JPS6335849B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for adjusting the excitation of an electromagnet in a magnetic bearing device.

[Prior art] As shown in Fig. 3, a magnetic bearing device has a rotating shaft 1.
Two pairs of electromagnets 2a, 2b, 2c, and 2d are provided on the outer peripheral surface of the
A pair of electromagnets 2a and 2b are arranged symmetrically on the X axis perpendicular to the rotation axis, and another pair of electromagnets 2c and 2d
are similarly arranged on the Y-axis different from the X-axis by 90 degrees, and displacement detectors 3x and 3y are arranged close to the electromagnets corresponding to each pair of the electromagnets and whose centers are on the X-axis and the Y-axis, respectively. Prepared.

The detected values a and a' of these two displacement detectors are
As shown in the figure, the displacement reference value S of the displacement reference setter 4 is compared with the comparators 5 and 5', and the output values b and b' of the comparators 5 and 5' are sent to the phase control devices 6 and 6'. It is given as a displacement correction command value, and the excitation devices 7a, 7
The coils of the electromagnets 2a, 2b, 2c, and 2d of each pair are strengthened on one side and weakened on the other side for each pair through b, 7c, and 7d to correct the holding position of the rotating shaft. Then, the detection value a of the displacement detector is
Control is performed so that a' becomes equal to the displacement reference value S.

Note that the displacement reference value S is determined by the displacement detectors 3x and 3y.
This corresponds to the reference sky of the rotation axis 1 and the rotation axis 1.

[Problems to be Solved by the Invention] However, the rotating shaft 1 is not a perfect circle due to manufacturing precision or scratches, and there are errors in the radius depending on the position in the circumferential direction. Even when the shaft center of the bearing is held at the center position of the bearing, the detected values a and a' of the displacement detectors 3x and 3y are not constant, and for example, as shown in the characteristic curve of FIG. It fluctuates in the same waveform with rotation as a period, and a difference B from the displacement reference value S occurs depending on the error in the radius, and this difference causes the outputs b and b' from the comparators 5 and 5' to become the displacement correction command value. The excitation device outputs an excitation correction command to the electromagnet to change the holding position of the rotating shaft, causing the true shaft center position to vibrate at regular intervals.

Furthermore, if there is a peak p in the comparator output due to a scratch or the like, a sudden correction command will be output, which will cause a shock to the shaft.

Such unnecessary corrections are caused by the phase control device 6,
The higher the gain of 6', the more amplified it becomes, impairing the stability of the operation of the magnetic bearing device. In addition, such 1
In order to suppress the constant fluctuation of the excitation current that repeats with each rotation, there is a method to remove noise by inserting a low-pass filter, but this requires the passband of the filter to be widened, which has the disadvantage of reducing responsiveness.

[Means for Solving the Problems] The present invention is designed to eliminate such drawbacks, and uses detected values including the displacement reference value and the radius error of the rotating shaft itself in advance to determine the rotation of the shaft. Comparing the detected value of the displacement detector with the stored data in response to the position signal of the angular position detector which is stored in relation to the angular position and detects the rotational angular position from the reference position during operation; The comparison value is given to the phase control device as a displacement correction command value to adjust the electromagnet excitation device.

[Example] This will be explained with reference to the embodiment shown in FIG.

1 is a rotating shaft; 2a, 2b, 2c, and 2d are pairs of electromagnets disposed orthogonally to the outer peripheral surface of the rotating shaft 1; 3x and 3y are displacement detectors provided corresponding to the axes of each pair; 5 and 5' are comparators, 6 and 6' are phase control devices, 7a, 7b, 7c, and 7d are excitation devices for each electromagnet, and 8 is rotated by a magnetic type, capacitance type, or optical type. This is an angular position detector that detects the circumferential position of the shaft 1. In this embodiment, the protrusion 8a outputs a pulse signal C (FIG. 2) indicating the circumferential position of the rotating shaft 1 to the counter 9. ,
The counter 9 counts the rotational angular position of the rotary shaft 1 from the reference point and outputs eight angular position classification signals.

Reference numerals 10 and 10' denote storage devices, which store in advance the displacement reference position S and the total value of the radial error of the rotating shaft itself such as machining accuracy and scratches of the shaft, and store the angular position classification from the counter 9. For example, the median value of the stored contents is converted into a D/A converter 11 in response to the signal.
Output e converted to analog via 11' and
The outputs e′ with different phases by 90° are sent to comparators 5 and 5, respectively.
5'.

12 and 12' are low-pass filters, 13 is a refresh controller operated by the refresh command g, 14 and 14' are A/D converters, 15,
15' is a switching device.

Note that FIGS. 2 and 5 are characteristic curves showing a case where there is no actual axial displacement of the rotating shaft 1, but only a radius error of the rotating shaft itself, and the amount of displacement is exaggerated for the sake of explanation.

