JP3680226B2 - Magnetic bearing device - Google Patents

Description

式(22)において、Δ⁴ ＜＜Ｘ_O ⁴ として、Δ⁴ の項を削除すると、

式(23)をΔについて整理すると、次のようになる。
【００８４】

式(24)はΔに関する２次式であり、Δ² 、Δ¹ 、Δ⁰ の各係数をそれぞれａ、ｂ、ｃとすると、２次方程式の解の公式より式(19)が得られる。
【００８５】
図４(c) の倒立姿勢であって、飽和状態の場合、次の式(25)によりずれΔが演算され、前記同様に、磁気的中心位置が求められる。
【００８６】
Δ＝−Ｘ_O ＋Ｉ_Z1√（Ｋ／Ｍｇ） … (25)
Ｘ_O は予め設定された値、Ｉ_Z1は測定値、Ｋは定数、Ｍｇは回転体(1) の重量である。したがって、式(25)を用いてΔを演算することができる。
【００８７】
倒立姿勢で飽和状態の場合、Ｉ_Z2が０であって、Ｆ₂ が０であるため、回転体(1) の重量ＭｇはＦ₁ によって支持される。したがって、次の式(26)が成立つ。
【００８８】
Ｆ₁ ＝Ｍｇ … (26)
そして、図４(b) の正立姿勢で飽和状態の場合と同様の手順により、式(26)から式(25)が導かれる。
【００８９】
図４(c) の倒立姿勢であって、非飽和状態の場合、次の式(27)によりずれΔが演算され、前記同様に、磁気的中心位置が求められる。
【００９０】
Δ＝〔−ｂ−√（ｂ² −４・ａ・ｃ）〕／２・ａ … (27)
ここで、
ａ＝Ｉ_Z1 ² −Ｉ_Z2 ² ＋２・Ｘ_O ² ・Ｍｇ／Ｋ
ｂ＝−（２・Ｉ_Z1 ² ・Ｘ_O ＋２・Ｉ_Z2 ² ・Ｘ_O ）
ｃ＝Ｉ_Z1 ² ・Ｘ_O ² −Ｉ_Z2 ² ・Ｘ_O ² −Ｘ_O ⁴ ・Ｍｇ／Ｋ
である。
【００９１】
Ｘ_O は予め設定された値、Ｉ_Z1、Ｉ_Z2は測定値、Ｋは定数、Ｍｇは回転体(1) の重量である。したがって、式(27)を用いてΔを演算することができる。
【００９２】
正立姿勢で非飽和状態の場合、Ｆ₁ 、Ｆ₂ 、Ｍｇのつりあいより、次の式(28)が成立つ。
【００９３】
Ｆ₁ −Ｆ₂ ＝Ｍｇ … (28)
そして、図４(b) の正立姿勢で非飽和状態の場合と同様の手順により、式(28)から式(27)が導かれる。
【００９４】
Ｘ軸方向およびＹ軸方向の磁気的中心位置の推定は、各ラジアル磁気軸受(3)(4)について、それぞれ、上記と同様に行われる。
【００９５】
Ｘ軸方向の磁気的中心位置の推定についてさらに詳細に説明すると、正立姿勢、倒立姿勢、Ｙ軸正立姿勢あるいはＹ軸倒立姿勢の場合、Ｘ軸は水平になっているので、図４(a) の横置姿勢におけるＺ軸方向の磁気的中心位置の推定の場合と同様の式を用いて、Ｘ軸方向の磁気的中心位置を求めることができる。Ｘ軸正立姿勢の場合は、図４(b) の正立姿勢におけるＺ軸方向の磁気的中心位置の推定の場合と同様の式を用いて、Ｘ軸方向の磁気的中心位置を求めることができる。なお、Ｘ軸正立姿勢あるいはＸ軸倒立姿勢の場合、式(14)、(19)、(25)あるいは(27)に相当する式において、回転体(1) 重量Ｍｇのかわりに、各ラジアル磁気軸受(3)(4)の部分における重量Ｍｇの分力が用いられる。この各分力は、回転体(1) の重心位置、各ラジアル磁気軸受(3)(4)の位置に関するデータなどを用いて求めることができる。Ｙ軸方向の磁気的中心位置の推定についても同様である。
【００９６】
磁気的中心位置の推定を行った結果、いずれかの対の電磁石(12)(13)(14)の部分において仮浮上位置（対センサ中立位置）と磁気的中心位置とのずれが予め定められた所定値より大きい場合は、警報信号が制御装置(9) から警報装置(18)に出力され、警報装置(18)から光や音で警報が発せられる。
【００９７】
ステップ103 における回転体(1) の設置姿勢および磁気的中心位置の推定が終了したならば、Ｘ、Ｙ、Ｚ各制御軸の制御パラメータの決定が行われる（ステップ104 ）。制御装置(9) における電磁石(12)(13)(14)の制御は各制御軸ごとに行われるが、前述のように、制御軸が水平に配置されている場合と垂直に配置されている場合とで力のつり合いの条件が異なるので、各制御軸の姿勢によって最適な制御パラメータは異なる。このため、制御装置(9) には、各制御軸ごとに水平な姿勢の場合に最適な制御パラメータと垂直な姿勢のときに最適な制御パラメータが記憶されており、各制御軸ごとに姿勢によって最適な制御パラメータが選択される。なお、具体的な制御パラメータとしては、たとえば磁気軸受制御系の伝達関数や各電磁石に供給されるバイアス電流値があり、予め設定された複数の伝達関数、バイアス電流値の中から最適なものが選択される。
【００９８】
ステップ104 において制御パラメータの決定が行われたならば、各磁気軸受(3)(4)(5) を制御することにより、回転体(1) が磁気的中心位置に浮上させられ、その位置に保持される（ステップ６）。そして、モータ(8) を駆動することにより、回転体(1) の回転が開始される。
【００９９】
次に、図５のフローチャートを参照して、第２実施形態における回転体(1) 起動時の制御装置(9) の動作の１例について説明する。
【０１００】
図５において、磁気軸受装置の起動指令が制御装置(9) に入力すると、次のように、機械的中心位置の検出が行われる（ステップ201 ）。すなわち、まず、第１アキシアル電磁石(12a) にのみ所定の励磁電流が供給される。これにより、回転体(1) はＺ軸の負方向に吸引され、みぞ(17)の後側の側面が保護軸受(10)の内輪の後側の端面に接触するＺ軸負方向極限位置まで移動するので、このときのアキシアル位置センサ(5) の出力から、Ｚ軸上の所定位置を原点とするＺ軸負方向極限位置座標Ｚ_A が求められる。次に、第２アキシアル電磁石(12b) にのみ所定の励磁電流が供給される。これにより、回転体(1) はＺ軸の正方向に吸引され、みぞ(17)の前側の側面が保護軸受(10)の内輪の前側の端面に接触するＺ軸正方向極限位置まで移動するので、このときのアキシアル位置センサ(5) の出力から、Ｚ軸正方向極限位置座標Ｚ_B が求められる。そして、〔（Ｚ_A ＋Ｚ_B ）／２〕を演算することにより、アキシアル方向の機械的中心位置座標Ｚ_D が求められる。次に、２組のラジアル磁気軸受(3)(4)の第１Ｘ軸電磁石(13a)(14a)に所定の励磁電流が供給される。これにより、回転体(1) はＸ軸の負方向に吸引され、外周面が２組の保護軸受(10)(11)の内輪の内周面に接触するＸ軸負方向極限位置まで移動するので、このときの第１のラジアル位置センサユニット(6) の１対のＸ軸センサ(15a)(15b)の出力から、これらのセンサ(15a)(15b)間の中央を原点とする第１のラジアル磁気軸受(3) の近傍におけるＸ軸負方向極限位置座標Ｘ_1Aが求められるとともに、第２のラジアル位置センサユニット(7) の１対のＸ軸センサ(16a)(16b)の出力から、これらのセンサ(16a)(16b)間の中央を原点とする第２のラジアル磁気軸受(4) の近傍におけるＸ軸負方向極限位置座標Ｘ_2Aが求められる。次に、２組のラジアル磁気軸受(3)(4)の第２Ｘ軸電磁石(13b)(14b)に所定の励磁電流が供給される。これにより、回転体(1) はＸ軸の正方向に吸引されて、Ｘ軸正方向極限位置まで移動するので、上記と同様に、第１のラジアル磁気軸受(3) の近傍におけるＸ軸正方向極限位置座標Ｘ_1Bが求められるとともに、第２のラジアル磁気軸受(4) の近傍におけるＸ軸正方向極限位置座標Ｘ_2Bが求められる。そして、〔（Ｘ_1A＋Ｘ_1B）／２〕を演算することにより、第１のラジアル磁気軸受(3) の近傍におけるラジアル方向の機械的中心位置座標Ｘ_1Dが求められるとともに、〔（Ｘ_2A＋Ｘ_2B）／２〕を演算することにより、第２のラジアル磁気軸受(4) の近傍におけるラジアル方向の機械的中心位置座標Ｘ_2Dが求められる。次に、２組のラジアル磁気軸受(3)(4)の第１Ｙ軸電磁石(13c)(14c)に所定の励磁電流が供給される。これにより、回転体(1) はＹ軸の負方向に吸引され、外周面が２組の保護軸受(10)(11)の内輪の内周面に接触するＹ軸負方向極限位置まで移動するので、このときの第１のラジアル位置センサユニット(6) の１対のＹ軸センサ(15c)(15d)の出力から、これらのセンサ(15c)(15d)間の中央を原点とする第１のラジアル磁気軸受(3) の近傍におけるＹ軸負方向極限位置座標Ｙ_1Aが求められるとともに、第２のラジアル位置センサユニット(7) の１対のＹ軸センサ(16c)(16d)の出力から、これらのセンサ(16c)(16d)間の中央を原点とする第２のラジアル磁気軸受(4) の近傍におけるＹ軸負方向極限位置座標Ｙ_2Aが求められる。次に、２組のラジアル磁気軸受(3)(4)の第２Ｙ軸電磁石(13d)(14d)に所定の励磁電流が供給される。これにより、回転体(1) はＹ軸の正方向に吸引されて、Ｙ軸正方向極限位置まで移動するので、上記と同様に、第１のラジアル磁気軸受(3) の近傍におけるＹ軸正方向極限位置座標値Ｙ_1Bが求められるとともに、第２のラジアル磁気軸受(4) の近傍におけるＹ軸正方向極限位置座標値Ｙ_2Bが求められる。そして、〔（Ｙ_1A＋Ｙ_1B）／２〕を演算することにより、第１のラジアル磁気軸受(3) の近傍におけるラジアル方向の機械的中心位置座標Ｙ_1Dが求められるとともに、〔（Ｙ_2A＋Ｙ_2B）／２〕を演算することにより、第２のラジアル磁気軸受(4) の近傍におけるラジアル方向の機械的中心位置座標Ｙ_2Dが求められる。
【０１０１】
ステップ201 において機械的中心位置が検出されたならば、各磁気軸受(3)(4)(5) を制御することにより、回転体(1) が機械的中心位置に仮浮上させられ、その位置に保持される（ステップ202 ）。なお、この発明においては、回転体(1) の機械的中心位置への浮上は、以下に述べる磁気的中心位置の推定に必要なデータをとるためのものであるので、前述の特開平２−１０７８１５号公報に記載されているような厳密な機械的中心位置でなくてもよく、これから多少ずれたていてもよい。すなわち、厳密な機械的中心位置ではなく、その近傍の機械的略中心位置を求めて、その位置の近傍に回転体(1) を浮上させればよい。回転体(1) が機械的中心位置に保持されたならば、そのときに各電磁石(12)(13)(14)に流れる励磁電流が検出され（ステップ203 ）、次に説明するように、上記の励磁電流から、回転体(1) の設置姿勢と磁気的中心位置の推定が行われる（ステップ204 ）。この動作は第１実施形態の図３のステップ102 および103 のものと同じであり、この場合も、仮浮上位置（機械的略中心位置）と磁気的中心位置とのずれが所定値より大きければ、前記同様に、警報装置(18)から警報が発せられる。そして、以下、第１実施形態の場合と同様に、制御パラメータの決定（ステップ205 ）および回転体(1) の磁気的中心位置への磁気浮上（ステップ206 ）が行われる。
【図面の簡単な説明】
【図１】この発明の実施形態を示す磁気軸受装置の部分切り欠き斜視図である。
【図２】図１の磁気軸受装置の電気的構成の１例を示すブロック図である。
【図３】第１実施形態における図２の電磁石制御装置の動作の１例を示すフローチャートである。
【図４】回転体の設置姿勢の推定および磁気的中心位置の推定を説明するための説明図である。
【図５】第２実施形態における図２の電磁石制御装置の動作の１例を示すフローチャートである。
【符号の説明】
(1) 回転体
(2) アキシアル磁気軸受
(3)(4) ラジアル磁気軸受
