JPH0743486Y2 - Magnetic bearing control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a circuit for controlling the posture of a rotating body that is levitated and supported by a magnetic bearing and maintaining it stably.

(Industrial field of use) A magnetic bearing floats and supports a rotating body with an electromagnet, and the current flowing through this electromagnet coil is controlled to adjust the position of the rotating body. FIG. 2 is a schematic diagram of a magnetic bearing that levitates and supports a rotating body by means of 16 electromagnets. In FIG. 2, 1 is a rotating body of a magnetic body, 2 is a rotating shaft, 3 is a rotating body, and 401 to 416 are electromagnets and gap sensors. X axis, Y as shown in the coordinate axes
Take the axis and the Z axis. The rotating body 1 has a disk-shaped rotating body 3 formed at the center of a cylindrical rotating shaft 2 and rotates about the rotating shaft 2. A motor rotor (not shown) is attached to the outer periphery of the rotating body 1, and is rotated by an electromagnetic force between the rotor and a motor stator (not shown). 4 around the upper part of the rotary shaft 2.
Electromagnets and gap sensors 401 to 404 are arranged at equal intervals, and electromagnets and gap sensors 405 to 408 are similarly arranged around the lower portion of the rotary shaft 2. Electromagnets and gap sensors 409 to 412 are arranged at equal intervals near the circumference of the upper surface of the rotary body 3, and electromagnets and gap sensors 413 to 416 are similarly arranged near the circumference of the lower surface of the rotation body 3. Electromagnet 401m
˜416 m is to generate an attractive force between the rotator 1 and the rotating body 1 by passing an electric current through the gap sensor 401s.
˜416s are for detecting the distance from the rotating shaft 2 or the rotating body 3. The person in charge of controlling each of the electromagnets 401m to 416m is as follows.

Note that θ is an axis around the X axis, and ψ is an axis around the Y axis.

Since the arrangement of the electromagnets and the gap sensors 401 to 416 and their charge of control are as described above, when moving in the positive direction of each axis, the electromagnet that strengthens the attraction force is set to (+), and the attraction force is compared with that. If the electromagnet that weakens is (-),
The relationship between each axis and the electromagnets 401 to 416 is expressed as shown in FIG.

FIG. 4 shows a functional block diagram of a conventional magnetic bearing control circuit that applies a signal to the electromagnet in this way to perform closed-loop control of the position and orientation of the rotating body. In FIG. 4, 11
1, 112 and 113 are torque converters of a transfer function G (S) for converting an input position signal or angle signal into a torque signal,
121, 122, 123, 124 and 125 are proportional constant parts of the proportional constant K, 131, 132, 133, 134 and 135 are angular velocity conversion parts of the transfer function 1 / Js which output the output angular velocity with respect to the input torque, J is the moment of inertia (Ix or Iy) about the input shaft (X axis, Y axis), and J = Ix = Iy. 141, 142, 14
Reference numerals 3, 144, and 145 are angular displacement conversion units having a transfer function 1 / s that integrate the angular velocity and convert it into an angular displacement. 154 and 155 are transfer functions G1 for converting an input angle signal into a torque signal
(S) torque converters 164, 165 perform a predetermined operation from the angle change to calculate a torque error. A precession calculation unit that calculates a precession torque by applying a proportional constant of Iω (I is the moment of inertia of the rotary body about the Z axis, and ω is the angular velocity of the rotary body 1 around the Z axis).

As shown in FIG. 4, the control of the X axis, the Y axis, the Z axis, the θ axis, and the ψ axis is controlled by each closed loop. Rotating body 1
The position is always detected by the gap sensors 401s to 416s, which is fed back as a position signal or an angle signal, and the electromagnet 401m keeps a predetermined position and posture.
The current flowing to ~ 416m is controlled. Further, regarding the θ axis and the ψ axis, cross feedback is adopted in the connection of the torque correction units 164 and 165 and the precession calculation units 134 and 135. When the rotating body 1 rotates at high speed, the torque in the rotating direction is output as the torque around the orthogonal rotating shafts (this is referred to as precession torque). Therefore, the torque to be controlled should be input to the orthogonal rotating shafts. Thus, the output torque comes out to the control shaft and can be controlled. For example, when a torque around the X axis is input to the rotating body as shown in FIG. 5A, the rotating body 1 outputs the torque (precession torque) around the Y axis. Therefore, in the case of controlling around the Y axis, obtaining the control amount around the Y axis by the position detector (gap sensor) and inputting it around the X axis is called cross feedback. Therefore, in order to control the control axis, an input is given to the orthogonal axes and torque is output around the control axis. For this purpose, a cross feedback circuit is used to input the torque to be input sensed by the control shaft to the orthogonal shaft.

(Problems to be Solved by the Invention) In the conventional magnetic bearing control circuit, the transfer functions Kcs of the torque correction units 164 and 165 related to cross feedback are constant. Therefore, when the rotating direction of the rotating body 1 changes, the kinematic precession torque of the rotating body 1 changes, so that the cross-feedback torque that corrects the posture variation of the rotating body 1 becomes positive feedback, and the cross-feedback torque extends over both rotating direction ranges. It was not possible to obtain stable and good control performance. That is, the constant value of cross feedback is one rotation direction,
For example, it is determined to obtain an appropriate cross feedback torque with respect to a change in one rotation direction ω within a certain range. Therefore, during reverse rotation, stable control of the rotating body 1 cannot be obtained due to the influence of cross feedback. Further, if the cross feedback torque having the same magnitude as the precession torque can be given, the posture of the rotating body 1 is stabilized, but the precession torque becomes positive or negative depending on the rotation direction. Therefore, the cross feedback torque becomes positive or negative with respect to the proper torque. That is, as shown in FIG. 5 (b), the precession torque becomes negative at the time of reverse rotation, and since the cross feedback torque corresponding thereto is a constant value (negative torque), it is added and becomes positive feedback.

