JPH01137302A - Controller for magnetic bearing - Google Patents

Abstract

PURPOSE:To improve the rigidity of a magnetic bearing against the disturbance of a large amplitude at a low frequency and at the same time to improve the stability of a rotor against the natural vibration at a high frequency by setting a variable gain circuit between a position sensor and a PID control circuit. CONSTITUTION:An electromagnet 13 of a magnetic bearing is controlled by a PID control circuit 11 via an electromagnet power amplifier 12 based on the output signal of a position sensor 10 for a rotor. A variable gain circuit 14 is set between the sensor 10 and the circuit 11. This circuit 14 has a small output change to a small displacement change of the rotor and a large output change to a large displacement change of the rotor respectively. In other words, the rigidity of the magnetic bearing is improved against the disturbance of a large amplitude at a low frequency because the circuit 14 has a large output change with a large displacement of the rotor. While the stability of the rotor is improved against the natural vibration at a high frequency because the circuit 14 has a small output change with a small displacement of the rotor.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a magnetic bearing control device.

BACKGROUND TECHNOLOGIES AND THEIR PROBLEMS A known magnetic bearing control device includes a PID control circuit that controls an electromagnet via an electromagnet power amplifier using an output signal from a position sensor that detects the position of a rotating body. . Such conventional control devices normally supply a control amount proportional to the displacement of the rotating body, but when attempting to obtain greater bearing rigidity, a larger control amount is required. On the other hand, if an attempt is made to obtain a larger control amount, the feedback gain of the control system will increase, resulting in an uncontrollable state due to the influence of the natural vibration of the rotating body.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a magnetic bearing control device that has high bearing rigidity and good stability.

Means for Solving the Problems A magnetic bearing control device according to the present invention controls an electromagnet of a magnetic bearing via an electromagnet power amplifier using a PID control circuit based on an output signal of a position sensor that detects the position of a rotating body. between the position sensor and the PrD control circuit, a variable control circuit is provided between the position sensor and the PrD control circuit that causes a small change in output in response to a change in displacement when the displacement of the rotating body is small, and a large change in output in response to a change in displacement when the displacement of the rotating body is large. It is characterized by being provided with a gain circuit.

The amplitude of the natural vibration (high-frequency vibration) of the working rotating body is small, and the amplitude of vibration caused by low-frequency disturbance is large.

When the displacement of the rotating body is large, the change in the output of the variable gain circuit with respect to the change in displacement is large, so the feedback gain becomes large, and the bearing rigidity against low-frequency, large-amplitude disturbances becomes high.

When the displacement of the rotating body is small, the change in the output of the variable gain circuit with respect to the change in displacement is small, so the feedback gain is small and the stability against high frequency natural vibrations of the rotating body is high.

Example FIG. 1 shows one embodiment of the invention.

This magnetic bearing is connected to an electromagnet (13) of the magnetic bearing via an electromagnet power amplifier (12) by a PID control circuit (11) based on an output signal of a position sensor (10) that detects the position of a rotating body (path shown). ), between the position sensor (io) and the PID control circuit (11),
When the displacement of the rotating body is small, the change in output in response to a change in displacement is small, and when the displacement of the rotating body is large, the change in output in response to a change in displacement is large.
) is provided. Position sensor (10), P I
D Although the control circuit (11), the power amplifier (12), and the electromagnet (13) can have any known configuration, a detailed description thereof will be omitted.

FIG. 1 shows the basic configuration of an example of a variable gain circuit (14). When the displacement of the rotating body is small, that is, when the output of the position sensor (1o) is between 1σ and +σ (range A in FIG. 2), the output of the variable gain circuit (14) is 15), the output changes so that the change in output with respect to the change in displacement of the rotating body becomes smaller. When the displacement of the rotating body is positive and the absolute value is large, that is, when the output of the position sensor (10) is larger than +σ (range B in Fig. 2), the output of the variable gain circuit (14) is 16), the output changes in response to changes in the displacement of the rotating body.

When the displacement of the rotating body is negative and the absolute value is large, that is, when the output of the position sensor (10) is smaller than -σ (range C in Fig. 2), the output of the variable gain circuit (■4) is The resistance (17) changes the output so that the change in output with respect to the change in displacement of the rotating body increases. In addition, in Fig. 2, -X and +X indicate the rotating body and the protective bearing (path shown).
It shows the gap between

In the rotating body of a magnetic bearing, vibrations mainly occur due to natural vibrations (high-frequency vibrations) and low-frequency disturbances, but the amplitude of the natural vibrations is small, and the amplitude of vibrations due to low-frequency disturbances is large.

When the displacement of the rotating body is large, the change in the output of the variable gain circuit (14) with respect to the change in displacement is large, so the feedback gain becomes large and the bearing rigidity against low-frequency, large-amplitude disturbances becomes high. Therefore, it is reliably prevented that the rotating body is largely displaced and comes into contact with the protective bearing.

When the displacement of the rotating body is small, the change in the output of the variable gain circuit (14) with respect to the change in displacement is small, so the feedback gain becomes small and the stability against high-frequency natural vibrations of the rotating body becomes high.

Effects of the Invention According to the magnetic bearing control device of the present invention, between the position sensor and the PID control circuit, when the displacement of the rotating body is small, the change in output in response to a change in displacement is small, and when the displacement of the rotating body is large, the change in output is small. Since a variable gain circuit is provided that has a large change in output in response to changes in play.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a magnetic bearing control device showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between input (displacement) and output of a variable gain circuit. (10)... Position sensor, (11)... PID control circuit, (12)... Power amplifier for electromagnet, (13)
...electromagnet, (14)...variable gain circuit. Figure 2 above

Claims (1)

[Scope of Claims] A device for controlling an electromagnet of a magnetic bearing via an electromagnet power amplifier by a PID control circuit based on an output signal of a position sensor that detects the position of a rotating body, the device comprising: a position sensor and a PID control circuit In between, a variable gain circuit is provided which causes a small change in output in response to a change in displacement when the displacement of the rotating body is small, and a large change in output in response to a change in displacement when the displacement of the rotating body is large. Control device for magnetic bearings.