JP3718561B2 - Structural vibration instability prevention device and method, magnetic bearing control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structural vibration instability prevention device and method for preventing vibration of a structural system, and a magnetic bearing control device. In particular, the present invention relates to structural vibration resistance suitable for positioning magnetic bearings, magnetic disk heads, manipulators, and the like. The present invention relates to a stabilization prevention device and method, and a magnetic bearing control device.
[0002]
[Prior art]
In a positioning control device such as a magnetic bearing or a magnetic disk head, a feedback control system is used for causing a position of a control target or a state quantity such as speed to follow a predetermined target function. Since the object to be controlled has mechanical and structural dynamics, it is necessary to stabilize these vibration modes in the design of the control system.
[0003]
FIG. 4 is a block diagram of the magnetic bearing control system. The rotor 1 is attracted by the electromagnets 3a and 3b facing each other and supported in the air. In order to stably support the rotor 1, the position of the rotor 1 is constantly monitored and measured by the displacement sensor 2, the sensor converter 4, the notch filter 9, the stabilization compensation circuit 5 (generally a PID control circuit), and the positive / negative selection. The current of the electromagnets 3a and 3b is controlled via the device 6 and the power amplifiers 7a and 7b. The notch filter 9 is used to cut off the frequency band of the higher-order bending mode of the rotor and prevent oscillation of the higher-order bending mode. The basic technology of this type of magnetic bearing is described in detail in “Magnetic Levitation and Magnetic Bearing (issued on June 30, 1993)”.
[0004]
[Problems to be solved by the present invention]
In the above-mentioned magnetic bearing control system, increasing the phase advance amount of the stabilization compensation circuit or the gain of the feedback loop in order to improve the bearing rigidity or damping performance causes the higher-order mode of the rotor to become unstable and oscillate. There was a case. In order to avoid such oscillation, it is generally performed to add a notch filter that cuts off a high-order mode frequency band that causes oscillation. In general, the notch filter is used in most cases where the gain is stabilized by cutting off the oscillation component, but the phase is stabilized by using the phase transition characteristic of the notch filter.
[0005]
However, the gain stabilization method that prevents the loop from oscillating in the vicinity of ω ₁ by greatly reducing the gain of the feedback loop at the bending natural vibration frequency ω ₁ cannot be controlled at the frequency ω _1. There is a drawback that the disturbance of ₁ cannot be suppressed. In addition, if the sensitivity of the vibration response of the higher order mode is as large as the response sensitivity of the lower order mode, the oscillation may not be suppressed due to the lack of the blocking effect or phase transition effect by the notch filter. There was a problem of coming.
[0006]
On the other hand, as a measure for improving the notch filter, as shown in Japanese Patent Laid-Open No. 7-114420, the gain of the loop is raised at the frequency ω ₁ so that it can be controlled even at ω ₁ and the oscillation is stopped by phase adjustment. A method has been proposed. However, this method makes it difficult to adjust for stabilization by increasing the gain.
[0007]
The object of the present invention is to provide a structural vibration instability prevention device and method, and a magnetic bearing control device that are excellent in stability by adding a phase shift circuit that compensates for the disadvantages of the notch filter described above. is there.
[0008]
[Means for Solving the Problems]
The present invention comprises a detecting means for detecting a vibration state quantity of a controlled object;
A transfer function in which complex conjugate zeros are arranged outside the unit circle on the right half plane of the s plane or the z plane for giving a phase transition to the detected value of the means in the frequency band of the higher-order mode generated in the control target Phase shifting means;
Compensation means for performing a compensation operation on the output of the means;
Disclosed is an apparatus for preventing structural vibration instability, comprising operation means for controlling a controlled object in accordance with the output of the means.
[0009]
Further, the present invention sets the complex conjugate zero to the right of the s plane so that the signal output from the means for detecting the vibration state quantity of the controlled object has a phase transition in the higher-order mode frequency band generated in the controlled object. Disclosed is a structural vibration instability prevention method that feeds back to the vibration state quantity control means via a compensation means having a transfer function arranged outside a unit circle on a half plane or z plane.
[0010]
The present invention further includes a detecting means for detecting the vibration amount of the rotor supported by the magnetic bearing;
A transfer function having a transfer function in which a complex conjugate zero is arranged outside the unit circle in the right half plane of the s plane or the z plane in order to give a phase transition to the detected value of the means in the frequency band of the higher order mode generated in the rotor. Phase means,
Compensation means for performing a compensation operation on the output of the means;
Disclosed is a magnetic bearing control device comprising operating means for controlling a controlled object in accordance with the output of the means.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail using embodiments.
FIG. 1 is a block diagram showing an example of a magnetic bearing control device according to the present invention. This figure is almost the same as FIG. 4, and the reference numerals common to FIG. 4 indicate the same parts as the control system shown in FIG. 4, and the only difference is the feature of the present invention instead of the notch filter circuit 9. This is that a phase shift circuit 8 is provided. In response to the output of the phase shift circuit, the compensation circuit 5 performs PID control or phase advance / delay calculation. The power amplifiers 7a and 7b control the current supplied to the electromagnets 3a and 3b in response to the signal divided into positive and negative by the positive / negative selector 6.
[0012]
The transfer function of the phase shift circuit 8 is designed as follows.
[Expression 1]
^{H (s) = (s 2} -2ζ 2 ω 2 s + ω 2 2) / (s 2 + 2ζ 1 ω 1 s + ω 1 2)
Here, ζ ₂ > 0, ζ ₁ > 0, and normally, ω ₂ ≧ ω ₁ is designed. The complex conjugate zeros appearing in the numerator of (Equation 1) are (ζ ₂ ω ₂ , ± jω ₂ (1-ζ ₂ ² ) ^1/2 ), and the phase shift circuit 8 is obtained by attaching a negative sign to ζ _2. Are placed in the right half plane on the s plane and have phase characteristics of a non-minimum phase transition system. When ζ ₂ = 0 and ω ₂ = ω ₁ , a normal notch filter circuit is obtained.
[0013]
FIG. 2 shows a frequency characteristic example of (Equation 1) by a solid line, and a frequency characteristic example of a normal notch filter circuit is shown by a broken line for comparison. It can be seen that the phase of the phase shift circuit 8 continuously changes from 0 to −2π, whereas the phase of the notch filter does not have a value in a range including 1π, and changes only in other ranges. . On the other hand, the amplitude characteristic is attenuated to some extent at the natural vibration frequency ω ₁ of the bending mode, but does not completely cut the component of the frequency ω ₁ unlike the notch filter. Therefore, the phase shift circuit 8 performs stabilization by adjusting the phase characteristics. For this purpose, it is desirable to arbitrarily adjust the phase characteristic. However, as described above, the phase shift circuit 8 can obtain a phase transition from 0 to −2π, and is ideal. In phase adjustment using a notch filter, only a narrower range of adjustment than in the present invention can be achieved.
[0014]
FIG. 3 shows a frequency characteristic of the magnetic bearing control device according to the present invention and an example of the frequency characteristic of the rotor. The characteristic of the magnetic bearing control device is the frequency characteristic of the loop in FIG. Natural frequency omega ₁ of the bending first-order and the bending of the secondary rotor, with respect to omega _2, in the second-order natural frequency omega ₂ of the front bending, the phase is steeply changes, the frequency omega ₂ in again phase Advance (2nπ <θ <(2n + 1) π, where n is an integer). In a normal control system for a magnetic bearing, stabilization can be obtained by setting the phase advance. However, according to the configuration of the present invention, a desired phase advance can be easily realized and stabilization is achieved.
[0015]
In the case of actually making the phase shift circuit, which is a feature of the present invention, it can be configured as an analog circuit using an operational amplifier or the like, but it is better to realize it as an IIR (Infinite Impulse Response) filter using digital processing. Easy. The arithmetic coefficient of the IIR filter can be obtained using sz conversion. By this sz conversion, the complex conjugate zeros arranged in the right half plane on the s plane are arranged outside the unit circle on the z plane. This is a natural consequence of mathematics. That is, in (Equation 1), for example, the following conversion is performed.
[Expression 2]
s = (2 / T) ・ (1-1 / z) / (1 + 1 / z)
Here, T is a sampling time for digital processing, and 1 / z is an operator for delaying one sample. By applying this conversion to (Equation 1) to obtain the 1 / z coefficient, the phase shift circuit of the present invention can be realized as an IIR filter.
[0016]
【The invention's effect】
When the zeros are arranged as described above, the filter becomes a non-minimum phase positioning system, and the phase transition amount can be changed over a wider range than the notch filter. Therefore, the phase characteristics of the control system can be adjusted over a wide range, and high-order bending mode oscillation can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a magnetic bearing control device according to the present invention.
FIG. 2 is a diagram comparing frequency characteristics of the phase shift circuit of FIG. 1 and a notch filter circuit.
FIG. 3 is a diagram showing an example of frequency characteristics of the control device of FIG. 1 and a characteristic diagram of a rotor.
FIG. 4 is a block diagram showing a configuration of a conventional magnetic bearing control system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotor 2 Displacement sensor 3a, 3b Electromagnet 4 Sensor converter 5 Compensation circuit 6 Positive / negative sorter 7a, 7b Power amplifier 8 Phase shift circuit 9 Notch filter

