JPS59113315A - Control method of magnetic bearing - Google Patents

Abstract

PURPOSE:To improve stability of control by performing electrification control for electromagnets, arranged in opposition to each other, on the basis of value of a gap and a bias current command or the like, in an opposition type control form magnetic bearing. CONSTITUTION:The captioned device makes two electromagnets 2-11 (22, 23). arranged in opposition to each other so as to hold a rotary body 1 (controlled body 21) between them, to float said body by means of their magnetic attractive force and support it, that is to say, each of electromagnet 22, 23 is controlled, to float and support the controlled body 21, through PID adjusting meter 25, electric current conversion parts 26, 27 according to deviation between a target gap x0 and a detected gap x1 from a gap detector 24. At this time, the value obtained, through multiplying by gap x1 the sum of output I0 of PID adjusting meter 25 and a bias current command Ib from a commander 35 by means of multipliers 33, 34, is inputted to the current converter 26, while the value obtained, through multiplying by gap X2, the balance after subtracting command Ib from command I0 is inputted to the current converter 27.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling magnetic attraction force in an opposed control type magnetic bearing device.

The opposed control type magnetic bearing system is composed of two electromagnets 2 and 3, 4 and 5, 6 and 7, which are arranged facing each other so as to sandwich a rotating object 1 or a controlled object as illustrated in FIG. 8 and 9,
This is a device that suspends the rotating object 1 or the controlled object entirely by the magnetic attraction forces of 10 and 11 and supports it in the air.It has the advantages of long life as it does not cause wear and does not require lubricating oil. However, there is a problem in that stable aerial support is difficult.

Note that the facing type is in contrast to the hanging type using magnets. Also, the term "controlled type" is used to distinguish between non-controlled types using permanent magnets.

Conventional opposed-type controlled magnetic bearing devices are simply a combination of two lower-type controlled magnetic bearings, and stable aerial support performance cannot be obtained with conventional technology even in the lower-angle type. Therefore, in order to facilitate the 1 degree process W4, in which good control performance was naturally not obtained even with the opposing type, a conventional example will be described with reference to FIG. 2.

The figure shows an electromagnet 22. 23'E is installed and is supported in the air by its magnetic attraction force.

+ 2 At this control system target gap XQ, a gap detector 1tI
Detection gap X detected in 24! The gap deviation ΔX is inputted to the current converter 26.27 through the PID controller 25, and the current 11. It is configured to be converted into I, .

In FIG. 2, if the current converter 27 and electromagnet 23 are removed and the % electromagnet 22 is placed vertically above the controlled object 21, a hanging type will be obtained. It turns out that it's just a combination of two things.

By the way, it is well known that the force with which an electromagnet attracts an object is expressed by the following equation (1).

However, F: Electromagnetic attractive force B: Magnetic flux density A: Magnetic pole area 116: Vacuum permeability N: Number of turns l: Current X: Gap (distance between electromagnet and object) The part of equation (1) above is also expressed in a block diagram. The result is shown in Figure 3.

Block 28 is a transfer function in which the mass of the controlled body 21 is m and the input is the F1 output total ΔX, and blocks 29 and 30 are multipliers (in the case of 2:, since the same human power is multiplied, it is a squarer). ), XI and X2 of blocks 31 and 32 are respectively indicated by dotted line arrows with the value determined by X6+ΔX and X6−ΔX.

That is, the current and the electromagnetic attraction force, and the gap and the electromagnetic attraction force each have a nonlinear relationship. Is this nonlinear characteristic controlled? It is also a well-known fact that this is a major cause of instability.

The present invention has been made with the object of solving the above-mentioned conventional problems, and is a feature of an opposed magnetic bearing device. The nonlinear characteristic is removed by cleverly utilizing the fact that the force acting on the controlled object is the sum of the four magnetic attraction forces of the two electromagnets.

A specific example will be described below with reference to FIG.

In the conventional device, the control current command 1. which is the output of the PID controller 25. was input as is to the current converter 26, 27, but in the present invention, multipliers 33 and 34 and a bias current command unit 35 are provided, and the bias current command Ib is calculated by 71II to the control current command 0. The value multiplied by the gap x1 is input to the current converter 26.

Control current command 1. The value obtained by subtracting the bias current command Ib'fr from the value multiplied by the gap x2.
It is configured so that it can be input.

With such a configuration, the control current command I. and the force F acting on the controlled body 21 have a linear relationship. Now, to simply yc the transfer function G(S) of the current converter 26.27, if G(S) = 1, l1 = (Io + I b)
Xxs---(2112=(I.-Ib)
x X2 ++, +, + 8. + (3).

The (force F) acting on the controlled body 21 is obtained from equation (1), and this (
Substituting equation 12) and (3> into equation 4) yields =KF((
IO+Ib)2-(Io-Ib)")-4KpIb
Io -''.-(5) That is, since both KF and Ib are foot-loaded, the force F acting on the controlled body 21 and the control current command IO have a linear relationship VC.

The block 36 is a multiplier, and the xzk formula 2 xo −
Since it is intended to be guided by xl, it is unnecessary if the gap detector for x2 is provided independently and inputted to block 24 for X2.

As described above, with the present invention, the control current command and the force acting on the controlled object can be linearized, so the control stability can be greatly improved, resulting in an extremely high-performance magnetic bearing device. Can be provided.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of a magnetic bearing device, Figure 2 is a block diagram of a conventional control method, Figure 3 is a detailed block diagram of the conventional example, and Figure 4 is a specific example of the present invention. This is the block diagram. 21...ffi! I body, 22.23...electromagnet, 24...gap detector, 25...P
ID controller, 26, 21...Current converter, 29.3
0,33° 34... Multiplier, 35... Bias current command unit, 36... Multiplier.

Claims (1)

[Claims] In an opposed control type magnetic bearing device, the command current given to one electromagnet is the gap value between that electromagnet and the controlled object, plus the control current command and the noisy current command. and the command current given to the other electromagnet is given by multiplying the gap value between the electromagnet and the controlled object by the value obtained by subtracting the bias current command from the control current command. Control method.