JP2007263144A - Magnetic bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing device for preventing the overflow of an integral element even if a shift continuously occurs between a flotation reference position and a flotation position. <P>SOLUTION: A plurality of pairs of electromagnets support a rotor 5 in no contact therewith in directions of an axial control shaft and a radial control shaft. The magnetic bearing device comprises a position detecting means for detecting the position of the rotor in the direction of each control shaft to output a position detection signal, a flotation reference position signal output means for outputting a flotation reference position signal, an electromagnet control signal output means for outputting an electromagnet control signal including at least integral output in accordance with the flotation reference position signal and the position detection signal, and an electromagnet driving means for driving the electromagnets in accordance with the electromagnet control signal. The electromagnet control signal output means has an integral input restricting means for making an integral input zero when a difference between the flotation reference position signal and the position detection signal is a predetermined value or smaller, and an integral output restricting means for restricting an integral output to be a predetermined value or smaller. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic bearing device, and more particularly, to a magnetic bearing device that magnetically levitates by supporting a rotating body in a non-contact manner in the axial control axis direction and the radial control axis direction with a plurality of sets of magnetic bearings.

  As this type of magnetic bearing device, a plurality of control type magnetic bearings having a plurality of electromagnets that non-contact support the rotating body in the axial control axis direction and the radial control axis direction, the axial control axial direction of the rotating body, and the radial control axis direction A position detection device that detects a position and outputs a position detection signal, an electromagnet control device that controls an electromagnet of a magnetic bearing based on the position detection signal, and a movable range of the rotating body in the axial control axis direction and the radial control axis direction One having a protective bearing (touch-down bearing) as a mechanical restricting means is known (Patent Document 1).

  Each magnetic bearing includes one or two pairs of electromagnets facing each other with the rotating body sandwiched from both sides in the control axis direction. The position detection device includes a plurality of position sensors. In general, the position sensor in the axial control axis direction includes one axial position sensor facing the position detection end surface of the rotating body from one side in the axial control axis direction. The position sensor in the radial control axis direction includes a plurality of pairs of radial position sensors that are opposed to each other while sandwiching the rotating body from both sides in the two control axis directions orthogonal to each other. The electromagnet control device includes a levitation reference position signal output unit that outputs a levitation reference position signal for each control axis direction, an electromagnet control signal output unit that outputs an electromagnet control signal based on the levitation position reference signal and the position detection signal, and an electromagnet Electromagnet driving means for driving the electromagnet based on the control signal is provided.

  The electromagnet control signal output means of each control axis outputs an excitation current signal for the pair of electromagnets of the control axis, and the electromagnet drive means outputs an excitation current proportional to the excitation current signal to the pair of electromagnets. Supply. The excitation current signal for each electromagnet is a combination of the steady current signal and the control current signal, and the excitation current supplied to each electromagnet is the combination of the steady current and the control current. The steady current (and steady current signal) is a constant value regardless of the position of the rotating body in the control axis direction. The control current (and control current signal) varies depending on the position of the rotating body in the control axis direction. For a pair of electromagnets on each control axis, the absolute values of the control current (and control current signal) are equal to each other, and their signs are opposite to each other.

  In a normal magnetic bearing device, the electromagnet of the magnetic bearing is controlled so that the rotating body is held at the center position of the sensor, that is, the center of the rotating body matches the center position of the sensor. For this reason, the rotating body is held at a substantially magnetic center position. Alternatively, the rotating body is held at the magnetic center position. As described above, when the rotating body is held at the magnetic center position or the substantially magnetic center position, the size of the gap (gap) between the pair of electromagnets and the rotating body is equal to or approximately equal to each other.

  If the axial control axis is the Z-axis and the two radial control axes are the X-axis and the Y-axis, respectively, in the vertical magnetic bearing device, the Z-axis is vertical, and in the horizontal magnetic bearing device, Usually, one of the X axis and the Y axis is in the vertical direction.

