JP2519537Y2 - Magnetic bearing control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The present invention is applied to a space-related device, a high-speed rotating device, and the like, and relates to a magnetic bearing control circuit for magnetically supporting a rotating body in a non-contact manner. .

"Prior Art" Magnetic bearings use a magnetic attraction force and a repulsive force to rotatably support a rotating body without contact, and are characterized by low friction, low vibration, low noise, etc. Since it can be rotated at high speed and used in vacuum, it is used for reaction wheels for attitude control of artificial satellites, vacuum pumps for discharging the gas in the vacuum chamber, etc.

FIG. 3 is a perspective view showing the structure of a part of this type of magnetic bearing. In this figure, 1 is a rotatable shaft,
Reference numeral 2 is a cylindrical rotor fixed to the outer periphery of one end of the shaft 1, and is composed of a soft iron laminated plate. M ₁ ~
M ₄ are four electromagnets that are opposed to the outer peripheral surface of the rotor 2 with a gap therebetween, and the electromagnets M ₁ arranged in the x-axis direction shown in FIG.
M ₂ is paired with each other, and electromagnets M ₃ and M ₄ arranged in the y-axis direction orthogonal to the x-axis are paired with each other and firmly fixed to the inner peripheral portion of the stator. S _{1 to} S ₄ are opposed to the outer peripheral surface of the shaft 1 with a gap therebetween, and a displacement sensor (for example, an eddy current type non-contact sensor) that detects the radial displacement (radial direction) of the shaft 1 and the rotor 2 accompanying this A contact displacement sensor), which is fixed to the inner peripheral surface of the stator in the same positional relationship as the electromagnets M _{1 to} M ₄ .

Then, the coils C _{1 of the} electromagnets M ₁ and M ₂ paired with each other are
An exciting current is supplied to each C ₂ to attract the rotor 2 in the positive or negative direction of the x-axis, and each coil of the electromagnets M ₃ and M ₄
An exciting current is supplied to each of C ₃ and C ₄ , and the rotor 2 is attracted in the positive or negative direction of the y-axis, so that the rotor 2 is held at the equilibrium position and floated in a non-contact manner.
Further, although not shown, a radial magnetic bearing similar to that shown in FIG. 3 is provided at the other end of the shaft 1 and a thrust magnetic bearing is provided at the center of the shaft 1 for a total of 5 shafts. The magnetic attraction force of is controlled so that the entire shaft 1 is rotatably supported in a non-contact manner.

Now, with reference to FIG. 4, a description will be given of the above-mentioned control circuit of the magnetic bearing, particularly the configuration of the control circuit for controlling the magnetic attraction force in the x-axis direction. In this figure, 5 is based on the difference between the output signal of the displacement sensor S ₁ and S _2, the rotor 2
Is a displacement detection circuit that detects the displacement amount from the equilibrium position in the x-axis direction of the force command signal.
Output as Sf. This force command signal Sf corresponds to the force F required to return the rotor 2 to the equilibrium position and is supplied to the current command signal generator 6. The current command signal generator 6 determines the values of the exciting currents to be supplied to the coils C ₁ and C ₂ of the electromagnets M ₁ and M ₂ based on the force command signal Sf and responds to these values. Outputs current command signals Sia and Sib. These current command signals Sia and Sib are supplied to the current control circuits 7a and 7b after adding the bias current values respectively. The current control circuits 7a and 7b control the exciting currents Ia and Ib supplied to the coils C ₁ and C ₂ of the electromagnets M ₁ and M ₂ , respectively, according to the current command signal to which the bias current value is added. Yes, the signals detected by the current detectors 8a and 8b are fed back to
Compensation for Ia and Ib is made.

In such a configuration, the rotor 2 moves from the equilibrium position to x
It is displaced in the axial direction, and as shown in FIG.
When the force command signal Sf changes in accordance with the amount of displacement from the equilibrium position of, the exciting currents Ia and Ib supplied to the coils C ₁ and C ₂ from the current control circuits 7a and 7b, respectively, are changed as shown in FIG. As shown in (c), the force F as shown in FIG. 5 (d) acts on the rotor 2 as a result, and the rotor 2 is pulled back to the equilibrium position.

Here, the reason why the bias current is always supplied to the coils C ₁ and C ₂ is as follows. That is, assuming that the bias current is 0 and the rotor 2 is gravity,
It is assumed that the displacement is always in the positive direction of the x axis. Then, the maximum exciting current Ia from the current control circuit 7a is continuously supplied to the coil C ₁ of the _one electromagnet M ₁ and the other electromagnet M ₂
The exciting current Ib is not supplied to the coil C _{2 of} at all, and as a result, the amplifier in the current control circuit 7a reaches a saturation state and does not operate following the polarity reversal of the force command signal Sf. However, the responsiveness of the entire control system deteriorates. In order to improve the response delay when the polarity of the force command signal Sf is inverted, it is necessary to constantly supply the bias current to the coils C ₁ and C ₂ .

[Problems to be Solved by the Invention] In the above-described conventional magnetic bearing control circuit, the coils C _{1 of the} electromagnets M ₁ and M ₂ forming a pair
In order to control the exciting currents Ia and Ib supplied to C ₂ and C ₂ , respectively, separate current control circuits 7a and 7b must be provided. For example, 10 electromagnets perform 5-axis magnetic attraction force control. For this purpose, the same number of current control circuits as those of these electromagnets are required, and as a result, the circuit configuration becomes complicated and there is a problem that it cannot be constructed at low cost. Further, in order to improve the response delay at the time of polarity reversal described above, a bias current had to be constantly supplied to each coil C ₁ and C ₂ , so an electromagnet with a large coil rating must be used for that bias current. There is also a problem that the size of the entire device cannot be reduced.

