# US 11,306,777 B2 · Magnetic bearing control apparatus, control method and high speed rotating motor using the same

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- Number: US 11,306,777 B2
- Document ID: US11306777B2
- Status: Granted
- Kind: B2
- Application number: 16/169,311
- Filed: 2018-10-24
- Published: 2019-04-25
- Granted: 2022-04-19
- Earliest claimed: 2017-10-24
- Assignees: LG Electronics Inc.
- Applicants: LG Electronics Inc.
- Inventors: Keun Woo Jung; Kyung Min Kim; Jonghyun Jeon; Joonsik An
- Web page: https://patentgrep.com/patent/US11306777B2

## CPC

- F16C 32/0446: {Determination of the actual position of the moving member, e.g. details of sensors}
- F16C 32/0451: {Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control}
- F16C 32/0455: {including digital signal processing [DSP] and analog/digital conversion [A/D, D/A]}
- F16C 32/0461: {of stationary parts of the magnetic circuit}
- F16C 32/0468: {of moving parts of the magnetic circuit, e.g. of the rotor}
- F16C 32/0493: {integrated in an electrodynamic machine, e.g. self-bearing motor}
- H02K 7/09: with magnetic bearings
- H02P 6/12: Monitoring commutation; Providing indication of commutation failure
- H02P 6/17: and for generating speed information
- H02P 6/28: Arrangements for controlling current (H02P6/10 takes precedence)
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A magnetic bearing control apparatus includes a plurality of output elements configured to generate electromagnetic force, a magnetic bearing configured to float a rotation shaft from a surface of the magnetic bearing based on the electromagnetic force generated by the plurality of output elements, at least one displacement sensor configured to sense a displacement of the rotation shaft, and a controller. The controller is configured to control a current supplied to the plurality of output elements, to control a position of the rotation shaft based on the current supplied to the plurality of output elements according to the displacement of the rotation shaft, and to determine a failure of the displacement sensor.

## Claims

### Claim 1

A magnetic bearing control apparatus, comprising:
a plurality of output elements configured to generate electromagnetic force;
a magnetic bearing configured to float a rotation shaft from a surface of the magnetic bearing based on the electromagnetic force generated by the plurality of output elements;
at least one displacement sensor configured to sense a displacement of the rotation shaft;
a current sensor configured to detect a current supplied to the plurality of output elements; and
a controller configured to:
control the current supplied to the plurality of output elements,
control a position of the rotation shaft based on the current supplied to the plurality of output elements according to the displacement of the rotation shaft,
determine a failure of the displacement sensor, and
determine a failure of the plurality of output elements or the current sensor,
wherein the controller is further configured to:
perform a plurality of control cycles until the position of the rotation shaft corresponds to a set optimal control range,
control the rotation shaft to move by a predetermined distance per each control cycle of the plurality of control cycles,
sense the position of the rotation shaft in each control cycle,
based on the position of the rotation shaft sensed in each control cycle, determine whether floating of the rotation shaft from the magnetic bearing has failed, and
based on determining that the floating of the rotation shaft from the magnetic bearing has failed, determine a failure position of the current sensor or the plurality of output elements.

### Claim 2 (depends on 1)

The magnetic bearing control apparatus of claim 1, wherein the displacement sensor comprises:
a photo coupler arranged adjacent to the rotation shaft and configured to output a waveform having a frequency according to the displacement of the rotation shaft;
a mixing portion configured to, based on a difference between a reference frequency and the frequency of the waveform, convert the waveform into a first signal having a conversion frequency;
a differential amplifier configured to amplify a magnitude of the first signal;
a noise filter configured to reduce a noise of the first signal amplified by the differential amplifier;
a comparator configured to convert the first signal filtered by the noise filter into a conversion waveform according to the position of the rotation shaft;
a multiplexer (MUX) configured to simplify the conversion waveform; and
a digital signal processor (DSP) input port configured to convert the conversion waveform simplified by the MUX into a digital signal.

### Claim 3 (depends on 1)

The magnetic bearing control apparatus of claim 1, wherein the controller is further configured to:
adjust the electromagnetic force by increasing or decreasing the current supplied to the plurality of output elements based on the displacement of the rotation shaft; and
based on adjustment of electromagnetic force, maintain a floated state of the rotation shaft at a set position.

### Claim 4 (depends on 1)

The magnetic bearing control apparatus of claim 1, wherein the displacement sensor is configured to detect a frequency of a signal corresponding to the position of the rotation shaft, and
wherein the controller is further configured to determine that the displacement sensor is disconnected from the controller based on the detected frequency being equal to zero.

### Claim 5 (depends on 4)

The magnetic bearing control apparatus of claim 4, wherein the controller is further configured to determine a failure of the displacement sensor based on the detected frequency being outside of a predetermined frequency range.

