JPH0343767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling magnetic attraction force in a controlled magnetic bearing device or the like.

A controlled magnetic bearing device refers to an uncontrolled magnetic bearing device that uses permanent magnets. For example, as shown in FIG. Although it has excellent features such as a long service life without wear and no need for lubricating oil, it has the problem that stable support in the air is difficult.

Conventionally, in order to control the magnetic attraction force and maintain a stable air support state, among the four state quantities of displacement, velocity (differential of displacement), acceleration, and current,
Methods of feeding back one or more signals are known, but none of them provide good control performance due to nonlinear characteristics.

By the way, the method of controlling the magnetic attraction force in a controlled magnetic bearing device and the method of controlling the attraction levitation force of an attraction type magnetic levitation train, etc. are theoretically exactly the same, and a person skilled in the art can easily apply it to both. Since it is possible, the following explanation will be made without distinction.

Now, as pointed out in "About a new control method for magnetic bearings" (Toru Watanabe et al., Transactions of the Japan Society of Mechanical Engineers, 1972-4), the method of feedbacking the displacement depends on the time constant and nonlinear characteristics of the electromagnet. As a result, stable control is impossible.

In addition, the method of performing linear feedback by combining some of the four state quantities described above is based on the ``magnetic attraction suspension string suitable for this amplitude operation'' (Fumio Matsumura et al.
As pointed out in the Journal of the Institute of Electrical Engineers of Japan, 54-B4), there is a risk of loss of control if the operating point changes significantly.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a magnetic attraction force control method that allows stable aerial support.

First, the problems of the conventional example will be explained in detail using the drawings.

In FIG. 2, the current I flowing through the electromagnet 5 is changed to the current converter 7 based on the output of the PID controller ₆ so that the detected displacement x of the controlled object 3 detected by the displacement detector 4 coincides with the target displacement x 0. This conceptually shows a system for controlling the electromagnet 5 via the electromagnet 5.

By the way, it is well known that the electromagnetic attractive force F is expressed by the following equation (1).

F≒μ ₀ A/8 (NI/x) ² = K _F (I/x) ² ………(1
) However, μ ₀ : Vacuum permeability A : Pole area N : Number of turns I : Current x : Displacement K _F = μ ₀ AN ² /8 This relational expression is expressed in more detail in Figure 2 as shown in Figure 3. It is a diagram.

Block 7 of the current converter in FIG.
1, 72, 73.

Block 8 represents a transfer function in which the mass of the controlled object is m, the force F acting on the controlled object is input, and the displacement deviation is output.

Block 9 is a multiplier, and in this case it multiplies the same input, so it becomes a squarer.

The dotted arrow input to block 10 indicates that x in block 10 is determined by Δx+x ₀ .

As you can see from the block diagram in Figure 3, the current I and the electromagnetic attraction force F, and the displacement x and the electromagnetic attraction force F are:
Each has a nonlinear relationship. This means that
It is well known that this is the biggest cause of control instability in the past.

Therefore, the present invention devises a feedback signal in order to reduce the influence of the above-mentioned nonlinear characteristics.

An embodiment of the present invention will be described using FIG. 4.

The present invention converts the input signal to the current converter 7 into a PID
Current feedback signal from output Is of controller 6
The result obtained by dividing I _f1 by the detected displacement x using the divider 11 is
This is a method in which the value I _f2 squared by the multiplier 12 is subtracted.

By using such a method, the signal corresponding to the unit system of the force F, which is the same as in equation (1) above, that is, the square of (current/displacement), is directly fed back, so it is not necessary to use the actual process. Since the response is faster than the loop of the displacement signal x that is fed back through block 8, it is possible to cancel out the nonlinear characteristics between I and F corresponding to equation (1) above.

As described above, according to the present invention, the adverse effects of the nonlinear characteristics of the electromagnet can be removed, so stable control can be realized.

The present invention can be widely applied to fields where magnetic attraction is controlled, such as the hanging type magnetic bearing device illustrated in FIG. 1, opposed type magnetic bearings, and magnetically levitated trains.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a suspended magnetic bearing device, Figure 2 is a block diagram of a conventional control circuit, and Figure 3 is a
A detailed block diagram thereof, FIG. 4, is a block diagram of an embodiment of the present invention. 3... Controlled object, 4... Displacement detector, 5... Electromagnet, 6... PID controller, 7... Current converter, 7
1, 73... Amplification element, 72... Primary delay element, 9, 12... Multiplier, 11... Divider.

Claims (1)

[Claims] 1 In a controlled magnetic attraction device that magnetically attracts and supports a controlled object in the air by controlling the current flowing through the electromagnet, the value obtained by dividing the command current given to the electromagnet from the control current command by the current feedback signal by the detected displacement x A method for controlling magnetic attraction force, characterized by subtracting the squared value of .