JP5495172B2 - Magnetic bearing control device and method - Google Patents

Description

  The present invention relates to a control device and a control method for a magnetic bearing that supports a rotating body (rotor) that rotates at high speed.

In high-speed rotating machines such as a turbo compressor, a cryogenic rotating machine, a turbocharger, and a flywheel, a magnetic bearing may be used as a bearing that supports a rotating body (rotor) that rotates at high speed.
One of the features of magnetic bearings compared to conventional oil bearings is the difference in dynamic bearing stiffness, where oil bearings are rigidly supported while magnetic bearings are softly supported. Therefore, the vibration mode of the rotor in the magnetic bearing is close to the free-free mode, and the operating range is, for example, between the third and fourth critical speeds of the elastic bending mode.
Therefore, when the rotating body is supported by the magnetic bearing, it is necessary to stabilize not only the eigenvalue (critical speed) that passes through but also all eigenvalues that exist within the control band (generally about 2 kHz or less).

  In order to stabilize the eigenvalue, the phase in the vicinity of the eigenvalue may be advanced to give attenuation. The simplest means is to use a differentiation circuit, but there are other phase adjustment methods using various filters such as phase lead compensation, phase lag compensation, phase shift compensation, and stabilization filter. There are also means for advancing the phase of only the rotational synchronization component, such as N-cross control, and applications thereof, and techniques for reducing the gain, such as a low-pass filter and a notch filter.

These means are disclosed in Non-Patent Documents 1 and 2 and Patent Documents 1 to 5, for example.

"Magnetic Bearing Guidebook for Rotating Machine Designers", p. 91-94, Tracking Logic, N-cross Control Description, published by Nihon Kogyo Publishing Co., Ltd., July 30, 2004 "Basic Course of Mechanical Engineering Mechanical Mechanics I-Linear Practical Vibration Theory", Science and Engineering

Japanese Patent Application Laid-Open No. 61-262225, “Electromagnetic Bearing Control Device” Japanese Patent Publication No. 06-037895, “Electromagnetic bearing control device” Japanese Patent No. 2565438, “Electromagnetic Bearing Control Device” Japanese Patent No. 3072994, “Control circuit with tracking filter” Japanese Patent No. 3718561, “Structural vibration instability prevention device and method, magnetic bearing control device”

Differentiating circuits and phase lead compensation have a problem that the phase advances, but the high frequency tends to become unstable because of high gain (referred to as “spillover”).
Phase delay compensation and phase shift compensation (Patent Document 5) adjust the phase by a stabilizing filter to create a phase advance, but have a problem that an unstable region can be formed.
The low-pass filter and the notch filter have a problem of generating an unstable region due to a phase delay, although the gain is reduced.
The N cross control (Patent Documents 1 and 4) can be improved only by the forward component of the rotation synchronization (Forward component), and there is a problem that the rest cannot be stabilized.
In application of N-cross control, Patent Document 3 stabilizes the forward and backward components (Backward component) of rotation synchronization, but does not improve other frequencies. In Patent Document 2, self-excited vibration is targeted, but there is a problem that a frequency generator (oscillator) synchronized with the target frequency is required.

  In order to solve these problems, F-cross control has been devised. Details of the F-cross control will be described later.

  According to the F cross control, only the rotor displacement signal in the preset frequency range or the current command signal of the feedback controller is extracted by the wide band filter, and the X axis and the Y axis are coupled by the cross circuit. The frequency band to be added can be arbitrarily expanded. Therefore, it is possible to easily add attenuation to an unbalanced external force having a frequency other than the rotation synchronization component, such as an electromagnetic force of an induction motor.

  Further, since the tracking filter is used as the wideband filter, the forward component (Forward component) is stabilized, but the backward component (Backward component) is not destabilized and is not affected.

  However, the above-described F-cross control has a problem that the backward component (Backward component) is not destabilized, but on the contrary, the stability is not improved.

The present invention has been developed to solve the above-described problems. That is, the object of the present invention is to stabilize both the forward component (Forward component) and the backward component (Backward component), and even when an external force different from the rotational frequency of the rotor acts, PLL that can pass the frequency stably, can advance the phase of the frequency band other than the rotation synchronization component, and does not lose tracking even when the acceleration / deceleration of the rotating body is fast, and extracts the rotation synchronization component ( It is an object of the present invention to provide a magnetic bearing control device and method that do not require a phase-locked loop.

