High-speed rotor and controller for controlling magnetic bearings used therefor

• US 5,576,587 A
• Filed: 03/15/1995
• Issued: 11/19/1996
• Est. Priority Date: 03/18/1994
• Status: Expired due to Term

• Current Assignee: Hitachi Plant Technologies Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: Fukushima, Yasuo, Hiroshima, Minoru, Takahashi, Naohiko
• Primary Examiner(s): Dougherty, Thomas M.
• Assistant Examiner(s): ENAD, ELVIN GENARGUE
• Application Number:
  US08/404,742
• Time in Patent Office: 615 Days
• Field of Search: 310/90.5, 318/632, 318/611, 361/144, 364/463
• US Class Current: 310/90.5
• CPC Class Codes: F16C 2300/02 General use or purpose, i.e. no use, purpose, special adaptation or modification indicated or a wide variety of uses mentioned
• CPC Class Codes: F16C 32/0453 for controlling two axes, i.e. combined control of x-axis and y-axis

Abstract

Active magnetic bearings supporting a rotor operated at high speeds is controlled by a controller. Tracking filters provided in the controller pick up forward vibration components in synchronism with the rotational speeds from the displacement signals of the rotor, and a mode separating circuit provided in a mode gain controller takes out displacements of the 3rd and 4th modes. Then, a gain controller provided in the mode gain controller determines suitable gains for the separated displacement signals. A mode synthesizing circuit provided in the mode gain controller synthesizes a controlled variable for each of the bearings from the control signals that are processed for the respective modes. By adding the control variable to the respective bearings, the vibration amplitude is suppressed in critical speed zones of high orders, and the rotor is stably operated up to a high-speed range.

Claims

1. A high-speed rotor assembly comprising a rotor, active magnetic bearings for supporting the rotor, displacement detection means for detecting a displacement of said rotor, and magnetic bearing control means for controlling said active magnetic bearings, wherein said magnetic bearing control means comprises filter means which picks up a rotational speed synchronous component of said rotor from a displacement in a complex domain detected by said displacement detection means, mode decomposing means which decomposes the output of said filter means into a N-th order mode vibration and a (N+1)-th order mode vibration, and means that generates a control signal such that the phase of said displacement in a complex domain is varied according to the rotational speed in which the displacement is detected by said displacement detection means for at least either the N-th order mode or the (N+1)-th order mode decomposed by said mode decomposing means.

2. A high-speed rotor assembly according to claim 1, wherein said magnetic bearing control means is provided with a means which:

when said rotational speed is a critical speed of said N-th order vibration mode, advances the phase of a control signal related to the decomposed N-th order vibration mode by 90 degrees ahead of the phase of the displacement in a complex domain thereof, to make the control signal related to the decomposed (N+1)-th order vibration mode represent a positive real gain;

when said rotational speed lies between the N-th order vibration mode and the (N+1)-th order vibration mode, sets to zero control gains related to the decomposed N-th order vibration mode and the (N+1)-th order vibration mode; and

when said rotational speed is smaller than a critical speed of the (N+1)-th vibration but is close thereto, makes the control signal related to the N-th order vibration mode represent zero or a negative real gain and makes the control signal related to the (N+1)-th order vibration mode represent a positive real gain.

3. A high-speed rotor assembly comprising a rotor, a plurality of magnetic bearings for rotatingly supporting the rotor, displacement detection means for detecting a displacement of said rotor, and magnetic bearing control means for controlling said magnetic bearings,

wherein said magnetic bearing control means comprises filter means which picks up a rotational speed component from a displacement detected by said displacement detection means, and a mode gain controller which mode-decomposes the output signal of said filter means into mode components, sets a gain for the mode components, synthesizes the mode components, and outputs a control signal for said plurality of magnetic bearings.