The problem to be solved by the present invention is to provide a control circuit for a magnetic bearing that can be stably controlled within the rotational speed range of the rotating body in both directions.

(Means for Solving the Problems) A control circuit for a magnetic bearing according to the present invention includes a difference between a rotation angle around two axes orthogonal to a rotation axis (Z axis) of a rotating body and a reference angle. A first and a second torque calculating means for calculating respective torques around the two axes by performing a predetermined operation on each of the two axes, and a predetermined difference for each difference between the rotation angle around the two axes and the reference angle. First and second corrections are performed to correct each torque error around the two axes by cross feedback.
And the difference between the output of the first torque calculating means and the output of the second torque correcting means, and the difference between the output of the second torque calculating means and the output of the first torque correcting means. A rotation direction detecting means for detecting a rotation direction of the rotating body, the rotor motion calculating means for calculating a rotation angle for imparting rotation around the two axes via the electromagnets of the magnetic bearings, It is characterized in that the apparatus further comprises code switching means for giving a code corresponding to the detected rotation direction to the outputs of the first and second torque correction means.

(Operation) In the magnetic bearing control circuit configured as described above, when the rotating body changes the rotating direction, the rotating direction detecting means detects this, and the code switching means gives the first and second codes corresponding to the rotating direction. To the torque correction means of. First and second
The torque correction means switches the sign of the cross feedback gain so as to correspond to the rotation direction, and stable and good control performance can be obtained over both rotation direction ranges.

(Embodiment) FIG. 1 is a functional block diagram of a magnetic bearing control circuit according to the present invention. The difference between FIG. 1 and FIG. 4 is that
The rotation direction detecting means 18 for detecting the rotation direction of the rotating body is provided, and the code switching means 191 and 192 are used as torque correction means 164 and 165.
Connected to each output side of. The rotation direction detecting means 18 is composed of two sets of phototransistors, and is arranged in the vicinity of a black and white surface formed in a tooth shape on the periphery of the rotating body 1. The rotation direction is measured by measuring the interval at which the light reflected from the surface is blocked. The sign switching means 191 and 192 are rotation direction detecting means.
The sign G2 of the rotation direction detected in 18 is given.

When the rotation direction changes during rotation, the code switching means 191, 192
Becomes a new rotation direction code G2 after the change, and the cross feedback code is switched so as to correspond to the rotation direction of the rotating body 1. When the precession torque of the rotor 1 is positive, the sign of cross feedback is positive,
When the precession torque of the rotating body 1 is reversely rotating, the sign of cross feedback is negative. In this way, the relationship of the error correction torque corresponding to the control error becomes negative feedback in both rotation directions, and proper control performance is obtained.

(Effects of the Invention) As described above, according to the magnetic bearing control circuit of the present invention, the gain sign of the cross feedback circuit for stabilizing the posture of the rotating body levitated and supported by the magnetic bearing is set in the rotational direction. By making them correspond, it is possible to stably control the posture of the rotating body over both rotation direction ranges.

Therefore, stable control characteristics can be obtained in the control of the rotating body such that the rotating body levitated and supported by the magnetic bearing rotates in both forward and reverse directions.

[Brief description of drawings]

FIG. 1 is a functional block diagram of a control circuit for a magnetic bearing according to the present invention, FIG. 2 is a block diagram schematically illustrating an example of the magnetic bearing, and FIG. 3 is a positive direction of each shaft and an attraction force of an electromagnet. FIG. 4 is a functional block diagram of a conventional magnetic bearing control circuit, and FIGS. 5 (a) and 5 (b) are explanatory diagrams of precession torque when the rotating body rotates in both forward and reverse directions. It is a figure. DESCRIPTION OF SYMBOLS 1 ... Rotating body, 2 ... Rotating shaft, 3 ... Rotating main body, 401-416 ... Electromagnet and gap sensor, 111,112,113 ... Torque converting part, 121,122,123,124,125 ... Proportional constant part, 131,132,133,1
34,135 ... Angular velocity converting section, 141, 142, 143, 144, 145 ... Angular displacement converting section, 154, 155 ... Torque converting section, 164, 165 ... Torque correcting section, 171, 172 ... Precession calculating section, 18 ... Rotation direction detecting means, 191, 192 ... Sign switching means.

Claims (1)

[Scope of utility model registration request] 1. Torques around the two axes by performing a predetermined operation on each difference between a rotation angle around two axes orthogonal to the rotation axis (Z axis) of the rotating body and a reference angle. The first and second torque calculating means for calculating and the difference between the rotation angle around the two axes and the reference angle are subjected to a predetermined operation to cross-feedback each torque error around the two axes. And the difference between the output of the first torque calculating means and the output of the second torque correcting means, and the second torque calculating means and the first torque correcting means. Is a control circuit of a magnetic bearing having a rotor motion calculating means for calculating a rotation angle for inputting a difference from the output of the magnetic bearing and applying rotation about the two axes via an electromagnet of the magnetic bearing, Rotation direction detecting means for detecting the rotation direction of the The control circuit of the magnetic bearing, characterized in that it includes a code switching means for providing a code corresponding to the rotational direction to the output of the first and second torque correcting means.