(5) アキシアル位置センサ
(9) 電磁石制御装置
(10)(11) 保護軸受（規制手段）
(12a)(12b) アキシアル電磁石
(13a)(13b)(13c)(13d) ラジアル電磁石
(14a)(14b)(14c)(14d) ラジアル電磁石
(15a)(15b)(15c)(15d) ラジアル位置センサ
(16a)(15b)(16c)(16d) ラジアル位置センサ
(18) 警報装置（警報手段）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic bearing device, and more particularly to a magnetic bearing device that supports a rotating body in a non-contact manner in the axial direction and the radial direction with a plurality of magnetic bearings.
[0002]
[Background Art and Problems to be Solved by the Invention]
As this type of magnetic bearing device, a plurality of magnetic bearings having a plurality of electromagnets that non-contact support the rotating body in the axial direction and the radial direction, and a plurality of position sensors for detecting the axial direction and the radial direction of the rotating body And an electromagnet control means for controlling an electromagnet of a magnetic bearing based on a signal from a position sensor, and a protective bearing as a regulating means for regulating a movable range in the axial direction and radial direction of a rotating body are known. Yes.
[0003]
In such a magnetic bearing device, the axial and radial mechanical center positions of the rotating body with respect to the movable range by the protective bearing, the axial and radial magnetic center positions with respect to the position of the electromagnet of the magnetic bearing, There is a sensor neutral position with respect to the sensor position. The mechanical center position is the center position of the movable range regulated by the protective bearing. Each magnetic bearing is provided with one or two pairs of electromagnets that oppose each other with the rotating body sandwiched from both sides in the control axis direction, and the magnetic center position in each control axis direction makes a pair in the control axis direction. This is the position of the center of each electromagnet. Usually, the axial position sensor includes one axial position sensor facing the position detection end face of the rotating body from one side in the axial direction, and the radial position sensor includes two rotating bodies orthogonal to each other. A plurality of pairs of radial position sensors facing each other from both sides in the control axis direction are included. The sensor-neutral position in the axial direction is a position where the distance between the position detection end face of the rotating body and the axial position sensor becomes a predetermined value set in advance. The neutral position of the pair of sensors in each control axis direction in the radial direction is the center position of the two radial position sensors paired in the control axis direction. The magnetic bearing device is designed so that the mechanical center position, the magnetic center position, and the neutral position with respect to the sensor all coincide with each other, but an error may occur between them due to manufacturing errors and assembly errors.
[0004]
In the conventional magnetic bearing device, the electromagnet of the magnetic bearing is controlled so that the rotating body is held at the center position of the sensor, which is the designed center position, that is, the center of the rotating body coincides with the neutral position of the sensor. Is done. For this reason, when the neutral position with respect to the sensor does not coincide with the mechanical center position and the magnetic center position, the rotating body cannot be held at the mechanical center position and the magnetic center position. In this case, if the error between the mechanical center position of the rotating body and the neutral position with respect to the sensor is large, the gap between the rotating body and the protective bearing is partially reduced when the rotating body is held at the neutral position with respect to the sensor. Various problems occur. In order to avoid such a problem, as described in, for example, JP-A-2-107815, the mechanical center position is determined from the output of the position sensor when the rotating body is moved to both extreme positions of the movable range. Accordingly, a magnetic bearing device has been proposed in which a rotating body is magnetically levitated at the mechanical center position. However, in this apparatus, when the mechanical center position does not coincide with the magnetic center position, the rotating body cannot be held at the magnetic center position. If the rotating body is displaced from the magnetic center position, the relationship between the excitation current supplied to the pair of electromagnets of the magnetic bearing and the attractive force by the pair of electromagnets is not linear, and the control becomes unstable. There is a problem of becoming. Even when the rotating body is held at the neutral position with respect to the sensor from the beginning as described above, the same problem occurs when the magnetic center position does not coincide with the neutral position with respect to the sensor.