According to the present invention, a pair of x-axis electromagnets arranged opposite to each other on the x-axis in a xy plane perpendicular to the axis of the rotor rotating at high speed, and the rotor sandwiched between And a pair of y-axis electromagnets arranged opposite to each other on the y-axis.
A feedback controller for holding the rotor in a neutral position based on the displacement of the rotor;
An F cross control filter that extracts only the forward displacement signal of the rotor that matches the target frequency Nf based on the input target frequency Nf other than the rotation synchronization component ;
A B cross control filter that extracts only the backward displacement signal of the rotor that matches the target frequency Nb based on the input target frequency Nb other than the rotation synchronization component ;
The forward displacement signal and the backward displacement signal are multiplied by a predetermined gain to be superimposed on the current command signal Iy of the y-axis electromagnet, and the extracted y-axis signal is multiplied by a predetermined gain to be applied to the x-axis electromagnet. A cross circuit superimposed on the current command signal Ix,
The transformation matrix T _b and the inverse transformation matrix T _b ⁻¹ constituting the B cross control filter are the same as the transformation matrix T _f and the inverse transformation matrix T _f ⁻¹ constituting the F cross control filter. There is provided a magnetic bearing control device characterized by being replaced with the above.

The transfer function Gf (s) of the F cross control filter is
Gf (s) = (jk) / (τ (s−Ω) +1) (3)
The transfer function Gb (s) of the B cross control filter is
Gb (s) = (jk) / (τ (s + Ω) +1) (6)
Here, j is an imaginary number, k is a coefficient relating to output, Ω is a rotation frequency, and s is jω (ω is an angular frequency).

Furthermore, the feedback controller includes an x-axis controller that feedback-controls the current command signal Ix of the x-axis electromagnet based on the x-direction displacement of the rotor;
A y-axis controller that feedback-controls the current command signal Iy of the y-axis electromagnet based on the y-direction displacement of the rotor.

Further, according to the present invention, a pair of x-axis electromagnets disposed on the x-axis opposite to each other in the xy plane perpendicular to the axis of the rotor rotating at high speed, and the rotor, A method of controlling a magnetic bearing having a pair of y-axis electromagnets disposed opposite to each other on the y-axis,
Feedback control to hold the rotor in a neutral position based on the displacement of the rotor,
Based on the input target frequency Nf other than the rotation synchronization component, only the forward displacement signal of the rotor that matches the target frequency Nf is extracted by the F cross control filter,
Based on the input target frequency Nb other than the rotation synchronization component, only the backward displacement signal of the rotor that matches the target frequency Nb is extracted by the B cross control filter,
The transformation matrix T _b and the inverse transformation matrix T _b ⁻¹ constituting the B cross control filter are the same as the transformation matrix T _f and the inverse transformation matrix T _f ⁻¹ constituting the F cross control filter. Is replaced with
The forward displacement signal and the backward displacement signal are multiplied by a predetermined gain to be superimposed on the current command signal Iy of the y-axis electromagnet, and the extracted y-axis signal is multiplied by a predetermined gain to be applied to the x-axis electromagnet. A magnetic bearing control method is provided that is superimposed on the current command signal Ix.

  According to the above-described apparatus and method of the present invention, the displacement signal (forward displacement signal and forward displacement signal) of the preset frequencies (the forward target frequency Nf and the backward target frequency Nb) are set by the F cross control filter and the B cross control filter. Since only the rearward displacement signal is extracted and the X axis and the Y axis are coupled by the cross circuit, it is possible to arbitrarily increase the frequency at which attenuation is added. Therefore, it is possible to easily add attenuation to an unbalanced external force having a frequency other than the rotation synchronization component, such as an electromagnetic force of an induction motor.

  In addition, with this configuration, it is possible to increase attenuation in a plurality of frequency bands.

