JPS59200812A - Control variable compensating device of magnetic bearing - Google Patents

Abstract

PURPOSE:To contrive to renew the correction value due to the variation of data by means of online by a method wherein the correction value is calculated under decreasing of the gain of a phase control device by the transient skidding of a rotator, in the stage of increasing or decreasing of a rotator speed for the setting speed. CONSTITUTION:When the detecting speed of a motor increases to approximate half of the setting speed, a control command device 14 once opens a contactor 19 and stops the exciting of a motor, also outputs a gain decreasing command to a phase control device 6, then the gain is decreased to the lower limit. When a rotating position detector 10 detects the reference point of a rotating position of a rotator at said condition, a calculating device 12 outputs a data collecting command, a memory device 13 stores the outputs from a displacement detector 3x and a number of rotation setting unit 15. The calculating device 12 calculates the displacement quantity of each rotating position at the setting speed from the displacement data under the non-control condition, and makes the memory device to store those data, then compensates the detecting value of the displacement detector 3x at the setting speed.

Description

Detailed Description of the Invention (Object of the Invention) The present invention detects the air gap of a magnetic bearing supporting a nine-rotating body using a displacement detector, and compares it with a reference gap to control the excitation of an electromagnet. Detects online the amount of displacement that does not need to be corrected due to machining accuracy, scratches, non-uniformity of quality, unbalanced load, etc.

This is to correct the detected value of the displacement detector.

(Conventional technology) When supporting a rotating body with a magnetic bearing, please refer to Figures 1 and 2.
As shown in the figure, two pairs of electromagnets 2a have magnetic pole surfaces facing the outer circumferential surface of a two-rotating body 1 with an air gap in between.

2b, 2C, and 2d are arranged on the X and Y axes, and the detected value a is detected by displacement detectors ax and :13y provided on each axis.

a' is compared with the displacement reference value S of the displacement reference setter 4 by the comparator 5.5', and the output values s and b' are given to the phase control device ffff6, 6' as a displacement correction command value, and the excitation device 7. Intensify the excitation of one of the coils of each pair of electromagnets 2a, 2b and 2c, 2cl through 7',
Control is performed such that the detected values a and a' of the displacement detector become equal to the displacement reference value S by weakening the other one.

(Problems with Prior Art) However, the displacement reference value S corresponds to the reference gap between the displacement detectors ax, ay and the rotating body 1.

Rotating body 1 is not a perfect circle due to manufacturing precision and scratches.

In addition, the shaft may become deflected due to unbalanced loads, etc.2
Even if the rotating body I is held at the center position, the detected values a, a of the displacement detector are not constant and vary depending on the rotation angle +YJ. For example, there is a scratch P not shown in the first part 1.
If there is, the displacement detection value of this part will be large, and ′=also. As shown in Fig. 3, when an unbalanced load M is applied to the 9-rotator 1 and it becomes deflected, in order to hold the entire 9-rotator in the center position, the shaft center 0 of the bearing section rotates around with a radius δ. As a result, the detected value of the displacement detector fluctuates in a waveform with a period of one rotation as illustrated in FIG. This fluctuation is not due to displacement of the holding position of the rotating body, so
It is not necessary to correct the excitation of the electromagnet based on the detected value, and it is necessary to remove the above-mentioned fluctuation from the detected value and compare only the displacement with respect to the predetermined holding position with the displacement reference value S.

For this reason, the patent application No. 57-1473 proposed a device in which data that can be determined in advance is stored, and the fluctuation values that do not affect the holding position are processed to correct the detected values.
It was proposed as No. 72, but if there is a change that affects the fluctuation value, such as when a tool is replaced, the accuracy of a single rotating body changes, or new scratches occur, such as on the motor shaft for driving the main spindle of a machine tool. , the data had to be measured again and the memory updated, which required time and effort to correct.

(Embodiment of the present invention) The present invention solves the above-mentioned drawbacks by updating correction values based on such changes in data on-line, and an embodiment shown in FIG. 5 will be described. Note that this is for the purpose of simplifying the explanation.

Only the X-axis electromagnet will be explained.

1 is a rotating body, 2a and 2b are electromagnets with magnetic bearings, 3N is a displacement detector, 6 is a phase control device, 7a and 7b are excitation devices,
10 is a rotational position detector that detects the rotational position from the reference point and base f/i point of the rotational position of the rotating body 1; 11 is an interface; and 12 is a calculation device.

