JPH03199711A - Method and apparatus for eliminating vibration of rotary machine with magnetic bearing - Google Patents

Abstract

PURPOSE: To eliminate vibration by moving a rotor shaft through adjustment of standard magnetic support bearings according to signals corresponding to vibration of a stator or frame of a rotary machine detected. CONSTITUTION: A rotary machine has a stationary armature 28, a frame 24, vibration detectors 23, 25, position detectors Dx-Dx', Dy-Dky'. Signals detected by the respective detectors are processed together with a signal input of a tachometer converter 40, at an automatic balance processing circuit, and signals detected by the vibration detectors and skynchronization signals 38 are processed at an adaptive signal processor (stator vibration controller). Output signals thereof and an output signal of the automatic balance processing circuit are input to a control circuit, and electromagnetic coils Ex-Ex, Ey-Ey' are controlled. Accordingly, the vibration of rotary machine is eliminated, reliability of operation is enhanced, and generation of wear is reduced.

Description

BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for reducing vibration in rotating machines. More particularly, the invention supports a rotor on a frame by magnetic journal bearings, a radial position detector for detecting the position of the rotor, an additional detector for detecting vibrations of the frame, and The present invention relates to a method and apparatus for reducing vibrations of a rotating machine comprising a servo control circuit connected to both the detector and the electromagnetic coil for the magnetic bearing.

U.S. Pat. No. 4,626,754 entitled "Method and Apparatus for Detecting Vibrations in a Rotating Machine Equipped with Magnetic Bearing Support Means" (Content) shows a conventional method for reducing vibrations in a rotating machine. Reducing the effects of rotor imbalance (vibrations) is accomplished by lowering the gain in the servo control circuit within a very narrow frequency band that is a direct function of the rotor's rotational speed. This causes automatic balancing of the rotor by aligning the rotor's axis of rotation with its axis of inertia. Stabilizing the frame of a rotating machine and preventing repetitive vibrations caused by elements coupled to the rotor or other reference source of the rotating machine from being transmitted to said frame is carried out by supporting the frame. This is achieved by a vibration detector and a selective feedback control circuit with narrow band and high gain. The center frequency of this narrow band is synchronized with a reference frequency, to which is added the detection signal generated by the vibration detector.

The conventional automatic balancing technology has been shown to be effective in suppressing vibrations caused by rotary balance. However, it has been shown that frame vibrations cannot be suppressed very effectively.

Also, although the vibrations of the bearing pedestal can be greatly reduced, the suppression of vibrations in other areas of the machine frame is less effective due to varying impedances and phase shifts.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to make a rotating machine essentially vibration-free and to avoid damage to industrial processes, environmental conditions, or any other technology requiring a vibration-free rotating machine. An object of the present invention is to provide an improved method and apparatus that can be applied to various types of rotating machines and that do not generate significant vibrations that cause vibrations.

Another object of the invention is to provide an improved method and apparatus for more reliable operation and less wear in rotating machines.

Yet another object of the present invention is to provide an improved method and apparatus that significantly reduces the need for repairs when applied to a variety of rotating machines.

Still another object of the present invention is that when applied to various rotating machines, an electronic control system using a rotor position indicator coupled with a shaft position detection control mechanism by magnetic force can
An object of the present invention is to provide an improved method and apparatus for continuously maintaining a rotor of a rotating machine in an accurately aligned position.

Yet another object of the present invention, when applied to a variety of rotating machines, is to maintain the rotor of the rotating machine in perfect equilibrium even when conditions that would normally result in unbalanced forces change. An object of the present invention is to provide an improved method and apparatus that can perform the following steps.

Yet another object of the present invention is an improved method and apparatus capable of significantly suppressing such vibrations in the stator or frame of a rotating machine, which would normally vibrate when applied to various rotating machines. The goal is to provide the following.

Stabilizing the frame of a rotating machine and preventing repetitive vibrations generated by elements connected to the rotor or other reference source of the rotating machine from being transmitted to the frame This can be achieved by arranging at least two vibration detectors to detect vibrations of the rotating machine. The measured vibration signals are analyzed and appropriate modifications of the bearing control signals are performed by one of several applicable signal processing techniques. If the disturbance is rotor-induced, such as shaft unbalance, the bearing control signal will be small at the natural frequency of that disturbance, thereby freeing the rotor from the stator and causing it to rotate about its axis of inertia. It brings about an equilibrium system. If the disturbance is not rotor-induced, the bearing control signal is one that increases the natural frequency of that disturbance and couples the rotor to the stator, thereby causing the rotor to act as an inertial mass that moves to compensate for the frame disturbance. It is.