Further, according to the present invention, since the F cross control filter uses a tracking filter, the forward component (Forward component) is stabilized, but the backward component is not destabilized and is not affected.
Further, the transformation matrix T _b and the inverse transformation matrix T _b ⁻¹ constituting the B cross control filter replace the angular frequency ω with −ω in the transformation matrices T _f and T _f ⁻¹ constituting the F cross control filter. Therefore, the B cross control stabilizes only the backward component, and the forward component is not affected.
Therefore, according to the present invention, both the forward component (Forward component) and the rear component (rear component) can be stabilized.

Further, since no PLL (phase locked loop) is used, no rotation pulse signal is required.
Further, since a complicated calculation is not required unlike the PLL, the amount of calculation can be reduced as compared with the N-cross control.
Even if acceleration / deceleration is performed at a high speed, since the PLL (phase locked loop) is not used, tracking is not lost.

It is a block diagram of the magnetic bearing of this invention. It is 1st Embodiment figure of the magnetic bearing control apparatus 20 which implements F cross control. It is 2nd Embodiment figure of the magnetic bearing control apparatus 20 which implements F cross control. It is explanatory drawing of the tracking filter 26 in F cross control. FIG. 6 is a relationship diagram between an angular frequency and a phase of a transfer function Gf (s) in F-cross control. It is an embodiment figure of magnetic bearing control device 30 by the present invention. It is a relationship figure of the angular frequency and phase of transfer function Gb (s) in B cross control.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

FIG. 1 is a configuration diagram of a magnetic bearing of the present invention.
In this figure, a magnetic bearing 10 is a pair of x-axis electromagnets arranged on the xy plane orthogonal to the axis Z of the rotor 11 that rotates at high speed and opposed to the x-axis across the rotor 11. 12x, and a pair of y-axis electromagnets 12y arranged opposite to each other on the y-axis with the rotor 11 interposed therebetween.

In FIG. 1, the magnetic bearing control device 20 receives the x-direction displacement X and the y-direction displacement Y of the rotor 11 and the desired frequency N (referred to as “target frequency”) to which the damping is to be added, for the x-axis. The current command signal Ix of the electromagnet 12x and the current command signal Iy of the y-axis electromagnet 12y are controlled.

FIG. 2 is a first embodiment diagram of the magnetic bearing control device 20 that performs the above-described F-cross control, and FIG. 3 is a second embodiment diagram.
In these drawings, the magnetic bearing control device 20 includes a feedback controller 22, a tracking filter 26, and a cross circuit 28. In FIG. 2, the x-direction displacement X and the y-direction displacement Y of the rotor 11 are directly input to the tracking filter 26. On the other hand, in FIG. 3, outputs from an x-axis controller 23 x and a y-axis controller 23 y described later are input to the tracking filter 26. In other respects, FIG. 2 and FIG. 3 are the same.

2 and 3, the feedback controller 22 includes an x-axis controller 23x and a y-axis controller 23y.
The x-axis controller 23 x performs feedback control of the current command signal Ix of the x-axis electromagnet 12 x based on the x-direction displacement X of the rotor 11. The y-axis controller 23y feedback-controls the current command signal Iy of the y-axis electromagnet 12y based on the y-direction displacement Y of the rotor 11.

  Based on the input target frequency N, the tracking filter 26 extracts only the rotor displacement signal (the rotor x-direction displacement X and the y-direction displacement Y) that matches the target frequency N.

  The cross circuit 28 applies a predetermined gain k to the x-axis signal (x-direction displacement X) extracted by the tracking filter 26 and superimposes it on the current command signal Iy of the y-axis electromagnet 23y, and extracts the extracted y-axis. The signal (y-direction displacement Y) is multiplied by a predetermined gain k by a gain 27x and superimposed on the current command signal Ix of the x-axis electromagnet 23x.

FIG. 4 is an explanatory diagram of the tracking filter 26 in the F-cross control. Hereinafter, this filter is referred to as an “F cross control filter”.
As shown in this figure, the tracking filter 26 (F cross control filter) includes a conversion step 29a for converting from a stationary coordinate system to a rotating coordinate system, a low-pass filter 29b in the rotating coordinate system, and a rotating coordinate system reversed to a stationary coordinate system. It comprises an inverse conversion step 29c for conversion.

Conversion step 29a is the transformation matrix _{T f} showing the x-direction displacement _{X in} the y-direction displacement _{Y in} input from the stationary coordinate system to the number 1 of the formula (1), the x-direction displacement _{X 1} in a rotating coordinate system y into a direction displacement _{Y 1.}
As the low-pass filter 29b, for example, a second-order Chebyshev type low-pass filter having a flat and wide characteristic, for example, having a cutoff frequency of several tens of Hz is used. The signal passing through the filter and x-direction displacement X ₂ and y-direction displacement Y _2.
In the inverse transformation step 29c, the x-direction displacement X ₂ and the y-direction displacement Y ₂ in the rotating coordinate system are converted into the x-direction displacements X _out and y in the stationary coordinate system by the inverse transformation matrix T _f ⁻¹ shown in Equation (2). Reverse conversion to the direction displacement _Yout .

  The transfer function Gf (s) of the F-cross control filter 26 described above is expressed by Equation (3) in Equation 1 when a first-order LPF is used.

  When the stationary coordinate system (x, y) is represented by x + ii and a complex number, the forward (counterclockwise) rotational frequency can be represented as + Ω, and the backward (clockwise) rotational frequency can be represented as −Ω. Equation (3) described above is a transfer function of the tracking filter when a typical first-order low-pass filter is applied, and k is a coefficient related to the output. The frequency response (response of an arbitrary angular frequency ω) is obtained by substituting the angular frequency jω for s in the above equation.

FIG. 5 is a relationship diagram between the angular frequency and the phase of the transfer function Gf (s) in the F-cross control. In this figure, (A) shows forward vibration and (B) shows backward vibration.
As shown in this figure, in the case of the transfer function Gf (s) in the F cross control, when + jΩ is substituted for s, the output becomes jk, but when −jΩ is substituted for s, the output becomes very small. That is, it can be seen that the filter passes through the forward component but does not pass the backward component.
Thus, it can be seen that the F cross control stabilizes only the forward component and the backward component is not affected.

FIG. 6 is an embodiment of the magnetic bearing control device 30 according to the present invention. In this embodiment, as in FIG. 3, the outputs of an x-axis controller 33x and a y-axis controller 33y described later are input to three tracking filters 36A, 36B, and 37.
Note that the present invention is not limited to this example, and it may be configured such that the x-direction displacement X and the y-direction displacement Y of the rotor 11 are directly input to the tracking filters 36A, 36B, 37 as in FIG. Good.

  In FIG. 6, the magnetic bearing control device 30 according to the present invention includes a feedback controller 32, three tracking filters 36A, 36B, and 37, and three cross circuits 38A, 38B, and 38C.

The feedback controller 32 includes an x-axis controller 33x and a y-axis controller 33y. The x-axis controller 33x and the y-axis controller 33y are the same as the x-axis controller 23x and the y-axis controller 23y shown in FIGS.
The outputs X _in and Y _in of the x-axis controller 33x and the y-axis controller 33y are input to the three tracking filters 36A, 36B, and 37, respectively.

The two tracking filters 36A and 36B are F cross control filters similar to the tracking filter 26 of FIGS. 2 and 3, and based on the input target frequencies Nf1 and Nf2, the rotors match the target frequency numbers Nf1 and Nf2. Only the displacement signal (the x-direction displacement X and y-direction displacement Y of the rotor) is extracted.
Note that one or more F cross control filters may be used.
One tracking filter 37 is a tracking filter different from the tracking filter 26 of FIGS. 2 and 3, but based on the similarly input target frequency Nb1, the displacement signal (rotor of the rotor) that matches the target frequency number Nb1. Only the x-direction displacement X and the y-direction displacement Y) are extracted. Details of the tracking filter 37 will be described later.

The cross circuits 38A, 38B, and 38C apply predetermined gains k1, k2, and k3 to the x-axis signals (x-direction displacements _Xout1 , _Xout2 , and _Xout3 ) extracted by the three tracking filters 36A, 36B, and 37, respectively. The y-axis electromagnet 23y is superimposed on the current command signal Iy, and the extracted y-axis signals (y-direction displacements Y _out1 , Y _out2 , Y _out3 ) are _multiplied by predetermined gains k1, k2, k3, and the x-axis electromagnet. The current command signal Ix of 23x is superposed.

