JPH0112970B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of controlling magnetic attraction force in an opposed control type magnetic bearing device. [Prior art and its problems] An opposed control type magnetic bearing device consists of two electromagnets 2, 3, and 4 placed oppositely to sandwich a rotating object 1 or a controlled object, as illustrated in FIG. 5, 6 and 7, 8 and 9, 10 and 11 is a device that suspends the rotating object 1 or the controlled object and supports it in the air by the magnetic attraction force of 5, 6 and 7, 8 and 9, 10 and 11, and it has a long life because it does not cause wear. Although it has excellent features such as not requiring lubricating oil, it has the problem that stable aerial support is difficult. Note that the facing type is used for the hanging type using a single magnet. 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 suspended-type controlled magnetic bearings, and even in the suspended type, stable aerial support performance has not been achieved with conventional technology. Naturally, good control performance was not obtained even with the opposed type. To facilitate understanding, a conventional example will be explained with reference to FIG. 2. The figure shows the controlled object 21 (rotating or not,
If rotating, use axial support type (thrust type)
This conceptually shows how electromagnets 22 and 23 are provided to sandwich a magnet (regardless of whether it is a radial support type or a radial support type (or radial type)) and are supported in the air by their magnetic attraction force. This control system is controlled so that the detected gap x ₁ detected by the gap detector 24 matches the target gap x ₀ of the control system, and the gap deviation Δx is
Currents _I 1 and I 2 are input to the current exchange units 26 and 27 through the PID controller 25 and are to be passed to the electromagnets 22 and ₂₃ .
It is configured to be converted to In FIG. 2, a current converter 27 and an electromagnet 23
If the electromagnet 22 is removed and the electromagnet 22 is placed vertically above the controlled body 21, it becomes a hanging type, so it can be seen that the conventional facing type is simply a combination of two hanging types. By the way, the force with which an electromagnet attracts an object is as follows (1)
It is well known that it is expressed by the following formula. F≒B ² A/2μ ₀ ≒μ ₀ A/8 [NI/x] ² ≡K _F [I/x] ²
...(1) However, F: Electromagnetic attractive force B: Magnetic flux density A: Magnetic pole area μ ₀ : Vacuum permeability N: Number of turns I: Current x: Gap (distance between electromagnet and object) K _F = μ ₀ AN ² / 8. Figure 3 also represents the part of equation (1) above as a block diagram. The block 28 is a transfer function, where the mass of the controlled body 21 is m, the input is F, and the output is Δx. Blocks 29 and 30 are multipliers (in this case, they are multipliers because they are multiplied by the same input). ), block 3
x ₁ and x ₂ of 1 and 32 are x ₀ +Δx and x ₀ −Δx, respectively
The dotted arrow indicates that it is determined by . That is, the output Fs of the PID controller 25 (which serves as a force command) and the electromagnetic attraction forces F ₁ and F ₂ have a nonlinear relationship, respectively. It is also a well-known fact that this nonlinear characteristic is a major cause of unstable control. [Means for Solving the Problems] The present invention was made for the purpose of solving the above-mentioned conventional problems, and the force acting on the controlled body, which is a feature of the opposed magnetic bearing device, is 2. This method cleverly utilizes the fact that the electromagnetic attractive force of each electromagnet is the sum of the electromagnetic attraction forces of the individual electromagnets to eliminate nonlinear characteristics. That is, the present invention takes the gap deviation as input.
In an opposed-type controlled magnetic bearing device equipped with a PID controller, the current given to each electromagnet is determined by the gap between each electromagnet and the controlled object.
The value is multiplied by the respective magnetic flux commands Bs ₁ and Bs ₂ , and the above magnetic flux commands are calculated using the following formula: -100%≦Fs ^* ≦-a%, _Bs1 ^* =0, _Bs2 ^* =10√− ^* When % -a%≦Fs ^* ≦+a% When a%≦Fs ^* ≦100%, Bs ₁ ^* = 10√ ^* , Bs ₂ ^* = 0 However, Fs ^* is the magnitude of the output of the PID controller expressed in %, and a is greater than 0 and less than 100. It can be obtained using a small arbitrary constant. [Example] A specific example of the present invention will be described below with reference to FIG. The differences between the conventional system shown in FIG. 2 and the embodiment of the present invention shown in FIG.
5 and 36, and input the gap deviation.
The output Fs (force command) of the PID controller 25 is input to the function generators 33 and 34, respectively, and the outputs Bs ₁ ,
The signals Is ₁ and Is 2 obtained by multiplying Bs ₂ (magnet command) by the gap detection values x ₁ and x ₂ , respectively, are sent to the current converters 26 and ₂ .
7, respectively.

