# US 9,438,158 B2 · Motor control device controlling synchronous motor

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- Number: US 9,438,158 B2
- Document ID: US9438158B2
- Status: Granted
- Kind: B2
- Application number: 14/609,494
- Filed: 2015-01-30
- Published: 2015-09-03
- Granted: 2016-09-06
- Earliest claimed: 2014-02-28
- Assignees: Fanuc Corporation
- Applicants: FANUC Corporation
- Inventors: Hidetoshi Uematsu
- Web page: https://patentgrep.com/patent/US9438158B2

## CPC

- H02P 21/22: Current control, e.g. using a current control loop
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A motor control device includes: a calculating unit for calculating a speed reference value that decreases as a torque command increases; a determining unit for determining a magnitude relationship between a speed command and a speed reference value calculated for a torque command by the calculating unit; a q-axis-current commanding unit for generating a q-axis current command on the basis of a torque command and an inverse number of a torque constant of the synchronous motor when a speed command is smaller than a speed reference value, and generating the q-axis current command on the basis of a function of which independent variable is a speed command, the torque command, the inverse number of the torque constant, and when a speed command is equal to or larger than a speed reference value; and a d-axis-current commanding unit generating a d-axis current command, on the basis of a q-axis current command.

## Claims

### Claim 1

A motor control device that generates a q-axis current command and a d-axis current command, and uses the commands to control a synchronous motor having saliency, the motor control device comprising:
a calculating unit calculating a speed reference value that takes an initial value when a torque command is zero, and that decreases as the torque command increases;
a determining unit determining a magnitude relation between a speed command and the speed reference value calculated for the torque command by the calculating unit;
a q-axis-current commanding unit that
generates, when the determining unit determines that the speed command is smaller than the speed reference value, the q-axis current command of commanding a q-axis current to flow to the synchronous motor, on the basis of
the torque command, and
an inverse number of a torque constant of the synchronous motor, and
generates, when the determining unit determines that the speed command is equal to or larger than the speed reference value, the q-axis current command of commanding the q-axis current to flow to the synchronous motor, on the basis of
a function of which an independent variable is the speed command,
the torque command, and
the inverse number of the torque constant of the synchronous motor;
a d-axis-current commanding unit generating the d-axis current command of commanding a d-axis current to flow to the synchronous motor, on the basis of the q-axis current command generated by the q-axis-current commanding unit; and
an inverter configured to supply power to the synchronous motor in accordance with the q-axis-current command and the d-axis-current command,
wherein
the speed reference value is ωn,
the initial value of the speed reference value when the torque command is zero is ω0,
a change ratio of the speed reference value is k,
the torque command is TCMD, and
the calculating unit calculates the speed reference value ωn on the basis of the equation:
ωn=ω0−k×TCMD.

### Claim 2 (depends on 1)

The motor control device according to claim 1, further comprising a storing unit storing the speed-reference-value initial value and the change ratio.

### Claim 3 (depends on 1)

The motor control device according to claim 1, wherein
the q-axis current command is Iq*,
the speed command is ωCMD,
the inverse number of the torque constant of the synchronous motor is R, coefficients are a, b, and c,
when the determining unit determines that the speed command ωCMD is smaller than the speed reference value ωn,
the q-axis-current commanding unit generates the q-axis current commanding Iq* on the basis of the equation:
Iq*=TCMD×R
when the determining unit determines that the speed command ωCMD is equal to or larger than the speed reference value ωn,
the q-axis-current commanding unit generates the q-axis current command Iq* on the basis of the equation:
Iq*=TCMD×R×(aωCMD2+bωCMD+c).