JPH1193953A - Control device of magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the gain of a PID regulator by using a proper control constant according to the rotating speed of a rotor even if the natural frequency of bending vibration is changed according to the change of the rotating speed. SOLUTION: The voltage control of an electromagnet 1 is performed on the basis of a power instruction signal 6 obtained by subtracting the displacement signal 7 between an electromagnet 1 and a rotor 2 detected by a displacement sensor 3 from a position instruction value 10 by a subtracter 21, and passing the resulting deviation signal 11 through a notch filter built in a control arithmetic circuit 14, thereby canceling the resonance peak of bending vibration of the rotor 2, and thereafter inputting the signal to a PID regulator to perform a 'proportional, integrating, and differential' control. In a control device for magnetic bearing, the rotating speed of the rotor 2 is detected by a rotating speed detector 12 and inputted to a control constant designating circuit 13, and a proper control constant 15 corresponding to the rotating speed is selected within the control constant designating circuit 13, and outputted to a control arithmetic circuit 14 side. Since the safe tolerance of a magnetic bearing is thus increased, the gain of the PID regulator can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device applied to a magnetic bearing of a rotating machine such as a turbine, and more particularly to a deviation signal between a displacement signal and a position command value between an electromagnet for a magnetic bearing and a rotor and a subtractor. The present invention relates to a magnetic bearing control device that controls a magnetic force of the electromagnet based on a force command signal obtained by performing a “proportional / integral / differential” control by inputting a signal through a notch filter to a PID controller.

[0002]

2. Description of the Related Art Conventionally, oil film type contact type bearings have been used as bearings for rotating machines such as turbines. The contact type bearing has an advantage of being inexpensive, but has a problem in durability due to wear of the contact surface. On the other hand, magnetic bearings can hold the rotor in a non-contact manner by using magnetic force, so they have the outstanding feature that wear, which was an essential problem of contact type bearings, does not occur and durability can be greatly improved. is there.

As shown in FIG. 2, the magnetic bearing uses the attraction force of the electromagnet 1 to support the magnetic rotor 2 in a non-contact manner. As is well known, since a magnetic force is generated only in the direction of attraction to the magnetic material, another electromagnet 1 is provided at a position opposite to the rotor 2 so as to generate a force in both directions by using the mutual attraction force. I have to. Since the attraction force received by the rotor 2 from the electromagnet 1 is inversely proportional to the square of the distance, the closer the rotor 2 is to the electromagnet 1, the more the rotor 2 is attracted, and eventually the rotor 2 sticks to the electromagnet 1. As described above, since the magnetic bearing has no function of holding the rotor at an appropriate position, the magnetic force must be actively adjusted to position the rotor.

Referring to FIG. 2, in a conventional magnetic bearing,
How the positioning of the rotor 2 has been performed will be described. A displacement sensor 3 is provided in the vicinity of the electromagnet 1 and transmits a displacement signal 7 of the rotor 2. A controller 4 including a PID controller 8 and a notch filter 9 transmits the displacement signal 7 of the rotor 2 to the electromagnet 1 from the displacement signal 7 of the rotor 2. A force command signal 6 is transmitted. That is, the displacement signal 7 between the electromagnet 1 and the rotor 2 detected by the displacement sensor 3 and the position command value 10 are subtracted by the subtractor 21,
After passing the deviation signal 11 through the notch filter 9 to cancel the resonance peak of the bending vibration of the rotor 2, the PID
A force command signal 6 obtained by inputting to the controller 8 and performing “proportional / integral / differential” control is sent to a drive circuit on the electromagnet 1 side to control the voltage of the electromagnets 1 and 1. Although FIG. 2 shows only the control method for the electromagnet 1 on the right end of the rotor 2, the same control is performed on the other electromagnets 1 on the left end.

The basic part of the control of the magnetic bearing is performed by the PID controller 8 in the controller 4. The notch filter 9 in front of the PID controller 8 prevents the bending vibration of the rotor 2 from being excited by the positioning of the rotor 2 performed by the PID controller 8. That is, the gain characteristic from the generated force u of the magnetic bearing to the displacement y of the rotor is shown in FIG.
And the natural frequency ω _b of the bending vibration of the rotor
Has a resonance peak. Due to this resonance peak, the positioning control of the rotor 2 may become unstable. Therefore, as shown in FIG. 4, by inserting a notch filter 9 having a function of locally lowering the gain near the frequency where bending vibration occurs, the resonance peak of the bending vibration of the rotor 2 is canceled to stabilize. I have.

