JPS61286610A - Control device of control type radial magnetic bearing - Google Patents

Abstract

PURPOSE:To restrain runout of a rotary shaft near the natural frequency by superposing a signal of a position sensor, the phase of which is advanced 90 deg., and advancing the phase of control force to obtain phase margin. CONSTITUTION:Runout detected by a Y-axis position sensor 25 is output from a filter 10, with the phase thereof advanced a little. The displacement output is added to an output through an X-axis control circuit, the phase of which is delayed 90 deg. with respect to the Y-axis, and the power of the total output is amplified to excite a Y-axis electromagnet. Accordingly, the X-axis control output is similar to that of the case where a differentiating circuit is added in parallel in the frequency, so that phase margin is given to restrain runout round a rotary shaft.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention detects the radial position of a rotating shaft using a position sensor, and inputs the signal as a feedback signal to a control circuit to control the electromagnetic force of an electromagnet. The present invention relates to a control device for a controlled radial magnetic bearing that maintains the radial position of a shaft at a fixed position.

[Conventional technology]

In recent machine tool spindles or turbo fans, etc., rotational speeds of shafts such as 7 drive parts have come to be in the range of several hundred to over 100,000 revolutions per minute to improve performance or downsize. There is a non-contact type magnetic bearing device as one of the bearings used for such high-speed rotation, which is expected to increase even further in the future.

The control circuit of such a magnetic bearing device generally operates in the radial direction of the rotating shaft independently for each control direction in two axial directions mutually orthogonal to the center of rotation within the same plane perpendicular to the rotating shaft. A position sensor that detects the position, a deviation amplifier that amplifies the deviation signal of the detection signal from the rotation axis reference position signal, a PID adjuster that compensates the phase of the output signal, and an electromagnet by the output signal of the PID adjuster. and a power amplifier for controlling the current to.

A control device for a magnetic bearing having a control circuit having the above-mentioned configuration has a vibration frequency lower than the mechanical natural frequency of the shaft, for example, approximately 75% of the natural frequency.
It is often used at a rotation speed of around 80%. Therefore, the conventional magnetic bearing device rotates around 30,000 to 40,000 revolutions per minute, for example.
Minutes are often used as the upper limit of rotation speed.

[Problem that the invention seeks to solve]

When it is desired to use a conventional magnetic bearing device at a higher rotational speed than the natural bending frequency of the shaft, for example, at a high speed of several hundred thousand revolutions per minute, a problem arises when passing through the natural vibration of the shaft. That is, when the rotational speed of the shaft increases near the bending natural frequency of the shaft and approaches a critical speed, the shaft resonates at the natural frequency of the shaft. However, as mentioned above, conventional magnetic bearing devices are generally designed to be used at rotational speeds below 75 to 80% of the natural frequency of the shaft, so the cross in the loop transfer function of the control circuit is The over frequency is set considerably low with respect to the bending natural vibration of the shaft, and the gain and phase of the control system are set so as to obtain a predetermined phase margin at this crossover frequency. Therefore, there is no phase margin at or above the bending natural frequency of the shaft, and there is no damping force. Therefore, the shaft cannot be rotated beyond the bending natural frequency of the shaft.

The present invention has been made in view of the above-mentioned current situation, and its purpose is to provide a control device for a magnetic bearing that can rotate at a higher speed than the natural bending frequency of the shaft.

[Means for solving problems]

As a means for solving the above problems, in the present invention, control circuits are provided for electromagnets in coaxial directions in the X-axis direction and the Y-axis direction, which are mutually orthogonal to the rotation center within the same plane perpendicular to the rotation axis. Each control circuit amplifies the deviation signal of the position sensor and its output signal from the set position signal, compensates for one phase, adds this to the input signals from another 10,000 control circuits, and then amplifies the combined output. and a circuit that outputs the deviation amplified signal of the position sensor through a bandpass filter whose center frequency is set slightly higher than the mechanical natural frequency of the rotating shaft. The detection signal of the position sensor is added to another 10,000 control circuit located at a position 90 degrees out of phase in the rotational direction with respect to the coaxial direction of each electromagnet via the circuit having the bandpass filter. A configuration is adopted in which the detection signal of the position sensor of the control circuit is similarly added to the one control circuit.