PID control is often used for magnetic bearing control. However, in the case of this PID control, if a slight deviation from the levitation reference position continues, the integral element overflows and the control becomes unstable. was there.
JP 2002-349567 A

  In the device described in Patent Document 1, by considering the integral element, the load capacity by the electromagnet can be increased without increasing the excitation current supplied to the electromagnet. The problem of overflow when the displacement from the position continues is not solved.

  An object of the present invention is to provide a magnetic bearing device that solves the above-described problem and prevents the integral element from overflowing even when the deviation between the levitation reference position and the levitation position continues.

  A magnetic bearing device according to the present invention includes a control type axial magnetic bearing and a control that magnetically levitates by supporting the rotating body in a non-contact manner in the axial control axis direction and the two radial control axis directions orthogonal to each other by the magnetic attractive force of a plurality of pairs of electromagnets A pair of electromagnets arranged so as to sandwich the rotating body from both sides of the control axis direction, and detecting the position of the rotating body in the control axis direction Position detecting means for outputting a position detection signal, levitation reference position signal output means for outputting a levitation reference position signal, and an electromagnet for outputting an electromagnet control signal including at least an integral output based on the levitation reference position signal and the position detection signal. Control signal output means, and magnetic bearing device comprising electromagnet drive means for driving the electromagnet based on the electromagnet control signal The electromagnet control signal output means includes an integral input limiting means for setting the integral input to zero when the difference between the levitation reference position signal and the position detection signal is equal to or less than a predetermined value, and an integral output to be equal to or less than the predetermined value. And an integral output limiting means for limiting.

  For each control axis, a pair of electromagnets having the same characteristics are usually used. For each electromagnet, the electromagnet control signal output means outputs a constant steady current signal and the position of the rotating body in the direction of the control axis. An excitation current signal that is combined with the changing control current signal is output, and an excitation current that is a combination of a constant steady current proportional to the steady current signal and a control current proportional to the control current signal is supplied from the electromagnet driving means.

  In the pair of electromagnets of each control shaft, the values of the steady current are equal to each other, the absolute values of the control current are equal to each other, and the signs are opposite. The absolute value of the control current is proportional to the integral output of the electromagnet control signal output means.

  The electromagnet control signal output means includes, for example, a subtraction means, a levitation reference position signal output means, a control current calculation means, and an excitation current calculation means. The control current calculation means includes an integration operation unit, a proportional / differential calculation. The control current value for the electromagnet is calculated by PID calculation based on the displacement value from the subtracting means. The integral input limiting means is provided on the input side of the integral operation unit, and the integral output limiting means is provided on the output side.

  According to the electromagnet control signal output means, it is cut when the deviation between the magnetic levitation reference position and the actual levitation position is, for example, less than 1% of the operating range, and as a result, it corresponds to the deviation x time output from the integral calculation unit. The integral output does not increase while the deviation is less than 1%, and even if a minute deviation of less than 1% continues for a long time, the integration element does not overflow. In addition, since the integration output is limited so as not to output more than a predetermined value, the integration element does not overflow even when a deviation of 1% or more continues for a long time.

  According to the magnetic bearing device of the present invention, the integral input is set to zero when the difference between the levitation reference position signal and the position detection signal is equal to or smaller than the predetermined value, so that even if a slight deviation continues, overflow of the integral element is prevented. At the same time, since the integral output is limited to a predetermined value or less, overflow is prevented even if the integral input is not made zero. Further, overflow due to calculation rounding error is also prevented. In addition, when the overflow is prevented, the flying reference position signal is not changed, so that the processing program of the electromagnet control signal output means can be simplified.

  Hereinafter, an embodiment in which the present invention is applied to a five-axis control type magnetic bearing device will be described with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a main part of a mechanical part of a 5-axis control type magnetic bearing device, and FIG. 2 is a block diagram showing an example of the electrical configuration thereof.

  The magnetic bearing device includes a machine body (1) and a controller (2) connected by a cable. This magnetic bearing device is of a vertical type in which a vertical shaft-like rotating body (5) rotates inside a vertical cylindrical casing (4). As described above, the axis in the axial direction (vertical direction) of the rotating body (5) is the Z axis, and two radial directions (horizontal directions) that are orthogonal to the Z axis and orthogonal to each other are the X axis and the Y axis. .