[0005]
The object of the present invention is to solve the above-mentioned problems and to automatically correct the deviation between the neutral position of the sensor or the mechanical center position and the magnetic center position, and to maintain the rotating body at the magnetic center position. The object is to provide a magnetic bearing device with good performance.
[0006]
[Means for Solving the Problems and Effects of the Invention]
  A magnetic bearing device according to the present invention includes a plurality of magnetic bearings having a plurality of electromagnets that non-contact support the rotating body in the axial direction and the radial direction, and a plurality of positions for detecting the positions of the rotating body in the axial direction and the radial direction. In a magnetic bearing device comprising a sensor and an electromagnet control means for controlling the electromagnet of each magnetic bearing based on a signal from the position sensor, the electromagnet control means comprises:The neutral position of the sensor in the axial and radial directions determined from the position of the position sensor is defined as a temporary levitation position.From the exciting current that flows through each electromagnet of each of the magnetic bearings during the temporary levitation, The installation posture of the rotating body,Axial and radial magnetic center positions relative to the electromagnet position of each magnetic bearingWhenAnd the rotor is magnetically levitated at the magnetic center position.
[0007]
  The electromagnet control meansThe neutral position of the sensor in the axial and radial directions determined from the position of the position sensor is defined as the temporary levitation position.From the exciting current that flows through each electromagnet of each magnetic bearing during the temporary levitation, The installation posture of the rotating body,Since the magnetic center position with respect to the position of the electromagnet of each magnetic bearing is estimated and the rotating body is magnetically levitated at this magnetic center position,Even if the installation posture of the rotating body is not known in advance, it is possible to estimate the magnetic center position by estimating the installation posture of the rotating body during temporary ascent,Sensor neutral positionAndEven when there is a deviation from the magnetic center position, the deviation can be corrected and the rotating body can always be held at the magnetic center position, so that the control does not become unstable. That is, when the rotating body is held at the magnetic center position, the relationship between the excitation current supplied to the pair of electromagnets of the magnetic bearing and the attractive force by the pair of electromagnets becomes linear, and the control becomes stable. Control performance is improved.
[0013]
  The magnetic bearing device according to the present invention also includes a plurality of magnetic bearings having a plurality of electromagnets that non-contact support the rotating body in the axial direction and the radial direction, and a plurality for detecting positions of the rotating body in the axial direction and the radial direction. Position sensor, electromagnet control means for controlling the electromagnet of each magnetic bearing based on a signal from the position sensor, and magnetic bearing comprising restriction means for restricting the movable range in the axial direction and radial direction of the rotating body In the apparatus, the electromagnet control means obtains a mechanical center position in the axial direction and radial direction of the rotating body with respect to a movable range by the restriction means, and sets the position as a temporary levitation position, and the rotation to the temporary levitation position. The body is temporarily levitated, and from the exciting current flowing through each electromagnet of each magnetic bearing at the time of, The installation posture of the rotating body,Axial and radial magnetic center positions relative to the electromagnet position of each magnetic bearingWhenAnd the rotor is magnetically levitated at the magnetic center position.
[0014]
  The electromagnet control meansA mechanical approximate center position in the axial direction and radial direction of the rotating body with respect to the movable range by the regulating means is obtained, and this position is set as a temporary levitation position, and the rotating body is temporarily levitated at the temporary levitation position. From the excitation current flowing through each electromagnet of the magnetic bearing, the installation posture of the rotating body and the axial and radial magnetic center positions with respect to the position of the electromagnet of each magnetic bearing are estimated, and the rotating body is located at this magnetic center position. TheBecause the magnetic levitationEven if the installation posture of the rotating body is not known in advance, it is possible to estimate the magnetic center position by estimating the installation posture of the rotating body during temporary ascent,Even when the mechanical center position and the magnetic center position are deviated from each other, the deviation can be corrected and the rotating body can be held at the magnetic center position, so that the control does not become unstable.
[0016]
For example, the electromagnet control means includes alarm means for issuing an alarm when it is determined that the difference between the temporary levitation position and the magnetic center position is greater than a predetermined value.
[0017]
For example, the restricting means is constituted by a protective bearing. Then, the electromagnet control means moves the rotating body to each extreme position in contact with the protective bearing in each of the axial direction and the radial direction, obtains the output of the position sensor at each extreme position, and then approximates the mechanical center. Find the position. The magnetic bearing device includes a pair of axial magnetic bearings having an axial direction control shaft and two sets of radial magnetic bearings having two radial direction control shafts orthogonal to each other. A pair of electromagnets that are paired with the rotating body sandwiched from both sides in the control axis direction, and each radial magnetic bearing has two sets of electromagnets that are paired with the rotating body sandwiched from both sides in the two control axis directions. The electromagnet control means estimates the installation posture of the rotating body based on the excitation current flowing through the pair of electromagnets in the direction of each control axis during temporary ascent, and determines the approximate mechanical center position and magnetic center position. The deviation is estimated and the magnetic center position is estimated.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, two embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 shows an example of a magnetic bearing device that supports a shaft-like rotating body (1) in a non-contact manner, and FIG. 2 shows an example of its electrical configuration. The configurations of FIGS. 1 and 2 are common to the two embodiments. In the following description, the axial control axis of the rotator (1) is the Z axis, one radial control axis orthogonal to the Z axis is the X axis, and another radial direction orthogonal to the Z axis and the Y axis. The control axis is defined as the Y axis. FIG. 1 shows a state in which the Z-axis direction is the front-rear direction, the X-axis direction is the up-down direction, and the Y-axis direction is the left-right direction.
[0020]
The magnetic bearing device includes a pair of axial magnetic bearings (2) for non-contact support of the rotating body (1) in the axial direction, and two sets of radial magnetism for non-contact support of the rotating body (1) in the radial direction. Axial position sensor (5) for detecting axial displacement of bearing (3) (4) and rotating body (1), 2 sets for detecting radial displacement of rotating body (1) The radial position sensor unit (6) (7), high-frequency motor (8) for rotating the rotating body (1) at high speed, axial position sensor (5), and signals from the radial position sensor units (6) (7) Based on the electromagnet control device (9) and alarm device (18) as the electromagnet control means for controlling the magnetic bearings (2), (3), and (4), and the movable range in the axial and radial directions of the rotating body (1). If the rotor (1) cannot be supported by the magnetic bearings (2), (3), and (4) due to regulation, this is mechanically Has two sets of protective bearings as regulating means for supporting (10) (11).
[0021]
The axial magnetic bearing (2) includes a pair of axial electromagnets (12a) (12b) arranged so as to sandwich a flange portion (1a) formed integrally with the front portion of the rotating body (1) from both sides in the Z-axis direction. ). The axial electromagnets are collectively referred to by reference numeral (12), and when it is necessary to distinguish them, one electromagnet (12a) is referred to as a first axial electromagnet, and the other electromagnet (12b) is referred to as a second axial electromagnet.
[0022]
The axial position sensor (5) is arranged so as to face the front end face (position detection end face) of the rotating body (1) from one side in the Z-axis direction, and is at a distance (gap) from the front end face of the rotating body (1). Output a proportional distance signal. Then, the control device (9) obtains the axial position, that is, the displacement of the rotating body (1) from the distance signal of the axial position sensor (5).
