Electricity: motive power systems – Positional servo systems – Frequency- or phase-modulated systems
Patent
1987-08-12
1989-06-20
Dobeck, Benjamin
Electricity: motive power systems
Positional servo systems
Frequency- or phase-modulated systems
318632, 310 905, G05B 101
Patent
active
048412120
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a control apparatus for a magnetic floating type rotor supported by an electromagnetic bearing and more particularly to an electromagnetic bearing control apparatus suitable for suppressing to a minimum the vibration amplitude of whirling motion of the rotor.
BACKGROUND ART
A rotor of rotary machine supported by an electromagnetic bearing using attraction type electromagnets as a bearing is typically controlled as will be described below. Electromagnetic coils are arranged along one axis on the right and left sides of the rotor and when the rotor is displaced to the right, a control current flows into one electromagnetic coil on the left side to exert attractive force so that the rotor is forcibly deflected to the left. Conversely, when the rotor is displaced to the left, a control current flows into the other electromagnetic coil on the right side to exert attractive force. In this way, the rotor is servo-controlled such that responsive to displacement of the rotor to the right or left, the control current is passed to the electromagnetic coil on the side opposite to the displacement and attractive force generated by that electromagnetic coil brings the rotor into the center position.
U.S. Pat. No. 4,128,795 discloses a prior art electromagnetic bearing control apparatus of this type, which is schematically illustrated in FIG. 14 of this application.
In this known apparatus, detected x and y-component signals of displacement (hereinafter simply referred to as displacement signals x and y) are differentiated to produce x and y-component signals of velocity (hereinafter simply referred to as velocity signals x and y) and the velocity signals x and y are added to the displacement signals x and y at blocks 11 and 12, providing ax+bx and ay+by. The displacement signals added with the velocity signals are passed through a rotation synchronous tracking filter 7 (triggered by a pulse signal) to extract only rotation synchronous components of the displacement signals and velocity signals, x.sub.o =ax.sub.N +bx.sub.N and y.sub.o =ay.sub.N +by.sub.N, which are respectively added with the displacement signals x and y processed by being passed through control circuits 6 and 8, respectively. The sum signals are supplied to electromagnetic coils 2 and 3 through associated amplifiers 9 and 10 in order to control only a rotation synchronous unbalanced vibration. Thus, the bearing stiffness can be adjusted by changing the magnitude of the displacement signals and the bearing damping can be adjusted by changing the magnitude of the velocity signals.
Disadvantageously, the prior art control apparatus requires that the velocity signals be produced from the displacement signals by means of the differentiation circuits, thus complicating the circuit design of the apparatus. Further the addition of the rotational synchronous components of displacement and velocity extracted from the displacement signals x and y and velocity signals x and y by means of the rotation synchronous tracking filter to the displacement signals x and y prevents the rotation synchronous unbalanced vibration from being sufficiently suppressed, due to not to make enough differential signal increase.
DISCLOSURE OF INVENTION
An object of this invention is to provide an electromagnetic bearing control apparatus capable of reducing the resonance amplitude of rotation synchronous unbalanced vibration.
According to this invention, to accomplish the above object, a selective extraction unit, for example, a rotation speed or number tracking filter for extracting rotor rotation synchronous component signals is provided in servo-circuits which control currents in X and Y directions being supplied to electromagnetic coils in accordance with x and y-component signals of radial displacement of the rotor (displacement signals x and y) such that the rotor is held in a predetermined radial position, and rotation synchronous x and y-component signals delivered out of the selective extraction unit and crossed and added to the
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Matsushita Osami
Saito Ikuhiro
Sugaya Toyomi
Takagi Michiyuki
Yoneyama Mitsuho
Dobeck Benjamin
Hitachi , Ltd.
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