  The machine body (1) has a set of control type axial magnetic bearings (6) for non-contact support of the rotating body (5) in the Z-axis direction, and the rotating body (5) at two locations in the axial direction. And two sets of upper and lower control radial magnetic bearings (7), (8) and non-contact supporting in the Y-axis direction, the position in the axial direction of the rotating body (5), and the position in the X-axis direction and the Y-axis direction at the above two locations The position detector (9) for detecting each, the built-in type electric motor (10) for rotating the rotating body (5) at high speed, and the movable range in the axial direction and radial direction of the rotating body (5) are regulated. Up and down 2 as mechanical regulating means for mechanically supporting the rotating body (5) at the extreme position of the movable range when the rotating body (5) can no longer be supported by the magnetic bearings (6), (7) and (8). A set of protective bearings (11), (12) is provided. The Z axis is a control axis in the axial direction. The X-axis control axis in the upper magnetic bearing (7) is the upper X-axis, the Y-axis control axis is the upper Y-axis, and the lower magnetic bearing (8) is the X-axis control axis. The control axis in the lower X-axis and Y-axis directions is the lower Y-axis.

  The controller (2) is provided with a sensor circuit (13), an electromagnet driving circuit (14) as an electromagnet driving means, an inverter (15), and a DSP board (16). The DSP board (16) has a software program. A DSP (18), ROM (31) as possible digital processing means, a flash memory (19) as storage means, an AD converter (20), and a DA converter (21) are provided. The DSP is an abbreviation for a digital signal processor. The digital signal processor refers to dedicated hardware that can input a digital signal and output the digital signal, can be software-programmed, and can perform high-speed real-time processing.

  The position detector (9) includes one axial position sensor (23) for detecting the position of the rotating body (5) in the Z-axis direction, and the position of the rotating body (5) in the X-axis direction and the Y-axis direction. Are provided with two sets of upper and lower radial position sensor units (24), (25).

  The axial magnetic bearing (6) is a pair of magnetically attracting the rotating body (5) which is disposed so as to sandwich the flange part (5a) integrally formed at the lower part of the rotating body (5) from both sides in the Z-axis direction. The axial electromagnets (26a) and (26b) are provided. The axial electromagnet is generically designated by reference numeral (26). The pair of axial electromagnets (26) having the same characteristics is used.

  The axial position sensor (23) is disposed so as to face the lower end surface of the rotating body (5) from the lower side in the Z-axis direction, and is a distance signal proportional to the size of the gap with the lower end surface of the rotating body (5). Is output.

  The two sets of radial magnetic bearings (7) and (8) are arranged at predetermined intervals in the vertical direction on the upper side of the axial magnetic bearing (6), and the motor (10) is arranged therebetween. . The upper radial magnetic bearing (7) includes a pair of upper radial electromagnets (27a) (27b) arranged so as to sandwich the rotating body (5) from both sides in the X-axis direction and magnetically attracting the rotating body (5), and A pair of upper radial electromagnets (27c) and (27d) are provided so as to sandwich the rotating body (5) from both sides in the Y-axis direction and magnetically attract the rotating body (5). These radial electromagnets are collectively referred to by reference numeral (27). Similarly, the lower radial electromagnet (8) includes two pairs of lower radial electromagnets (28a) (28b) (28c) (28d). These radial electromagnets are also collectively referred to by reference numeral (28). As for the radial bearings (27) and (28), at least one pair of electromagnets of the same control shaft has the same characteristics. Preferably, all the radial electromagnets (27) and (28) have the same characteristics.