The displacement detection values a, a' detected by the displacement detectors 3x, 3y are the outputs e, a' from the D/A converters 11, 11'.
It is compared with e' by comparators 5 and 5'. Since the outputs e and e' are the total value including the radius error and displacement reference value of the rotary shaft itself written in advance in the storage devices 10 and 10', if there is no actual displacement of the center of the shaft,
From the comparator, a displacement output f (Fig. 2) that becomes zero at the center for each angular position division and f' whose phase is shifted by 90 degrees are outputted by low-pass filters 12 and 12', after which the high-frequency sawtooth output is removed and the phase is changed. It is given as a displacement correction command input to the control devices 6, 6'. For this reason, the excitation devices 7a, 7b and 7c,
7d does not modify the excitation of the coils of electromagnets 2a, 2b and 2c, 2d.

In the above example, the output f is set to zero at the center of each angular position division, but the invention is not limited to this, and the output may be set to zero at the rise of the pulse signal C, for example.

When setting the memory value at the beginning of operation, or when it becomes necessary to calibrate or change the memory value due to heat generated by axis operation or long-term operation, a refresh command g is sent to the refresh controller 13.
, the refresh controller 13 outputs a gain reduction signal j to the phase control devices 6, 6', lowering the gain of the phase control device to the lower limit, and the refresh controller 13 confirms this and outputs the gain reduction signal j to the storage devices 10, 6'. After outputting a command h for switching to the write mode to 10' and preparing to rewrite the stored value, the switching devices 15 and 15' are closed. Therefore, the detected values of the displacement detectors 3x and 3y are inputted to the A/D converters 14 and 14', respectively, corresponding to the angular position of the rotating shaft 1 output from the counter 9, and the stored data is converted into the rotation at that time. Rewrite according to the situation. When the data for one rotation is rewritten, the switching command h from the refresh controller 13 is erased to return the storage devices 10, 10' to the read mode, and at the same time, the switching devices 15, 1
5' is opened. Also, turn off the gain reduction signal j,
Return the gain of the phase control device to its normal operating state.

[Effects of the Present Invention] As described above, the present invention includes an angular position detector that detects the angular position of the rotating shaft, and lowers the adjustment gain in advance for each angular position division to adjust the displacement reference value and the rotating shaft itself. The total value including the radius error is memorized, and the gain is set high during operation to compare the memorized value and the detected value of the displacement detector for each angular position division, so corrections due to machining accuracy etc. can be made. The excitation device is not unnecessarily corrected due to an unnecessary radius error, and correction is performed only by the amount of displacement due to the true displacement of the rotating shaft, and vibrations caused by excessive correction can be eliminated.

In addition, since the comparator output compares the detected displacement value with the stored value in a range divided according to the pulse signal from the angular position detector, the time constant of the low-pass filter can be shortened, and the waveform of the output signal The high value is lowered, and the delay in response caused by the low-pass filter can be practically ignored, making it possible to increase the gain of the control device, improving controllability and maintaining stability, and making it possible to set and modify memorized values. It can be done easily.

Furthermore, accuracy can be further improved by subdividing the angular position divisions, and good bearing retention can be achieved without strictly maintaining the machining accuracy of the rotating shaft or material non-uniformity, thereby preventing poor machining accuracy. It also reduces the number of defective shafts due to material defects, etc., and is also effective in terms of resource conservation.

It is clear that this magnetic bearing control device can also be applied to thrust bearings.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an output characteristic diagram of each part, Fig. 3 is a layout diagram of electromagnets in a magnetic bearing device, and Fig. 4 is a block diagram showing an example of a conventional control device. Figures 5 and 5 show output characteristic diagrams of each part. 1 is a rotating shaft, 2a, 2b, 2c, 2d are electromagnets, 3x, 3y are displacement detectors, 4 is a displacement reference value setter, 5, 5' are comparators, 6, 6' are phase control devices, 7a, 7b, 7c, 7d are excitation devices, 8 is an angular position detector, 9 is a counter, 10, 10' is a storage device, 11, 11' is a D/A converter, 12, 1
2' is a low-pass filter, 13 is a refresh controller, 14, 14' is an A/D converter, 15,
15' is a switching device.

Claims (1)

[Claims] 1. A plurality of electromagnets that support a rotating shaft in a non-contact manner, and a displacement detector that faces the outer periphery of the rotating shaft with a space between them and detects changes in space between the outer circumferential surface of the rotating shaft and the outer circumferential surface of the rotating shaft. In addition, in a magnetic bearing device that adjusts the excitation of an electromagnet according to the detected value of a displacement detector so as to eliminate fluctuations, the angular position detector of the rotating shaft and the radius error of the rotating shaft due to the machining accuracy of the shaft in advance are detected. and a storage device that stores the rotational angular position in relation to the rotational angular position, and for each angular position division divided by the angular position detector, a comparison value between the detected value of the displacement detector and the stored value of the storage device is provided. A control device for a magnetic bearing device, characterized in that it adjusts electromagnet excitation. 2. The storage device includes a refresh controller, and lowers the gain of excitation adjustment by a refresh command, and inputs the detected value of the displacement detector via an A/D converter to update the stored contents of the storage device. A control device for a magnetic bearing device according to claim 1.