13 is a storage device, 14 is a control command device, 15 is a rotation speed command device, 16.17 is an A/D converter, 18 is a frequency converter, and 19 is a contactor for a motor excitation coil (not shown).

(Function) When the starting conditions are established, the electromagnets 7a and 7b are energized and the rotating body 1 is activated.
surface. Control command device 14 to 1 rotation speed command device 1
A detection speed Ni smaller than the set speed N, for example, about half of the set degree N, is commanded via the frequency converter 18. The motor excitation coil is excited via the contactor 19.

When the electric motor reaches the detected speed Ni, the control command device ff1
14 once opens the contactor 19 to cut off motor excitation and issues a gain lowering command to the one-phase control device 6 to lower the gain to the lower limit.

Therefore, the rotating body 1 of the electric motor, which is supported by the magnetic bearing, idles, and the noise in the control system of the magnetic bearing is extremely small, and the rotation 1 is in an uncontrolled state in which no external force is applied. In this state, when the rotational position detector IO detects the reference point of the rotational position of the rotating body, the arithmetic unit 12 issues a data collection command, and the displacement detector 3 16 and 17 from the interface 11 and stores the displacement data for each rotational position of one rotating body in the storage device 13. When the displacement data for one rotation is stored, the control command device 14 issues a gain return command to the phase control device 6, sets the speed command from the one rotation speed command device 15 to the set speed N, closes the contactor 19, and closes the contactor 19. Move rotating body 1 to the set speed.

From the displacement data of the uncontrolled state of the position, the displacement amount of each rotational position at the set speed N is calculated and stored, the detected value of the displacement detector 3X at the set speed N is corrected, and the displacement reference value S is calculated.
In comparison, a command is given to the phase control device 6 via the control command device 12.

In addition, 2 detector degrees N! The calculated correction value can be made even more accurate by setting it in several stages and detecting the displacement at each speed. Furthermore, if there is no need to modify the correction value because one condition remains the same, it is natural to omit the operation of the rotating body at the detected speed, and this can also be applied to the case where the speed is lowered.

(Effects of the Invention) In this way, (1) the present invention temporarily idles the rotating body during the process of raising or lowering the rotating body to a set speed, and lowers the gain of the control device to bring it into an uncontrolled state. .

Since the displacement value detected in this state is used to calculate the correction value at the set rotation speed, the electromagnet is controlled according to the gap in the magnetic bearing.

The amount of displacement that does not require correction due to machining accuracy or unbalanced loads due to tool changes can be updated online in a short time, saving the time and effort of separately calculating the correction value, and ensuring the correct magnetic bearing. This has the effect of controlling the

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the structure of a magnetic bearing, Fig. 2 is a control block diagram of a conventional magnetic bearing, Fig. 3 is an explanatory diagram showing distortion due to an unbalanced load on the shaft, and Fig. 4 is a displacement detector. Output characteristic diagram,
FIG. 5 is a control block diagram showing an embodiment of the present invention, and FIG. 6 is a characteristic diagram showing an example of the speed increasing process. ■ is a rotating body, 2a and 2b are electromagnets, 3rd place is a displacement detector,
4 is a displacement reference setter, and 6 is a phase control device. 7a and 7b are three magnetic devices, 10 is a rotational position detector, and 11 (
d interface, 12 a computing device, 13 a storage device, 14 a control command device, 15 a rotational speed command device, 18 a frequency conversion device, and 19 a contactor 4. Figure 1 Figure 2 Bacteria Figure 3 Figure 4 Figure 5 M Figure 6

Claims (1)

[Claims] 1. In a magnetic bearing control device that corrects electromagnet control according to the machining accuracy of the rotating body, unbalanced mass, etc. 2. In the process of raising or lowering the rotating body to a set speed,
Temporarily cut off the excitation of the rotating body and lower the gain of the phase control device of the magnetic bearing, leaving the rotating body in an uncontrolled state.
A magnetic bearing comprising: an arithmetic/arithmetic device that calculates a displacement amount at a set speed based on the detected displacement value in the uncontrolled state, and corrects Mli of the displacement amount detected at the set speed based on the calculated value. Controlled amount correction device. 2. The control amount correction device for a magnetic bearing according to claim 1, wherein the uncontrolled state is provided a plurality of times at different rotation speeds.