnetic bearing device according to claim 1. 3. The transfer function setting unit is composed of a transfer function measuring device and a pulse generator, and a pulse generated by the pulse generator is input to a power amplifier to give a disturbance to the rotary shaft. The displacement of the rotating shaft is detected by the displacement sensor, and the transfer function of the rotating shaft system is obtained from the displacement signal.
Magnetic bearing device. 4. The transfer function setting unit comprises a transfer function setting device for setting the transfer function of the rotating shaft system obtained by calculation or other means. Magnetic bearing device. 5. When the error is detected by the identification error detection circuit and the adaptive digital filter is adaptively corrected, when the error gradually increases and the correction becomes difficult, a pulse is regenerated by the pulse generator, The magnetic bearing device according to claim 2, wherein the transfer function is set again. 6. The transfer function setting unit is composed of a transfer function measuring device, estimates the transfer function of the rotating shaft system from the output of the compensating circuit or power amplifier and the displacement signal of the displacement sensor, and rotates the rotating shaft system. 2. The transfer function of is obtained by superimposing the output signal of another compensation circuit of the rotary shaft system or the power amplifier by a plurality of transfer function measuring devices and an adaptive digital filter, and is simulated. The magnetic bearing device according to claim 2. 7. The transfer function setting section is composed of an eigenmode measuring device, estimates a natural vibration mode of a rotary shaft system from a displacement signal of the displacement sensor, and simulates the natural vibration frequency component by the adaptive digital filter. 3. The magnetic bearing device according to claim 1, wherein a pseudo signal is generated and the transfer function of the rotating shaft system is simulated by being superposed by a plurality of eigenmode measuring devices and an adaptive digital filter.