### Claim 6 (depends on 1)

The magnetic bearing control apparatus of claim 1, wherein the controller comprises a storage portion that is configured to:
accumulate data including a floating completion time that is taken to float the rotation shaft from a first position to a set position, a stabilization time in which the rotation shaft is disposed at the set position, and an amount of current consumed by the plurality of output elements to maintain the rotation shaft at a floated state; and
based on the accumulated data, determine a reference floating completion time, a reference stabilization time, and a reference current value.

### Claim 7 (depends on 6)

The magnetic bearing control apparatus of claim 6, wherein the controller is further configured to:
based on measurement of the displacement sensor, determine a present floating completion time and a present stabilization time;
compare the present floating completion time to the reference floating completion time;
compare the present stabilization time to the reference stabilization time; and
determine a failure of the plurality of output elements or the current sensor based on at least one of (i) a difference between the present floating completion time and the reference floating completion time or (ii) a difference between the present stabilization time and the reference stabilization time.

### Claim 8 (depends on 7)

The magnetic bearing control apparatus of claim 7, wherein the controller is further configured to:
determine a present amount of current supplied to the plurality of output elements;
compare the present amount of current to the reference current value; and
determine a failure of the plurality of output elements or the current sensor based on a difference between the present amount of current and the reference current value.

### Claim 9 (depends on 6)

The magnetic bearing control apparatus of claim 6, wherein the current sensor comprises a plurality of current sensors configured to detect the current supplied to the plurality of output elements,
wherein the displacement sensor comprises a plurality of displacement sensors,
wherein the controller is further configured to:
based on the accumulated data, determine a failure of at least one of the plurality of displacement sensors, the plurality of output elements, or the plurality of current sensors;
determine one or more displacement sensors that operate in a normal operation state, and one or more output elements that operate in a normal state; and
based on determination of the failure, control the rotation shaft to stop rotating in a floated state by controlling the one or more displacement sensors that operate in the normal operation state or the one or more output elements that operate in the normal state.

### Claim 10 (depends on 9)

The magnetic bearing control apparatus of claim 9, wherein the controller is further configured to, based on the rotation shaft stopping rotation, dispose the rotation shaft to an unfloated state by controlling the one or more output elements that operate in the normal state.

### Claim 11

A high speed rotating motor, comprising:
a stator configured to generate first electromagnetic force;
a rotation shaft arranged inside of the stator and configured to rotate based on the first electromagnetic force;
a magnetic bearing configured to float the rotation shaft from a surface of the magnetic bearing, the magnetic bearing comprising a plurality of output elements configured to generate second electromagnetic force and configured to enable the magnetic bearing to maintain a predetermined distance between the rotation shaft and the stator based on the second electromagnetic force;
at least one displacement sensor configured to sense a displacement of the rotation shaft;
a current sensor configured to detect a current supplied to the plurality of output elements; and
a controller configured to:
control a current supplied from the plurality of output elements to the magnetic bearing,
control a position of the rotation shaft based on the displacement of the rotation shaft,
determine a failure of the displacement sensor, and
determine a failure of the plurality of output elements or the current sensor, wherein the controller is further configured to:
perform a plurality of control cycles until the position of the rotation shaft corresponds to a set optimal control range,
control the rotation shaft to move by a predetermined distance per each control cycle of the plurality of control cycles,
sense the position of the rotation shaft in each control cycle,
based on the position of the rotation shaft sensed in each control cycle, determine whether floating of the rotation shaft from the magnetic bearing has failed, and
based on determining that the floating of the rotation shaft from the magnetic bearing has failed, determine a failure position of the current sensor or the plurality of output elements.

### Claim 12 (depends on 11)

The high speed rotating motor of claim 11, wherein the displacement sensor comprises:
a photo coupler arranged adjacent to the rotation shaft and configured to output a waveform having a frequency according to the displacement of the rotation shaft;
a mixing portion configured to, based on a difference between a reference frequency and the frequency of the waveform, convert the waveform into a first signal having a conversion frequency;
a differential amplifier configured to amplify a magnitude of the first signal;
a noise filter configured to reduce a noise of the first signal amplified by the differential amplifier;
a comparator configured to convert the first signal filtered by the noise filter into a conversion waveform according to the position of the rotation shaft;
a multiplexer (MUX) configured to simplify the conversion waveform; and
a digital signal processor (DSP) input port configured to convert the conversion waveform simplified by the MUX into a digital signal.

### Claim 13 (depends on 11)

The high speed rotating motor of claim 11, wherein the controller is further configured to:
adjust electromagnetic force by increasing or decreasing the current supplied from the plurality of output elements to the magnetic bearing based on the displacement of the rotation shaft; and
based on adjustment of electromagnetic force, maintain a floated state of the rotation shaft at a set position.

### Claim 14 (depends on 11)

The high speed rotating motor of claim 11, wherein the displacement sensor is configured to detect a frequency of a signal corresponding to the position of the rotation shaft, and
wherein the controller is further configured to determine that the displacement sensor is disconnected from the controller based on the detected frequency being equal to zero.