JP2006300119A - Controller for magnetic bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for a magnetic bearing device which is capable of reducing power consumption without deteriorating control stability over a wide-range frequency band. <P>SOLUTION: The controller for a magnetic bearing device controls an exciting current supplied to electromagnets 12, 13, and 14 of controlled magnetic bearings 2, 3, and 4 on the basis of the displacement of a rotator 1. The exciting current, which is composed by combining a stationary current not varying by the displacement of the rotator 1 with a control current varying by the displacement of the rotator 1, is supplied to the electromagnets 12, 13, and 14. The controller is provided with a stability evaluation means for evaluating the control stability of a feedback control system including a plant and a controller, a stationary current value control means for changing a stationary current value on the basis of the evaluation results of the control stability, and an optimization means for executing identification of the plant and optimization of the controller on the basis of the evaluation results of the control stability. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a magnetic bearing device used in a flywheel energy storage device or the like.

  As a magnetic bearing device used for a flywheel energy storage device, a rotary body having a flywheel, two sets of control-type radial magnetic bearings that support the rotary body in a radial control axial direction (radial direction), and a rotary body A set of control-type axial magnetic bearings that support non-contact in the axial control axis direction (axial direction), a built-in electric motor that rotates the rotating body at high speed, and the displacement of the rotating body in the radial control axial direction and the axial control axis direction. A so-called five-axis control type magnetic bearing device is known which includes a displacement detection device to detect and an electromagnet control device for controlling an electromagnet of the radial magnetic bearing and the axial magnetic bearing based on the output of the displacement detection device.

  In the conventional magnetic bearing device, the electromagnet controller supplies an excitation current, which is a combination of a constant steady current (bias current) that does not change due to displacement of the rotating body, and a control current that varies depending on displacement of the rotating body, to the electromagnet of the magnetic bearing. I was supposed to.

  When the magnetic bearing device is applied to a flywheel energy storage device, reduction of power consumption of the electromagnet and control stability are important.

As a measure for reducing power consumption, a zero-bias control magnetic bearing device has been proposed in which a steady current supplied to an electromagnet is set to 0 to save power (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-022730

  However, when the steady current supplied to the electromagnet is set to 0, there is a problem that the control stability is deteriorated.

  By the way, the rotating body to which the flywheel is attached branches greatly with the increase in the number of rotations due to the effect of the gyro. Therefore, it is necessary to set a control parameter having a sufficient damping effect over a wide frequency range, but this setting is often very difficult.

  Therefore, as a measure for improving the control stability, at present, control parameters that satisfy the control stability over a wide frequency range from 0 rpm to a high-speed rotation range are set by a trial error method.

  However, this trial method has a problem that it takes a very long time. In some cases, a control parameter that satisfies control stability over a wide frequency range may not be set.

  An object of the present invention is to provide a control device for a magnetic bearing device that solves the above problems and can reduce power consumption without degrading control stability over a wide frequency range.

  A control device for a magnetic bearing device according to the present invention is a control device for a magnetic bearing device that controls an excitation current supplied to an electromagnet of a control type magnetic bearing based on the displacement of the rotating body, and is a steady state that does not change due to the displacement of the rotating body. Stability evaluation means for evaluating the control stability of a feedback control system including a plant and a controller, in which an excitation current that combines a current and a control current that changes depending on the displacement of a rotating body is supplied to an electromagnet; It is characterized by comprising a steady current value control means for changing the steady current value based on the evaluation result, and an optimization means for performing plant identification and controller optimization based on the evaluation result of the control stability. To do.

  The stability evaluation means evaluates the control stability by, for example, a closed loop transfer function or a sensitivity function of the feedback control system.

  For example, the steady current value control means decreases the steady current value if the control stability is greater than or equal to a predetermined value, and increases the steady current value if the control stability is less than the predetermined value.

  The optimization means, for example, identifies a plant using a controller and a closed loop transfer function, and optimizes the controller by H∞ control.

  The steady current value control means can change the steady current value based on the evaluation result of the control stability, thereby reducing the power consumption by reducing the steady current value as much as possible without degrading the control stability. it can. In addition, the optimization means can identify control parameters that satisfy control stability over a wide frequency range by performing plant identification and controller optimization based on the control stability evaluation results.

  According to the control device for a magnetic bearing device of the present invention, as described above, power consumption can be reduced without deteriorating control stability over a wide frequency range.

  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 schematically showing main parts of a magnetic bearing device, and FIG. 2 is a block diagram showing an electrical configuration of the magnetic bearing device.

  The magnetic bearing device is a vertical type in which a vertical rotating body (1) rotates inside a vertical cylindrical housing (not shown), and the rotating body (1 ) Two sets of control type radial magnetic bearings (2) (3) for non-contact support in the radial control axis direction, and one set of control type axial magnetic bearings (1) for non-contact support of the rotating body (1) in the axial control axis direction ( 4) Two sets of radial displacement sensor units (6) and (7) and one set of axial displacement sensor units (8) that constitute the displacement detection device (5), and a built-in electric motor that rotates the rotating body (1). A stator (9), a rotation sensor (not shown) for detecting the rotation speed of the rotating body (1), a protective bearing for touchdown (not shown), and the like are arranged.

  In this specification, an axial control axis (axial control axis) is a Z-axis, and two radial control axes (radial control axes) orthogonal to the Z-axis and orthogonal to each other are an X-axis and a Y-axis.

  The radial magnetic bearings (2) and (3) are respectively opposed to the target portions (10) and (11) provided on the outer peripheral portion of the rotating body (1), and the rotating body (1) is arranged in the X-axis direction and the Y-axis direction. There are four (two pairs) electromagnets (radial electromagnets) (12, 13) arranged at equal intervals in the circumferential direction so as to be sandwiched from both sides in the axial direction.

  The axial magnetic bearing (4) includes a pair of annular electromagnets (14) arranged so as to sandwich the flange portion (1a) formed on the rotating body (1) from both sides in the Z-axis direction. ing.

  Each radial displacement sensor unit (6) (7) is opposed to the target portion (15) (16) provided on the outer periphery of the rotating body (1), and the rotating body (1) is placed in the X-axis direction and the Y-axis There are four (2 pairs) radial displacement sensors (17), (18) arranged at equal intervals in the circumferential direction so as to be sandwiched from both sides in the direction.

  Each radial displacement sensor (17), (18) is an inductance type displacement sensor.

  The axial displacement sensor unit (8) includes one axial displacement sensor (19) disposed so as to face a target portion (not shown) provided on the lower end surface of the rotating body (1).

  The axial displacement sensor (19) is an inductance type displacement sensor similar to the radial displacement sensors (17) and (18).

  Each target part (10) (11) (15) (16) is formed by laminating an annular silicon steel plate, which is a magnetic material, and adjacent to each target part (10) (11) (15) (16). The outer periphery of the rotating body (1) is made of a nonmagnetic material.

  The displacement detection device (5) includes the displacement sensor unit (6), (7), (8), the radial displacement sensors (17), (18), and the output of the axial displacement sensor (19) from the X of the rotating body (1). Displacement calculation means (20) that calculates displacement in the axial direction, Y-axis direction, and Z-axis direction, and the displacement sensor (17) by individually driving the radial displacement sensor (17) (18) and the axial displacement sensor (19) (18) Nine sensor drive circuits (21) that output signals from (19) and displacement sensors (17), (18), and (19) outputs from the sensor drive circuit (21) are AD-converted for displacement And nine AD converters (22) for outputting to the arithmetic means (20).

  The magnetic bearing device includes magnetic bearings (2), (3), (4) based on displacements of the rotating body (1) detected by the displacement detector (5) in the X-axis direction, Y-axis direction, and Z-axis direction. An electromagnet control device (23) for controlling the electromagnets (12), (13), and (14) is provided.

  The electromagnet control signal from the electromagnet controller (23) is input to the power amplifier (25) via the DA converter (24), and the excitation current is sent from the power amplifier (25) to the electromagnets (12), (13), and (14). Is supplied.

  The displacement calculation means (20) and the electromagnet control device (23) are constituted by digital processing means capable of a software program. In this example, it is configured by a DSP.

  The excitation current supplied to each electromagnet (12), (13), and (14) is the sum of the steady current that does not change with the displacement of the rotating body (1) and the control current that changes with the displacement of the rotating body (1). is there.

  In the above magnetic bearing device, the feedback control system for controlling the electromagnets (12), (13) and (14) of each control shaft is represented as a model as shown in FIG. In FIG. 3, (26) is a plant to be controlled, and (27) is a controller that is part of the control device (23).

  Assuming that the transfer functions of the plant (26) and the controller (27) are P and C, respectively, the transfer function Gcl and the sensitivity function Gsen of the entire feedback control system are expressed as follows.