  The upper radial position sensor unit (24) is disposed in the vicinity of the upper radial magnetic bearing (7), and the rotating body (5) from both sides in the X-axis direction in the vicinity of the electromagnets (27a) and (27b) in the X-axis direction. A pair of upper radial position sensors (29a) (29b) arranged so as to sandwich the rotor, and the rotating body (5) from both sides in the Y-axis direction in the vicinity of the electromagnets (27c) (27d) in the Y-axis direction Are provided with a pair of upper radial position sensors (29c) (29d). These radial position sensors are collectively referred to by reference numeral (29). Similarly, the lower radial position sensor unit (25) is disposed in the vicinity of the lower radial magnetic bearing (8), and includes two pairs of lower radial position sensors (30a) (30b) (30c) (30d). Yes. These radial position sensors are also collectively referred to by reference numeral (30). Each radial displacement sensor (29), (30) outputs a distance signal proportional to the size of the gap with the outer peripheral surface of the rotating body (5).

  The electromagnets (26) (27) (28) and the position sensors (23) (29) (30) are fixed to the casing (4).

  The upper protective bearing (11) is a rolling bearing such as a deep groove ball bearing, for example, and can receive a radial load. The outer ring (11a) of the bearing (11) is fixed to the casing (4), and the inner ring (11b) is disposed so as to face the outer peripheral surface of the rotating body (5) with an appropriate gap. The lower protective bearing (12) is a rolling bearing such as a deep groove ball bearing, for example, and can receive both an axial load and a radial load. The outer ring (12a) of the bearing (12) is fixed to the casing (4), and the inner ring (12b) is axially and radially aligned with the annular groove (17) formed on the outer peripheral surface of the rotating body (5). It is faced with a suitable gap. The axial movable range of the rotating body (5) is restricted by the size of the gap in the axial direction between the inner ring (12b) of the lower bearing (12) and the rotating body (4), and each bearing (11 ) (12) The radial movable range of the rotating body (5) is restricted by the size of the radial gap between the inner rings (11b) and (12b) of the rotating body (5). Even when the rotating body (2) is supported by the protective bearings (11) and (12) at the extreme position of the movable range, the rotating body (5) and the electromagnets (26) (27) (28) and the position sensor ( 23) (29) (30) there is a gap between the rotating body (5) and the electromagnets (26) (27) (28) and the position sensors (23) (29) (30) Absent.

  The sensor circuit (13) of the controller (2) drives the position sensors (23), (29), and (30) of the position detector (9), and outputs the signals from the position sensors (23), (29), and (30). Based on a certain distance signal, the position of the rotating body (5) in the Z-axis direction and the positions of the upper and lower radial position sensor units (24) and (25) in the X-axis direction and the Y-axis direction are calculated. The resulting position signal is output to the DSP (18) via the AD converter (20). The position detection unit (9) and sensor circuit (13) constitute a position detection device as position detection means for detecting the position of the rotating body (5) in each control axis direction and outputting a position detection signal.

  The ROM (31) stores a processing program for the DSP (18). The flash memory (19) is provided with a control parameter table storing the control parameters of the magnetic bearing, a bias current value table storing a bias current (steady current) value, which will be described later, and the like. For each control axis, the DSP (18) is based on a digital position signal representing the position of the rotating body (5) input from the AD converter (20), and each of the magnetic bearings (6), (7), (8). An excitation current signal (electromagnet control signal) for the electromagnets (26) (27) (28) is output to the electromagnet drive circuit (14) via the DA converter (21). The drive circuit (14) supplies the excitation current based on the excitation current signal from the DSP (18) to the electromagnets (26), (27), (28) of the corresponding magnetic bearings (6), (7), (8). Thus, the rotating body (5) is supported in a non-contact manner at a floating reference position described later. The DSP (18) constitutes an electromagnet control signal output means for outputting an electromagnet control signal based on a levitation reference position signal and a position detection signal described later.

  The DSP (18) also outputs a rotation speed command signal for the motor (10) to the inverter (15), and the inverter (15) controls the rotation speed of the motor (10) based on this signal. As a result, the rotating body (5) is rotated at high speed by the motor (10) while being supported in a non-contact manner at the target floating position by the magnetic bearings (6), (7), and (8).

