US Patent No. 9,257,923

CONTROL SYSTEM FOR SYNCHRONOUS MOTOR INCLUDING ABNORMALITY DETECTION AND DIAGNOSIS FUNCTION


Patent No. 9,257,923
Issue Date February 09, 2016 
Title Control System For Synchronous Motor Including Abnormality Detection And Diagnosis Function
Inventorship Naoto Sonoda, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,257,923

1. A control system for a synchronous motor with an abnormality detection and diagnosis function, the control system comprising:
a current control unit providing, in detection of a magnetic pole position of a rotor of a motor during the initial start-up
of the motor in which permanent magnets are disposed, a first current command to a first excitation phase of a stator winding
of the motor over a first period of time when the motor is to be stopped and providing a second current command to a second
excitation phase different from the first excitation phase over a second period of time when the motor is to be caused to
operate;

a magnetic pole position detector correcting an excitation phase on the basis of a magnetic pole position of the stopped motor;
a current error calculator calculating a current error, the current error being a difference between a current flowing through
the motor in the second period of time and the second current command; and

an abnormality detection and diagnosis unit detecting an abnormality on the basis of
a speed of the motor in the first period of time, and
the speed of the motor, the direction of movement and the amount of movement of the motor, and the magnitude of the current
error in the second period of time,

wherein when the speed of the motor is higher than a predetermined speed while the first current command is provided to the
first excitation phase of the motor over the first period of time, the abnormality detection and diagnosis unit judges that
a first abnormality has occurred in a current feedback from the motor to the current control unit or in a speed feedback from
the motor to the abnormality detection and diagnosis unit.