[0023]
The two sets of radial magnetic bearings (3) and (4) are arranged at predetermined intervals in the front-rear direction on the rear side of the axial magnetic bearing (1), and the motor (8) is arranged between them. Yes. The first radial magnetic bearing (3) on the front side includes a pair of radial electromagnets (13a) (13b) arranged so as to sandwich the rotating body (1) from both sides in the X-axis direction, and the rotating body (1). A pair of radial magnetic bearings (13c) (13d) are provided so as to be sandwiched from both sides in the Y-axis direction. These radial electromagnets are collectively referred to by reference numeral (13), and when it is necessary to distinguish them, one electromagnet (13a) in the X-axis direction is set as the first X-axis electromagnet, the other electromagnet (13b) as the second X-axis electromagnet, One electromagnet (13c) in the axial direction is referred to as a first Y-axis electromagnet, and the other electromagnet (13d) is referred to as a second Y-axis electromagnet. Similarly, the rear second radial electromagnet (4) also includes a first X-axis electromagnet (14a), a second X-axis electromagnet (14b), a first Y-axis electromagnet (14c), and a second Y-axis electromagnet (14d). Yes. These radial electromagnets (14a), (14b), (14c), and (14d) are also collectively referred to by reference numeral (14).
[0024]
The first radial position sensor unit (6) on the front side is arranged in the vicinity of the first radial magnetic bearing (3) and rotates from both sides in the X-axis direction in the vicinity of the X-axis electromagnets (13a) and (13b). A pair of radial position sensors (15a) (15b) arranged so as to sandwich the body (1), and the rotary body (1) from both sides in the Y-axis direction in the vicinity of the Y-axis electromagnets (13c) (13d) Are provided with a pair of radial position sensors (15c) (15d). These radial position sensors are collectively referred to by reference numeral (15), and when it is necessary to distinguish them, one sensor (15a) in the X-axis direction is the first X-axis sensor, the other sensor (15b) is the second X-axis sensor, One sensor (15c) in the Y-axis direction is referred to as a first Y-axis sensor, and the other sensor (15d) is referred to as a second Y-axis sensor. Similarly, the second radial position sensor unit (7) on the rear side is also arranged in the vicinity of the second radial magnetic bearing (4). The first X-axis sensor (16a) and the second X-axis sensor (16b) The first Y-axis sensor (16c) and the second Y-axis sensor (16d) are provided. These radial position sensors (16a), (16b), (16c), and (16d) are also collectively designated by reference numeral (16). Each radial position sensor (15), (16) outputs a distance signal proportional to the distance from the outer peripheral surface of the rotating body (1). Then, the control device (9) calculates the difference between the distance signals of the pair of X-axis sensors (15a) and (15b) of the first unit (6), thereby the first radial magnetic bearing (3). By calculating the position or displacement of the rotating body (1) in the vicinity in the X-axis direction and calculating the difference between the distance signals of the pair of Y-axis sensors (15c) and (15d) of the unit (6), The position, that is, the displacement of the rotating body (1) in the Y-axis direction is obtained. Similarly, the control device (9) determines the difference between the distance signals of the pair of X-axis sensors (16a) and (16b) of the second unit (7) and the distance of the pair of Y-axis sensors (16c) and (16d). From the signal difference, the position, that is, the displacement of the rotating body (1) in the vicinity of the second radial magnetic bearing (4) in the X-axis direction and the Y-axis direction is obtained.
[0025]
The first protective bearing (10) on the front side is, for example, a combination of two angular ball bearings, and can receive both an axial load and a radial load. The outer ring of the bearing (10) is fixed to a casing of a magnetic bearing device (not shown), and the inner ring has an appropriate gap in the axial and radial directions in the circumferential groove (17) formed on the outer peripheral surface of the rotating body (1). Opened up. The rear-side second protective bearing (11) is formed of, for example, a deep groove ball bearing and can receive a radial load. The outer ring of the bearing (11) is fixed to the casing, and the inner ring is arranged to face the outer peripheral surface of the rotating body (1) with an appropriate gap. The axial movable range of the rotating body (1) is restricted by the size of the gap in the axial direction between the inner ring of the first bearing (10) and the rotating body (1). The radial movable range of the rotating body (1) is restricted by the size of the radial gap between the inner ring of (11) and the rotating body (1).
[0026]
The control device (9) calculates the displacement in the Z-axis direction of the rotating body (1) obtained as described above, the displacement in the X-axis direction and the Y-axis direction in the vicinity of the two sets of radial magnetic bearings (3) and (4). Based on this, the magnitude of the excitation current flowing in each electromagnet (12), (13), (14) is controlled, so that the rotating body (1) is held at the magnetic center position described later. .
[0027]
The magnetic bearing device has a mechanical center position, a magnetic center position, and a sensor neutral position. The mechanical center position is the center position of the movable range controlled by the protective bearings (10) and (11). In the axial direction, the inner ring of the first protective bearing (10) is only the rotating body (1). In the center of the axial direction of (17), the axial gap between the end face of the inner ring and the side surface of the groove (17) facing this is the same on both sides. The center of 1) coincides with the center of the two sets of protective bearings (10) and (11), and the radial clearance between the rotating body (1) and the inner ring of the protective bearings (10) and (11) is the same over the entire circumference. Is the position. The magnetic center position is the center position of each pair of electromagnets (12), (13) and (14) facing each of the magnetic bearings (2), (3) and (4). The neutral position with respect to the sensor is a position where the distance between the front end face of the rotating body (1) and the axial position sensor (5) becomes a predetermined value in the axial direction. This is the center position of each pair of radial position sensors (15) and (16) facing each other of the radial position sensor units (6) and (7).
[0028]
In the above magnetic bearing device, when the rotating body (1) is stopped, the magnetic bearings (2), (3), and (4) are not driven, and the rotating body (1) is not connected to the electromagnet (2). It is supported by protective bearings (10) and (11) so as not to contact (3) (4) and sensors (5), (15) and (16). Before the rotating body (1) starts rotating, the magnetic bearings (2), (3), and (4) are controlled by the control device (9), and the rotating body (1) is protected by the protective bearings (10) (11). It is levitated from and is held at the magnetic center position.
[0029]
FIG. 3 is a flowchart showing an example of the operation of the control device (9) at the time of starting the rotating body (1) in the first embodiment, and FIG. 5 is a similar flowchart in the second embodiment.
[0030]
In the case of the first embodiment, the control device (9) temporarily floats the rotating body (1) using the neutral position with respect to the sensor as the temporary floating position, and at this time, the excitation flowing through the electromagnets (12), (13) and (14). The installation posture and magnetic center position of the rotating body (1) are estimated from the current, and the rotating body (1) is magnetically levitated at this magnetic center position. In the case of the second embodiment, the control device (9) temporarily levitates the rotating body (1) with the mechanical center position as the temporary levitation position. At this time, the excitation flowing through the electromagnets (12) (13) (14) The installation posture and magnetic center position of the rotating body (1) are estimated from the current, and the rotating body (1) is magnetically levitated at this magnetic center position.
[0031]
The alarm device (18) is composed of, for example, a lamp, a buzzer, a display device and the like. In the case of the first embodiment, the alarm device (18) constitutes alarm means for issuing an alarm when the difference between the neutral position with respect to the sensor and the magnetic center position is large. In the case of the second embodiment, the alarm device (18) constitutes alarm means for issuing an alarm when the difference between the mechanical center position and the magnetic center position is large.
[0032]
Next, an example of the operation of the control device (9) at the time of starting the rotating body (1) in the first embodiment will be described with reference to the flowchart of FIG.
[0033]
In FIG. 3, when the start command of the magnetic bearing device is input to the control device (9), first, the rotating body is controlled by controlling the magnetic bearings (3), (4), and (5) with the neutral position of the sensor as a target value. (1) is temporarily levitated to the sensor neutral position (temporary levitating position) and held at that position (step 101).
[0034]
If the rotating body (1) is held in the neutral position with respect to the sensor, the excitation current flowing through the electromagnets (12), (13), and (14) at that time is detected (step 102). From the excitation current, the installation posture and magnetic center position of the rotating body (1) are estimated (step 103).