Description of examples The method and apparatus according to the present invention are applied to a rotating machine (No. 2A).

In order to effectively reduce the total vibration force of the magnetic support system (Fig. 2B), the magnetic support system (Fig. This constitutes a control system that can control the

Referring to FIG. 1, the control system is shown for controlling an active magnetic support system.

That is, FIG. 1 shows a position detector (7) and an adder (11).
), (12), (21), (22), error signal 5xSS
y, feedback circuit xs, ys, automatic balance processing circuit (18),
control circuit (13), bearing electromagnets Ex-Ex' and II-EV', amplifiers Ax-Ax' and Ay-Ay',
Phase converters (16), (17), bearing phase advance circuits (14), (15), tachometer converter (20) and narrow band frequency filter (19) with high negative gain matched to the rotational frequency. It is shown.

Figure 2A shows vibration detectors (23), (25), position detectors Dx-Dx' and Dy-Dy', rotor (26), fixed armature (28), frame (24), and electromagnetic coil Ex.
-Ex' and EY-Ey', synchronization input (38), tachometer transducer (40), and position detector winding (42) are shown.

FIG. 2B shows a magnetic journal bearing (36) including a frame (24), a rotor (26), an annular armature (32) (which is fixed to the rotor (26)), and a stationary armature (28). , a radial position detector (34), an electronic coil (30), and a mutually orthogonal vibration detector (2).
5) is shown.

The rotating machine further includes a set of auxiliary secondary bearings adapted to contact and support the rotating shaft in the event of a malfunction of the primary or -order magnetic bearings. These secondary hair rings are arranged to prevent the rotating shaft from contacting the primary magnetic bearing in the event that the primary magnetic bearing malfunctions.

Prior art control systems for controlling active magnetic support systems employ inductive sensors to detect the precise radial position of the rotor of a rotating machine and provide position feedback signals to control electronics. This sensor utilizes the air gap between the rotor and stator to generate a response signal between the two. When the air gap increases or decreases, the inductance of the sensor conversely decreases or increases. This change in inductance with shaft position provides the position signal necessary for closed loop servo control of the primary bearing support system.

The rotor displacement signal is demodulated and filtered before being compared to the position reference signal. Any difference between the two signals generates an error signal that is used to control rotor position. This error signal is amplified in the primary gain section of the control circuit to preset the optimal control loop gain and to define the in-shell bearing hardness characteristics. The amplified error terminology is filtered to remove harmonics before entering the signal processing circuit.

A logical decision is made to command the bearing quadrant.

When this logical decision is implemented, a square root function is obtained since the bearing support force is proportional to the square of the current in the bearing. This provides a linear function of Kerr displacement. Pulse width modulation synchronized with the radio frequency is then performed and used to drive the switching power amplifier. The amplifier feedback signal is provided by current generating means for detecting low frequency interference or by magnetic flux sensing means for detecting high frequency interference. The power amplifier provides switched DC current to its corresponding bearing quadrant, thereby maintaining shaft position. The response time of the system is less than 1-2 mn+ seconds.

A control circuit for canceling repetitive mechanical vibrations uses a vibration detector placed on the frame to measure the vibrations of the rotating machine. The measured vibration signals are analyzed and then modulated into bearing control signals by one of several well-known signal processing techniques. If the disturbance is rotor-induced, such as a complete shaft unbalance, the bearing control signal will decrease at the natural frequency of the disturbance, thereby freeing the rotor from the stator and allowing it to rotate about its axis of inertia. As a result, a perfect equilibrium system is established. Also, if it is not completely rotor-induced, the bearing control signal will increase at its perturbed natural frequency, thereby coupling the rotor to the stator,
It compensates for frame disturbances by acting as an inertial mass.

As will be obvious to those skilled in the art, several suitable adaptive signal processing techniques can be selected and used in the above process according to the characteristics of the intended mechanical device. for example,
One suitable technique is disclosed in U.S. Pat. No. 4,490,841 entitled "Method and Apparatus for Eliminating Vibration."

Figure 3 shows commutators (50), (52), Fourier transformers (40), (46), processor (44), vibration canceling driver (54), rotating machine (56), and vibration detector (58). ),
and a synchronization input (60).

The necessary cancellation oscillations are generated as follows. That is,
The detected value of residual vibration from the vibration detector (58) is determined by the commutator (
52) and transformers (40), the residual vibrations at a plurality of different locations are defined in that frequency domain, and the processor (44) generates an individual signal representing each different frequency domain location. The elements of the transformer (46) and commutator (50) are modulated separately.
The previously processed elements are converted back into drive signals and fed into the control circuit loop of the active magnetic support system. This signal along with the control signal for positioning the rotor of a rotating machine is one that produces a force of equal amplitude and opposite polarity to the vibration.

