JPH0534336Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention relates to a control device for magnetic bearings, and in particular,
To control a magnetic bearing in which two rotors are provided on a rotating shaft with a predetermined distance in the axial direction, and two electromagnets are arranged so that each has a predetermined offset in the axial direction with respect to the rotor. The present invention relates to a control device.

[Prior Art] FIG. 9 is a diagram showing an outline of a conventional magnetic bearing device. In FIG. 9, a rotary shaft 1 is provided with rotors 11 and 12 made of magnetic material, and position sensors 2 and 3 are provided at both ends of the rotary shaft 1 to detect the position of the rotary shaft 1 in the radial direction. provided, rotation axis 1
A speed sensor 4 is provided on one end surface of the motor.
Furthermore, l with respect to the rotors 11 and 12 of the rotating shaft 1
electromagnets 5 and 6, 7 so as to have an offset of
and 8 are provided symmetrically. As described above, since the electromagnets 5 and 6, 7 and 8 are installed so as to have an offset of l with respect to the rotors 11 and 12, the magnetic flux generated by the electromagnets 5 to 8 causes the magnetic flux to be shifted in the axial direction of the rotating shaft 1. will be ensured. This eliminates the need for a thrust magnetic bearing that performs axial control, and enables four-axis control. Such magnetic bearing devices are used when there is a restriction on the axial length or in applications where manufacturing costs need to be reduced.

[Problems to be Solved by the Invention] However, the above-described magnetic bearing device has a drawback in that vibrations in the axial direction caused by disturbances are not damped because there is no damping force in the axial direction. That is, when a force is applied from one end of the rotating shaft 1 due to a disturbance, the rotating shaft 1 moves toward the other end, and the electromagnets 5 and 6 each try to pull back.
The rotating shaft 1 is moved to one end side. When the rotating shaft 1 moves to one end, the electromagnets 7 and 8 try to move it to the other end, but this vibration is easy because there is no damping force against the axial vibration of the rotating shaft 1. does not attenuate.

Therefore, the main purpose of this invention is to provide a control device for a magnetic bearing that can damp vibrations in a short period of time even when vibrations are applied due to external disturbances.

[Means for Solving the Problem] This invention has rotating shafts provided at a predetermined distance in the axial direction of two rotors, and a predetermined offset in the axial direction with respect to the two rotors. A control device for a magnetic bearing comprising two electromagnets arranged as shown in FIG. According to the detection output of the detection means, the bias current flowing through the bias coil is controlled to linearize the attraction force and excitation current of the two electromagnets, and the vibration in the axial direction of the rotating shaft is damped. and a control means for controlling.

[Function] The magnetic bearing control device according to this invention can damp vibrations in the axial direction of the rotating shaft by controlling the bias current according to the current flowing through the control coil of the electromagnet. Vibration of the rotating shaft due to disturbance can be attenuated in a short time.

[Embodiment of the invention] First, before describing an embodiment of the invention, the function of the bias coil of the electromagnet constituting the magnetic bearing will be explained.

FIG. 2 is a diagram showing the relationship between the rotating shaft and the radial magnetic bearing, and FIG. 3 is a diagram showing the relationship between the current flowing through the radial magnetic bearing and the electromagnetic force.

As shown in FIG. 2, electromagnets 5 and 6 are provided symmetrically with respect to the rotating shaft 1, and have control coils 51 and 61 and bias coils 52 and 62, respectively.
including. Control coils 51 and 61 are for adjusting electromagnetic force, and bias coils 52 and 6
2 is provided to linearize the relationship between the attractive force F ₁ of the electromagnets 5 and 6 and the current i. That is,
The relationship between the attractive force F ₁ of the electromagnets 5 and 6 and the current i is expressed as F ₁ =K ₁ ·i ² (K ₁ is a constant) and is nonlinear.

Here, a control current i _C is applied to the control coils 51 and 61, and a bias current is applied to the bias coils 52 and 62.
If i _B flows and both electromagnets 5 and 6 located symmetrically with respect to the rotation axis attract the rotation axis 1 to each other, the force acting on the rotation axis 1, that is, both electromagnets 5 and 6 The force F ₂ that is the result of combining the attraction forces of is expressed as F ₂ =K ₂・i _B・i _C (K ₂ is a constant) using first-order approximation. Therefore, by keeping the bias current i _B constant, the force F ₂ is applied to the control coils 51 and 61.
Since a proportional relationship holds true with the control current i _C flowing in
The force F ₂ and the control current i _C can be linearized as shown by the dashed-dotted line in FIG.

Fig. 4 is a diagram for explaining the principle of an embodiment of this invention, Fig. 5 is a diagram showing the relationship between the control current and the load, and Fig. 6 is a diagram showing the relationship between the control current and the offset l. FIG.

In FIG. 4, if the gap δ ₁ between the electromagnet 5 and the rotating shaft 1 and the gap δ ₂ between the electromagnet 6 and the rotating shaft 1 are equal, and the load F including gravity is 0, then the electromagnet 5
The control current i _C flowing through the control coils 51 and 61 of
becomes 0, and the rotating shaft 1 is located approximately at the center due to the attractive force of the electromagnets 5 and 6 due to the bias current i _B flowing through the bias coils 52 and 62. Here, when the load F changes, the control current changes as shown in FIG.

On the other hand, while keeping the load F constant, the rotor 11,
When the axial offset l between the electromagnets 12 and the electromagnets 5 and 6 is changed, the control current changes as shown in FIG. That is, at offset 0, where the area where the electromagnets 5 and 6 face the rotors 11 and 12, which is the largest, the control current i _C becomes the minimum, and when an offset l occurs on either the left or right side, the control current
i _C increases. That is, the position of the rotating shaft 1 can be determined according to the magnitude of the control current i _C.

Therefore, in one embodiment of this invention, the bias current i B flowing through the bias coils 52 and 62 is controlled according to the control current i _C flowing through the control coils 51 and 61, so that the bias current i _B flowing through the bias coils 52 and 62 is controlled. Dampen vibrations. That is, as shown in FIG.
The output of the deviation amplifier 28 is subjected to PID adjustment by the PID regulator 29, current amplified by the current amplifier 24, and the control current _iC is applied to the control coil 5.
1,61. Note that the control coils 51 and 61 are wound in opposite directions, and are connected in series. Bias current source 21
depends on the current flowing through the control coils 51 and 61,
The current flowing through the bias coils 52 and 62 is controlled.

FIG. 1 is a block diagram of one embodiment of this invention.

In FIG. 1, bias current source 21 includes a differentiator 211, a gain adjustment circuit 212, an adder 213, and a current amplifier 214. The output of the differentiator 211 is given to a gain adjustment circuit 212, and its gain is adjusted. The gain-adjusted current detection signal is given to an adder 213. A bias current command value is given to the adder 213, and the adder 213
13 adds a current detection signal to a bias current command value and supplies the result to a current amplifier 214, where the current is amplified and then supplied to bias coils 52 and 62.

Configuring the bias current source 21 as described above,
When the bias current is increased, the attractive force acting on the rotating shaft 1 from the electromagnets 5 and 6 increases, and a force is applied to the rotating shaft 1 to reduce the offset l. In other words,
By detecting the control current, adding the differential value of the detected current and the original bias current command value, and controlling the bias current using that signal, it is effective even when disturbances act on the rotating shaft 1. vibration can be damped.

FIG. 7 is a block diagram showing another embodiment of this invention. The embodiment shown in FIG. 7 is similar to the bias coil 5 of the embodiment shown in FIG.
2 and 62 are omitted, and the control current and bias current are supplied to the control coils 51 to 81 in a superimposed manner. That is, the shaft position reference circuit 27 generates a reference signal indicating the reference position of the left electromagnets 5 and 6, and this reference signal is applied to the deviation amplifier 28. The deviation amplifier 28 is supplied with the position signal detected by the left position sensor 2. The deviation amplifier 28 compares the reference signal with the left position signal and supplies it to the PID controller 29. PID controller 29 performs PID adjustment on the output of deviation amplifier 28 and provides a control signal to adder 25 and to adder 23 via inverter 22 . The outputs of the adders 23 and 25 are sent to the full wave rectifier 45,
46, the current amplifiers 24, 2
6 and after being amplified, the control coil 5
1,61.

On the other hand, the shaft position reference circuit 37 includes the electromagnet 7 on the right side,
A reference signal indicating the reference position of No. 8 is generated and applied to the deviation amplifier 38. The deviation amplifier 38 is supplied with the position signal detected by the position sensor 3 on the right side. The deviation amplifier 38 amplifies the difference between the reference signal and the position signal, and supplies the amplified signal to the PID controller 39. After PID adjustment, the PID controller 39 sends the control signal to the adder 3.
3 and also to an adder 35 via an inverter 32. The outputs of adders 33 and 35 are full-wave rectified by full-wave rectifiers 47 and 48, current amplified by current amplifiers 34 and 36, and then supplied to control coils 71 and 81.

As described above, the control coils 51, 61, 7
1 and 81 are supplied with a control current, and the control coil 5
1, 61, 71, and 81 have resistors 53 and 6, respectively.
3, 73, and 83 are connected in series. resistance 63
The voltage difference between and 73 is detected by an inverter 217 and an adder 218, and the detected voltage is differentiated by a differentiator 211. After that, the gain adjustment circuit 21
After the gain is adjusted in step 2, it is applied to the adder 216 and is also applied to the adder 21 via the inverter 215.
given to 3. A bias current command value is given to adders 213 and 216 from a bias current command circuit 219. Adders 216 and 213 add and subtract the detected current value from the bias current command value and provide the result to adders 23, 25, 33, and 35.
Therefore, the adders 23, 25, 33, and 35 add the bias current to the control current.

By configuring as described above, adder 2
A bias current is added to the control current by the control coils 51, 61, 7.
1 and 81 are supplied with a control current on which a bias current is superimposed. When the offset l changes due to the vibration of the rotating shaft 1, the current flowing through the control coils 51 and 71 changes, and the bias current is superimposed on the control current so as to cancel out the change.
It is possible to provide damping to vibrations.

FIG. 8 is a diagram showing another example of a magnetic bearing to which an embodiment of this invention is applied. In the magnetic bearing shown in FIG. 8, the rotors 11 and 12 are arranged inside so as to have an offset l with respect to the electromagnets 5 to 8. Even with this configuration of the magnetic bearing, the embodiments shown in FIGS. 1 and 7 described above can be applied by changing the polarity.

[Effects of the invention] As described above, according to this invention, the bias current is controlled according to the current flowing through the control coil of the electromagnet, so vibrations in the axial direction of the rotating shaft can be suppressed for a short time. can provide attenuation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of this invention. FIG. 2 is a diagram showing the relationship between the rotating shaft and the radial magnetic bearing. FIG. 3 is a diagram showing the relationship between the current flowing through the radial magnetic bearing and the electromagnetic force. Fourth
The figure is a diagram for explaining the principle of an embodiment of this invention. FIG. 5 is a diagram showing the relationship between control current and load. FIG. 6 is a diagram showing the relationship between control current and offset l. FIG. 7 is a block diagram showing another embodiment of this invention. FIG. 8 is a diagram showing another example of a magnetic bearing to which this invention is applied. FIG. 9 is a diagram showing a conventional magnetic bearing. In the figure, 1 is a rotating shaft, 2 and 3 are position sensors, 4 is a speed sensor, 5, 6, 7, and 8 are electromagnets,
11, 12 rotors, 21 is a bias current source, 2
3, 25, 33, 35, 213, 216, 218
is an adder, 28, 38 is a deviation amplifier, 29, 39
is a PID controller, 24, 26, 34, 36 are current amplifiers, 27, 37 are axis position reference circuits, 211 is a differentiator, 212 is a gain adjustment circuit, 51, 61, 7
1 and 81 are control coils, 52 and 62 are bias coils, and 53, 63, 73, and 83 are resistors.

Claims (1)

[Claims for Utility Model Registration] Two rotors are arranged such that two rotors have rotating shafts spaced apart from each other at a predetermined distance in the axial direction, and each rotor has a predetermined offset in the axial direction with respect to the two rotors. A magnetic bearing control device comprising two electromagnets, each of which includes a control coil and a bias coil, and current detection means for detecting a current flowing through the control coil. , and according to the detection output of the current detection means, the second
control means for controlling the bias current flowing through the bias coil in order to linearize the attractive force and excitation current of the electromagnets, and controlling the bias current flowing in the bias coil so as to provide damping to vibrations in the axial direction of the rotating shaft. , magnetic bearing control device.