Claims (3)

Detection means for detecting the vibration state quantity of the control object;
A transfer function in which complex conjugate zeros are arranged outside the unit circle on the right half plane of the s plane or the z plane for giving a phase transition to the detected value of the means in the frequency band of the higher-order mode generated in the control target Phase shifting means;
Compensation means for performing a compensation operation on the output of the means;
An apparatus for preventing structural vibration instability, comprising: operating means for controlling an object to be controlled in accordance with the output of the means.   The signal output from the means for detecting the vibration state quantity of the controlled object is a complex conjugate zero point in the right half plane of the s plane, or z so that it has a phase transition in the high-order mode frequency band generated in the controlled object. A method for preventing structural vibration instability, comprising feeding back to the vibration state quantity control means via a compensation means having a transfer function arranged outside a unit circle on a plane. Detecting means for detecting the vibration amount of the rotor supported by the magnetic bearing;
A transfer function having a transfer function in which a complex conjugate zero is arranged outside the unit circle in the right half plane of the s plane or the z plane in order to give a phase transition to the detected value of the means in the frequency band of the higher order mode generated in the rotor. Phase means,
Compensation means for performing a compensation operation on the output of the means;
A magnetic bearing control device comprising: operating means for controlling a controlled object in accordance with the output of the means.

Images