Since the transform method is used to quantify a pair of components at each selected frequency location, the magnitudes of these elements are then individually controlled in a suitable manner. The frequency components are separated into real and imaginary components of amplitude at each frequency of interest. Each of these components can be erased individually without interfering with each other.

The changes to the cancellation component are used to calculate the conversion factor between the driver and detector. This transform coefficient can be used in the next iteration of the cancellation algorithm in the detector to produce an approximation for the cancellation necessary to produce the zero value.

Various algorithms well known in the art may be used to provide rapid processing to substantially complete the erasure. For optimal cancellation, the minimum time required for the system is only a few cycles of the fundamental frequency of the first repeating vibration.

A fast Fourier transformer is used to reconstruct the time waveform from the transformed frequency components. Synchronous input (60)
is supplied to the control circuit processor when eliminating repetitive vibrations of the rotating machine, thereby constraining various frequency components to the repetitive frequency of the vibration source.

Figures 4 and 5 plot two vibration-frequency characteristics from an accelerometer placed on the frame of a rotating machine with an active magnetic support system. First graph (Figure 4)
does not include the operation of the noise cancellation control circuit, and the second graph (FIG. 5) includes the operation of the noise cancellation control circuit. The table in FIG. 6 also shows the effectiveness of the noise cancellation control circuit at selected frequencies.

Although the present invention has been described above, it does not exclude a situation where an appropriate phase response cannot be obtained between the erasure driver and the vibration detector.

Examples of systems with poor phase response include vibrations in room acoustics, structures, containers, and aircraft, and the invention promises particular benefits in these applications as well.

[Brief explanation of drawings]

1 is a circuit diagram showing the basic control system for an active magnetic bearing support system including a self-balancing function; FIG. 2A is a schematic block diagram of the control system according to the invention; FIG. 2B is a position sensor and a Figure 3 is a functional block diagram according to the present invention, Figure 4 is a frequency graph with the noise cancellation control circuit cut off, and Figure 5 is a noise control control circuit. Figure 6 is a table showing the quantitative effect of the noise cancellation control circuit.

Claims (8)

[Claims] (1) In a rotating machine having a rotor shaft, (a) a basic magnetic support bearing for supporting the rotor shaft in the radial and axial directions in the rotating machine; (b) a positional alignment state of the rotor shaft and the an electronic control circuit for rotating the rotor shaft about its axis of inertia and substantially eliminating unbalanced forces on the rotor shaft by continuously controlling the hardness and damping characteristics of the basic magnetic bearing; ) means for detecting vibrations in a stator or frame of a rotating machine; and (d) adjusting said basic support bearing to drive the rotor shaft by transmuting said detected vibrations and generating a signal responsive thereto. A vibration cancellation device comprising: an adaptive signal processor for producing an inertial force that moves and thereby compensates for the detected vibrations. (2) the apparatus further comprises an auxiliary secondary bearing configured to contact and support the rotor shaft during a malfunction of the primary support bearing; The vibration canceling device according to claim 1, wherein the vibration canceling device is provided at a position that does not bring the rotor shaft into contact with the basic support bearing. (3) The secondary bearing comprises a rolling bearing element, and its inner diameter is larger than the diameter of the rotor shaft by a predetermined amount as small as the distance between the circumferential surface of the rotor shaft and the basic support bearing. The vibration canceling device according to claim 1, characterized in that: (4) The secondary bearing is a journal bearing, and its inner diameter is larger than the diameter of the rotor shaft by a predetermined amount smaller than the distance between the circumferential surface of the rotor shaft and the basic support bearing. The vibration canceling device according to claim 2. (5) the adaptive signal processor generates modulated time waveform samples that are provided to the stator or frame vibration detector including synchronization means, a first transformer for receiving time waveform samples, and an active magnetic control circuit; 2. The vibration canceling device according to claim 1, further comprising an electronic processing circuit connected to the second transformer. (6) The secondary bearing is a journal bearing, and its inner diameter is larger than the diameter of the rotor shaft by a predetermined amount that is shorter than the distance between the circumferential surface of the rotor shaft and the basic support bearing. The vibration canceling device according to claim 2. (7) The vibration canceling device according to claim 5, wherein the first and second transformers are Fourier transformers. 8. The vibration canceling device of claim 5, wherein the electronic control circuit includes means for controlling the hardness of the active magnetic bearing at the rotational speed of the rotor shaft and its multipliers.