MOTOR CONTROL DEVICE CONTROLLING SYNCHRONOUS MOTOR

• US 20150249418A1
• Filed: 01/30/2015
• Published: 09/03/2015
• Est. Priority Date: 02/28/2014
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: UEMATSU, Hidetoshi
• Granted Patent: US 9,438,158 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop

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

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, as an initial value, a value when a torque command is zero, and that decreases as a torque command increases;

a determining unit determining magnitude relation between an input speed command and a speed reference value calculated for an input torque command by the calculating unit;

a q-axis-current commanding unit that generates, when the determining unit determines that a speed command is smaller than a speed reference value, a q-axis current command of commanding a q-axis current to be flowed to the synchronous motor, on the basis of a 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, a q-axis current command of commanding a q-axis current to be flowed to the synchronous motor, on the basis of a function of which independent variable is a speed command, the torque command, and the inverse number of the torque constant of the synchronous motor; and

a d-axis-current commanding unit generating a d-axis current command of commanding a d-axis current that is made to flow to the synchronous motor, on the basis of a q-axis current command generated by the q-axis-current commanding unit.

2. The motor control device according to claim 1, further comprising a storing unit storing a speed-reference-value initial value set as an initial value of a speed reference value when a torque command is zero, and storing a change ratio of a speed reference value used in a calculating process by the calculating unit.

3. The motor control device according to claim 1, wherein when a speed reference value is ω

_n, a speed-reference-value initial value set as an initial value of a speed reference value when a torque command is zero is ω

₀, a change ratio of a speed reference value is k, and an input torque command is T_CMD,

on the basis of the equation;

ω

_n=ω

₀−

k×

T_CMD,

the calculating unit calculates a speed reference value ω

_n.

4. The motor control device according to claim 3, wherein when a q-axis current command of commanding a q-axis current that is made to flow to the synchronous motor is I_q* an input torque command is T_CMD, an input speed command is ω

_CMD, an inverse number of a torque constant of the synchronous motor is R, and coefficients are a, b, and c,

when the determining unit determines that a speed command ω

_CMD is smaller than a speed reference value ω

_n,

on the basis of the equation;

I_q*=T_CMD×

R,

the q-axis-current commanding unit generates a q-axis current command I_q*,

and when the determining unit determines that a speed command ω

_CMD is equal to or larger than a speed reference value ω

_n,

on the basis of the equation;

I_q*=T_CMD×

R×

(aω

_CMD² bω

_CMD C),

the q-axis-current commanding unit generates a q-axis current command I_q*.