[0035]
The control device (9) includes the radius of each radial magnetic bearing (3) and (4) of the rotating body (1), the thickness (axial dimension) of the flange (1a), weight, center of gravity, and each magnetic bearing. The characteristics of the electromagnets (12), (13), and (14) in (2), (3), and (4), the mutual distance between the opposing electromagnets (12), (13), and (14) are stored. First, the installation posture of the rotating body (1) is estimated from the excitation current of each pair of electromagnets (12), (13), and (14).
[0036]
The rotary body (1) is installed in a horizontal position with the Z-axis horizontal, ie, the upright position with the Z-axis positive direction up with the rotary body (1) vertical. There is an inverted posture in which the rotating body (1) is vertical and the positive direction of the Z-axis is down. In the horizontal posture, the X-axis is vertical and the X-axis positive direction is up, the X-axis upright posture, the X-axis positive direction is down, and the Y-axis is vertical. Thus, there are a Y-axis erect posture in which the Y-axis positive direction is up and a Y-axis inverted posture in which the Y-axis positive direction is down.
[0037]
Even if there is a deviation between the neutral position with respect to the sensor and the magnetic center position, the deviation is generally small. In general, two electromagnets in a pair have the same characteristics. When the distance (gap) between the two electromagnets and the rotating body (1) and the excitation current of each electromagnet are equal to each other, The magnetic attractive forces exerted by the electromagnet on the rotating body (1) are equal to each other.
[0038]
Next, the estimation of the Z-axis attitude will be described by taking two electromagnets (12) of the axial magnetic bearing (2) as an example. As shown in FIG. 1, when the Z-axis is placed horizontally, that is, when two axial electromagnets (12) making a pair are placed horizontally, the rotating body in the Z-axis direction Only the horizontal attractive force by the two electromagnets (12) acts on (1), and when the rotating body (1) is held in the neutral position with respect to the sensor, the two electromagnets (12) are attracted. The forces are balanced with each other. When the neutral position with respect to the sensor matches the magnetic center position, the distance between the two electromagnets (12) and the flange (1a) of the rotating body (1) is equal to each other. The exciting currents of the electromagnet (12) are equal to each other. If the neutral position of the sensor is shifted from the magnetic center position, the excitation currents of the two electromagnets (12) are not equal, but the deviation is small as described above, so the excitation of the two electromagnets (12) The difference in current is small. Therefore, when the difference between the excitation currents of the two electromagnets (12) is smaller than a predetermined value, it is estimated that the Z-axis is in a horizontal posture in which it is horizontally arranged. On the other hand, when the Z axis is arranged vertically, that is, when two electromagnets (12) that make a pair are arranged in the vertical direction, the rotating body (1) has its own in the Z axis direction. The vertical force due to the weight of the two and the vertical attractive force due to the two electromagnets (12) act, the downward attractive force due to the lower electromagnet (12) plus the downward force due to the weight, The upward attracting force by the electromagnet (12) is balanced with each other. For this reason, even if the rotating body (1) is held in the neutral position with respect to the sensor, the attractive force by the upper electromagnet (12) is considerably larger than the attractive force by the lower electromagnet (12). Therefore, when the difference between the excitation currents of the two electromagnets (12) is larger than a predetermined value, it is estimated that the Z axis is arranged in the vertical direction, and among these, the excitation current of the first electromagnet (12a) is the first. If it is greater than the excitation current of the two electromagnets (12b), it is estimated that it is in an upright posture, and in the opposite case, it is in an inverted posture.
[0039]
Next, the estimation of the Z-axis attitude will be described in more detail with reference to FIG.
[0040]
The exciting current flowing through the first axial electromagnet (12a) is I_Z1The exciting current flowing through the second axial electromagnet (12b)_Z2Then, these are expressed by the following equations (1) and (2).
[0041]
I_Z1= I_O+ I_C  … (1)
I_Z2= I_O-I_C  … (2)
Where I_OIs a predetermined constant steady-state current, I_CIs a control current that varies depending on the position of the rotating body (1).
[0042]
When the rotating body (1) is at the magnetic center position, the gap between the first axial electromagnet (12a) and the rotating body (1) and the gap between the second axial electromagnet (12b) and the rotating body (1) are mutually separated. equal. The size of the gap at this time is X_OAnd When the error between the neutral position of the sensor and the magnetic center position in the axial direction, that is, mechanical deviation (Z coordinate value of the sensor neutral position−Z coordinate value of the magnetic center position) is Δ, the rotating body (1) The gap between the first axial electromagnet (12a) and the rotating body (1) when in the sensor neutral position is (X_O+ Δ), the gap between the second axial electromagnet (12b) and the rotating body (1) is (X_O−Δ). Further, the magnetic attraction force by the first axial electromagnet (12a) when the rotating body (1) is in the neutral position with respect to the sensor is F.₁The magnetic attraction force by the second electromagnet (12b) is F₂Then, these are expressed by the following equations (3) and (4).
[0043]
F₁= K ・ [I_Z1/ (X_O+ Δ))²  … (3)
F₂= K ・ [I_Z2/ (X_O-Δ))²  … (Four)
Here, K is a constant.
[0044]
As shown in FIG. 4 (a), in the horizontal posture where the Z-axis is horizontal,_Z1And I_Z2Are always unsaturated, and the above equations (1) and (2) hold, and therefore, the following equation (5) holds between them.
[0045]
I_Z1+ I_Z2= (I_O+ I_C) + (I_O-I_C) = 2 · I_O  … (Five)
In the case of the horizontal posture, as described above, I_Z1And I_Z2The difference is small. Therefore, the above equation (5) holds and I_Z1And I_Z2When the difference is small, it is estimated that the posture is horizontal.
[0046]
In the case of an upright posture with the Z-axis positive direction facing upward as shown in FIG._Z1A saturation state in which is saturated to 0, and I_Z1And I_Z2Are both unsaturated.
[0047]
When the erect posture is saturated, the following equations (6) and (7) hold.
[0048]
I_Z1+ I_Z2> 2.I_O  … (6)
I_Z1= 0 (7)
Therefore, when the above equations (6) and (7) are satisfied, it is estimated that the posture is upright (saturated state).
[0049]
In the case of the unsaturated state in the upright posture, the above equations (1) and (2) hold, and therefore I_Z1And I_Z2The above equation (5) is established during this period. In the upright posture, as described above, I_Z1Is I_Z2Smaller, these differences are large. Therefore, the above equation (5) holds and I_Z1Is I_Z2If it is smaller and the difference between them is large, it is estimated that the posture is upright (unsaturated state).
[0050]
As shown in FIG. 4 (c), in the inverted posture with the Z-axis positive direction down,_Z2A saturation state in which is saturated to 0, and I_Z1And I_Z2Are both unsaturated.
[0051]
In the saturated state of the inverted posture, the above equation (6) and the following equation (8) are satisfied.
[0052]
I_Z1= 0 (8)
Therefore, when Expressions (6) and (8) are satisfied, it is estimated that the posture is inverted (saturated state).
[0053]
In the non-saturated state of the inverted posture, the above equations (1) and (2) hold, and therefore I_Z1And I_Z2The above equation (5) is established during this period. In the inverted posture, as described above, I_Z1Is I_Z2Larger, these differences are large. Therefore, the above equation (5) holds and I_Z1Is I_Z2If it is larger and the difference between them is large, it is estimated that the posture is inverted (non-saturated state).
[0054]
The X-axis attitude is estimated by comparing the excitation currents of the two X-axis electromagnets (13a) and (13b) of the first radial magnetic bearing (3) and / or the two of the second radial magnetic bearing (4). This is performed in the same manner as described above by comparing the exciting currents of the X-axis electromagnets (14a) and (14b). The same applies to the estimation of the Y-axis posture.