[Effect]

In the control device with the above configuration, while the rotational speed of the shaft is 75 to 80 degrees below the bending natural frequency of the shaft, the deviation amplified signal from the predetermined position of the detection signal by the position sensor of each control circuit is Due to the characteristics of the bandpass filter of the control circuit, the output signal is cut off by this filter, so the output passes through the control circuit without being added to the signal and controls the excitation force of the electromagnet.

When the rotational speed of the shaft reaches around the bending natural frequency of the shaft, the deviation amplified signal is transmitted to the position sensor of another 10,000 control circuit whose phase is advanced by 90 degrees when viewed from the axial direction of the control circuit in the rotational direction of the shaft. The deviation amplified signals of are added through the bandpass filter, and the electromagnet is excited by the combined output. As a result, for one control output, an effect similar to that obtained when a differential circuit is added in parallel at the above rotation speed, that is, a damping effect appears, and a sufficient vibration damping force is ensured, allowing rotation at an even higher speed beyond the evil speed. become.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the overall circuit diagram of a control device for a controlled radial magnetic bearing according to this embodiment.

In the figure, 1 is the rotation axis, 2X, 2Y are the X-axis directions,
Axial position sensor, 3X and 3Y are X-axis direction and X-axis position setting section, 4 and 4' are adders, 5 is a deviation amplifier, 6 is a phase compensation circuit, 7 is a power amplifier, 8 is an electromagnet,
9 is a coil, 10 is a band pass filter, and 11 is an inverting circuit.

The X-axis direction and X-axis direction position sensors 2X and 2Y are connected to the X-axis and
They are respectively arranged at predetermined positions between the rotary shaft 1 and the electromagnet 8 so as to detect displacement of the shaft 1 in the radial direction in the axial direction. In the following explanation, the X-axis direction control circuit is the same in configuration as the X-axis direction control circuit except for a part, so the X-axis direction control circuit will be mainly explained.

As is clear from the illustrated circuit diagram, the control circuit for the X-axis direction includes the electromagnets 8 and 8 for the X-axis direction. In order to control the excitation force of A deviation amplifier 5 that amplifies the deviation signal, a phase compensation circuit that compensates for the phase of the amplified deviation signal, and adds the phase-compensated signal to the input signal from the bandpass filter 10 of the X-axis direction control circuit. Another adder 4' and an electromagnet 8. A power amplifier 7 for controlling the current in the auxiliary field is further provided, and the signal amplified by the deviation amplifier 5 is passed through in a predetermined frequency band, and the phase in the circuit is adjusted with respect to the control circuit in the X-axis direction. It is equipped with a bandpass filter 10 for transmitting data.

The center frequency of this bandpass filter 10 is set to a frequency slightly higher than the natural frequency of the shaft.

The control circuit for the X-axis direction is the same as the control circuit for the X-axis direction, but an inversion circuit 11 is included in the circuit of the band-pass filter 10 for the control circuit for the X-axis direction to completely invert the phase of the bandpass filter 10. The only difference is in the way it is set up.

The operation of the magnetic bearing control device according to this embodiment configured as described above will be explained below.

The directions of the X and Y axes that are perpendicular to each other with respect to the rotating shaft 1 in FIG. 1 are designated as X-X' and Y-Y' as shown.

In this figure, when the shaft is rotated at a rotational speed equal to the natural frequency of the shaft, the vibration of the shaft appears on each position sensor as the whirling of the shaft. This whirling is detected by the position sensor in the X-axis direction as a displacement whose phase is advanced by 90° at the Y position.

