US Patent No. 9,225,270

CURRENT CONTROL DEVICE OF SYNCHRONOUS MOTOR


Patent No. 9,225,270
Issue Date December 29, 2015
Title Current Control Device Of Synchronous Motor
Inventorship Kenji Takahashi, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,225,270

1. A current control device of a synchronous motor, generating a current command in a predetermined sampling period on the
basis of an orthogonal dq coordinate system, the current control device comprising:
a provisional d-phase current command calculation unit calculating a provisional d-phase current command on the basis of a
torque command, a current at no load, and a current at maximum load;

a voltage amplitude calculation unit obtaining a voltage command vector, which is an output of a current control in a previous
sampling period, that is one cycle prior to the present sampling period, and calculating a magnitude of the voltage command
vector;

a voltage ratio calculation unit determining a voltage ratio between the magnitude of the voltage command vector and a maximum
output voltage of an amplifier;

a target d-phase current calculation unit obtaining a d-phase current command in the previous sampling period, and calculating
a target d-phase current command from the voltage ratio and the d-phase current command;

a correction value calculation unit determining a correction value by passing a difference between the provisional d-phase
current command in the present sampling period and the target d-phase current command through a low-pass filter; and

an adder adding the correction value to the provisional d-phase current command in the present sampling period in order to
calculate a new d-phase current command.