[0055]
More specifically, when the X axis is horizontal, the horizontal orientation shown in FIG. 4 (a) is applied between the exciting currents flowing through the first X axis electromagnet (13a) and the second X axis electromagnet (13b). Case I_Z1And I_Z2The same relationship occurs between the two. In the case of the X-axis upright posture, the excitation current flowing in the first X-axis electromagnet (13a) and the second X-axis electromagnet (13b) and the I in the upright posture shown in FIG._Z1And I_Z2The same relationship occurs between the two. In the case of the X-axis inverted posture, the excitation current flowing in the first X-axis electromagnet (13a) and the second X-axis electromagnet (13b) during the inverted posture shown in FIG._Z1And I_Z2The same relationship occurs between the two. Accordingly, by examining the excitation current flowing through the pair of electromagnets (13a) and (13b), it can be estimated whether the X axis is in the horizontal posture, the X axis upright posture, or the X axis inverted posture. Similarly, for the Y-axis, by examining the excitation current flowing through the first Y-axis electromagnet (13c) and the second Y-axis electromagnet (14d), the Y-axis can be either horizontal, Y-axis upright or Y-axis inverted. Can be estimated.
[0056]
Although the procedure for estimating the installation posture of the rotating body (1) is arbitrary, for example, it is performed in the order of the Z axis, the X axis, and the Y axis. As a result of the estimation with respect to the Z axis, when the posture is an erect posture or an inverted posture, the X axis and the Y axis are horizontal, so there is no need to estimate the postures of the X axis and the Y axis. However, as described above, it can be confirmed that the X axis and the Y axis are horizontal. As a result of the estimation with respect to the Z axis, when the posture is in the horizontal orientation, the attitude is estimated with respect to the X axis. As a result, in the case of the X-axis upright posture or the X-axis inverted posture, the Y-axis is horizontal, so there is no need to estimate the Y-axis posture. You can see that it is level. If the X-axis is horizontal as a result of the estimation about the X-axis, the posture about the Y-axis is estimated, and whether it is the Y-axis upright posture or the Y-axis inverted posture as described above Presumed.
[0057]
When the estimation of the installation posture of the rotating body (1) is completed, the magnetic center position in the Z-axis direction of the axial magnetic bearing (2) based on the excitation current of each pair of electromagnets (12), (13), and (14), In addition, the magnetic center positions of the radial magnetic bearings (3) and (4) in the X-axis direction and the Y-axis direction are estimated.
[0058]
Next, the estimation of the magnetic center position in the Z-axis direction will be described using the two electromagnets (12) of the axial magnetic bearing (2) as an example. As described above, the attractive force by each electromagnet (12) is proportional to the square of the excitation current and inversely proportional to the square of the distance between the electromagnet (12) and the rotating body (1). ). Normally, the two electromagnets that make a pair have the same characteristics as described above, and therefore the above proportionality constants are equal to each other. When the Z-axis is horizontally arranged as shown in FIG. 1, as described above, the attraction force by the two electromagnets (12) is balanced, and this balanced state is proportional constant, electromagnet (12). And the distance between the rotating body (1) and the excitation current of the electromagnet (12). The proportionality constant is the characteristic of the electromagnet (12), and the sum of the distance between the two electromagnets (12) and the rotating body (1) is the mutual distance between the two electromagnets in the axial direction and the flange of the rotating body (1) ( The thickness of 1a) is known, and the excitation current of each electromagnet (12) is detected in step 3. Therefore, the distance between each electromagnet (12) and the rotating body (1) is calculated from the above balance equation. Is required. Thus, the deviation between the magnetic center position where the distance between each electromagnet (12) and the rotating body (1) is equal to the neutral position with respect to the sensor is obtained, and the magnetic center position is obtained. On the other hand, when the Z axis is arranged vertically, as described above, the downward attracting force due to the weight of the rotating body (1) is added to the downward attracting force by the lower electromagnet (12), and The upward attracting force by the upper electromagnet (12) balances with each other, and the state of this balance is expressed by a formula in which a force due to the weight of the rotating body (1) is added to the above balance formula. Since the force due to the weight is known from the weight of the rotating body (1), the deviation between the magnetic center position and the neutral position with respect to the sensor and the magnetic center position are obtained as described above. In the portion of the first radial magnetic bearing (3), the magnetic center position in the X-axis direction is estimated based on the excitation currents of the two X-axis electromagnets (13a) and (13b). Is estimated in the same manner as described above based on the excitation currents of the two Y-axis electromagnets (13c) and (13d). In the second radial magnetic bearing (4), the magnetic center position in the X-axis direction is estimated based on the excitation currents of the two X-axis electromagnets (14a) and (14b). The estimation of the center position is performed in the same manner as described above based on the excitation currents of the two Y-axis electromagnets (14c) and (14d). When the Z-axis is arranged vertically, the X-axis and the Y-axis are both arranged horizontally, so that the estimation of the magnetic center position in the X-axis direction and the Y-axis direction is the weight of the rotating body (1). However, if the Z-axis is placed horizontally, either the X-axis or the Y-axis is placed vertically, so the control shaft placed vertically is rotated. The magnetic center position is estimated in consideration of the force (component force) due to the weight of the body (1). When the Z-axis is placed horizontally, the weight of the rotating body (1) is supported by two sets of radial magnetic bearings (3) (4), but at each radial magnetic bearing (3) (4) The force due to the weight acting on the rotating body (1) is obtained from the weight of the rotating body (1) and the position of the center of gravity.
[0059]
Next, the estimation of the magnetic center position in the Z-axis direction will be described in more detail with reference to FIG.
[0060]
In the case of the horizontal posture shown in FIG. 4A, the deviation Δ is calculated by the following equation (9), and the magnetic center position is obtained by adding this Δ to the neutral position of the sensor.
[0061]
Δ = X_O・ (I_Z1-I_Z2) / (I_Z1+ I_Z2(9)
X_OIs a preset value and I_Z1, I_Z2Is a measured value. Therefore, Δ can be calculated using equation (9).
[0062]
For reference, the procedure by which the above equation (9) is derived will be described.
[0063]
In the horizontal posture, the attractive force F by the first axial electromagnet (12a)₁And the attractive force F by the second axial electromagnet (12b)₂Since they are balanced with each other, the following equation (10) is established between them.
[0064]
F₁= F₂  … (Ten)
Substituting Equations (3) and (4) into Equation (10) gives the following Equation (11).
[0065]
K ・ [I_Z1/ (X_O+ Δ))²= K ・ [I_Z2/ (X_O-Δ))²  … (11)
In formula (11), I_Z1, I_Z2, (X_O+ Δ), (X_OSince -Δ) is a positive value, it can be rewritten as follows.
[0066]
I_Z1/ (X_O+ Δ) = I_Z2/ (X_O−Δ)… (12)
When formula (12) is expanded and arranged, it can be rewritten sequentially as follows.
[0067]
I_Z1・ (X_O−Δ) = I_Z2・ (X_O+ Δ)
I_Z1・ X_O-I_Z1Δ = I_Z2・ X_O+ I_Z2・ Δ
(I_Z1+ I_Z2) ・ Δ = (I_Z1-I_Z2) ・ X_O  (13)
From this equation (13), equation (9) is obtained.
[0068]
In the erect posture shown in FIG. 4B and in a saturated state, the deviation Δ is calculated by the following equation (14), and the magnetic center position is obtained in the same manner as described above.
[0069]
Δ = X_O-I_Z2√ (K / Mg) (14)
X_OIs a preset value, I_Z2Is a measured value, K is a constant, and Mg is the weight of the rotating body (1). Therefore, Δ can be calculated using Equation (14).
[0070]
For reference, the procedure by which the above equation (14) is derived will be described.
[0071]
When in an upright position and saturated, I_Z1Is 0 and F₁Is 0, so the weight Mg of the rotating body (1) is F₂Supported by. Therefore, the following equation (15) is established.
[0072]
F₂= Mg (15)
Substituting equation (4) into equation (15) yields:
[0073]
K ・ [I_Z2/ (X_O-Δ))²= Mg (16)
From the equation (16), the following equation (17) is obtained.
[0074]
I_Z2/ (X_O−Δ) = √ (Mg / K) (17)
If formula (17) is rearranged, it can be rewritten as follows.
[0075]
I_Z2= (X_O-Δ) · √ (Mg / K)
(X_O−Δ) = I_Z2・ √ (K / Mg) (18)
Then, equation (14) is obtained from equation (18).