  FIG. 3 shows the operation of the DSP (18) regarding the control of the pair of electromagnets in the magnetic bearing (in this example, the control of the axial electromagnets (26a) and (26b) in the Z-axis direction) in the configuration of the controller (2). It is expressed in blocks. The DSP (18) functionally includes a subtracting means (22), a floating reference position signal output means (32), a control current calculating means (37), and an exciting current calculating means (38).

  The subtracting means (22) subtracts the levitation reference position signal Zo input from the levitation reference position signal output means (32) as will be described later from the position signal Zs input from the AD converter (20). The displacement value ΔZ from the levitation reference position in 5) is obtained and output to the control current calculation means (37).

  The control current calculation means (37) calculates the control current value Ic for the electromagnets (26a) and (26b) by PID calculation based on the displacement value ΔZ from the subtraction means (22). (Integration operation section) (40), proportional / differentiation operation section (proportional / differentiation operation section) (41), and addition section (42).

  The integral calculation unit (40) calculates the integral component Ici of the control current value Ic based on the displacement value ΔZ using the integral calculation control parameter stored in the table of the flash memory (19). On the input side of the integral calculation unit (40), there is provided input limiting means (43) that replaces the input displacement value ΔZ with 0 when the displacement value ΔZ is very small, and on the output side of the integral calculation unit (40). Is provided with output limiting means (44) for replacing the output value with a predetermined value when the output value exceeds a certain value.

  The proportional / differential calculation unit (41) uses the proportional calculation control parameter and the differential calculation control parameter stored in the table of the flash memory (19), and based on the displacement value ΔZ, the proportional / differential component Icpd of the control current value Ic. Is calculated. The adder (42) calculates the control current value Ic by adding the integral component Ici and the proportional / differential component Icpd, and outputs this to the exciting current calculation means (38).

  The proportional / differential calculation unit (41) is divided into a proportional calculation unit and a differential calculation unit.The proportional component that is the output of the proportional calculation unit, the differential component that is the output of the differential calculation unit, and the integral calculation unit ( The control current value Ic may be obtained by adding the integral component Ici which is the output of 40). The excitation current calculation means (38) adds the control current value Ic from the control current calculation means (37) to the bias current value Io stored in the table of the flash memory (19), and the value ( (Io + Ic) is output to the DA converter (21) as a first excitation current signal, and the control current value Ic is subtracted from the bias current value Io, and the value (Io-Ic) obtained as a result is second. Is output to the DA converter (21) as an excitation current signal. The levitation reference position signal output means (32) outputs a levitation reference position signal Zo described later.

  Although not shown in the drawing, the same applies to the portion related to the control of the pair of radial electromagnets (27) and (28) in the upper and lower X-axis and Y-axis.

  FIG. 4 is a flowchart showing processing on the input side and output side of the integral calculation unit (40), and FIG. 5 is a time chart showing changes in the integral component of the control current value at that time. In FIG. 5, (a) is a deviation between the magnetic levitation reference position and the levitation position, (b) is an integral input to be input to the integral calculation unit (40), and (c) is output from the integral calculation unit (40). Represents the integral output.

  With reference to FIGS. 4 and 5, an example of the operation of the Z-axis control current calculation means (37) in the above embodiment will be described.

  In the flowchart of FIG. 4, when the control of the magnetic bearing is started, first, the magnetic levitation reference position is set to Zo (for example, the magnetic center position), and the magnetic levitation of the rotating body (5) is started (S1). At the same time, a deviation ΔZ between the magnetic levitation reference position Zo and the actual levitation position Zs obtained from the position signal from the sensor circuit (13) is obtained (S2). For this deviation, for example, 1% of the operating range of the rotating body (5) is set as a control threshold value, and the input restriction means (43) compares this threshold value with the actual deviation amount (%). (S3). If the deviation is less than 1%, the input value 0 is input to the integral calculation unit (40) (S4). When the deviation is 1% or more, the deviation amount is input to the integral calculation unit (40). The integral calculation unit (40) outputs an integral component Ici corresponding to the input value (Ici = 0 if the deviation is less than 1%), which is added to the output value Icpd from the proportional / differential calculation unit (41). The control current value Ic is set. Also, the integral output from the integral calculation unit (40) is compared with the limiter value that defines the upper limit of the output value in the output limiting means (44) (S6). The values are equal (S7). If the integral output is less than the limiter value, the steps from (S2) to (S7) are repeated based on that value, and if it is greater than the limiter value, based on the limiter value.