4. A high-speed rotor assembly according to claim 3, wherein said magnetic bearings are radial magnetic bearings disposed at respective end portions of said rotor, said displacement detection means is disposed near said rotor and detects four independent displacements in radial directions of the rotor, and wherein said mode gain controller comprises a mode decomposing means which decomposes vibration modes of two consecutive orders of said rotor based upon an output of said filter means, a gain setting means which adjusts the output gain of the mode decomposing means, and a mode synthesizing means which outputs said control signal for of the bearings based upon the output of the gain setting means.

5. A controller for controlling active magnetic bearings for rotatingly supporting a rotor, which controller outputs control currents for driving the active magnetic bearings based upon the output of a displacement detection means which is located close to the magnetic bearings and which detects four independent displacements in radial directions of the rotor,

wherein said controller comprises a filter means which receives displacement amounts detected by said displacement detection means and picks up a nutation component of the rotor, and a mode decomposing means which decomposes an output of the filter means into vibration components of two independent vibration modes based upon a vibration mode shape at a displacement sensor of said rotor, so as to independently subject the vibration components decomposed for the respective vibration modes to a control law.

6. A controller for controlling active magnetic bearings according to claim 5, wherein said controller further comprises a means which picks up a nutation component of said rotor from at least either the N-th order vibration mode or the (N+1)-th order vibration mode, where N is a positive integer;

a means which forms a displacement vector from displacements in two independent radial directions that are picked up, converts said displacement vector based upon a phase difference between said displacement vector at said rotational speed and an imbalance force calculated from said displacement vector, and determines a complex gain used for feedback control; and

a means which determines a control variable for each of the modes by multiplying said displacement vector by said complex gain and effects an inverse conversion of a mode decomposition.

7. A controller for controlling active magnetic bearings according to claim 6, further including means which:

when said rotational speed is a critical speed of said N-th order vibration mode, advances the phase of said complex gain related to the displacement vector of the N-th order vibration mode that is picked up by 90 degrees ahead of the phase of the displacement vector, and causes said complex gain related to the displacement vector of the (N+1)-th order vibration mode that is picked up to represent a real gain;

when said rotational speed lies between the N-th order vibration mode and the (N+1)-th order vibration mode, sets complex gains, related to both the displacement vectors of the N-th and (N+1)-th order vibration modes that are picked up, to zero; and

when said rotational speed is smaller than a critical speed of the (N+1)-th vibration but is close thereto, causes a complex gain related to the displacement vector of the N-th order vibration mode to represent zero or a less than zero real gain and a complex gain related to the displacement vector of the (N+1)-th order vibration mode to represent a positive real gain.

8. A controller for controlling active magnetic bearings comprising an operation means which calculates control amounts for control of radial magnetic bearings, disposed near displacement detection means based upon the outputs of said displacement detection means, which are disposed at respective of a rotor, and which detects four displacements (XL, YL), (XR, YR) in radial directions of the rotor, said controller further comprising:

filter means for picking up nutation components (XNL, YNL) and (XNR, YNR) which are synchronous with the rotational speed of said rotor, from said four displacement signals (XL, YL) and (XR, YR);

a mode decomposing means which subjects said nutation components (XNL, YNL) and (XNR, YNR) to a linear transform according to a first control signal obtained by inputting to said operation means the difference between the displacement signals (XL, YL), (XR, YR) and amounts proportional to said nutation components (XNL, YNL) and (XNR, YNR), and according to the specific amplitude of said rotor at a bearing position of two independent vibration modes, and which decomposes them into components (XN1, YN1) and (XN2, YN2) for the respective vibration modes;

a gain setting means for linearly transforming complex vectors formed from the components (XN1, YN1) and (XN2, YN2) of each of said modes into other complex vectors (AN1, BN1) and (AN2, BN2);

a mode synthesizing means which converts said complex vector components (AN1, BN1) and (AN2, BN2) into components for the respective bearings according to specific amplitudes at the bearings of the two vibration modes, and which calculates the total amount of control signals for each of the bearings; and

a means which adds up and amplifies a second control signal generated by said mode synthesizing means and the first control signal, and which supplies drive currents to said radial magnetic bearings.