[0076]
In the upright posture shown in FIG. 4B and in a non-saturated state, the deviation Δ is calculated by the following equation (19), and the magnetic center position is obtained in the same manner as described above.
[0077]
Δ = [− b−√ (b²-4 ・ a ・ c)] / 2 ・ a ... (19)
here,
a = I_Z1 ²-I_Z2 ²-2 ・ X_O ²・ Mg / K
b = − (2 · I_Z1 ²・ X_O+ 2 · I_Z2 ²・ X_O)
c = I_Z1 ²・ X_O ²-I_Z2 ²・ X_O ²+ X_O ^Four・ Mg / K
It is.
[0078]
X_OIs a preset value, I_Z1, I_Z2Is a measured value, K is a constant, and Mg is the weight of the rotating body (1). Therefore, Δ can be calculated using Equation (19).
[0079]
For reference, the procedure by which the above equation (19) is derived will be described.
[0080]
F in the upright position and non-saturated₁, F₂From the balance of Mg, the following equation (20) is established.
[0081]
F₂-F₁= Mg (20)
Substituting Equations (3) and (4) into Equation (20) yields:
[0082]
K ・ [I_Z2/ (X_O-Δ))²-K ・ [I_Z1/ (X_O+ Δ))²= Mg ... (21)
When formula (21) is rearranged, it can be rewritten in the following order.
[0083]
[I_Z2/ (X_O-Δ))²-[I_Z1/ (X_O+ Δ))²= Mg / K
[I_Z2/ (X_O−Δ) + I_Z1/ (X_O+ Δ))
・ [I_Z2/ (X_O−Δ) −I_Z1/ (X_O+ Δ)] = Mg / K
{[I_Z2・ (X_O+ Δ) + I_Z1・ (X_O−Δ)] / (X_O ²-Δ²)}
・ {[I_Z2・ (X_O+ Δ) -I_Z1・ (X_O−Δ)] / (X_O ²-Δ²)}
= Mg / K
[I_Z2 ²・ (X_O+ Δ)²-I_Z1 ²・ (X_O-Δ)²] / (X_O ²-Δ²)²
= Mg / K
(X_O ²-Δ²)²・ Mg / K
= I_Z2 ²・ (X_O+ Δ)²-I_Z1 ²・ (X_O-Δ)²

In equation (22), Δ^Four<< X_O ^FourAs Δ^FourIf you delete the term

The equation (23) can be rearranged for Δ as follows.
[0084]

Equation (24) is a quadratic equation for Δ, and Δ², Δ¹, Δ⁰Equation (19) is obtained from the formula of the solution of the quadratic equation, where a, b, and c are the coefficients.
[0085]
In the inverted posture shown in FIG. 4C and in the saturated state, the deviation Δ is calculated by the following equation (25), and the magnetic center position is obtained in the same manner as described above.
[0086]
Δ = −X_O+ I_Z1√ (K / Mg) (25)
X_OIs a preset value, I_Z1Is a measured value, K is a constant, and Mg is the weight of the rotating body (1). Therefore, Δ can be calculated using Equation (25).
[0087]
If the head is saturated in an inverted position, I_Z2Is 0 and F₂Is 0, so the weight Mg of the rotating body (1) is F₁Supported by. Therefore, the following equation (26) is established.
[0088]
F₁= Mg (26)
Then, equation (26) is derived from equation (26) by the same procedure as in the saturated state in the upright posture of FIG. 4 (b).
[0089]
In the inverted posture of FIG. 4 (c) and in a non-saturated state, the deviation Δ is calculated by the following equation (27), and the magnetic center position is obtained in the same manner as described above.
[0090]
Δ = [− b−√ (b²-4 · a · c)] / 2 · a (27)
here,
a = I_Z1 ²-I_Z2 ²+ 2 · X_O ²・ Mg / K
b = − (2 · I_Z1 ²・ X_O+ 2 · I_Z2 ²・ X_O)
c = I_Z1 ²・ X_O ²-I_Z2 ²・ X_O ²-X_O ^Four・ Mg / K
It is.
[0091]
X_OIs a preset value, I_Z1, I_Z2Is a measured value, K is a constant, and Mg is the weight of the rotating body (1). Therefore, Δ can be calculated using Equation (27).
[0092]
F in the upright position and non-saturated₁, F₂From the balance of Mg, the following equation (28) is established.
[0093]
F₁-F₂= Mg (28)
Then, equation (27) is derived from equation (28) by the same procedure as in the case of the non-saturated state in the upright posture of FIG.
[0094]
The estimation of the magnetic center position in the X-axis direction and the Y-axis direction is performed in the same manner as described above for each of the radial magnetic bearings (3) and (4).
[0095]
The estimation of the magnetic center position in the X-axis direction will be described in more detail. In the case of the upright posture, the inverted posture, the Y-axis upright posture, or the Y-axis inverted posture, the X-axis is horizontal. The magnetic center position in the X-axis direction can be obtained using the same formula as in the case of estimating the magnetic center position in the Z-axis direction in the horizontal posture of a). In the case of the X-axis upright posture, the magnetic center position in the X-axis direction is obtained using the same formula as in the case of estimating the magnetic center position in the Z-axis direction in the upright posture shown in FIG. Can do. In the case of the X-axis upright posture or the X-axis inverted posture, in the equations corresponding to the equations (14), (19), (25) or (27), the rotating body (1) each radial instead of the weight Mg A component force of weight Mg in the magnetic bearings (3) and (4) is used. Each component force can be obtained by using data on the position of the center of gravity of the rotating body (1), the positions of the radial magnetic bearings (3) and (4), and the like. The same applies to the estimation of the magnetic center position in the Y-axis direction.
[0096]
As a result of the estimation of the magnetic center position, the deviation between the temporary levitation position (paired sensor neutral position) and the magnetic center position is predetermined in any of the pairs of electromagnets (12), (13), and (14). If it is greater than the predetermined value, an alarm signal is output from the control device (9) to the alarm device (18), and an alarm is emitted from the alarm device (18) with light or sound.
[0097]
When the estimation of the installation posture and magnetic center position of the rotating body (1) in step 103 is completed, the control parameters of the X, Y, and Z control axes are determined (step 104). Control of the electromagnets (12), (13), and (14) in the control device (9) is performed for each control axis, but as described above, the control axes are arranged vertically as compared with the case where they are arranged horizontally. Since the condition of force balance differs depending on the case, the optimum control parameter differs depending on the attitude of each control axis. For this reason, the control device (9) stores the optimal control parameter for each control axis in the horizontal posture and the optimal control parameter for the vertical posture, depending on the posture for each control axis. Optimal control parameters are selected. Specific control parameters include, for example, a transfer function of a magnetic bearing control system and a bias current value supplied to each electromagnet, and an optimum one among a plurality of preset transfer functions and bias current values. Selected.
[0098]
If the control parameter is determined in step 104, the rotating body (1) is levitated to the magnetic center position by controlling the magnetic bearings (3), (4), and (5). Is held (step 6). Then, the rotation of the rotating body (1) is started by driving the motor (8).
[0099]
Next, an example of the operation of the control device (9) at the time of starting the rotating body (1) in the second embodiment will be described with reference to the flowchart of FIG.
[0100]
In FIG. 5, when the start command for the magnetic bearing device is input to the control device (9), the mechanical center position is detected as follows (step 201). That is, first, a predetermined exciting current is supplied only to the first axial electromagnet (12a). As a result, the rotating body (1) is sucked in the negative direction of the Z-axis and reaches the Z-axis negative direction extreme position where the rear side surface of the groove (17) contacts the rear end surface of the inner ring of the protective bearing (10). Therefore, from the output of the axial position sensor (5) at this time, the Z-axis negative direction limit position coordinate Z with the predetermined position on the Z-axis as the origin_AIs required. Next, a predetermined exciting current is supplied only to the second axial electromagnet (12b). As a result, the rotating body (1) is sucked in the positive direction of the Z-axis and moved to the Z-axis positive forward limit position where the front side surface of the groove (17) contacts the front end surface of the inner ring of the protective bearing (10). Therefore, from the output of the axial position sensor (5) at this time, the Z-axis positive direction limit position coordinate Z_BIs required. And [(Z_A+ Z_B) / 2] to calculate the mechanical center position coordinate Z in the axial direction._DIs required. Next, a predetermined exciting current is supplied to the first X-axis electromagnets (13a) and (14a) of the two sets of radial magnetic bearings (3) and (4). As a result, the rotating body (1) is sucked in the negative direction of the X-axis, and the outer peripheral surface moves to the X-axis negative-direction extreme position where it contacts the inner peripheral surfaces of the inner rings of the two sets of protective bearings (10) and (11). Therefore, from the outputs of the pair of X-axis sensors (15a) and (15b) of the first radial position sensor unit (6) at this time, the first point whose center is between these sensors (15a) and (15b) is the first. X-axis negative limit coordinate X near the radial magnetic bearing (3)_1AIs obtained from the output of the pair of X-axis sensors (16a) and (16b) of the second radial position sensor unit (7), with the center between these sensors (16a and 16b) as the origin. X-axis negative direction extreme position coordinate X in the vicinity of radial magnetic bearing (4)_2AIs required. Next, a predetermined exciting current is supplied to the second X-axis electromagnets (13b) and (14b) of the two sets of radial magnetic bearings (3) and (4). As a result, the rotating body (1) is attracted in the positive direction of the X axis and moves to the extreme position in the positive direction of the X axis, so that the positive X axis in the vicinity of the first radial magnetic bearing (3) is the same as described above. Direction limit position coordinate X_1BX-axis positive limit position coordinate X in the vicinity of the second radial magnetic bearing (4)_2BIs required. And [(X_1A+ X_1B) / 2] to calculate the mechanical center position coordinate X in the radial direction in the vicinity of the first radial magnetic bearing (3)._1DAs well as [(X_2A+ X_2B) / 2] to calculate the mechanical center position coordinate X in the radial direction in the vicinity of the second radial magnetic bearing (4)._2DIs required. Next, a predetermined exciting current is supplied to the first Y-axis electromagnets (13c) and (14c) of the two sets of radial magnetic bearings (3) and (4). As a result, the rotating body (1) is attracted in the negative direction of the Y-axis and moved to the extreme position in the negative Y-axis direction where the outer peripheral surface is in contact with the inner peripheral surfaces of the inner rings of the two sets of protective bearings (10) and (11). Therefore, from the outputs of the pair of Y-axis sensors (15c) and (15d) of the first radial position sensor unit (6) at this time, the first point whose center is between these sensors (15c) and (15d) is the first. Y-axis negative limit position coordinate Y near the radial magnetic bearing (3)_1AIs obtained from the output of the pair of Y-axis sensors (16c) and (16d) of the second radial position sensor unit (7), with the center between these sensors (16c) and (16d) as the origin. Y-axis negative limit position coordinate Y near the radial magnetic bearing (4)_2AIs required. Next, a predetermined exciting current is supplied to the second Y-axis electromagnets (13d) and (14d) of the two sets of radial magnetic bearings (3) and (4). As a result, the rotating body (1) is attracted in the positive direction of the Y axis and moves to the extreme position in the positive direction of the Y axis, so that the positive Y axis in the vicinity of the first radial magnetic bearing (3) is the same as described above. Direction limit position coordinate value Y_1BY-axis positive direction limit position coordinate value Y in the vicinity of the second radial magnetic bearing (4)_2BIs required. And [(Y_1A+ Y_1B) / 2] to calculate the mechanical center position coordinate Y in the radial direction in the vicinity of the first radial magnetic bearing (3)._1DAs well as [(Y_2A+ Y_2B) / 2] to calculate the mechanical center position coordinate Y in the radial direction in the vicinity of the second radial magnetic bearing (4)._2DIs required.
[0101]
If the mechanical center position is detected in step 201, the rotary body (1) is temporarily levitated to the mechanical center position by controlling the magnetic bearings (3), (4), and (5). (Step 202). In the present invention, the levitation of the rotating body (1) to the mechanical center position is for obtaining data necessary for estimating the magnetic center position described below. The exact mechanical center position as described in JP-A-107815 may not be used, and it may be slightly deviated from this. That is, instead of the exact mechanical center position, the approximate mechanical center position in the vicinity thereof is obtained, and the rotating body (1) may be floated in the vicinity of the position. If the rotating body (1) is held at the mechanical center position, the excitation current flowing in each electromagnet (12), (13), and (14) is detected at that time (step 203). From the excitation current, the installation posture and magnetic center position of the rotating body (1) are estimated (step 204). This operation is the same as that in Steps 102 and 103 in FIG. 3 of the first embodiment. In this case, too, if the deviation between the temporary levitation position (mechanical approximate center position) and the magnetic center position is larger than a predetermined value. In the same manner as described above, an alarm is issued from the alarm device (18). Thereafter, as in the case of the first embodiment, control parameter determination (step 205) and magnetic levitation (step 206) to the magnetic center position of the rotating body (1) are performed.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view of a magnetic bearing device showing an embodiment of the present invention.
2 is a block diagram showing an example of an electrical configuration of the magnetic bearing device of FIG. 1. FIG.
FIG. 3 is a flowchart showing an example of the operation of the electromagnet control device of FIG. 2 in the first embodiment.
FIG. 4 is an explanatory diagram for explaining the estimation of the installation posture of the rotating body and the estimation of the magnetic center position.
FIG. 5 is a flowchart showing an example of the operation of the electromagnet control device of FIG. 2 in the second embodiment.
[Explanation of symbols]
(1) Rotating body
(2) Axial magnetic bearing
(3) (4) Radial magnetic bearing
(5) Axial position sensor
(9) Electromagnet controller
(10) (11) Protective bearing (regulation means)
(12a) (12b) Axial electromagnet
(13a) (13b) (13c) (13d) Radial electromagnet
(14a) (14b) (14c) (14d) Radial electromagnet
(15a) (15b) (15c) (15d) Radial position sensor
(16a) (15b) (16c) (16d) Radial position sensor
(18) Alarm device (alarm means)

Claims (3)

A plurality of magnetic bearings having a plurality of electromagnets for non-contact support of the rotating body in the axial direction and the radial direction, a plurality of position sensors for detecting the position of the rotating body in the axial direction and the radial direction, and from the position sensor In a magnetic bearing device comprising electromagnet control means for controlling the electromagnet of each magnetic bearing based on a signal,
The electromagnet control means temporarily sets the rotary body to the temporary levitation position with the neutral position of the sensor in the axial direction and radial direction determined from the position of the position sensor as the temporary levitation position. from the excitation current flowing through each electromagnet, said the installation posture of the rotating body, and estimates the magnetic center position of the axial and radial directions relative to the position of said each magnetic bearing electromagnet, the rotating body to the magnetic center position The magnetic bearing device is characterized in that it is magnetically levitated. A plurality of magnetic bearings having a plurality of electromagnets for non-contact support of the rotating body in the axial direction and the radial direction, a plurality of position sensors for detecting the positions of the rotating body in the axial direction and the radial direction, and signals from the position sensors In the magnetic bearing device comprising electromagnet control means for controlling the electromagnet of each magnetic bearing based on the above, and regulation means for regulating the movable range in the axial direction and radial direction of the rotating body,
The electromagnet control means obtains a mechanical center position in the axial direction and radial direction of the rotating body with respect to a movable range by the restricting means, and sets this position as a temporary floating position, and temporarily puts the rotating body at the temporary floating position. Estimate the installation posture of the rotating body and the axial and radial magnetic center positions with respect to the position of the electromagnet of each magnetic bearing from the excitation current that flows to each electromagnet of each of the magnetic bearings during the levitation. A magnetic bearing device characterized in that the rotating body is magnetically levitated at the magnetic center position. The electromagnet control means, the temporary difference levitated position and the magnetic central position, characterized in that it comprises an alarm means for issuing an alarm when it is determined to be larger than a predetermined value according to claim 1 or 2. Magnetic bearing device.

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