[Table] The variables Fs ^* , Bs ₁ ^* , Bs ₂ ^* in Table 1 and the variables F ₁ ^* , F ₂ ^* , F ^* in Figure 5 are the standard values of the variables in Figure 4, Fso, Bs ₁₀ , Bs ₂₀ , F ₁₀ , F ₂₀ ,
F ₀ and these are expressed as 100%. Therefore, Fs ^* = a ₁ Fs…Fs = Fs ₀ and Fs ^* = 100% Bs ₁ ^* = a ₂ Bs…Bs ₁ = Bs ₁₀ and Bs ₁ ^* = 100% Bs ₂ ^* = a ₂ Bs…Bs ₂ = Bs ₂ ^* = 100% at Bs ₂₀ ...... F ₁ ^* = a ₃ F ₁ ... F ₁ = F F 1 ^* = 100% at F ₁₀ F ₂ ^* = a _{3 F 2} ... F ₂ = F ₂ at F ₂₀ ^* = 100% F ^* = a ₃ F...F = F ₀ and F ^* = 100% However, a ₁ to a ₃ are constants. Table 2 shows an example in which the value of a in Table 1 was set to 25.

[Table] An example in which the value of a is 25 will be described below. Figure 5a is a graph of the relationships in Table 2. With the above configuration, force command
It will be described next that Fs and the force F (the resultant force of F ₁ and F ₂ ) acting on the controlled body 21 have a linear relationship. Here, ignoring the primary delay factor of the current converters 26 and 27, the gains of the current converters 26 and 27 are
Assuming K ₁ , from Fig. 4, I ₁ = Kix ₁ Bs ₁ ...(2) I ₂ = Kix ₂ Bs ₂ ...(3). Substituting equations (2) and (3) into equation (1), the electromagnetic attractive force F ₁ ,
To find F ₂ , F ₁ = K _F [I ₁ /x ₁ ] ² = K _F [Kix ₁ Bs ₁ / x ₁ ] ² = K _F Ki ² Bs ₁ ² ......(4) F ₂ = K _F [I ₂ /x ₂ ] ² = K _F [Kix ₂ Bs ₂ / x ₂ ] = K _F Ki ² Bs ₂ ² ...(5). From equations (4) and (5), Table 2, and the above relationships, Fs ^* , F ₁ ^* ,
The relationship between F ₂ ^* is shown in Table 3.

[Table] Figure 5b is a graph of the relationships in Table 3. Finally, the force F that moves the controlled object is the resultant force of F ₁ and F ₂ , so the formula F = F ₁ - _{F 2} , or F ^* = F ₁ ^*
Table 4 shows the relationship between Fs ^* and F ^* based on −F ₂ ^* .

[Table] In other words, over the entire range of Fs ^* = -100% to +100%, F ^* = Fs ^* , that is, F∝Fs, and it can be seen that there is a linear relationship as shown in Figure 5c. The case where a is set to 25 has been explained above, but it goes without saying that the same linear relationship holds for other values as well. Although the proof is omitted, if you increase the value of a, the response will improve, but the copper loss and eddy current loss will increase, and if you decrease the value of a, the opposite will occur. It is desirable to set the As described above, according to the present invention, it is possible to establish a linear relationship between the force command and the force acting on the controlled object over the entire range, so it is possible to provide a method of controlling a magnetic bearing device with extremely high stability.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a magnetic bearing device;
Fig. 2 is a block diagram of a conventional control method, Fig. 3 is a detailed block diagram of the conventional example, Fig. 4 is a block diagram of a specific embodiment of the present invention, and Figs. 5a to 5c illustrate the principle of the present invention. FIG. 21... Controlled object, 22, 23... Electromagnet, 2
4...Gap detector, 25...PID
Controller, 26, 27...Current converter, 33, 34
...Function generator, 35, 36... Multiplier.

Claims (1)

[Claims] 1. In an opposed control type magnetic bearing device equipped with a PID controller that receives gap deviation as input, the command current given to each electromagnet is determined by the gap (gap) between each electromagnet and the controlled object. The value is multiplied by the respective magnetic flux commands Bs ₁ and Bs ₂ , and the above magnetic flux commands are calculated using the following formula: -100%≦Fs ^* ≦−a%, _Bs1 ^* =0, _Bs2 ^* =10√− ^* When % -a%≦Fs ^* ≦+a% When a%≦Fs ^* ≦100%, Bs ₁ ^* = 10√ ^* , Bs ₂ ^* = 0 However, Fs ^* is the magnitude of the output of the PID controller expressed in %, and a is greater than 0 and less than 100. A method of controlling a magnetic bearing device, characterized in that the control method is obtained using a small arbitrary constant.