US Patent No. 9,136,789

SYNCHRONOUS MOTOR CONTROL APPARATUS


Patent No. 9,136,789
Issue Date September 15, 2015
Title Synchronous Motor Control Apparatus
Inventorship Hidetoshi Uematsu, Yamanashi (JP)
SeungJun Lee, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,136,789

1. A synchronous motor control apparatus that performs current vector control of a permanent-magnet synchronous motor based
on a q-phase current command and a d-phase current command, comprising:
a first candidate value calculating unit which, using the motor speed of said synchronous motor and a control apparatus current
limit value and control apparatus voltage limit value preset in said control apparatus, calculates a first d-phase current
limit candidate value and a first q-phase current limit candidate value, based on points of intersection at which a current
limiting circle representing a current vector locus that said control apparatus current limit value describes on a d-q current
coordinate plane intersects a voltage limiting ellipse representing a current vector locus that said control apparatus voltage
limit value describes as a function of said motor speed;

a second candidate value calculating unit which, using the motor speed of said synchronous motor and said control apparatus
voltage limit value, calculates a second d-phase current limit candidate value and a second q-phase current limit candidate
value, based on points of intersection at which a maximum torque/flux curve representing a current vector locus that maximizes
torque for the same flux linkage on said d-q current coordinate plane intersects said voltage limiting ellipse representing
the current vector locus that said control apparatus voltage limit value describes as a function of said motor speed;

a first q-phase current command unit which, when the absolute value of said first d-phase current limit candidate value is
smaller than the absolute value of said second d-phase current limit candidate value, then sets said first q-phase current
limit candidate value as a q-phase current limit value, but otherwise sets said second q-phase current limit candidate value
as the q-phase current limit value and, when a first q-phase current command candidate value created based on a torque command
exceeds said q-phase current limit value, then limits said first q-phase current command candidate value to said q-phase current
limit value and outputs said limited first q-phase current command candidate value;

a first d-phase current command unit which, when the absolute value of said first d-phase current limit candidate value is
smaller than the absolute value of said second d-phase current limit candidate value, then sets said first d-phase current
limit candidate value as a d-phase current limit value, but otherwise sets said second d-phase current limit candidate value
as the d-phase current limit value and, when a first d-phase current command candidate value created based on said motor speed
and said first q-phase current command candidate exceeds said d-phase current limit value, then limits said first d-phase
current command candidate value to said d-phase current limit value and outputs said limited first d-phase current command
candidate value;

a third candidate value calculating unit which calculates a third d-phase current limit candidate value and a third q-phase
current limit candidate value, based on points of intersection at which a maximum torque/current curve representing a current
vector locus that maximizes generated torque for the same current on said d-q current coordinate plane intersects said current
limiting circle representing the current vector locus that said control apparatus current limit value describes;

a second q-phase current command unit which, when a second q-phase current command candidate value created based on said torque
command exceeds said third q-phase current limit candidate value, then limits said second q-phase current command candidate
value to said third q-phase current limit value and outputs said limited second q-phase current command candidate value;

a second d-phase current command unit which outputs a second d-phase current command candidate value that is created by using
said second q-phase current command candidate value output from said second q-phase current command unit and said maximum
torque/current curve representing on said d-q current coordinate plane said current vector locus that maximizes generated
torque for the same current; and

a d-q phase current command judging unit which, when the absolute value of said second d-phase current command candidate value
is larger than the absolute value of said first d-phase current command candidate value, then outputs said second d-phase
current command candidate value and said second q-phase current command candidate value, otherwise outputs said first d-phase
current command candidate value and said first q-phase current command candidate value, as said d-phase current command and
said q-phase current command, respectively.