[0006]

However, since the rotor is subject to the gyro effect, the natural frequency of vibration ω _b
Vary according to the rotation speed of the rotor. On the other hand, since the natural frequency of the notch filter is fixed, if the rotation speed of the rotor changes, the resonance peak of bending vibration cannot be canceled as intended, and there is a problem that resonance of bending vibration occurs. Therefore, in the conventional device, even if the natural frequency of the bending vibration changes due to a change in the rotational speed, the P P is reduced to such an extent that the resonance of the bending vibration does not occur.
While measures have been taken to reduce the gain of the ID controller, when the gain of the PID controller is small, there has been a problem that the rotor is easily displaced by the influence of the fluid flowing through the turbine and the safety is impaired.

[0007] In view of the drawbacks of the prior art, the present invention provides
Even if the natural frequency of bending vibration changes due to a change in the rotation speed, an appropriate control constant can be used according to the number of rotations of the rotor, thereby increasing the gain of the PID controller. It is an object of the present invention to provide a magnetic bearing control device that can be used.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is directed to a control for outputting an appropriate control constant according to the rotation speed of a rotor 2 supported by a magnetic bearing. A gist comprising a constant designating circuit 13 and a control operation circuit 14 for performing a control operation based on the control constant vector 15 output from the control constant designating circuit 13,
In particular, the invention according to claim 1 provides a force obtained by inputting a displacement signal between an electromagnet for a magnetic bearing and a rotor and a position command value to a PID controller after passing a deviation signal from a subtractor through a notch filter. A control device for a magnetic bearing that controls the magnetic force of the electromagnet based on a command signal, wherein a control constant designating circuit that outputs a control constant corresponding to the rotation speed of the rotor,
A notch filter for obtaining a filter value to which an error signal corresponding to a change in rotation speed is added based on the control constant output from the control constant specifying circuit; a control constant and the filter value output from the control constant specifying circuit And a PID controller that performs “proportional / integral / differential” control by increasing the proportional gain based on the PID controller.

According to the present invention, it is possible to obtain a filter value of a notch filter in which an error signal corresponding to a change in rotation speed is added using an appropriate control constant according to the rotation speed of the rotor. by when natural frequency omega _b of the rotor vibration is varied in accordance with the rotational speed of the rotor is also locally can lower the gain in the vicinity of the frequency of occurrence of this variation flexural vibration, as a result, change due to the rotational speed This effectively cancels the resonance peak of the bending vibration of the rotor, thereby stabilizing it. As a result, the proportional gain of the PID controller can be increased, and the displacement of the rotor can be kept small. Moreover, since the proportional gain can be appropriately increased based on the control constant output from the control constant designating circuit and the filter value, the displacement of the rotor can be increased while further increasing the safety margin of the magnetic bearing. Can be kept small.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However, unless otherwise specified, the types of components, their relative arrangements, and mathematical expressions described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.

FIG. 1 and FIG. 5 show a control device for a magnetic bearing according to an embodiment of the present invention, in which a displacement signal 7 between an electromagnet 1 and a rotor 2 detected by a displacement sensor 3 and a position command value 10 are shown.
Is subtracted by a subtractor 21, and the deviation signal 11 is passed through a notch filter 9 built in the control operation circuit 14 to cancel the resonance peak of the bending vibration of the rotor 2.
The basic configuration of controlling the voltage of the electromagnet 1 based on the force command signal 6 obtained by performing the “proportional / integral / differential” control by inputting to the ID controller 8 is the same as that of the magnetic bearing according to the present invention. In the control device, the rotation speed ω of the rotor 2 is detected by the rotation speed detector 12 and the control constant designating circuit 13
And selects an appropriate control constant 15 corresponding to the rotational speed ω in the control constant designating circuit 13 and
Output to the side.