Next, the tracking filter 37 described above will be described. Hereinafter, this filter is referred to as a “B cross control filter”, and control using this filter is referred to as “B cross control” (B-cross).
Note that one or more B cross control filters may be used.
The basic configuration of the tracking filter 37 (B cross control filter) is the same as that of the tracking filter 26. As shown in FIG. 4, a conversion step 29a for converting from a stationary coordinate system to a rotating coordinate system, and a low-pass filter in the rotating coordinate system. 29b and an inverse transformation step 29c for inversely transforming the rotating coordinate system into the stationary coordinate system.

Conversion step 29a in B cross control filter 37, the transformation matrix _{T b} showing the x-direction displacement _{X in} the y-direction displacement _{Y in} input from the stationary coordinate system to the number 2 in formula (4), x in a rotating coordinate system into a direction displacement _{X 1} and y-direction displacement _{Y 1.}
As the low-pass filter 29b, for example, a second-order Chebyshev type low-pass filter having a flat and wide characteristic, for example, having a cutoff frequency of several tens of Hz is used. The signal passing through the filter and x-direction displacement X ₂ and y-direction displacement Y _2.
B inverse transformation step 29c in the cross control filter 37, x in the stationary coordinate system by the inverse transformation matrix _T ^{b -1} indicating the x-direction displacement _{X 2} and y-direction displacement _{Y 2} in a rotating coordinate system with the number 2 in the formula (5) It reversely converts to a directional displacement _Xout and a y-directional displacement _Yout .

The transformation matrix T _b and the inverse transformation matrix T _b ⁻¹ of the B cross control filter 37 described above replace ω with −ω in the transformation matrices T _f and T _f ⁻¹ of the F cross control filter 26 (36A, 36B). Is equivalent to
In addition, the transfer function Gb (s) of the B-cross control filter 37 described above is expressed by Expression (6) of Equation 2 when the primary LPF is used.

  When the stationary coordinate system (x, y) is expressed by x + ii and a complex number, the forward (counterclockwise) rotational frequency can be expressed as + Ω, and the backward (clockwise) rotational frequency can be expressed as −Ω. Equation (6) described above is a transfer function of the tracking filter when a typical first-order low-pass filter is applied, and k is a coefficient related to the output. The frequency response (response of an arbitrary angular frequency ω) is obtained by substituting the angular frequency jω for s in the above equation.

FIG. 7 is a relationship diagram between the angular frequency and the phase of the transfer function Gb (s) in the B-cross control. In this figure, (A) shows forward vibration and (B) shows backward vibration.
As shown in this figure, in the case of the transfer function Gb (s) in the B cross control, the output becomes jk when -jΩ is substituted for s, but the output becomes very small when + jΩ is substituted for s. That is, it can be seen that the filter passes the backward component but does not pass the forward component.
Thus, it can be seen that the B cross control stabilizes only the backward component and the forward component is not affected.

  As described above, in the F cross control, since the principle of the tracking filter is used, only the forward component is stabilized, and the backward component is not affected and is not destabilized. By changing the matrix calculation (corresponding to coordinate transformation) from Equations (1), (2) to Equations (3), (4), only the backward component is stabilized, and the forward component is not affected (B Cross control) is possible. In the present invention, this B cross control is used together with the F cross control.

Comparing the features of the B cross control with the F cross control, it is the same as the F cross control except that the object to be stabilized is different. Further, since the principle of the tracking filter is used, the backward component is stabilized, but the forward component is not destabilized and is not affected. Since the F cross control and the B cross control do not interfere with each other due to the principle of the tracking filter, the F cross control and the B cross control can be used together to stabilize the forward component and the backward component.
Therefore, by using a plurality of these, stabilization of the forward component and the backward component of all eigenvalues in the control band can be easily achieved.