  Therefore, for example, as shown in FIG. 5, if the deviation between the magnetic levitation reference position and the actual levitation position is as shown in FIG. 5 (a), the integral input input to the integral calculation unit (40) is As shown in the figure (b), less than 1% is cut. As a result, the integral output corresponding to the deviation × time output from the integral calculation unit (40) does not increase while the deviation is less than 1%, and a minute deviation of less than 1% continues for a long time. Even in this case, the integral element never overflows. In addition, since the integration output is limited so that it does not output more than the set value of the limiter, even if a deviation of 1% or more continues for a long time, the integration element does not overflow. Thus, overflow of the integral element is prevented and stable control is continuously performed.

  In the above embodiment, the levitation reference position signal output means (32) is constituted by the DSP (18). However, the levitation reference position signal output means is constituted by something other than the DSP, such as a personal computer or a microprocessor. Also good.

  In the above embodiment, the inner rotor type magnetic bearing device that rotates inside the casing whose rotating body is a fixed portion is shown. However, the present invention is an outer rotor type magnetic bearing device in which the rotating body rotates outside the fixed portion. It can also be applied to.

  In the above embodiment, the vertical magnetic bearing device in which the rotating body is arranged vertically is shown. However, the present invention can also be applied to a horizontal magnetic bearing device in which the rotating body is arranged horizontally. .

FIG. 1 is a longitudinal sectional view of a main part of a mechanical part of a magnetic bearing device showing an embodiment of the present invention. FIG. 2 is a block diagram showing an example of the electrical configuration of the magnetic bearing device. FIG. 3 is a block diagram showing the functions of the DSP portion relating to the pair of axial electromagnets of the controller of FIG. FIG. 4 is a flowchart showing an example of processing in the control current calculation means. FIG. 5 is a time chart showing changes in the signals on the input side and output side of the integral calculation unit when the processing according to the embodiment of the present invention is performed.

Explanation of symbols

(5) Rotating body
(6) Axial magnetic bearing
(13) Sensor circuit
(18) Digital signal processor (DSP)
(19) Flash memory
(23) Axial position sensor
(26a) (26b) Axial electromagnet
(27a) (27b) (27c) (27d) Radial electromagnet
(28a) (28b) (28c) (28d) Radial electromagnet
(29a) (29b) (29c) (29d) Radial position sensor
(30a) (30b) (30c) (30d) Radial position sensor
(37) Control current calculation means
(32) Levitation reference position signal output means
(40) Integration unit
(43) Input restriction means
(44) Output limiting means

Claims (1)

A control-type axial magnetic bearing and a control-type radial magnetic bearing are provided that magnetically levitated by non-contact support of the rotating body in the axial control axis direction and two radial control axis directions orthogonal to each other by the magnetic attraction force of a plurality of pairs of electromagnets For each control axis direction, a pair of electromagnets arranged so as to sandwich the rotating body from both sides of the control axis direction, and detecting the position of the rotating body in the control axis direction and outputting a position detection signal Position detection means, levitation reference position signal output means for outputting a levitation reference position signal, electromagnet control signal output means for outputting an electromagnet control signal including at least an integral output based on the levitation reference position signal and the position detection signal, and the electromagnet In a magnetic bearing device comprising electromagnet driving means for driving the electromagnet based on a control signal,
The electromagnet control signal output means includes an integration input limiting means for setting an integration input to zero when a difference between the levitation reference position signal and the position detection signal is a predetermined value or less, and an integration for limiting the integration output to a predetermined value or less. A magnetic bearing device comprising output limiting means.

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