The control constant designating circuit 13 has control constants such as a PID controller 8 and a notch filter 9 incorporated in a predetermined control operation circuit 14, ie, a proportional gain, an integration time, and a differentiation time for the PID controller 8. Are K _P (ω), T _I (ω), and T _D (ω) as functions of the rotational speed ω, respectively.
Is stored as follows. For the notch filter 9, the natural frequency ω _n and the attenuation rate ξ of the notch filter 9,
The gain α is stored as a function of the rotation speed, such as ω _n (ω), ξ (ω), α (ω), and the rotation speed of the rotor 2 is set at predetermined time intervals set by a timer (not shown). When ω is input, an appropriate control constant 15 is output.

Each element of the control constant vector 15 can be expressed as a function of the rotational speed ω, for example, as follows. (Control constant vector of PID controller 8) [k _P , T _I , T _D ,] ← [K _P (ω), T _I (ω), T _D (ω)] 1A) (Control of notch filter 9) Constant vector) [ω _n , ξ _n , α] ← [ω _n (ω), ξ _n (ω), α (ω)] ... 1B)

In the control operation circuit 14, as shown in FIG. 5, based on the control constant vector 15 obtained from the control constant designating circuit 13 and obtained from the expression 1B), the operation unit 9a calculates the following "Equation 1". a predetermined calculation based on performed, to generate a filter value u _n of the notch filter 9. That is, in the calculator 9a of the notch filter 9, for example, the rotational speed ω is determined based on the control constant [ω _n , ， _n , α] obtained from the control constant designating circuit 13 based on the following differential equation.
Generating a filter value u _n corresponding to the notch filter 9
In performing the filter control based on the filter value u _n.

[0015]

(Equation 1)

In the expression 1, 8 is the error signal 1
1, u _n is the output signal of the notch filter.

In the control operation circuit 14, the operation unit 8a of the PID controller 8 calculates the following expression 2 based on the control constant vector 15 obtained from the expression 1A) obtained from the control constant designating circuit 13. The PID controller 8 outputs a force command signal u. That PID controller in eight computing units 8a, for example, the following resulting control constants from the control constant specifying circuit 13 based on the differential equation _{[k P, T I, T} D,] and notch filter filter values u _n , A force command signal u corresponding to the rotation speed ω is generated, and the force command signal u is sent to a drive circuit (not shown) on the electromagnet 1 side to control the voltages of the electromagnets 1 and 1.

[0018]

(Equation 2)

[0019] Incidentally, in the "number 2", x is a PID controller, indicates the internal variable notch filter, x _n is the deviation signal obtained by filtering in response to the rotation speed omega, x _I is x
integral value of _n, x _D is the differential value of x _n.

[0020]

As described above, according to the present invention, it is possible to use an appropriate control constant according to the number of revolutions of the rotor, so that the safety margin of the magnetic bearing is increased.
The gain of the PID controller can be increased, and the displacement of the rotor can be kept small.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a control device for a magnetic bearing according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional magnetic bearing control device.

FIG. 3 is a gain diagram of a vibration characteristic of a rotor.

FIG. 4 is a gain diagram of a notch filter.

FIG. 5 is a main part block diagram showing an internal configuration of the control operation circuit of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnet 2 Rotor 3 Displacement sensor 4 Controller 5 Magnetic bearing control device 6 Force command signal 7 Displacement signal 8 PID controller 9 Notch filter 10 Position command value 11 Error signal 12 Speed detector 13 Control constant designating circuit 14 Control arithmetic circuit 15 Control constants

Claims (1)

[Claims] 1. A displacement signal between an electromagnet for a magnetic bearing and a rotor, and a position command value, based on a force command signal obtained by passing a deviation signal from a subtracter through a notch filter and then inputting the signal to a PID controller. A control device for controlling the magnetic force of the electromagnet, comprising: a control constant designating circuit for outputting a control constant corresponding to the rotational speed of the rotor; and a control constant designating circuit output from the control constant designating circuit. A notch filter for obtaining a filter value to which an error signal corresponding to the change is added, a PID controller for performing a predetermined control by increasing a proportional gain based on the control constant output from the control constant designating circuit and the filter value A control device for a magnetic bearing, comprising: