JPS6411845B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a magnetic bearing. In the magnetic bearing, two permanent magnets 1 and 2 and two control coils 3 and 4 are installed as shown in FIG.
When considering a system that supports two yokes 6 and 7 fixed to the rotating shaft 5 by suction, it is possible to connect yokes 3 and 4 in series and control them by considering the winding direction. In some cases, control is performed by driving 3 and 4 in parallel to increase the control power.
In the present invention, 3 and 4 are driven and controlled in parallel.

As a control method, when permanent magnets and control coils are used together, the control current of the two control coils is reduced to zero when the load on the supported body (rotating body) and the attraction force of the permanent magnet are balanced. There is a VZP method called. Generally, in a method that does not use the VZP method, as shown in FIG. , the current is passed through the control coil 12, and the other side is the phase inversion circuit 13.
After that, the power is amplified by the power amplifier circuit 14, and a current is passed through the control coil 15 to control the position of the rotating body.

Conventionally, the control circuit of a magnetic bearing using the VZP method, as shown in Fig. 3, is based on the basic circuit shown in Fig. 2.
Addition circuits 16 and 17, integration circuits 18 and 19, and current detection circuits 20 and 21 are added. Explain the operation. The displacement signal from the displacement sensor 22 passes through a displacement signal processing circuit 23 and a phase compensation circuit 24, and one of the phase-compensated signals directly enters 16, passes through a power amplifier circuit 25, and causes a control current to flow through a control coil 26. The other signal that has passed through 24 passes through a phase inversion circuit 27 17 and a power amplification circuit 28 to cause a control current to flow in a control coil 29 so that a magnetic field in the direction opposite to that of 26 is generated. At this time, if the position of the rotating body is not at the equilibrium point between the attractive force of the permanent magnet and the load, current is further passed through 26 and 29. Detect the current at 20 and 21, integrate it at 18 and 19, and
By positive feedback to , the rotating body is moved to an equilibrium point, and the currents 26 and 29 are made zero. In the conventional magnetic bearing control circuit using the VZP method, adder circuits such as 16 and 17 are required, and two integration circuits, 18 and 19, are required, and constants must be adjusted for each other. It had the disadvantage of being.

FIG. 4 shows a control circuit for a magnetic bearing using the VZP method according to the present invention. A displacement signal from the displacement sensor 30 is phase-compensated through a displacement signal processing circuit 31 and a phase compensation circuit 32, and one directly passes through a power amplification circuit 33 where the power is amplified and a control current flows through the control coil 34. The other one that has passed through 32 passes through a phase inversion circuit 35 and enters a power amplification circuit 36 , causing a control current to flow through a control coil 37 to generate a magnetic field opposite to that of 34 . At this time, if the phase of the rotating body is not at the equilibrium point between the attraction force of the permanent magnet and the load, an additional 3
Control current continues to flow through 4 and 37. The signals of the current components detected by the current detection circuits 38 and 39 that detect this control current are used as two inputs of the differential amplifier circuit 40 considering the positive and negative directions, and the output thereof is passed through the integrating circuit 41 to the 31 positive feedback to move the rotating body to a position where the load and the attraction force of the permanent magnet are balanced,
The currents at 34 and 37 are made zero.

As described above, by using the control circuit according to the present invention, if the output of 41 is positively fed back to 31 using 40, 16 and 17 as in the conventional control circuit are not needed, and the constants of 18 and 19 can be reduced. The need for adjustment is eliminated, the circuit configuration is simplified, and the number of adjustment points is reduced. In addition, the output of 41 can be regarded as equivalent to a displacement signal, and after positive feedback to 31,
Since the phase is compensated, stable control can be performed. In addition, 13, 27, 35 in Figures 2, 3, and 4
may become unnecessary if the direction of the current flowing through 15, 29, and 37 is considered.

[Brief explanation of drawings]

Figure 1 is a side sectional view showing an example of the structure of a magnetic bearing.
Figure 2 is a block diagram showing the basic control circuit of a magnetic bearing that does not use the VZP method, and Figure 3 is a block diagram showing the basic control circuit of a magnetic bearing that does not use the VZP method.
A block diagram showing a control circuit for a magnetic bearing using the VZP method. FIG. 4 is a block diagram showing an embodiment of a control circuit for a magnetic bearing according to the present invention. 1, 2...Permanent magnet, 3, 4...Control coil,
5... Rotating shaft, 6, 7... Yoke, 8... Displacement sensor, 9... Displacement signal processing circuit, 10... Phase compensation circuit, 11... Power amplifier circuit, 12... Control coil, 13... Phase inversion circuit, 14... Power amplifier circuit, 15... Control coil, 16, 17... Addition circuit, 18, 19... Integrating circuit, 20, 21...
Current detection circuit, 22... Displacement sensor, 23... Displacement signal processing circuit, 24... Phase compensation circuit, 25...
...Power amplifier circuit, 26...Control coil, 27...
Phase inversion circuit, 28... Power amplifier circuit, 29...
Control coil, 30... Displacement sensor, 31... Displacement signal processing circuit, 32... Phase compensation circuit, 33...
Power amplifier circuit, 34... Control coil, 35... Phase inversion circuit, 36... Power amplifier circuit, 37... Control coil, 38, 39... Current detection circuit, 40...
...differential amplifier circuit, 41...integrator circuit.

Claims (1)

[Scope of Claims] 1. A control circuit for a magnetic bearing comprising two control coils arranged to act in opposite directions with respect to a rotating shaft and a displacement sensor that detects displacement of the rotating shaft, the control circuit comprising: consists of a displacement signal processing circuit that processes the signal from the displacement sensor, a phase compensation circuit that compensates the phase of the displacement signal, one of the phase compensated displacement signals is passed through the phase inversion circuit, and the other is left as is. Two power amplification circuits for power amplification, the two control coils are connected to each of the amplification circuits, two current detection circuits for detecting the current flowing through these two control coils, and It consists of a differential amplifier circuit that inputs the current component detected by the circuit, and an integrating circuit connected to the differential amplifier circuit.The two current components flowing through each control coil are converted into one signal by the differential amplifier circuit. A control circuit for a magnetic bearing, characterized in that the signal is fed back to a displacement signal processing circuit via an integrating circuit.