For the control circuit in the X-axis direction, position sensor 2 in the X-axis direction
The deviation of the x output from the X direction position setting signal is amplified in the deviation amplifier 5, but at the same time the
The deviation amplified signal of the axial position sensor 2Y is added to the output of the X-axis direction in the adder 4' of the X-axis direction control circuit via the bandpass filter 10 of the X-axis direction control circuit, and the combined output is sent to the power amplifier. The power is amplified at 7 to excite the electromagnet 8° in the X-axis direction.

As mentioned above, the center frequency of the bandpass filter 10 is set at a frequency slightly S higher than the natural frequency of the shaft, and its phase-gain characteristics are shown in FIG.

In a control circuit equipped with a bandpass filter 10 having the center frequency and characteristics as described above, the deviation component of the displacement output in the X-axis direction passes through the bandpass filter 10 at a rotation speed near the natural frequency of the shaft. Therefore, the displacement is output with a somewhat advanced phase. That is, the X-axis direction position sensor 2
The wobbling detected in Y is outputted from the filter 10 with a somewhat advanced phase. This displacement output is added to the output through the X-axis control circuit whose phase is delayed by 90 degrees with respect to the X-axis direction, and the resulting output is power amplified and the X-axis direction electromagnet 8. Energize the reference. As a result, for the control output in the X-axis direction, an effect similar to that obtained when differentiating circuits are added in parallel at the same frequency, that is, a damping effect appears. At other rotational speeds, the bandpass filter 1
Due to the characteristics of 0, its output can be ignored and it is controlled only by the output that has passed through the X-axis control circuit.

The control circuit in the Y-axis direction has the same configuration.

However, since the phase of the X-axis position sensor 2x is delayed by 90 degrees with respect to the Y-axis, the output of the X-axis position sensor 2X from the bandpass filter 10 passes through an inversion circuit.
It is necessary to shift the phase by 1800 degrees. By configuring such a circuit, sufficient vibration damping force is ensured when the shaft rotates at its natural frequency, making it possible to rotate the shaft past the critical speed.

〔effect〕

As explained above, in the control device for a controlled radial magnetic bearing according to the present invention, the control circuits in the X-axis and Y-axis directions are superimposed with signals from position sensors that are 1-90 degrees ahead of each other in phase, so that signals near the natural frequency are obtained. Since it is possible to obtain a phase margin by advancing the phase of the control force at ,
It can be used in an extremely wide range of applications as a magnetic bearing for ultra-high speeds.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall circuit diagram of a control device for a controlled radial magnetic bearing according to an embodiment of the present invention, FIG. 2 is a diagram showing the transfer function of a band-pass filter, and FIG. FIG. 3 is a diagram in which the -1 control circuit output effect of the above control device is replaced with a Bode diagram of a one-loop transfer function having a similar effect. 1...Rotation axis, 2x, 2y...position sensor, 3.
...Position setting section, 4, 4'... Adder, 5... Deviation amplifier.

Claims (2)

[Claims] (1) A control method that detects the radial position of the rotating shaft using a position sensor, inputs the signal as a feedback signal to the control circuit, controls the electromagnetic force of the electromagnet, and maintains the radial position of the shaft at a fixed position. In a control device for a radial magnetic bearing, control circuits are provided for coaxial electromagnets in the X-axis direction and the Y-axis direction, which are mutually orthogonal to the rotation center within the same plane perpendicular to the rotation axis, and each control circuit a position sensor, a circuit that amplifies a deviation signal of its output signal from a set position signal, compensates for the phase, adds this to an input signal from another control circuit, and then amplifies the combined output; and the position sensor. It consists of a circuit that outputs the deviation amplified signal of The signal is added to the other control circuit located at a position 90° in phase in the rotational direction with respect to the coaxial direction of each electromagnet through the circuit having the band-pass filter, and the position sensor of this other control circuit is detected. A control device for a controlled radial magnetic bearing, characterized in that a signal is similarly added to one of the control circuits. (2) An inverting circuit for inverting the output of the other control circuit, which is located at a position 90 degrees out of phase in the rotational direction with respect to the coaxial direction of each electromagnet, is provided in the circuit having the bandpass filter. A control device for a controlled radial magnetic bearing according to claim 1.