The following effects can be obtained by the present invention described above.
(1) There is no increase in high frequency gain.
(2) No rotation pulse signal or oscillator is required.
(3) Some PLL circuits use analog circuits and some use digital operations in the DSP. In the present invention, since a PLL is not necessary in the first place, a separate device using an analog circuit can be dispensed with, or since complicated digital computation is not required, computation in the DSP can be greatly reduced.
(4) Even if acceleration / deceleration is performed at high speed, tracking will not be lost.
(5) Since the cutoff frequency of the low-pass filter in the tracking filter can be set freely, the frequency band to which attenuation is added can be arbitrarily expanded. Therefore, it is possible to easily add attenuation to an unbalanced external force having a frequency other than the rotation synchronization component, such as an electromagnetic force of an induction motor.

  In addition, this invention is not limited to the example mentioned above, Not only combined use of F cross control and B cross control but it can also be used together with another stabilization method.

  In addition, this invention is not limited to embodiment mentioned above, is shown by description of a claim, and also includes all the changes within the meaning and range equivalent to description of a claim.

10 magnetic bearing, 11 rotating body (rotor),
12x x-axis electromagnet, 12y y-axis electromagnet,
20 magnetic bearing control device, 22 feedback controller,
23x x-axis controller, 23y y-axis controller,
24 wideband filter, 25 multi-frequency generator,
26 Tracking filter (F cross control filter),
27x, 27y gain,
28 cross circuit, 29a conversion step,
29b low-pass filter, 29c inverse conversion step,
30 magnetic bearing control device, 32 feedback controller,
33x x-axis controller, 33y y-axis controller,
36A, 36B Tracking filter (F cross control filter),
37 Tracking filter (B cross control filter),
38A, 38B, 38C Cross circuit

Claims (3)

A pair of x-axis electromagnets arranged opposite to the x-axis across the rotor in the xy plane perpendicular to the axis of the rotor rotating at high speed, and opposite the y-axis across the rotor A control device for a magnetic bearing having a pair of y-axis electromagnets arranged as
A feedback controller for holding the rotor in a neutral position based on the displacement of the rotor;
An F cross control filter that extracts only the forward displacement signal of the rotor that matches the target frequency Nf based on the input target frequency Nf other than the rotation synchronization component ;
A B cross control filter that extracts only the backward displacement signal of the rotor that matches the target frequency Nb based on the input target frequency Nb other than the rotation synchronization component ;
The forward displacement signal and the backward displacement signal are multiplied by a predetermined gain to be superimposed on the current command signal Iy of the y-axis electromagnet, and the extracted y-axis signal is multiplied by a predetermined gain to be applied to the x-axis electromagnet. A cross circuit superimposed on the current command signal Ix,
The transformation matrix T _b and the inverse transformation matrix T _b ⁻¹ constituting the B cross control filter are the same as the transformation matrix T _f and the inverse transformation matrix T _f ⁻¹ constituting the F cross control filter. A magnetic bearing control device characterized by being replaced by. The feedback controller includes an x-axis controller that feedback-controls the current command signal Ix of the x-axis electromagnet based on the x-direction displacement of the rotor;
The magnetic bearing control device according to claim 1, further comprising a y-axis controller that feedback-controls a current command signal Iy of the y-axis electromagnet based on a y-direction displacement of the rotor. A pair of x-axis electromagnets arranged opposite to the x-axis across the rotor in the xy plane perpendicular to the axis of the rotor rotating at high speed, and opposite the y-axis across the rotor And a method for controlling a magnetic bearing having a pair of electromagnets for y-axis,
Feedback control to hold the rotor in a neutral position based on the displacement of the rotor,
Based on the input target frequency Nf other than the rotation synchronization component, only the forward displacement signal of the rotor that matches the target frequency Nf is extracted by the F cross control filter,
Based on the input target frequency Nb other than the rotation synchronization component, only the backward displacement signal of the rotor that matches the target frequency Nb is extracted by the B cross control filter,
The transformation matrix T _b and the inverse transformation matrix T _b ⁻¹ constituting the B cross control filter are the same as the transformation matrix T _f and the inverse transformation matrix T _f ⁻¹ constituting the F cross control filter. Is replaced with
The forward displacement signal and the backward displacement signal are multiplied by a predetermined gain to be superimposed on the current command signal Iy of the y-axis electromagnet, and the extracted y-axis signal is multiplied by a predetermined gain to be applied to the x-axis electromagnet. A magnetic bearing control method characterized by superimposing on a current command signal Ix.

Images