Gcl = C · P / (1 + C · P)
Gsen = Gcl / (C · P) = 1 / (1 + C · P)
The control device (23) evaluates the control stability of the feedback control system of FIG. 3 and performs optimization control. More specifically, based on the evaluation of the control stability, the control current value of the excitation current supplied to each electromagnet (12) (13) (14) is changed, and the identification of the plant (26) and the controller (27 ) Optimization.

  Next, an example of the above optimization control will be described with reference to the flowchart of FIG.

  When the magnetic bearing device is powered on, first, a preset initial setting value Cinit is set to the control parameter C of the controller (27), and the count value Count is set to 0 (S01). (12) An excitation current is supplied to (13) and (14), and magnetic levitation is started (S02).

  Next, the sensitivity function Gsen is measured for control stability evaluation (A01), and this is compared with a predetermined value a (for example, 8 dB) (A02). In A02, when Gsen is equal to or less than a, it is determined that the control stability is high, the process proceeds to A03, the steady current value io is decreased by a predetermined value b (for example, 0.01 A), and Count is set to 0 ( Return to A04), A01. In A02, when Gsen is larger than a, it is determined that the control stability is low, the process proceeds to A05, Count is increased by 1, and io is compared with the allowable maximum value imax (A06). In A06, if io is smaller than imax, it is checked whether Count is 3 or more (A07). Otherwise, the process proceeds to A08, io is increased by b, and the process returns to A01.

  If io is greater than or equal to imax in A06 and if Count is greater than or equal to 3 in A07, the process proceeds to S03, Count is set to 0, and P of the plant (26) is identified based on the above formula. (B01), C is optimized by H∞ control or the like (B02). Next, Gsen is measured (B03) and compared with a (B04). In B04, if Gsen is larger than a, the process proceeds to B05 to check whether Count is 5 or more. If not, the process proceeds to B06, where Count is incremented by 1, and the process returns to B01. In B05, when Count is 5 or more, the process proceeds to S04, Count is set to 0, and the process returns to A01. In B04, if Gsen is equal to or less than a, the process proceeds to S05, io is decreased by b, Count is set to 0 (S06), and the process returns to A01.

  In the above A01 to A08, the steady current value is controlled based on the evaluation of the control stability, and in B01 to B06, the identification of P and the optimization of the C are performed based on the evaluation of the control stability.

  In the above embodiment, the sensitivity function of the feedback control system is measured and thereby the control stability is evaluated. However, the transfer function is measured, and then the sensitivity function is calculated, and the control stability is determined by the sensitivity function. You may make it evaluate. Alternatively, the transfer function may be measured, thereby evaluating the control stability, or the sensitivity function may be measured, and then the transfer function may be calculated and the control function may be evaluated based on the transfer function. Also good.

  The control of the steady current value and the identification of the plant and the optimization of the controller are not limited to those in the above embodiment, and can be changed as appropriate.

  The overall configuration of the magnetic bearing device and the configuration of each part are not limited to those of the above-described embodiment, and can be changed as appropriate.

  The displacement detection device according to the present invention is also applied to a horizontal magnetic bearing device in which a rotating body is horizontally arranged.

FIG. 1 is a schematic longitudinal sectional view of a main part of a magnetic bearing device showing an embodiment of the present invention. FIG. 2 is a block diagram showing an electrical configuration of the magnetic bearing device of FIG. FIG. 3 is a block diagram showing a feedback control system in which a part of the magnetic bearing device is modeled. FIG. 4 is a flowchart illustrating an example of optimization control in the control device.

Explanation of symbols

(1) Rotating body
(2) (3) Radial magnetic bearing
(4) Axial magnetic bearing
(23) Electromagnet controller
(26) Plant
(27) Controller

Claims (1)

A control device for a magnetic bearing device that controls an exciting current supplied to an electromagnet of a control type magnetic bearing based on a displacement of a rotating body, a steady current that does not change due to the displacement of the rotating body, and a control current that changes according to the displacement of the rotating body To supply an exciting current combined with
Stability evaluation means for evaluating the control stability of the feedback control system including the plant and the controller, steady current value control means for changing the steady current value based on the evaluation result of the control stability, and the evaluation result of the control stability An apparatus for controlling a magnetic bearing device, comprising: optimization means for performing plant identification and controller optimization based on the controller.

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