The present invention has been made in view of the above-mentioned circumstances, and the exciting current supplied to each coil of the electromagnets forming a pair can be controlled by a single current control circuit, and the supply of the bias current is unnecessary. The purpose of the present invention is to provide a control circuit for a simple magnetic bearing.

"Means for Solving the Problem" The present invention is directed to a pair of electromagnets that attract rotors in opposite directions, a pair of displacement sensors that detect displacement of each of the electromagnets in the attraction direction, and each displacement. Based on the output of the sensor, a displacement detection circuit that detects the amount of displacement of the rotor from the equilibrium position, and an exciting current that is supplied to each coil of the pair of electromagnets in accordance with the output of the displacement detection circuit has a positive and negative polarity. And a current control circuit for controlling over,
Of the exciting currents, the coils are connected in series and a one-way current passing element is connected to each coil so that a positive component is supplied to one coil and a negative component is supplied to the other coil. And the unidirectional current passing elements are connected in parallel so that the polarities thereof are opposite to each other.

[Operation] According to the above configuration, when the rotor is displaced from the equilibrium position, the exciting current output from the current control circuit changes in both positive and negative polarities according to the amount of displacement, and among the exciting current, Since the positive component is supplied to the coil of one electromagnet and the negative component is supplied to the coil of the other electromagnet, the excitation current supplied to each coil of the pair of electromagnets is controlled by a single current control circuit. It can be controlled and no bias current is required.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.
As shown in this figure, the electromagnet M ₁ and each coil C ₁ and C ₂ of M ₂ which respectively suck the rotor 2 to the positive and negative directions of x-axis are connected in series, the respective coils C ₁ C ₂ is a diode
D ₁ and D ₂ are connected in parallel so that their polarities are opposite to each other. Further, the current control circuit 7, a force command signal Sf supplied from the displacement detecting circuit 5 considers the current command signal Si, an electromagnet M ₁ each coil C ₁ of the M ₂ and C ₂ in accordance with the current command signal Si The exciting current I is controlled by controlling the exciting current I. The exciting current I changes in both positive and negative polarities, and the signal detected by the current detector 8 is fed back to compensate the exciting current I. It has become.

In the above configuration, when the rotor 2 is displaced in the x-axis direction from its equilibrium position, the exciting current I output from the current control circuit 7 in accordance with the displacement amount is positive or negative as shown in FIG. It changes over both polarities. Then, of the exciting current I output from the current control circuit 7, the negative component is supplied to the coil C ₁ of the _one electromagnet M ₁ as the exciting current Ia shown in FIG. , And is supplied to the coil C ₂ of the other electromagnet M ₂ as the exciting current Ib shown in FIG. As a result, a force F as shown in FIG. 2D acts on the rotor 2 and the rotor 2 is pulled back to the equilibrium position.

Thus, according to the embodiment described above, a pair of electromagnets
Excitation current Ia supplied to each coil C ₁ and C ₂ of M ₁ and M ₂
Ib can be controlled by the single current control circuit 7, and the bias current is also unnecessary.

As described above, according to the present invention, the exciting current output from the current control circuit changes in both positive and negative polarities according to the displacement amount from the equilibrium position of the rotor. Of the exciting current, the positive component is supplied to the coil of one electromagnet,
Since the negative component is supplied to the coil of the other electromagnet, the exciting current supplied to each coil of the pair of electromagnets can be controlled by a single current control circuit,
As a result, the circuit configuration is simplified and the cost can be reduced, and since it is not necessary to supply a bias current to each coil, it is possible to use an electromagnet having a smaller coil rating than the conventional one. The effect that the entire device can be miniaturized is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention,
FIG. 2 is a waveform diagram for explaining the operation of the embodiment, and FIG.
FIG. 4 is a perspective view showing a part of the structure of the magnetic bearing, FIG. 4 is a block diagram showing the configuration of a conventional magnetic bearing control circuit, and FIG. 5 is a waveform diagram for explaining the operation of the control circuit. . M ₁ , M ₂ …… electromagnet, C ₁ , C ₂ …… coil, S ₁ , S ₂ …… displacement sensor, D ₁ , D ₂ …… diode (one-way current passing element), 2 ...... rotor, 5 …… Displacement detection circuit, 7 …… Current control circuit.

Claims (1)

(57) [Scope of utility model registration request] 1. A pair of electromagnets for attracting rotors in mutually opposite directions, a pair of displacement sensors for detecting displacements of the rotors in the attraction direction, and a pair of displacement sensors based on outputs of the displacement sensors. A displacement detection circuit that detects the amount of displacement from the equilibrium position of the rotor, and a current control circuit that controls the exciting current supplied to each coil of the pair of electromagnets in accordance with the output of the displacement detection circuit over both positive and negative polarities. And connecting the coils in series so that a positive component of the exciting current is supplied to one coil and a negative component of the exciting current is supplied to the other coil, and a unidirectional current passing element. Is connected in parallel to each coil, and the unidirectional current passing elements are connected so as to have mutually opposite polarities.